© 2025 Elsevier Inc.Objectives: To characterize two experimental zirconia bilayer materials compared to their monolithic controls, before and after hydrothermal aging. Methods: Commercial zirconia powders were utilized to fabricate two bilayer materials: 3Y-TZP+ 5Y-PSZ (3Y+5Y/BI) and 4Y-PSZ+ 5Y-PSZ (4Y+5Y/BI), alongside control groups 3Y-TZP (3Y/C), 4Y-PSZ (4Y/C), and 5Y-PSZ (5Y/C). Compacted specimens were sintered (1550 °C- 2 h, 3 °C/min), and half of them underwent hydrothermal aging (134 °C-20h, 2.2 bar). Characterizations were performed through scanning-electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, reflectance tests and biaxial flexural strength test (ISO:6872). Weibull statistics were applied to determine the characteristic strength and Weibull modulus. Grain size and optical properties were analyzed using two-way ANOVA followed by the Tukey test. Results: Degradation regions and monoclinic phase were observed at aged 3Y-TZP and 4Y-PSZ surfaces. Significant differences were observed in the evaluation of optical properties between the bilayer and control groups. The bilayer materials presented intermediate characteristic strength values compared to their controls and aging significantly increased the strength of some groups. Significance: Experimental bilayer materials presented lower mechanical properties than monolithic controls, 3Y/C and 4Y/C. Hydrothermal aging increased the characteristic strength of bilayered and monolithic controls, except for 5Y-PSZ. Both experimental bilayer systems, as well as monolithic controls, met the ISO 6872:2015 requirements for single-unit crowns (100 MPa), 3-unit fixed dental prostheses (FDPs) up to premolars (300 MPa), and 3-unit FDPs involving molars (500 MPa). However, for FDPs with four or more units, only monolithic 3Y-TZP and 4Y-PSZ, and bilayered 3Y+5Y met the required minimum flexural strength (≥800 MPa).

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Current approaches for developing bone substitutes prioritize materials with adequate mechanical properties, tailored structures, and resorbing ability under physiological conditions. In this way, new self-setting wollastonite-based apatite cements were prepared by mixing wollastonite powders with a liquid phase containing phosphoric acid and ammonium phosphate in different concentrations. The mixture formed a workable paste that can be molded in different shapes. The cement was analyzed through X-ray diffraction, Fourier Transform Infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The analysis showed that the main product of the hydration process is a mixture of crystalline wollastonite and hydroxyapatite. In addition, Raman spectroscopy confirmed the presence of an amorphous phase composed of silica and amorphous calcium phosphate for all samples. The setting times of the cement pastes were measured using a Gilmore needle indentation technique, and the compressive strength was determined using a Universal Testing Machine. The initial setting time was reduced from 142 ± 5 to 10 ± 1 min by increasing 30% of the concentration of phosphate ions in the solution. Furthermore, the higher content of phosphate ions enhanced the compressive strength by 310% compared with cements containing lower concentrations, reaching a resistance of 14 ± 2 MPa. The in vitro biocompatibility was confirmed by MTT assay, wherein no cytotoxicity of the cements was observed against murine embryonic fibroblast cells. Our results provided valuable information for designing wollastonite-based cements with optimal handling, mechanical, and biological properties using a liquid medium with adequate conditions to match the desired final product.

© 2024 Elsevier Ltd3D printing in scaffold production offers a promising approach, enabling precise architectural design that closely mimics the porosity and interconnectivity of natural bone. β-Tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP), with a chemical composition similar to the inorganic component of bone, is a widely used material for scaffold fabrication. Recent advances have made it possible to functionalize ceramic scaffolds to improve bone regeneration and repair while enabling the in situ release of therapeutic agents to treat bone infections. In this study, 3D-printed β-TCP scaffolds were coated with bioactive glasses, 45S5 (45SiO₂ – 24.5Na₂O – 24.5CaO – 6P₂O₅, wt.%) and 58S (58SiO₂ – 33CaO – 9P₂O₅, wt.%), using sol-gel solutions through a vacuum impregnation technique. The β-TCP ink exhibited pseudoplastic behavior, which facilitated its 3D printing. The resulting scaffolds demonstrated high fidelity to the designed model, featuring well-aligned filaments and minimal collapse of the lower layers after sintering. Elemental mapping revealed that 45S5 glass formed a surface coating around the scaffold struts, whereas 58S glass penetrated the internal structure, this occurred due to their differing viscosities at high temperatures. Compared to uncoated β-TCP scaffolds, the coatings significantly improved mechanical strength, with increases of 63% and 126% for scaffolds coated with 45S5 and 58S, respectively. Bioactivity was confirmed through an apatite mineralization assay in simulated body fluid, which demonstrated hydroxyapatite precipitation on both coated scaffolds, albeit with distinct morphologies. Since this study focused on acellular scaffolds, further research is necessary to fully explore the potential of these bioactive scaffolds with optimized mechanical properties in biological systems.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.In the published article, the identification of the samples in the bar chart in Fig. 12 is incorrectly given as CM5, CM6, and CM7: (Figure presented.) Viability of MEF cells cultured in contact with CM1, CM2, and CM3 for 24 h. Solid bars represent the viability of cells cultured directly on the specimens (Group 2), while striped bars show the viability of cells cultured around the specimens (Group 1) next to the samples. One-way ANOVA test significance levels **p < 0.01 and ***p < 0.0005 The correct identification on bar chart should be CM1, CM2, and CM3, respectively as showed below in Fig. 12: (Figure presented.) Viability of MEF cells cultured in contact with CM1, CM2, and CM3 for 24 h. Solid bars represent the viability of cells cultured directly on the specimens (Group 2), while striped bars show the viability of cells cultured around the specimens (Group 1) next to the samples. One-way ANOVA test significance levels **p < 0.01 and ***p < 0.0005 The original article has been corrected.

© 2024 Elsevier Ltd and Techna Group S.r.l.To evaluate the mechanical, antimicrobial, and optical properties of boron-doped soda-lime glass coatings on 3Y-TZP and 5Y-PSZ zirconia. Disc-shaped specimens of 3Y-TZP and 5Y-PSZ were divided into: as-sintered (3Y-C and 5Y-C), coated with commercial glaze (3Y-G and 5Y-G), with soda-lime glass (3Y-SL and 5Y-SL), and with silver-containing soda-lime glass (3Y-SLAg and 5Y-SLAg). Cytotoxicity (MTT assay), biaxial flexural strength (σB), X-ray diffraction (XRD), translucency (TP00), color difference (ΔE00), and roughness (Ra and Rz) were conducted. Biofilm formation was quantified by colony-forming units (CFU/mL) of C. albicans, S. sanguinis, and E. coli. Scanning electron microscopy (SEM) and fractography were conducted. Energy-dispersive X-ray diffraction (EDS) was performed on SL and SLAg samples. Weibull modulus (m) and characteristic strength (σ0) for biaxial flexural strength (95 % CI) were calculated. All data were analyzed by two-way ANOVA, and Dunn's method, while the CFU test was analyzed by one-way ANOVA (α = 0.05). The experimental glasses did not induce cytotoxic effects. The flexural strength of 3Y-TZP groups showed highest values: 3Y-C(847.45 MPa); 3Y-G(843.22 MPa); 3Y-SL(806.41 MPa); 3Y-SLAg(769.04 MPa); 5Y-G(589.77 MPa); 5Y-SLAg (576.20 MPa); 5Y-C(479.44 MPa); 5Y-SL(474.00 MPa). Diffractograms showed tetragonal and cubic phases for all groups. Higher translucency values were observed for 5Y-PSZ groups, while for ΔE00 were similar. The SL and SLAg groups exhibited the lowest roughness values (Ra) for both zirconia. The 5Y-SL group exhibited antimicrobial effects against all tested microorganisms, while the 5Y-SLAg group showed antimicrobial effects against E. coli. Fractures originated at the zirconia surface, while for the 5Y-G group at the glaze layer. SEM micrographs revealed flower-shaped crystals for 3Y-SL, 5Y-SL and 5Y-SLAg groups. EDS identified zirconia in the crystal's composition. The 5Y-SL group exhibited a significant antimicrobial effect. This cytocompatible glass (5Y-SL) provided a superior antibiofilm effect compared to 5Y-SLAg. Moreover, the mechanical and optical properties of both 5Y-PSZ and 3Y-TZP zirconia were maintained.

© 2024 Elsevier LtdThis study examined the impact of interfacial interactions on bilayer yttria-stabilized zirconia (YSZ) used in dental restorations. In-house bilayer structures of 3YSZ and 5YSZ composition underwent hydrothermal degradation to compare the properties of control and low-temperature degradation (LTD) treated groups. Biaxial flexural strength via piston-on-three-balls, staircase fatigue strength over 106 cycles at 15 Hz, phase characterization and quantification through XRD and Rietveld refinement, and fractography were conducted. Weibull analysis was employed to determine the Weibull modulus and characteristic strength. Results demonstrated an enhancement in the mechanical performance of 3YSZ composition after LTD treatment, whereas the mechanical properties of 5YSZ remained largely unaffected post-degradation. Fractographic analysis revealed that failure originated at the surface tensile location across all specimen groups. These findings offer insights into the mechanical behavior of bilayer zirconia structures and reinforce the significance of hydrothermal treatment in enhancing their performance, particularly in the case of 3Y compositions.

© 2024 John Wiley & Sons Ltd.The integration of bioglass with polymers in tissue engineering scaffolds holds promise for enhancing bone regeneration. This study explores the fabrication and characterization of composite scaffolds comprising polylactic acid (PLA)/polyethylene glycol (PEG) fibers incorporated with silicate-chlorinated bioglasses (45S5 and 58S). Electrospinning was utilized to produce the scaffolds, followed by physical–chemical and in vitro evaluations. Scanning electron microscopy (SEM) revealed uniform fiber formation, with bioglass incorporation observed in the composite groups. Bioglass incorporation led to a significant reduction in fiber diameter. Thermogravimetric analysis (TGA) estimated bioglass content, with 58S exhibiting the highest incorporation. Contact angle measurements indicated enhanced hydrophilicity in bioglass-containing groups. In vitro, bioactivity assessment in simulated body fluid (SBF) demonstrated apatite formation potential and the pH variance indicates a slightly alkaline to neutral condition. Cell culture studies revealed robust cellular adhesion and metabolic activity across all groups, with no cytotoxic effects observed. Overall, these findings suggest the potential of PLA/PEG bioglass composite scaffolds for bone tissue engineering applications.

© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.This study investigated the suitability of multiple bismuth sulfide (Bi2S3) samples for the photoreduction of Cr(VI) under simulated sunlight, aiming to elucidate the effect of different sulfide sources (thiourea, thioacetamide, sodium sulfide, potassium sulfide, and ammonium sulfide) on the final structural and photocatalytic properties of this semiconductor. The sulfides were produced through simple precipitation methods, without the necessity of complex methodologies or equipment. Additionally, the effect of thermal treatment on the properties of the Bi2S3 samples was also evaluated. The choice of the sulfide precursor imparted distinct characteristics onto the synthesized Bi2S3, such as distinct morphologies, specific surface areas (SSA), and crystalline structures. Notably, the efficiency of Cr(VI) photoreduction was found to be intricately linked to the adsorption capacity of Bi2S3. In this context, the calcination process emerged as a significant impediment, as it substantially diminished both the SSA and adsorption capacity of the materials. Among the sulfide sources investigated, Bi2S3 synthesized using K2S exhibited superior photoreduction efficiency, attributed primarily to its remarkable adsorption capacity and rod-like morphology. The photoreduction mechanism was determined to be carried out by the direct reaction between Cr(VI) and photogenerated electrons. Regarding operational parameters, initial concentration, pH and temperature had major effects on the photoreduction efficiency; high initial concentrations led to the saturation of the active sites and lower reaction rate constants, whereas lower pHs and higher temperatures favored the photoreduction process. As for the recycle tests of the best photocatalyst, it was discovered a significant efficiency loss between cycles, which was linked to the occlusion of active sites through the formation of chrome-based species on the surface of the photocatalyst. Graphical Abstract: (Figure presented.)

© 2024 Elsevier Ltd and Techna Group S.r.l.Two experimental ceramic systems, 3Y-TZP/5Y-PSZ (3Y/5Y) and 4Y-PSZ/5Y-PSZ (4Y/5Y), underwent analysis before (3Y/5Yi or 4Y/5Yi) and after hydrothermal aging (3Y/5Ya or 4Y/5Ya) to simulate low-temperature degradation (LTD). The samples were sintered and characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy, alongside nanoindentation tests to measure elastic modulus (Em) and hardness (H). Assessments were conducted on the external surfaces and at individual layers on cross-sectioned samples at predetermined regions of interest (ROIs). Degraded superficial regions were observed in the cross-sectional SEM images of the 3Y and 4Y zirconia layers after aging. XRD indicated a tetragonal→monoclinic phase transformation in the aged groups for both 3Y (66 % m-ZrO2) and 4Y (29 % m-ZrO2). Raman spectroscopy revealed monoclinic phase amounts of 86 % for 3Y and 62 % for 4Y in the degradation regions observed in the SEM micrographs. Monoclinic phase peaks were virtually no longer detected in either material beyond a depth of 15 μm. Hydrothermal aging significantly diminished the H and Em values for the 3Y and 4Y zirconia surfaces. For the analysis of different zirconia surfaces within the same subgroup, all pairwise comparisons showed statistically significant differences, except for the values of H of 3Y/5Yi and Em for 4Y/5Yi. Regarding the nanoindentation results of cross-sectioned samples, the aging protocol did not affect the H and Em values of the equivalent ROIs (layers), regardless of the bilayered system. However, significant differences in H values were observed among the ROIs (layers) within the same bilayered system. Despite surface changes, nanomechanical properties remained preserved below the surface and at the interfaces of bilayered materials after aging. Nanoscale H values varied among some layers and interfaces, whereas the Em values exhibited differences across certain surfaces.

© 2024 Elsevier Inc.Objectives: To assess the effects of different aging protocols on chemical, physical, and mechanical properties of an experimental ATZ composite compared to a zirconia. Methods: Disc-shaped specimens were obtained through uniaxial pressing of commercial powders (Tosoh), ATZ comprised of 80%ZrO2/20%Al2O3 (TZ-3YS20AB) and 3Y-TZP (3Y-SBE). The specimens of each material were divided into different groups according to the aging protocol: immediate, autoclave aging and hydrothermal reactor aging. The aging protocols were performed at 134 ºC for 20 h at 2.2 bar. Crystalline evaluations were performed using X-Ray Diffraction. The nanoindentation tests measured the elastic modulus (Em) and hardness (H). Biaxial flexural strength was performed, and Weibull statistics were used to determine the characteristic strength and Weibull modulus. The probability of survival was also determined. The Em and H data were analyzed by one-way ANOVA and Tukey test. Results: Diffractograms revealed the presence of monoclinic phase in both materials after aging. The hydrothermal reactor decreased the Em for ATZ compared to its immediate condition; and the H for both ATZ and 3Y-TZP regarding their immediate and autoclave aging conditions, respectively. The aging protocols significantly increased the characteristic strength for ATZ, while decreased for 3Y-TZP. No difference regarding Weibull modulus was observed, except for 3Y-TZP aged in reactor. For missions of up to 500 MPa, both materials presented a high probability of survival (>99 %) irrespective of aging condition. Significance: The synthesized ATZ composite exhibited greater physical and microstructural stability compared to 3Y-TZP, supporting potential application of the experimental material for long-span reconstructive applications.

© 2024 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.Modern dry pressing of ceramic powders using spray-dried granulates cannot avoid the occurrence of defects related to persisting inter- and intra-granulate interstitial voids. These constitute the parent defect size population limiting the application of polycrystalline ceramics in high-stress conditions. The mitigation of such defects could widen the range of application in technical and biomedical engineering, reduce the safety range for design, and extend the lifetime of components. Herein, the Weibull size-effect on strength in size-partitioned Yttria-stabilized zirconias (YSZ) feedstocks is used to explore the viability of changing the density distribution of granulate sizes as an effective strategy to obtain a denser particle packing that could reduce the size distribution of strength-limiting pressing defects. In a direct assessment of critical defect size using multiscale strength testing with a dataset of ≈1300 values, the success of such an approach in increasing the strength reliability for small volume components is demonstrated, along with its ultimate failure in altering the defect size distribution in sintered YSZ ceramics across several length scales. Finally, it is shown that granule morphology (spherical or dimpled) fails to affect the defect density and size distribution in YSZ ceramics.

© 2024 Wiley Periodicals LLC.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers embedded with borate glasses of 45B5 composition doped with Co2+, Cu2+, and Zn2+(46.1 B─O3-26.9-X CaO-24.4 Na─O-2.6 P─Os, X CoO/CuO/ZnO mol % (X = 0–5)) were produced by electrospinning for wound healing applications. Prior to their addition, the glasses exhibited two broad halos typical of a vitreous borate network, which were mainly composed of ring-type metaborate structural units. The particle distribution in the PHBV nanofibers embedded with 45B5 borate bioactive glasses is present in isolated and agglomerated states, being partially coated by a polymeric layer—except for the cobalt-doped glass, which resulted in a successful encapsulation with 100% embedding efficiency. The incorporation of the glasses reduced the PHBV crystallinity degree and its decomposition temperature, as well as its mechanical properties, including Young's modulus, tensile strength, and elongation at break. The neat PHBV fibers and those containing the cobalt-doped glasses demonstrated great cytocompatibility with human keratinocytes (HaCat), as suggested by the high cell viability after 7 days of exposure. Further studies are needed to fully understand the wound healing potential of these fibers, but our results significantly contribute to the area.

© 2024Conductive inks are essential components in electronics as they enable the printing of electronic circuits and components on diverse surfaces. Furthermore, they can be easily tailored to enhance chemical bonding with specific targets in sensing devices. This technology plays a crucial role in the development of both rigid and wearable sensors. Conductive inks for printed electronics and sensor devices should possess several key characteristics, including high conductivity, flexibility, affordability, and compatibility with various substrates. However, conventional conductive inks based on metal nanoparticles tend to be expensive and lack flexibility. This study aims to produce a conductive ink comprised of carbon-black-derived flash graphene (CBFG) and poly(o-methoxy aniline) (POMA), which can be applied to electronic devices. The structures and morphology of both precursors were assessed, and the electrical conductivity of ink coatings containing CBFG, POMA, and a combination of both was investigated. The effect of each component's concentration on the ink's electrical conductivity (EC) was investigated using a 23 factorial design of experiment. In conclusion, the most conductive film presented an EC of approximately 0.768 S m−1 when the concentrations of graphene, POMA, and binder were 40.0, 2.0, and 4.0 mg L−1, respectively. While further research is needed to explore the flexibility and adhesion properties of the ink on different substrates, our solvent and organic-based conductive ink offer environmental benefits and boost sensor performance.

© 2024 by the authors.This study focuses on the cytotoxic evaluation of functionalized multi-walled carbon nanotubes (MWCNT) and microbial biofilm formation on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites incorporating MWCNTs functionalized with gamma-aminobutyric acid (GABA) and carboxyl groups. The materials were characterized for cytotoxicity to fibroblasts and antimicrobial effects against Escherichia coli, Staphylococcus aureus and Candida albicans. The functionalization of MWCNTs was performed through oxidation (CNT-Ox) and GABA attachment (CNT-GB). The PHBV/CNT nanocomposites were produced via melt mixing. All MWCNT suspensions showed non-toxic behaviors after 24 h of incubation (viability higher than 70%); however, prolonged incubation and higher concentrations led to increased cytotoxicity. The antibacterial potential of PHBV/CNT nanocomposites against S. aureus showed a reduction in biofilm formation of 64% for PHBV/CNT-GB and 20% for PHBV/CNT-Ox, compared to neat PHBV. Against C. albicans, no reduction was observed. The results indicate promising applications for PHBV/CNT nanocomposites in managing bacterial infections, with GABA-functionalized CNTs showing enhanced performance.

© 2024 Elsevier LtdThe development of a novel TiO2/KNbO3/g-C3N4 photocatalyst for the degradation of sulfamerazine under artificial sunlight was investigated in this study, aiming to obtain a highly effective material through the formation of Z-scheme heterojunctions between the proposed semiconductors. The characterizations confirmed the formation of the intended heterojunctions in the ternary composite photocatalyst, as the presence of TiO2, KNbO3 and g-C3N4 was successfully verified. Furthermore, the coupling between the semiconductors in the form of the ternary photocatalyst led to structural, morphological, and optical modifications of the TiO2 base matrix, such as a higher specific surface area and larger visible light absorption. The optimized ternary material (TiO2-5% KNbO3-0.25% g-C3N4) exhibited the highest reaction degradation capacity for the sulfamerazine (SFMZ) in both solar (86.5% degradation) and visible light (60% degradation) tests, confirming a significant enhancement over the pure TiO2, which achieved 48% degradation under solar light and 10% degradation under visible light. This result was mainly attributed to the formation of Z-scheme heterojunctions between the semiconductors, which enhanced the charge-transport efficiency during photonic excitation. Lastly, the degradation pathway proposed using mass spectroscopy analysis indicated the formation of mainly less toxic intermediates, as estimated through quantitative structure-activity relationship (QSAR) predictions.

© 2024 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals LLC.The field of tissue engineering has witnessed significant advancements in recent years, driven by the pursuit of innovative solutions to address the challenges of bone regeneration. In this study, we developed an electrospun composite scaffold for bone tissue engineering. The composite scaffold is made of a blend of poly(L-lactide-co-ε-caprolactone) (PLCL) and polyethylene glycol (PEG), with the incorporation of calcined and lyophilized silicate-chlorinated bioactive glass (BG) particles. Our investigation involved a comprehensive characterization of the scaffold's physical, chemical, and mechanical properties, alongside an evaluation of its biological efficacy employing alveolar bone-derived mesenchymal stem cells. The incorporation of PEG and BG resulted in elevated swelling ratios, consequently enhancing hydrophilicity. Thermal gravimetric analysis confirmed the efficient incorporation of BG, with the scaffolds demonstrating thermal stability up to 250°C. Mechanical testing revealed enhanced tensile strength and Young's modulus in the presence of BG; however, the elongation at break decreased. Cell viability assays demonstrated improved cytocompatibility, especially in the PLCL/PEG+BG group. Alizarin red staining indicated enhanced osteoinductive potential, and fluorescence analysis confirmed increased cell adhesion in the PLCL/PEG+BG group. Our findings suggest that the PLCL/PEG/BG composite scaffold holds promise as an advanced biomaterial for bone tissue engineering.

© 2024This study aimed to compare two different compositions of sol-gel method-derived silicate chlorinated bioactive glasses - 45S5 and 58S - and explore the dehydration processes applied (lyophilization, lyophilization+calcination, and calcination). In the synthesis process, sodium metasilicate was used as a silica precursor, and it underwent ion exchange to form silicic acid. The samples underwent characterization through a variety of techniques, assessing their structural properties including Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, and regarding its bioactivity by the apatite mineralization assay in simulated body fluid. Raman spectroscopy revealed the lyophilization process led to the formation of Q1, Q2, and Q3 silicate structural units for both glasses, but following calcination these reacted to form solely Q2 units - as in the calcined-only glasses. X-ray diffraction analysis confirmed the amorphous nature of the 58S glass, while the 45S5 glass exhibited strong crystalline reflections, including a characteristic peak of sodium chloride. The apatite mineralization assay proved the high bioactivity of the produced glasses. The lyophilized only exhibited rapid hydroxyapatite conversion as a reflection of their structural units containing Q1 structures and of their porous microstructure. The calcined and lyophilized-calcined glasses formed calcium phosphate chloride (Ca2PO4Cl) as an intermediated phase in the glass conversion process. For the 45S5 glass in which both dehydration processes were applied, the intermediated phase led to pH equilibrium of the SBF solution. These findings contribute to the understanding of the structural and compositional properties of silicate chlorinated bioactive glasses synthesized via the sol-gel method. The evaluated glasses show potential for use in bone regeneration applications, with their bioactivity and structural characteristics playing key roles in promoting tissue healing and bonding with bone.

© 2024 Wiley Periodicals LLC.Zirconia implants are gaining attention as a viable alternative to titanium implants due to their comparable osseointegration development, improved soft tissue adaptation, and enhanced aesthetics. An encouraging avenue for improving zirconia implant properties involves the potential application of bioactive coatings to their surfaces. These coatings have shown potential for inducing hydroxyapatite formation, crucial for bone proliferation, and improving implant mechanical properties. This study aimed to evaluate the effect of coating zirconia implants with two bioactive glasses, 45S5 and BioK, on osteogenesis in vitro and osseointegration in vivo. Zirconia samples and implants were prepared using Zpex zirconia powder and blocks, respectively. The samples were divided into three groups: polished zirconia (ZRC), zirconia coated with 45S5 bioglass (Z + 45S5), and zirconia coated with BioK glass (Z + BK). Coatings were applied using a brush and sintered at 1200°C. Chemical analysis of the coatings was carried out using x-ray diffraction and Fourier Transform Infrared Spectroscopy. Surface topography and roughness were characterized using scanning electron microscopy and a roughness meter. In vitro experiments used mesenchymal cells from Wistar rat femurs, and the coated zirconia implants were found to promote cell viability, protein synthesis, alkaline phosphatase activity, and mineralization, indicating enhanced osteogenesis. In vivo experiments with 18 rats showed positive results for bone formation and osseointegration through histological and histomorphometric analysis and a push-out test. The findings indicate that bioactive glass coatings have the potential to improve cell differentiation, bone formation, and osseointegration in zirconia implants.

© 2023 Elsevier LtdThis study aimed to develop a recycling process for the remnants of milled 3Y-TZP and enhance their properties using glass infiltration. 3Y-TZP powder was gathered from the vacuum system of CAD–CAM milling equipment, calcined and sieved (x < 75 μm). One hundred twenty discs were fabricated and pre-sintered at 1000 °C/h. These specimens were then divided into four groups, categorized by glass infiltration (non-infiltrated [Zr] or glass-infiltrated [Zr-G]) and sintering temperature (1450 °C [Zr-1450] or 1550 °C [Zr-1550]/2h). After sintering, the specimens were characterized by X-Ray Diffraction (XRD), relative density measurement, and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). The biaxial flexural strength test was performed according to the ISO 6872 and followed by fractographic analysis. Subsequent results were analyzed using Weibull statistics. Relative density values of the sintered specimens from Zr-1450 and Zr-1550 groups were 86.7 ± 1.5% and 92.2 ± 1.7%, respectively. Particle size distribution revealed particles within the range of 0.1–100 μm. XRD analysis highlighted the presence of the ZrO2-tetragonal in both the Zr-1450 and Zr-1550 groups. Glass infiltration, however, led to the formation of the ZrO2-monoclinic of 9.84% (Zr-1450-G) and 18.34% (Zr-1550-G). SEM micrographs demonstrated similar microstructural characteristics for Zr-1450 and Zr-1550, whereas the glass-infiltrated groups exhibited comparable infiltration patterns. The highest characteristic strength was observed in the glass-infiltrated groups. Fractographic analyses suggested that fracture origins were related to defects on the tensile side, which propagated to the compression side of the samples. Both the sintering temperature and glass infiltration significantly influenced the mechanical properties of the 3Y-TZP recycled.

© (2024), (Sociedade Brasileira de Hematologia e Hemoterapia). All rights reserved.This study evaluated the effect of different occlusal surface finishes (glaze and silica glass infiltration) on surface characteristics and fatigue behavior of partially stabilized zirconia (PSZ) plates adhesively bonded onto epoxy resin discs. PSZ disc specimens (n = 15; Katana blocks STML, Kuraray Noritake Dental) were produced (Ø = 10 mm; thickness = 1.2 mm) and allocated into 3 groups: As sintered (S), silica glass infiltration (SGI), and glaze application (G). The PSZ intaglio surface was air-abraded with 50-μm alumina powder followed by bonding agent application. All produced PSZ were adhesively cemented onto dentin analogue discs made of epoxy resin material (Ø = 10 mm; thickness = 2 mm). Step stress fatigue test was performed (load ranging from 200 to 1800 N; step size 100 N and 10,000 cycles; 20 Hz). The topographic, microstructural, and fractographic analyses were performed by scanning electron microscopy. Results: No statistically significant difference in fatigue behavior was detected among the groups. All failures started at the bonding surface. Silica glass-infiltration and glaze layer application provided a smoothing effect, while the sintered group had a surface with grooves. The occlusal surface finishing method (silica glass infiltration or glazing) had no deleterious effect on fatigue behavior of adhesively bonded PSZ plates.

© 2024 Universidade Federal de Sao Carlos. All rights reserved.Borate bioactive glasses are more soluble than silicate’s and convert rapidly and completely into hydroxyapatite (Ca5(PO4)3(OH)), being more suitable for wound healing applications than their silicate counterparts. In this work, the 45B5 composition (46.1 B2O3 – 26.9 CaO – 24.4 NaO – 2.6 P2O5, mol%)) were embedded into electrospun PHBV (Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) nanofibers by encapsulation and/or electrospray deposition aiming to produce a wound dressing with optimized bioactivity and antibacterial properties for wound healing applications. The fibers were characterized regarding their physical, structural, and thermal properties, and in vitro by L929 Mouse Fibroblast Cell Line adhesion, migration, and cytotoxicity and by its antibacterial activity against the bacteria S. aureus. The set of characterizations evidences that the encapsulation method was the most promising for the 45B5 embedding into PHBV nanofibers, as it produced a wound dressing with great loading efficiency (70%) with a highly hydrophilic surface, leading to expressive adhesion, migration, and viability of L929 cells and antibacterial activity. Thus, the nanofibers produced by the encapsulation method alone provided a dressing with high potential in wound healing management.

© (2024), (Sociedade Brasileira de Hematologia e Hemoterapia). All rights reserved.Borosilicate glass was developed to enhance the mechanical behavior and smoothness of dental zirconia as an alternative to conventional glaze. This study assessed the mechanical and optical properties of 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) coated with borosilicate glass or a commercial glaze fired for an extended period of time. Disc-shaped 3Y-TZP zirconia specimens (Zpex, Tosoh) were sintered at 1550°C for 2 hours. The specimens were divided into three groups: as-sintered (control, C); commercial glaze (G); and borosilicate glass (SL). The glaze and borosilicate glass were applied over the zirconia and fired for 20 minutes at 950°C and 1200°C, respectively. Biaxial flexural strength, fractography, X-ray diffraction (XRD), roughness (Ra and Rz), fracture toughness (Vickers indentation method), color difference (∆E00), and translucency (TP00) analyses were conducted. The t-test or the one-way ANOVA and Tukey’s tests were used to analyze the data (α = 0.05). Flexural strength data were subjected to the Weibull analysis. The SL group exhibited the highest flexural strength (1025.8 MPa), whereas the C (859.41 MPa) and G (816.0 MPa) groups exhibited similar values. The SL group also had the highest characteristic strength. The fracture origin in all groups was on the zirconia surface. XRD analysis revealed that the specimens from the SL group contained tetragonal, cubic, and monoclinic phases. The SL group presented the lowest surface roughness. Fracture toughness in the SL group was lower than in the C group, but similar to that observed in the G group. The translucency and color differences observed in the G and SL groups were similar. Borosilicate glass enhanced the flexural strength of 3Y-TZP, promoted the smoothest surface, and exhibited optical properties similar to those of the glaze.

© 2023 Elsevier B.V.This paper explores the application of cross-linked cellulose beads as a sustainable and cost-effective support for the ZnO/SnO2/carbon xerogel hybrid photocatalyst. The application of the developed photocatalytic beads, named CB-Cat, was directed at a simultaneous adsorption/photocatalysis process, which was carried out under simulated sunlight. The characterization of the CB-Cat indicated a good dispersion of the photocatalyst of choice throughout the cellulose matrix, confirming its incorporation into the cellulose beads. Furthermore, it is possible to observe the presence of the photocatalyst on the surface of the CB-Cat, confirming its availability for the photonic activation process. The results showed that the simultaneous adsorption/photocatalysis process was optimal for enhancing the efficiency of methylene blue (MB) removal, especially when compared to the isolated adsorption process. Additionally, the regeneration of the CB-Cat between cycles was favorable toward the maintenance of the MB removal efficiency, as the process carried out without regeneration displayed significant efficiency drops between cycles. Finally, the mechanism evaluation evidenced that hydroxyl and superoxide radicals were the main responsible for the MB photocatalytic degradation during illumination with simulated sunlight.

© 2023 Wiley Periodicals LLC.Objective: To evaluate the effect of different hydrofluoric acid concentrations and etching times on the surface, chemical composition and microstructure of lithium disilicate. Material and Methods: Ninety specimens of pressed lithium disilicate (LDS) were obtained (IPS e.max Press, Rosetta SP and LiSi Press). The specimens of each material were divided in two groups according to the hydrofluoric acid concentration: 5% and 10% (n = 15/group), and subdivided according to the etching time: 20, 40 and 60 s (n = 5/group). Crystalline evaluations and chemical composition were performed through x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), respectively. Microstructural analyses were performed by scanning electron microscope (SEM), surface roughness (Ra), and material thickness removal evaluation. Thickness removal and Ra data were analyzed by ANOVA and Tukey test (p < 0.05). Results: XRD demonstrated characteristic peaks of lithium disilicate crystals, lithium phosphate and of a vitreous phase for all materials. EDS identified different compositions and SEM confirmed different surface responses to acid etching protocols. Material and etching time influenced Ra and material thickness removal (p < 0.05). Conclusion: Hydrofluoric acid concentration and etching time affect the surface characteristics of LDS differently. LiSi Press presented higher resistance to hydrofluoric acid etching compared to e.max Press and Rosetta SP. Clinical Significance: Applying the appropriate etching protocol is pivotal to avoid excessive material removal and to prevent jeopardize the mechanical and optical properties of the material.

© 2023 Wiley Periodicals LLC.The development of bioactive membranes with bone repair properties is great interest in the field of tissue engineering. In this study, we aimed to fabricate and characterize a composite membrane composed of sol–gel synthesized bioceramics and electrospun polycaprolactone (PCL) fibers for bone tissue regeneration applications. The bioceramics were prepared using the sol–gel method with nitrate (N) and chloride (CL) as precursors. PCL and bioceramic solutions were electrospun to obtain ultrafine fiber mats. Raman spectroscopy, x-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the materials. The results showed that both chlorinated and non-chlorinated bioceramics contained NBOs (non-bridge bonds) and crystallized the α-wollastonite phase, with the chlorinated version doing so at lower temperatures. In vitro tests were performed to evaluate cytotoxicity, cell adhesion, and mineralized matrix formation on the membranes. The composite membranes showed improved cell viability and promoted mineralization nodules formation. This study presents a promising approach for the development of bioactive membranes for bone tissue engineering, with potential applications in bone regeneration therapies.

© 2023In this work, our original glycol thermal method was applied to obtain borate bioactive glasses of the 45B5 composition (46.1 B2O3 – 26.9 CaO – 24.4 NaO – 2.6 P2O5, mol%) doped with therapeutic ions Co2+, Cu2+, and Zn2+ aiming toward wound healing applications. The structural analysis performed demonstrated the successful vitreous network obtention, while the apatite mineralization assay exhibited fast conversion into hydroxyapatite (HA, Ca5(PO4)3(OH)). Cell viability findings performed with human keratinocytes revealed an absence of cytotoxicity at concentrations below 0.5 mg/mL at day 1, manifested after 3- and 7-days, demonstrating a time- and dose-dependence in vitro outcome. The inhibition halo assay confirmed the antibacterial activity of all glasses against S. aureus. Considering the set of properties evaluated (i.e., bioactivity, cytocompatibility, and antibacterial activity), the synthesized glasses demonstrate potential for wound healing applications when incorporated into nanofibers, hydrogels, and dermal patches.

© 2023 Elsevier LtdSurface acoustic wave (SAW) sensors enhanced by a graphenic sensitive layer offer improved electrical response uniformity, and recent research has explored their potential for use in point-of-care platforms. These devices offer a unique combination of cost effectiveness, ease of handling, manufacturability, and remarkable sensor performance. This article summarizes the latest advancements in SAW sensors with graphenic-based nanomaterials, including their fabrication, operation mechanisms, and properties. Several recent studies are reviewed and compared to conventional SAW sensors. Furthermore, the challenges and prospects of using graphenic-based structures to enhance SAW devices and produce rapid actionable results are discussed.

© 2023, The Polymer Society, Taipei.Due to their extraordinary properties, functionalized carbon nanotubes (CNTs) have been added to epoxy matrices. In the marine industry, CNT/epoxy composite is applied in current turbines to obtain energy. For this, it is fundamental to understand the nanocomposites’ seawater absorption process. Therefore, this work aims to study how amino-functionalized CNTs and epoxy’s post-cure reaction influences the nanocomposites’ seawater absorption. The nanocomposites were prepared with ethylenediamine functionalized CNTs (0.25 wt%). Part of the samples was exposed to a post-cure treatment and artificial seawater for 504 days, accompanied by mass measurement. Then, the percentage of water absorbed throughout the period was obtained, and the post-cured samples absorbed the highest water amount, as well as showed the highest values of the glass transition temperature. The action of water as a plasticizer or pseudo-curing agent was observed by luminescence spectroscopy. Additionally, the three-point bending test showed that the highest modulus of elasticity was presented by the post-cured nanocomposites exposed to water, which also presented fracture with little plastic deformation, while the equivalent sample without the presence of CNT showed significant plastic deformation. Thus, since the marine industry requires materials with high bending forces, the amino-CNT/epoxy nanocomposites are suitable for this application.

© 2023 Elsevier Ltd and Techna Group S.r.l.The present work reports the development and application of potassium niobate (KNbO3) as a catalyst in a novel hybrid piezophotocatalytic ozonation process aimed at wastewater remediation. Pure KNbO3 samples were produced through a simple solid-state synthesis using water-soluble ammonium niobate (V) oxalate hydrate (C4H4NNbO9·xH2O) as niobium source, employing different potassium precursors (KNO3, K2CO3, KOH, and C8H5KO4). The synthesis was also carried out using powdered niobium oxide as a precursor, aiming to evaluate the differences between the niobates obtained. The results achieved in this study show that all the niobates produced using ammonium niobate (V) oxalate hydrate were composed solely of the orthorhombic structure of KNbO3, while the materials synthesized using niobium oxide exhibited the rhombohedral structure of KNbO3 along with niobium-rich potassium niobates (K3Nb8O21, K2Nb4O21, and KNb3O8) and residual niobium oxide. This behavior was attributed to the enhanced chemical homogeneity derived from the synthesis using ammonium niobate (V) oxalate hydrate, which facilitated the reaction between the components during the thermal treatment step. Furthermore, the optical and morphological properties of the niobates were considerably influenced by the application of different potassium salts. Owing largely to its morphological and electrical properties, the material synthesized using potassium hydrogen phthalate displayed the highest photocatalytic activity in terms of methylene blue discoloration among the niobates produced using C4H4NNbO9·xH2O. Finally, the proposed piezophotocatalytic ozonation process was found to be a highly efficient strategy for the discoloration of methylene blue, as it successfully harnessed the synergy between the multiple mechanisms involving active radical generation toward the development of a highly promising hybrid advanced oxidation process.

© 2023 Elsevier B.V.This work explored the development of C-Nb2O5 materials through the use of kraft lignin/cellulose carbon xerogel as a structure-directing agent in a simple precipitation synthesis pathway. This strategy was based on xerogel's low-cost and environmentally friendly nature, as well as the lignin's ability to promote structural changes through the chelation of metallic ions and stabilization of crystalline phases. The results showed that the addition of higher quantities of the kraft lignin/cellulose xerogel during the synthesis resulted in the formation of the hexagonal crystalline structure of niobium oxide, whereas the synthesis without the carbonaceous phase led to hexagonal K3NbO2F4 structure. The presence of the carbon xerogel also led to significant morphological changes, such as the formation of rod-like particles with smaller sizes and the augmentation of the specific surface area and pore volume. EDS and XPS show that the hexagonal Nb2O5 obtained was also doped with K and F atoms. The addition of the carbonaceous phase also led to the reduction of the bandgap energy of materials, whereas an increase in the calcination temperature caused a similar bandgap reduction. The material with the highest carbon content (Nb-0.25L) achieved the highest photoresponse under simulated solar light for the simultaneous photodegradation of methylene blue (MB) and photoreduction of Cr (VI), probably due to its lower bandgap energy, higher surface area, and enhanced methylene blue adsorption capacity. The effect of the calcination temperature implied that dye sensitization was an important factor for the Cr (VI) photoreduction, as faster MB degradation rates led to the suppression of Cr (VI) reduction. Finally, the study of the pH effect on the process showed that higher MB adsorption capacities are linked to higher MB removal rates, which coupled with mechanistic evaluation, proves that MB photodegradation is mainly linked to the direct oxidation reaction promoted by photogenerated vacancies.

© 2022 by the authors.The efficient remediation of the persistent organic pollutant known as 4-chlorophenol (4CP) in aqueous effluent presents a challenge for a wide array of industries due to its elevated toxicity and resistance to natural degradation processes. This study proposes the development of a hybrid photocatalyst composed of titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4), aiming to increase the efficiency of photocatalytic degradation of 4CP under solar and visible radiation through the formation of Z-scheme heterojunction between the semiconductors. The results showed that the synthesis of the TiO2/g-C3N4 binary material was successful by X-ray diffractometry and infrared spectrometry. Furthermore, the addition of g-C3N4 to TiO2 led to optical and morphological modifications, such as the pore volume increase and gap energy of TiO2/g-C3N4. Concerning the photocatalytic evaluation, the main results indicate that photocatalytic activity under visible radiation of the TiO2/g-C3N4 improved by 44.8% compared to pure TiO2, whereas an improvement of 30.5% was obtained under simulated solar radiation. This improvement in efficiency was further corroborated by chronoamperometry tests, which demonstrated a higher photocurrent generation for the TiO2/g-C3N4. The radical generation mechanism suggested the creation of an effective Z-scheme heterojunction between the semiconductors, as the formation of both hydroxyl and superoxide radicals was observed.

© 2023 The Author(s)This work proposed the study of a new lignin/cellulose carbon xerogel/ZnO/Bi2O3/Bi° composite photocatalyst for the degradation of bisphenol-A under sunlight. The reasoning behind the application of each component is based on the formation of multiple heterojunctions (p-n heterojunction between semiconductors, metal-semiconductor heterojunction, and carbon-semiconductor heterojunction) to hinder the recombination of photogenerated charges during the photocatalytic process. The lignin/cellulose carbon xerogel was employed as both a solid electron mediator and a reducing agent, promoting the reduction of the bismuth oxide into metallic bismuth. The results obtained from the characterization tests confirm the formation of all the intended phases in the hybrid photocatalyst. Furthermore, the inclusion of the carbon xerogel led to morphological modifications such as the formation of plate-like particles and the increase of specific surface area. The efficient formation of the heterojunctions between the composing phases of the hybrid composite led to an enhanced photocatalytic activity for the degradation of the bisphenol-A (BPA) molecule, under both simulated sunlight and visible light. The optimized composite achieved 84% degradation of the BPA under simulated sunlight and 27% under visible light irradiation, which is a great improvement in comparison to the pure ZnO, which obtained 55% degradation under simulated sunlight and 19% degradation under visible light. The enhanced photocatalytic activity of the lignin/cellulose carbon xerogel/ZnO/Bi2O3/Bi° composite was further verified by chronoamperometry tests, which evidenced its greater photocurrent generation capabilities.

© 2023 by the authors.The objective of this study was to investigate the osteogenic and antimicrobial effect of bioactive glass S53P4 incorporated into β-tricalcium phosphate (β-TCP) scaffolds in vitro and the bone neoformation in vivo. β-TCP and β-TCP/S53P4 scaffolds were prepared by the gel casting method. Samples were morphologically and physically characterized through X-ray diffraction (XRD) and scanning electron microscope (SEM). In vitro tests were performed using MG63 cells. American Type Culture Collection reference strains were used to determine the scaffold’s antimicrobial potential. Defects were created in the tibia of New Zealand rabbits and filled with experimental scaffolds. The incorporation of S53P4 bioglass promotes significant changes in the crystalline phases formed and in the morphology of the surface of the scaffolds. The β-TCP/S53P4 scaffolds did not demonstrate an in vitro cytotoxic effect, presented similar alkaline phosphatase activity, and induced a significantly higher protein amount when compared to β-TCP. The expression of Itg β1 in the β-TCP scaffold was higher than in the β-TCP/S53P4, and there was higher expression of Col-1 in the β-TCP/S53P4 group. Higher bone formation and antimicrobial activity were observed in the β-TCP/S53P4 group. The results confirm the osteogenic capacity of β-TCP ceramics and suggest that, after bioactive glass S53P4 incorporation, it can prevent microbial infections, demonstrating to be an excellent biomaterial for application in bone tissue engineering.

© 2022 Elsevier Ltd and Techna Group S.r.l.This work was performed aiming to develop a new and straightforward route for bioactive glasses obtention with minimal equipment and explore the structural, physical, and bioactivity properties of the resulting glass and its glass ceramics. Herein, the synthesis of the borate bioactive glass in the 45B5 composition (46.1 B2O3 – 26.9 CaO – 24.4 NaO – 2.6 P2O5, mol%) by the glycol thermal method was proposed; an original chemical route for bioactive glass obtention based on transesterification reaction between the precursors with a glycol. The suggested mechanism for the borate network formation was proven accurate, revealing a vitreous structure formed by ring-type metaborate structural units with a lamellar morphology upon calcination. Glass-ceramics obtained at 500 (45B5-500) and 700 °C (45B5-700) indicate the oxides were effectively incorporated into the network by crystallization of Ca–Na–B, Ca–B, and Na–B phases. The in vitro apatite mineralization assay performed on the glass and glass-ceramics revealed their great solubility and conversion rate into hydroxyapatite (HA, Ca5(PO4)3(OH)), which is taken as an indication of bioactivity. Besides HA, however, calcium carbonate species were identified at the early stages of mineralization for 45B5 and 45B5-500, suggesting the 45B5-700 glass-ceramic has a higher ability to form apatite as the majority of Ca2+ are directed to precipitate into hydroxyapatite. Overall, the 45B5 glass and glass-ceramics demonstrated their great bioactivity, having high application potential in soft tissue engineering on wound healing materials and devices, as incorporation in hydrogels and nanofibers. Furthermore, the glycol thermal method generated new perspectives for the synthesis of a broad range of bioactive glasses compositions and their application in tissue engineering.

© 2022 Elsevier B.V.This work proposed new black-wattle tannin/kraft lignin H3PO4-activated carbon xerogels as sustainable and efficient adsorbents. The precursors were chosen based on their eco-friendly and cost-effective nature, aiming to achieve adsorbents with high adsorption capacities. Carbon xerogels were synthesized through polycondensation with formaldehyde and alkaline catalyst in a simple one-pot procedure. Activation was performed using H3PO4 in a tubular furnace (500 °C), under a nitrogen atmosphere. Results show that the inclusion of the kraft lignin led to changes in the morphology of the materials, facilitating the development of their porous structure and increasing specific surface area and pore volume. The best adsorbent (XLT 50 %) was synthesized using a 1:1 tannin/kraft lignin mass ratio. This material presented an adsorption capacity of nearly 1150 mg g−1 of methylene blue (pH = 5 and T = 298 K), which was linked to its high specific surface area of 1348 m2 g−1. The adsorption process followed the pseudo-second-order kinetic model, whereas the adsorption isotherms were best fitted by the Sips model. The XLT 50 % presented good reusability properties, maintaining its adsorption capacity for 3 cycles. Finally, the XLT 50 % presented good adsorptive properties toward other pollutants (methyl orange, 4-chlorophenol, and hexavalent chromium), indicating its versatility for adsorption processes.

© 2023 Universidade Federal de Sao Carlos. All rights reserved.Bacterial infections after implant surgical procedures are a complication observed in many surgeries to treat bone injuries or diseases. Bacteria can attach to the surface of the implant producing biofilms, and if treatment with antibiotics does not work, further surgery is necessary to remove the infected implant. Among the biomaterials for bone implants, bioceramics based on calcium phosphates (CaPs) such as β-TCP stand out, due to their chemical similarity with bone and high bioresorbability. β-TCP has the characteristic of easily accommodating in its crystalline structure reasonable amounts of doping elements, such as monovalent and trivalent ions, which makes it an efficient transporter of drugs, molecules, and therapeutic ions The objective of this work was the incorporation of bioactive glass (BG 45S5) via sol-gel and silver nanoparticles (Ag-NPs) in β-TCP scaffolds, aiming to confer antimicrobial activity to the scaffolds, without prejudice to biocompatibility. XRD and FT-IR analysis indicated structural changes after the incorporation of BG 45S5 and Ag-NPs in β-TCP scaffolds, and these compounds induced the partial transformation of the β-TCP phase into α-TCP phase and the formation of sodium-calcium silicates and silver silicates. The FT-IR spectra showed characteristic bands of α-TCP after incorporation, in addition to the predominant bands of β-TCP. Biocompatibility after incorporation of BG 45S5 was improved, with a significant increase in cell viability. After the incorporation of Ag-NPs, cell viability was maintained at an acceptable level, no cytotoxic behavior was observed, and the scaffolds showed antibacterial and antifungal activity. The results indicate that BG 45S5 and the Ag-NPs incorporated showed a synergistic behavior, conferring antimicrobial activity to the scaffolds without compromising biocompatibility, showing great potential for applicability in tissue engineering.

© 2023, Faculdade de Odontologia de Bauru da Universidade de Sao Paulo. All rights reserved.The demands for dental materials continue to grow, driven by the desire to reach a better performance than currently achieved by the available materials. In the dental restorative ceramic field, the structures evolved from the metal-ceramic systems to highly translucent multilayered zirconia, aiming not only for tailored mechanical properties but also for the aesthetics to mimic natural teeth. Ceramics are widely used in prosthetic dentistry due to their attractive clinical properties, including high strength, biocompatibility, chemical stability, and a good combination of optical properties. Metal-ceramics type has always been the golden standard of dental reconstruction. However, this system lacks aesthetic aspects. For this reason, efforts are made to develop materials that met both the mechanical features necessary for the safe performance of the restoration as well as the aesthetic aspects, aiming for a beautiful smile. In this field, glass and high-strength core ceramics have been highly investigated for applications in dental restoration due to their excellent combination of mechanical properties and translucency. However, since these are recent materials when compared with the metal-ceramic system, many studies are still required to guarantee the quality and longevity of these systems. Therefore, a background on available dental materials properties is a starting point to provoke a discussion on the development of potential alternatives to rehabilitate lost hard and soft tissue structures with ceramic-based tooth and implant-supported reconstructions. This review aims to bring the most recent materials research of the two major categories of ceramic restorations: ceramic-metal system and all-ceramic restorations. The practical aspects are herein presented regarding the evolution and development of materials, technologies applications, strength, color, and aesthetics. A trend was observed to use high-strength core ceramics type due to their ability to be manufactured by CAD/CAM technology. In addition, the impacts of COVID-19 on the market of dental restorative ceramics are presented.

© 2022 Wiley Periodicals LLC.The objective was to synthesize and characterize fine polycaprolactone (PCL) fibers associated with a new 58S bioglass obtained by the precipitated sol–gel route, produced by the electrospinning process in order to incorporate therapeutic ions (Mg and Li). In PCL/acetone solutions were added 7% pure bioglass, bioglass doped with Mg(NO3)2 and Li2CO3 and were subjected to electrospinning process. The fibers obtained were characterized morphologically, chemically and biologically. The results showed the presence of fine fibers at the nanometric scale and with diameters ranging from 0.67 to 1.92 μm among groups. Groups containing bioglass showed particles both inside and on the surface of the fibers. The components of the polymer, bioglass and therapeutic ions were present in the fibers produced. The produced fibers showed cell viability and induced the formation of mineralization nodules. It was observed the applicability of that methodology in making an improved biomaterial, which adds the osteoinductive properties of the bioglass to PCL and to those of therapeutic ions, applicable to guided bone regeneration.

© 2022 by the authors.Soft reliner and glaze are materials used over full or partial dental prosthesis to prevent excessive pressure on the supporting tissues. They are also indicated as supportive treatment for dental stomatitis, especially when modified by the addition of medications. The objective of the work was to evaluate the antimicrobial effect of silver-coated silica nanoparticles in a glaze and a soft reliner. The nanoparticles were synthesized, characterized, and tested by minimum inhibitory concentration (MIC) for C. albicans SC5314. Then, the nanoparticles were incorporated to a glaze and a soft reliner, which were called nanocomposites. Then, the nanocomposites were divided into six groups (n = 12): CG: glaze/reliner; CR: reliner; G1: glaze + 1% nanoparticles/reliner; G2: glaze + 2.5% nanoparticles/reliner; R1: reliner + 1%; R2: reliner + 2.5%. The nanocomposites were characterized by a goniometer and by a scanning electron microscope. The antibiofilm test was performed against C. albicans SC5314. According to the MIC results, the non-functionalized nanoparticles reduced fungal growth at 1000 μg/mL and the functionalized nanoparticles at 2000 μg/mL. The functionalized nanoparticle had a superior dispersion being selected for the antibiofilm test. There was a reduction of 64% in CFU/specimen count for the glaze, not statistically significant (p = 0.244). For the soft reliner, there was an increase in CFU/specimen with the presence of nanoparticles, still not statistically significant (p = 0.264). In conclusion, it is necessary to conduct new studies to increase the release of silver, thus improving nanoparticles’ antifungal potential.

© 2022, The Polymer Society, Taipei.The integration of biomaterials in tissue regeneration has been showing effectiveness in the treatment of diseases related to bone structure and tissue repair. Membranes have aroused interest due to their ease of manufacture, variation in composition, and the structure of the biomaterial. The incorporation of bioactive glass (BG) increases bioactivity, and when doped with therapeutic ions, changes in the physical-chemical composition of the biomaterial are expected to enhance its biological effect. This study aimed to produce polycaprolactone (PCL) membranes incorporated with 58S bioactive glass, doped with Zinc (Zn) by the electrospinning technique, and evaluate the influence of this biomaterial in the activity and differentiation of mesenchymal stem cells. The BG was produced by using the sol-gel process; next, before the PCL preparation, the BG was doped with zinc in a solution. Then, PCL solutions were prepared with 7% by weight of BG and doped with 10% ZnCl2. Afterward, the electrospinning process was carried out using the fixed parameters: 2mLh-1 flow rate, 10kV voltage, and 12cm distance. Before the biological assays, the chemical elements present in the fibers were evaluated by energy dispersion X-ray spectroscopy (EDS), and the mapping technique. The morphology of the biomaterial and the diameter of fibers were analyzed by scanning electron microscopy (SEM), and the hydrophilicity of the membranes was evaluated by the contact angle technique. The in vitro tests consisted of cell plating with mesenchymal stem cells (MSC’s), previously obtained from rat femurs, at a density of 1x104 per well that contained three different groups: a) P: mesenchymal stem cells plated with PCL; b) PB: mesenchymal stem cells plated with the composite of PCL / BG; c) PBZ: mesenchymal stem cells plated with the Zn doped PCL / BG composite. To evaluate the influence of the biomaterial on osteoblastic activity and differentiation, osteogenic and non-osteogenic media were used in tests of cell viability (MTT assay), total protein content, alkaline phosphatase activity (ALP), and mineralization nodules. The analysis by SEM proved that the electrospinning technique was efficient for producing fibers incorporated with bioactive glass, and EDS and the mapping technique confirmed the chemical components of each group of fibers, including the doped zinc in the bioactive glass. The analysis of fibers diameter showed that P and PBZ had presented fibers with a larger diameter than the PB group, and the contact angle technique showed an increase in the hydrophilicity of the group containing doped Zinc when compared to the other groups analyzed. The MTT assay confirmed that the membranes weren´t cytotoxic and allowed cell viability, total protein content showed that all the groups had cell activity, with a statistically significant difference between the groups (p<0,05). Even with no statistically significant difference, osteogenesis was proved by ALP activity and the formation of mineralization nodules. Based on the results, the PCL membranes incorporated with 58S bioactive glass doped with zinc have shown promise in tissue engineering for use in bone tissue regeneration.

© 2022, Universidade Estadual Paulista, Institute of Science and Technology of Sao Jose dos Campos. All rights reserved.Objective: Thermally activated acrylic resins (RAATs) are widely used in dentures as a base material due to their good dimensional stability and biocompatibility. However, their low thermal conductivity is a disadvantage, as it affects acceptance when using dental prostheses. Thus, the objective of this work was to measure the conduction heat in RAATs with and without incorporation of silica and silver nanoparticles (NP) and rigid reline (RR). Material and Methods: For this, samples were made and divided into 10 groups (n = 6). The first five groups were 2-mm-thick samples: G1 (RAAT control), G2 (RAAT + RR control), G3 (RAAT and NP + RR), G4 (RAAT + RR and NP), and G5 (RAAT and RR modified by NP). In the other five groups, 8-mm-thick samples were made: G6 (RAAT control), G7 (RAAT + RR control), G8 (RAAT and NP + RR), G9 (RAAT + RR and NP), and G10 (RAAT and RR modified by NP). The heat that cross the surface of the specimens was quantified using a wireless device. The data were submitted to two-factor ANOVA statistical analysis and Tukey´s test with a 5% significance level. Results: After measuring the temperature variation as a function of time, it can be observed that there was a statistically significant difference for thermal conduction between the control groups and those modified with NP. Conclusion: Thus, it was possible to conclude that the NP improved the heat conduction in RAAT and in the RR because the nanoparticles have a higher thermal conductivity.

© 2022 Elsevier B.V.Recently, the release of antibiotics, such as sulfonamides, into the environment has raised significant concern due to the potential creation of antibiotic-resistant bacteria. Thus, the development of remediation technologies for effluents containing such compounds is of utmost urgency. In this context, this work evaluated the creation of a resorcinol-based carbon xerogel/zinc oxide photocatalyst (XC/ZnO) to efficiently promote the photodegradation of the antibiotic known as sulfamerazine in aqueous media. The employment of this carbonaceous structure as a co-catalyst is justified by its high surface area and electrical conductivity. The methodology used in the synthesis of the composites was a simple one-pot reaction, combining the simultaneous precipitation of zinc oxide and polycondensation of the resorcinol-based carbon gel. Regarding the composites' characterization, X-ray diffractometry confirms that the composites have the Wurtzite structure of the zinc oxide, whereas the carbon xerogel formation is evidenced by the infrared, diffuse reflectance, and X-ray photoelectron spectroscopies. Morphology-wise, the XC/ZnO is arranged as nodular particle agglomerates, with particles between 500 nm and 50 nm. The photocatalytic tests under simulated solar radiation show that the composites developed are superior to the pure oxide in the photodegradation of sulfamerazine, as all XC/ZnO materials developed achieved higher apparent reaction rate constants (kapp) than pure zinc oxide, with the XC/ZnO 0.5 material obtaining a kapp 75% higher than the one observed for the ZnO sample. Furthermore, the chronoamperometry tests confirmed that the optimized composite (XC/ZnO 0.5) has a greater capacity for photocurrent generation when compared to pure zinc oxide. Therefore, the modification proposed was successful to enhance the photodegradation of sulfamerazine in aqueous media, highlighting the viability of the composites developed for photocatalytic applications.

© 2021, Korean Society for Precision Engineering.Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

© BME-PT.Porous polymeric scaffolds provide a physical substrate for cells to attach and proliferate, allowing the formation of new tissue. These materials are broadly used in the tissue engineering field due to their ability to mimic native tissue. Each application requires specific morphologies and resistance, among other several features. To accomplish these requirements, various techniques are available, each one with its advantages and disadvantages. Among the most relevant techniques are salt leaching, solvent casting, gas foaming, thermally induced phase separation, freeze-drying, electrospinning, thermally induced self-agglomeration, and three-dimensional (3D) printing. In this review, a brief and simple explanation of each method is described, along with some recent results and each technique’s advantages and disadvantages. It is expected that this review will bring important guidance in the production of polymer scaffolds for tissue engineering.

© 2021 Elsevier LtdThe increasing demand for high performance gears requires in-depth investigations of alternative materials to those commonly used. In this respect, microalloyed steels may appear as an alternative with technical and economic potential. Microalloyed steels may exhibit a more refined grain structure than conventional steels, which is commonly induced by the precipitation of highly stable and dispersed second-phase particles. This investigation aimed at understanding how the steel grain structure obtained by the addition of niobium (Nb) and titanium (Ti) as microalloying elements correlates to the material surface integrity promoted by a conventional gear manufacturing chain. The results indicated that the addition of microalloying elements leads to a refined and homogeneous grain structure. The residual stress state also proved to be both more compressive and homogeneous and the roughness exhibited greater stability. Such characteristics place the microalloyed steels in a prominent position regarding their application in the gear manufacturing, indicating the possibility of fatigue lifetime improvement.

© 2021 Elsevier B.V.In this work, β-TCP (β-tricalcium phosphate) bioresorbable scaffolds were prepared by the gel casting method. Then, they were impregnated with a 45S5 bioglass sol gel solution to improve biocompatibility and promote bioactivity and antimicrobial activity. The β-TCP scaffolds had an apparent porosity of 72%, and after the incorporation of the bioglass, this porosity was maintained. The elements of the bioglass were incorporated into β-TCP matrix and there was a partial transformation from the β-TCP phase to the α-TCP (α-tricalcium phosphate) phase, besides the formation of bioactive calcium and sodium‑calcium silicates. The scaffolds β-TCP with 45S5 bioglass incorporated (β-TCP/45S5) did not show a reduction in their values of mechanical strength and Weibull modulus, despite the partial transformation to the α-TCP phase. Bioactivity, cell viability, and antimicrobial activity improved significantly for the β-TCP/45S5 scaffold comparing to the scaffold without the bioglass. The mineralization of carbonated hydroxyapatite was verified in Simulated Body Fluid (SBF). The cell viability, evaluated by the reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide – MTT in MG63 cells, increased by 178%, and β-TCP/45S5 scaffold also enhanced cell activity and osteoblast differentiation observed by means of total protein contend and alkaline phosphatase activity, respectively. The formation of growth inhibition zones was also observed in the disk diffusion assay for three tested microorganisms: Staphylococcus aureus, Escherichia coli and Candida albicans. To conclude, the vacuum impregnation method in 45S5 bioglass sol gel solution was effective in penetrating all the interconnected macroporosity of the scaffolds and covering the surface of the struts, which improved their biological properties in vitro, bioactivity and antibacterial activity, without reducing mechanical strength and porosity values. Thus, the β-TCP/45S5 scaffolds are shown as potential candidates for use in tissue engineering, mainly in bone tissue regeneration and recovery.

© 2020 Elsevier B.V.The authors regret Thus, our results from FTIR and Raman spectroscopies are in accordance with the possible structural model for the NbO6 groups in the silicate network for silicate glasses containing Nb2O proposed by Samuneva et al. [7] (Fig. 5). Fig. 5. Possible structural model for the NbO6 groups into the silicate network. R+ and R+2: alkaline ions used as compensator of the excess negative charge at Nb5+ cations [7]. The authors would like to apologise for any inconvenience caused.

© 2020 Wiley Periodicals LLC.To characterize the physicomechanical properties of an alumina-toughened zirconia (ATZ). ATZ synthesis consisted of the addition of alumina particles in an yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) matrix. Specimens were obtained by uniaxial and isostatic pressing ATZ and 3Y-TZP powders and sintering at 1600°C/1 h and 1550°C/1 h, respectively. Crystalline content and residual stress were evaluated using X-ray diffraction (XRD). Microstructure was characterized by scanning electron microscopy (SEM). Optical properties were determined by reflectance test. Mechanical properties were assessed by biaxial flexural strength test. All analyses were performed before and after aging (134°C, 20 h, 2 bar). XRD and SEM revealed a typical ATZ and 3Y-TZP crystalline content, chiefly tetragonal phase, with a dense polycrystalline matrix, though a smaller grain size for ATZ. Aging triggered a similar monoclinic transformation for both systems; however, ATZ exhibited higher residual compressive stresses than 3Y-TZP. While as-processed 3Y-TZP demonstrated significantly higher characteristic strength relative to ATZ, no significant difference was observed after aging (~215 MPa increase in the ATZ strength). ATZ presented significantly higher opacity relative to 3Y-TZP, although aging significantly increased the translucency of both systems (increase difference significantly higher in the 3Y-TZP compared to ATZ). ATZ physicomechanical properties support its applicability in the dental field, with a lower detrimental effect of aging relative to 3Y-TZP.

© 2020 Wiley Periodicals LLC.The adhesion of microorganisms on biomaterials can impair its effective application. The addition of antimicrobial agents is a promising alternative to overcome this limitation. In this work, films of polycaprolactone (PCL) and nanostructured β-AgVO3 (SV) were produced by solvent casting with 0.1, 0.5, and 1.0 wt% of SV. The effect of SV on the structure of PCL was investigate using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The antimicrobial activity of the films against Staphylococcus aureus and Escherichia coli was evaluated by the agar diffusion method and by direct contact test. FTIR confirmed the presence of SV into the PCL films, with chemical interaction between them. SEM showed that SV nanorods were well dispersed and with good interfacial adhesion with PCL. XRD diffraction and Raman spectroscopy showed that the presence of SV increased the number of nucleation sites, reducing the size of crystallites and increasing the amorphous domains in the PCL matrix, consequently reducing crystallinity. This behavior was confirmed by DSC, which showed a reduction in the crystallinity with increasing SV content. Films with 1 wt% of SV showed antimicrobial activity against Staphylococcus aureus in direct contact test.

© 2020This work studied the crystallization process of two bioglass series derived from 45S5® containing niobium (BGNb5 and BGNb10). In vitro biological analyzes of cell viability corroborate with the qualitative interpretation of the NC values, of a open and fragmented structure, which is interesting from a biological point of view and with the FTIR and Raman results which demonstrated that the breakdown of Si-O-Si bonds and the formation of Si-O-NBO bonds play an important role in the interface of the biological responses of the bioactive materials. X-ray diffraction (XRD) and Differential scanning calorimetry analysis (DSC) also generated insight into the structure of the glasses. To the best of our knowledge, this seems to be the first time that structural changes in bioactive glasses derived from 45S5 resulting from the addition of niobium are studied during its crystallization process.

© The Royal Society of Chemistry 2021.Cases of respiratory diseases have been increasing around the world, affecting the health and quality of life of millions of people every year. Chronic respiratory diseases (CRDs) and acute respiratory infections (ARIs) are responsible for many hospital admissions and deaths, requiring sophisticated treatments that facilitate the delivery of therapeutics to specific target sites with controlled release. In this context, different nanoparticles (NPs) have been explored to match this demand, such as lipid, liposome, protein, carbon-based, polymeric, metallic, oxide, and magnetic NPs. The use of NPs as drug delivery systems can improve the efficacy of commercial drugs due to their advantages related to sustained drug release, targeting effects, and patient compliance. The current review presents an updated summary of recent advances regarding the use of NPs as drug delivery systems to treat diseases related to the respiratory tract, such as CRDs and ARIs. The latest applications presented in the literature were considered, and the opportunities and challenges of NPs in the drug delivery field are discussed.

© 2020 Elsevier Ltd and Techna Group S.r.l.Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery.

© 2020The need for improved mechanical properties in regions of higher masticatory loads led to the introduction of zirconia in dentistry. However, zirconia needs a characterization and glaze to have a more natural, tooth-like appearance. An experimental glass was produced based on the sol-gel method to exhibit a thermal expansion coefficient similar to that presented by zirconia. The experimental glass was used as glazing material on the previously sintered zirconia (vita YZ) surface. There was a significant reduction in the roughness and hardness of the material, caused by the formation of smooth, void-free and highly uniform glass coating. The glass infiltrated among superficial zirconia grains and caused the formation of monoclinic zirconia at the zirconia/glass interface. A consequent decrease in surface roughness and an increase in flexural strength and reliability was then observed in the experimental glass group. On the other hand, a significant decrease in the reliability of conventionally glazed group was observed. Therefore, the use of experimental glass instead of conventional glaze can improve the mechanical properties, smoothness, and mechanical reliability of fully sintered zirconia.

© 2020 Elsevier Ltd and Techna Group S.r.l.This work aimed to study the development and properties of Bi-doped ZnO/β-Bi2O3/Carbon xerogel composites towards visible light photocatalysis applications. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, nitrogen adsorption isotherms, Raman spectroscopy, diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of the developed composites was evaluated through the photodegradation of the 4-chlorophenol molecule and by chronoamperometry tests. The results obtained show that the calcination temperature poses a major influence in the final structure of the materials developed. The calcination temperature of 600 °C resulted in the formation of the β-Bi2O3 and Bi0 phases, consequently enhancing the photocatalytic activity of the composites due to the increased charge mobility provided by the heterojunctions between zinc oxide, carbon xerogel, bismuth oxide and metallic bismuth. The composite with intermediate bismuth composition (XC/ZnO–Bi2O3 5%) displayed the best photocatalytic response among the materials tested, which was confirmed by its increased photocurrent generation capability. The photocatalytic mechanism is highly dependent in the generation of hydroxyl radicals and the composite presents good reusability properties.

© 2020 Informa UK Limited, trading as Taylor & Francis Group.Nanoparticles (NPs) have been studied for a wide variety of applications, due to the elevated surface area and outstanding properties. Several types of NPs are available nowadays, each one with particular characteristics and challenges. Bionanocomposites, especially composed by polymer matrices, are gaining attention in the biomedical field. Although, several studies have shown the potential of adding NPs into these materials, some investigation is still needed until their clinical use for in vivo application is consummated. Besides that, is essential to evaluate whether the addition of nanoparticles changes the matrix property. In this review, we summarize the latest advances concerning polymeric bionanocomposites incorporated with organic (polymeric, cellulosic, carbon-based), and inorganic (metallic, magnetics, and metal oxide) NPs.

© 2020 Elsevier LtdIt aimed to evaluate if silica infiltration might influence the hydrothermal degradation of zirconia by determining: the phases formed, hardness, microstructure, and flexural strength of a 3Y-TZP. Yttria partially stabilized zirconia discs (1.2 mm thickness x 13 mm diameter) (InCeram YZ, Vita Zanhfabrik) were produced and assigned into 6 groups, considering 2 factors: silica infiltration in 2 levels (as-sintered or infiltration) and hydrothermal aging (LTD-Low Temperature Degradation) in 3 levels (baseline, aging at 132 °C for 35 h or 140 h). All the groups were subjected to the biaxial flexural test (n = 30), and Vickers hardness (n = 42). Weibull analysis was performed to determine the Weibull moduli (m) and characteristic strenghts (σ0). The specimens were characterized by scanning electron microscopy (SEM) to evaluate microstructure and X-ray diffraction (XRD) for phases percentages determination. For as-sintered condition: there was saturation of the amount of monoclinic zirconia after 35 h of hydrothermal aging, with 66% of monoclinic zirconia formed on the surface. LTD generated a progressive reduction in hardness over time; flexural strength was increased by the 35-h treatment (baseline: 974 MPa; 35 h: 1161.5 MPa), but, the 140 °C treatment was deleterious (698.5 MPa). On the other hand, the infiltrated specimens had an increase in the amount of cubic zirconia on the surface and showed 26% (35h) and 31% (140h) of monoclinic zirconia after the hydrothermal aging ; the strength was kept unaltered after LTD–35 h (935.9 MPa) and an increase was observed after LTD–140 h (1033.6 MPa); the hardness values had no statistically significant changes during the process. Thus, one can concludes that the silica infiltration can prevent the decrease in the mechanical properties due to the LTD on partially stabilized zirconia materials.

© 2020 Elsevier Ltd and Techna Group S.r.l.This work studied the influence of two sol-gel synthesis routes in obtaining a bioactive glass-ceramic derived from the 45S5 composition: a polymeric and a colloidal route. The main difference between the routes is in the silica precursor employed. The tetraethyl orthosilicate metal alkoxide (Si(OC2H5)4 - TEOS) is used in polymeric route and the silicic acid (H4SiO4) was used in the colloidal route. The synthesized xerogels were calcined at different temperatures to eliminate undesirable compounds and to verify the crystallization behavior. Afterwards, the calcined xerogels were submitted to in vitro bioactivity assay. The samples were also characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and laser diffraction. After calcination, the glass-ceramics obtained by the colloidal route showed greater number of bioactive phases and, consequently, of NBO bonds. The larger amount of NBO bonds resulted in a higher bioactivity of the materials synthesized by the colloidal route. In addition, the long hydrolysis step of the metal alkoxides was eliminated with colloidal synthesis. This allowed a significant reduction in the total synthesis time from 13 days to 24 h. To the best of our knowledge, this seems to be the first time this colloidal route has been employed in the synthesis of bioglass 45S5.

© 2020, Springer Nature B.V.This paper evaluates the influence of synthesis route (acidic or alkaline) on the structure, morphology, and photocatalytic properties of ZnO/Carbon xerogel composites. Structurally, both classes of materials present the wurtzite phase of zinc oxide. Composites derived from acidic route displayed facile thermal degradation of the zinc oxalate precursor when compared with pure zinc oxalate. Morphology-wise, materials produced through alkaline route are composed of nodular and plate-like particles, whereas acidic route composites are heterogeneously formed by large polyhedral particles and small particle agglomerates. Elemental distribution analysis confirms the heterogeneity of the acidic route composites, showing clear phase separation between the ZnO and the carbon xerogel. The composites prepared using the alkaline route are superior in the photodegradation of 4-chlorophenol, probably due to higher homogeneity and synergy between the semiconductor and carbonaceous phases. The superiority of alkaline route composites is confirmed by electrochemical impedance spectroscopy, which shows that such materials have enhanced charge separation capability. [Figure not available: see fulltext.]

© 2020, Society for Experimental Mechanics.The multireflection grazing incidence X-ray diffraction method (MGIXD) was used to analyze the surface residual stresses in 7050 Al alloy samples. This technique can provide a non-destructive stress profile in function of sample depth, avoiding the relaxation effects intrinsic to destructive methods. The state of residual stress in aeronautical aluminium samples was modulated by milling and shot peening processes. After structural characterization, the residual stress states of the samples were analyzed by multireflection and conventional stress measurement methods. The milled samples presented tensile surface residual stress relaxation attributed to thermal effects and the shot peened samples showed strong compressive stress at sub-surface, which intensity was reduced near the surface. The residual stress profiles of the Al samples were obtained by MGIXD method that evidenced properties commonly undetected in conventional residual stress studies.

© 2019 Elsevier Ltd and Techna Group S.r.l.The phase of crystalline α-wollastonite (α-CaSiO3) powders was prepared at low temperature via sol gel method. The formation mechanisms of α-wollastonite (α-CaSiO3) using different calcium salts were examined. The synthesis was carried out in absence of organic solvents, using as starting materials silicic acid and inorganic salts (CaCl2.H2O and Ca(NO3)2.4H2O). The samples were analyzed by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetry/Differential Scanning Calorimetry (TGA-DSC), X-Ray Diffraction (XRD) and Field Emission Gun-Scanning Electron Microscopy (FEG-SEM). The experimental results demonstrate that the calcium source strongly influences the characteristics of the resultant powders, as phase purity and morphology of the wollastonite particles. XRD analysis showed that, using CaCl2.H2O on the synthesis, α-wollastonite started to crystallize as majority phase at 700 °C. The complete crystallization of α-wollastonite was observed after the calcination at 1000 °C for 5 h, while samples prepared with Ca(NO3)2.4H2O, only crystallized α-wollastonite at 1200 °C. This difference in crystallization temperature is probably related to the higher homogeneity and the elevated number of Si–O–Ca bonds present in samples prepared with CaCl2.H2O.

© 2019 Elsevier LtdThis study aimed to evaluate the effects of low temperature degradation (LTD) on commercial dental zirconias (conventional and high-translucent - HT) with different microstructures, as well as on their mechanical properties and t-m phase transformation. The amount of monoclinic zirconia in different depths was quantified using X-ray diffraction (XRD) with different anode tubes (Cr, Co and Cu). XRD was also used to measure the residual stress of the materials at 0 h, 26 h and 140 h aging times. Vickers microhardness and biaxial flexural strength tests were performed. Data were subjected to two-way ANOVA and Tukey's post-hoc test, both with α = 0.05 for means comparisons. Weibull parameters were calculated and compared based on the overlapping of confidence intervals (CI = 95%). HT Zirconia presented smaller grain sizes and had a higher rate of t-m transformation over time. The microstructure of the conventional zirconia showed an expressive increase of the grain size and consequently greater morphological variation with the LTD. The non-aged samples (control) did not present any residual stress and the aged ones presented compression stress. All zirconia showed a residual stress increase with the increase of LTD time, but the conventional one showed a decrease after 140 h. HT zirconia showed no significant change in flexural strength over LTD time, but the conventional one showed a strength decrease after 140 h (681.78 ± 121.18 MPa). Vickers hardness decreased for all zirconia samples after 26 h. The mechanics of LTD is significantly altered in different zirconia microstructures. Zirconias with smaller grains are more prone to t-m phase transformation, but present lower variation of residual stress, while larger grains zirconias have a lower surface area and therefore a more pronounced increase in stress over LTD time. Stress values close to the maximum compression stress generates ejection of the zirconia grains, producing defects and causing reduction of the compression stress and consequently decrease of flexural strength.

© 2019 Elsevier B.V.The effect of synthesis medium (ethanol and water) on ZnO/Carbon xerogel photocatalysts was studied in order to increase the efficiency of the photocatalytic degradation of 4-chlorophenol and bisphenol A. The use of carbon xerogel is justified due to its excellent electrical conductivity, high surface area and porosity. The effect of the carbon content in the composites was also evaluated. The composites were characterized using scanning electron microscopy, transmission electron microscopy, dispersive energy spectrometry, X-ray diffractometry, infrared spectroscopy, nitrogen isotherms, differential scanning calorimetry, thermogravimetry, electrochemical impedance spectroscopy and Raman spectroscopy. All materials present the hexagonal crystalline structure of zinc oxide. Materials without carbon in their composition also presented the zinc hydroxychloride monohydrate phase. X-ray diffractograms and bandgap values obtained confirm the incorporation of carbon in the crystalline structure of zinc oxide. Materials produced in ethanol medium have lower values of crystallite and particle size, as well as higher graphite contents in their composition and higher specific surface area. All materials displayed photocatalytic activity when subjected to visible and solar radiation. Materials produced in ethanol displayed superior performance when compared to those synthesized in aqueous medium. The maximum values found for the degradation of 4-chlorophenol and bisphenol A were 88% and 78%, respectively, after 5 h. The mechanism of photocatalysis is strongly influenced by the generation of hydroxyl radicals and the materials were stable for three cycles of reuse. The electrochemical impedance spectroscopy confirms that the charge separation efficiency was optimized in the presence of the carbon xerogel and when the composite was produced in ethanol medium.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Carbon nanotubes (CNT)-reinforced polymeric composites are being studied as promising materials due to their enhanced properties. However, understanding the behavior of polymers during non-isothermal crystallization is important once the degree of crystallinity and crystallization processes are affected when nanoparticles are added to matrices. Usually, crystallization kinetics studies are performed using a model-fitting method, though the isoconversional method allows to obtain the kinetics parameter without assuming a crystallization model. Therefore, in this work, CNTs were oxidized (CNT-Ox) and functionalized with gamma-aminobutyric acid (GABA) (CNT-GB) and incorporated into a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. The influence of the addition and functionalization of CNT in the crystallization kinetics of PHBV was evaluated using the isoconversional method with differential scanning calorimetry (DSC), and by polarized light optical microscopy (PLOM) and Shore D hardness. The incorporation and functionalization of CNT into PHBV matrix did not change the Šesták and Berggren crystallization model; however, the lowest activation energy was obtained for the composite produced with CNT-GB, suggesting a better dispersion into the PHBV matrix. PLOM and Shore D hardness confirmed the results obtained in the kinetics study, showing the smallest crystallite size for CNT-containing nanocomposites and the highest hardness value for the composite produced with CNT-GB.

© 2019 Elsevier Ltd and Techna Group S.r.l.Life expectancy has been growing, and more people are developing bone diseases such as arthritis and osteoporosis. Degenerative pathologies, injuries, and trauma can damage the bone tissues, requiring treatments that facilitate its repair, replacement, or regeneration. In this context, many materials have been developed to match this demand. Bioglasses and ceramics are promising inorganic materials to produce scaffolds for bone regeneration due to their attractive properties, such as biocompatibility, osteoinduction, and osteoconduction, besides their similarity with bone composition. Although their established advantages, these materials present limitations such as inadequate mechanical properties and fast degradation rate. Research work has been widely carried out to develop bioglasses, silicate, and phosphate calcium ceramics scaffolds with appropriated properties to enlarge their applications in bioengineering. Different fabrication techniques have also been evaluated. Incorporating other materials or particles, such as polymers, oxides and metal particles into the scaffolds has shown beneficial effects in mechanical strength and bone production stimulation. In this review, we provide an overview concerning the recent advances in developing calcium phosphates, calcium silicates, bioglasses, and composites scaffolds for bone regeneration in medical and dental applications.

© 2019, Springer Nature Switzerland AG.Silver vanadate, especially β-AgVO3, have a wide range of technological applications due to remarkable biological, optical, and electrical features. The structure, morphology, and properties of β-AgVO3 are directly affected by synthesis conditions. A comparative study between two different synthesis routes (precipitation and hydrothermal) of β-AgVO3 was systematically investigated in this work. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, zeta potential, and UV–visible spectrometry results showed that the hydrothermal method produced more homogeneous samples of β-AgVO3, with elevated purity and crystallinity. In addition, the sample of β-AgVO3 obtained by hydrothermal method had a wire-like morphology while that obtained by precipitation had irregular shape. Finally, the hydrothermal procedure showed more elevated reproducibility.

© 2019, Springer Nature Switzerland AG.Abstract: The improvement of compatibility between carbon nanotubes (CNTs) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was achieved using CNT functionalized with γ-aminobutyric acid (GABA). The efficiency of the CNT functionalization with GABA was evaluated by X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM). The PHBV/CNT nanocomposites were produced in the molten state with the addition of 0.5 wt% of CNT (pristine, oxidized and functionalized with GABA) and characterized concerning the Izod impact strength tests. The impact fracture morphologies were analyzed using scanning electron microscopy. The results showed that GABA was covalently attached to CNT, resulting in the detection of nitrogen in the XPS survey, the shift of carbonyl peak wavelength on FT-IR, and a higher degree of structural disorder, detected by Raman and observed in TEM images. The impact strength was not significantly affected by the introduction of CNT; however, the impact fracture mechanism was changed from fragile to ductile when CNT was functionalized with GABA. These results are promising for the production of environmentally friendly nanocomposites with superior properties. Graphic abstract: [Figure not available: see fulltext.]

© 2019, Springer Nature B.V.This study aimed to evaluate the effects of cold atmospheric pressure plasma (CAPP) jet on Trichophyton rubrum growth, germination and adherence to nail. The effects of plasma jet on T. rubrum conidia germination and on mycelial growth were evaluated by in vitro assays. An ex vivo nail infection model was used to evaluate the effects on conidia adherence and infection. Biochemical analyses of nail fragments exposed or not to CAPP were performed by attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy. Plasma jet exposure for 10 and 15 min completely inhibited mycelial growth after only one exposure. Fifteen minutes of exposure could reduce conidia germination in suspension. Fungal suspensions exposed to plasma jet for 10 and 15 min were not able to infect nail specimens. These results were corroborated by ATR–FTIR analyses of nail fragments. In conclusion, single exposure to CAPP for 15 min was able to inhibit fungal growth, adherence and infection capacity. The results suggest that cold atmospheric plasma jet can be a promising alternative for the treatment of onychomycoses caused by T. rubrum.

© 2019 Elsevier LtdSuper hydrophilic scaffolds of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with 3 wt % of acetylated (CNC-Ac) and PEGylated (CNC-PEG) cellulose nanocrystals (CNC) were prepared. PHBV, PHBV/CNC-Ac, and PHBV/CNC-PEG scaffolds were characterized with respect to their morphology by scanning electron microscopy (SEM) and X-ray microtomography. The crystallinity was evaluated by differential scanning calorimetry (DSC) and the mechanical properties by uniaxial compression tests. The presence of residual solvent was identified by gas chromatography (GC), wettability measured by static contact angle and aqueous adsorption by gravimetry. All the scaffolds showed porous morphology, being that, for neat PHBV the morphology was more regular with oriented pores. The porosity was reduced by 26% with the introduction of CNC-Ac and CNC-PEG, and the compression modulus increased by 25% and 72% for PHBV/CNC-Ac and PHBV/CNC-PEG scaffolds, respectively, compared to neat PHBV. Even with lower porosities, PHBV/CNC-Ac and PHBV/CNC-PEG adsorbed 16% and 67% more water than PHBV scaffold, following the intraparticle diffusion model for all the samples. No residual solvents were found and the crystallinity was slightly increased upon addition of CNC-Ac and CNC-PEG. Therefore, the addition of CNC-Ac and CNC-PEG can improve both compressive modulus and water uptake, turning PHBV nanocomposite scaffolds suitable for tissue engineering applications.

© 2019 IOP Publishing Ltd.In this work, a new strategy of carbon nanotubes (CNT) pre-dispersion (PD) in acetone to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/CNT nanocomposites was evaluated. PHBV/CNT nanocomposites were produced in the molten state with the addition of 0.5 wt% of CNT and evaluated by scanning electron microscopy with field emission gun (FEG-SEM), differential scanning calorimetry (DSC), Izod impact tests, nanohardness, and x-ray diffraction (XRD). FEG-SEM showed well-dispersed CNT for sample subjected to pre-dispersion (PHBV/CNT-PD), and DSC showed a reduction in the degree of crystallinity from 62% to neat PHBV to 55% for PHBV/CNT-PD. Impact resistance was positively affected by the pre-dispersion, and nanohardness showed more homogeneous values for PHBV/CNT-PD sample compared to PHBV/CNT (without pre-dispersion). XRD proved that hot pressing affects plans orientation, and so does the addition of CNT into PHBV. The CNT dispersion into PHBV analyzed by the ratio between planes area showed that PHBV/CNT-PD sample had homogeneously dispersed CNT.

© 2019, Springer Nature Switzerland AG.Titanate nanorod synthesis method is extremely important due to their large application in electronic, catalysis, and biological areas. However, works reporting the influence of synthesis parameters on the structure, morphology, and properties of titanate nanorods are still rare. Therefore, this work aims to analyze the preparation of titanate nanorods from TiO2 nanoparticles via hydrothermal reaction. The microstructure and morphological properties were evaluated as a function of time, temperature and precursor nature (anatase or anatase/rutile mixture) by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy and field-emission scanning electron microscopy. The crystallinity of the precursor was the main parameter for the titanate nanorods formation. Besides, temperature has also a direct influence in the fibril morphology. The use of low temperature and anatase/rutile mixture was not able to produce titanate nanorods. Only the use of higher temperatures and pure anatase resulted in rod-like titanates, which showed higher methylene blue photodegradation efficiency than TiO2 nanoparticles.

© 2018 Elsevier Ltd and Techna Group S.r.l.This paper reports the development of new ZnO/carbon xerogel composites (XZn w) for photocatalytic applications. The use of black wattle tannin as a precursor to the carbon xerogel aimed at reducing costs and environmental impacts. The composites were characterized by diffuse reflectance spectroscopy (DRS), BET surface area, scanning electron microscopy (FEG-SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray diffraction (XRD). The photocatalytic performance of the materials was evaluated in the decomposition process of methylene blue, a known toxic pollutant. The impacts of the catalyst dosage and calcination temperature on the photocatalytic process were also examined systematically. The X-ray profiles of the XZn w evidenced the existence of the hexagonal structure of the zinc oxide (wurtzite) in the composites. The XPS and XRD analyses confirmed the incorporation of carbon in the zinc oxide crystalline structure. The higher carbon content resulted in a larger surface area. All composites presented the ability to absorb radiation in less energetic wavelengths, contrary to pure zinc oxide that only absorbs radiation of wavelengths below 420 nm. The optimal dosage and calcination temperature were found to be 0.2 g L−1 and 300 °C. All the developed composites displayed significant photocatalytic activities in the decomposition of methylene blue under both visible and solar light. The composites had superior photocatalytic efficiency under visible light when compared to pure zinc oxide. The XZn 0.5 presented the best degradation efficiency under visible radiation. All materials presented similar photocatalytic responses under solar light, evidencing the synergy between the carbon xerogel and the zinc oxide. The photocatalytic mechanism was evaluated by trapping experiments to be mainly controlled by the electron vacancies that are generated during the photoexcitation of the composites.

© 2019 by the authors.Behavior studies of thermoplastic polymers during non-isothermal crystallization are extremely important since most of their properties are influenced by degree of crystallinity and the crystallization process. In general, an approach based on a model-fitting method is used to perform crystallization kinetic studies. Due to their inability to uniquely determine the reaction mode, many studies have used the isoconversional method, where it is not necessary to assume a crystallization model to obtain the kinetic parameters. Therefore, in this work, the influence of acid and octadecylamine functionalized carbon nanotubes (CNTs) in the crystallization kinetic of polyethylene (PE) was studied using an isoconversional method with differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The kinetic parameters and the crystallization model were determined. The incorporation of functionalized and non-functionalized CNTs into PE did not change the Johnson-Mehl-Avrami crystallization model. However, the CNTs increased the crystallization temperature and reduced the activation energy for crystallization. In addition, the Avrami coefficient values were lower for the nanocomposites when compared to pure PE. The incorporation of CNTs accelerated the crystallization of PE, reducing the crystallite sizes and modifying their morphology.

© 2019 by the authors. Licensee MDPI, Basel, Switzerland.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a widely studied polymer and it has been found that porous PHBV materials are suitable for substrates for cell cultures. A crucial factor for scaffolds designed for tissue engineering is the water uptake. This property influences the transport of water and nutrients into the scaffold, which promotes cell growth. PHBV has significant hydrophobicity, which can harm the production of cells. Thus, the addition of α-wollastonite (WOL) can modify the PHBV scaffold’s water uptake. To our knowledge, a kinetics study of water uptake of α-wollastonite phase powder and the PHBV matrix has not been reported. In this work, PHBV and WOL, (PHBV/WOL) films were produced with 0, 5, 10, and 20 wt % of WOL. Films were characterized, and the best concentrations were chosen to produce PHBV/WOL scaffolds. The addition of WOL in concentrations up to 10 wt % increased the cell viability of the films. MTT analysis showed that PHBV/5%WOL and PHBV/10%WOL obtained cell viability of 80% and 98%, respectively. Therefore, scaffolds with 0, 5 and 10 wt % of WOL were fabricated by thermally induced phase separation (TIPS). Scaffolds were characterized with respect to morphology and water uptake in assay for 65 days. The scaffold with 10 wt % of WOL absorbed 44.1% more water than neat PHBV scaffold, and also presented a different kinetic mechanism when compared to other samples. Accordingly, PHBV/WOL scaffolds were shown to be potential candidates for biological applications.

© 2019 Vinícius D. N. Bezzon et al.A brief review reporting the recent advances on the carbon nanostructured materials-based sensors covering recently published works is presented. Several works dealing with experimental and theoretical data are reviewed and discussed. The main results for carbon nanotubes, nanodiamonds, fullerene, graphene, and hybrid carbon-nanostructured devices that show sensing properties in different fields were considered for the discussions. The goal of this paper was to highlight sensor mechanisms, and the best results reached up to now are creating bases for further applications.

© 2019 The Royal Society of Chemistry.Carbon nanotubes (CNTs) have remarkable mechanical, thermal, electronic, and biological properties due to their particular atomic structure made of graphene sheets that are rolled into cylindrical tubes. Due to their outstanding properties, CNTs have been used in several technological fields. Currently, the most prominent research area of CNTs focuses on biomedical applications, using these materials to produce hybrid biosensors, drug delivery systems, and high performance composites for implants. Although a great number of research studies have already shown the advantages of CNT-based biomedical devices, their clinical use for in vivo application has not been consummated. Concerns related to their toxicity, biosafety, and biodegradation still remain. The effect of CNTs on the human body and the ecosystem is not well established, especially due to the lack of standardization of toxicological tests, which generate contradictions in the results. CNTs' toxicity must be clarified to enable the medical use of these exceptional materials in the near future. In this review, we summarize recent advances in developing biosensors, drug delivery systems, and implants using CNTs as smart biomaterials to identify pathogens, load/deliver drugs and enhance the mechanical and antimicrobial performance of implants.

© 2018, University of Tehran.Activated carbon (ACAcaí) was obtained from the activation of açaí seeds at 800 °C under CO2 flow. The surface groups of the material were determined by Boehm titration and information about surface charge was obtained using the methodology of the point of zero charge (PZC). Boehm titration and PZC tests showed that the ACAcaí sample has a basic character. The optimum pH range for the adsorption process is 3.5–8 and the optimum dosage is 0.1 g/50 mL of phenol solution. ACAcaí has a surface area of 496 m2 g−1 and pore volume of 0.217 cm3 g−1. The adsorption kinetics follows the pseudo-second-order model. The Langmuir isotherm model satisfactorily described the experimental data. The maximum adsorption capacity obtained was of 133 mg g−1 at 25 °C. Deionized water, NaOH solution (0.1 M), and ethanol were used as desorption agents, but none of them showed promising results for the regeneration of ACAcaí. The thermodynamic studies show that the adsorption process is exothermic, spontaneous, and favorable.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature.Homogeneous dispersion of carbon nanotubes (CNTs) in polymers has significantly improved their processing and application as nanomaterials. Generally, CNTs tend to agglomerate due to their high aspect ratios and strong van der Waals interaction. Surface functionalization appears to be a solution to this problem. This study presents a controlled dispersion of carbon nanotubes in polyethylene through surface modification using a mixture of concentrated acid and octadecylamine (ODA). CNTs were characterized by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, and transmission electron microscopy. The results confirmed that carboxyl and alkane groups were successfully introduced on CNT surfaces. The acid- and amine-functionalized carbon nanotubes were dispersed in four solvents with different polarities (water, ethanol, acetone, and xylene) to correlate the degree of dispersion of CNT with their polarity. The results showed that CNT dispersion stability strongly depends on solvent and carbon nanotube polarities after the functionalization step. The nanohardness and tensile tests showed that the addition of CNTs, especially the functionalized with ODA, leaded the polymer harder, increasing its Young’s modulus and tensile strength. However, its toughness and deformation capacity were reduced. The potential applications of CNT-based polymer nanocomposites broaden considerably due to the surface engineering of carbon nanotubes.

© 2018 Elsevier B.V.Activated carbon from coconut shells is known as an excellent adsorbent to remove contaminants, it was successfully inserted into the TiO2 structure via sol-gel method, and the sonocatalysis of methylene blue was evaluated. TiO2 nanoparticles and coconut shell were used for synthesizing activated carbon composite (TiO2–COC) with carbon contents in the range of 0.5–10% by weight. These nanomaterials were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, Emission gun scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared spectroscopy (FT-IR), Field Emission Gun Scanning Electron Microscope (FEG–SEM) and Transmission electron microscopy (TEM). The physical-chemical properties of the catalysts were investigated in depth; in particular the kinetic studies conducted to determine the real degradation capacity of each material. The nanocomposites with carbon content of 0.5, 1.0, 2.0% in mass presented better catalytic activity when compared to a commercial one (Degussa-P25) and a lower dye adsorption was observed. The catalyst with 10% of carbon mass removed all methylene blue content through the adsorption process. Some catalysts reached high activity; the ultrasound effect was increased in 22% after only 2 h using low effective power output (40 W). The main reason for the increased catalytic was the perfect insertion of TiO2, which fill the coconut structure, sealing pores, reducing the carbon roughness and decreasing the TiO2 particle size. The electrical charge recombination on TiO2 surface enhances the sonocatalytic activity.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature.The aim of this study was the development of low-cost tannin-formaldehyde xerogel/TiO2 (XTi-w) and carbon xerogel/TiO2 (XTiC-w) photocatalysts. The materials used as precursors were recycled titanium scraps and black wattle tannin extract, highlighting the low-cost approach employed in the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectrophotometry, X-ray diffractometry, infrared and Raman spectroscopy. X-ray diffractometry showed that the XTiC-w have tetragonal crystalline structure (anatase), whereas the XTi-w has an amorphous structure. The Raman and infrared analysis also showed the presence of titanium dioxide in the composition of both XTi-w and XTiC-w. XTi-w and XTiC-w showed photocatalytic activity at the visible wavelength. Titanium dioxide displayed no photocatalytic activity at the visible wavelength. The XTi-60 composite displayed the highest efficiency in the removal of the methylene blue from the system, as well as good reusability properties. The radicals with higher influence in the photocatalytic reaction mechanism are the photo generated electron and the singlet oxygen molecule. The effect of the heat treatment is negative on the photocatalytic properties of the hybrids produced, due to the removal of acid sites, adsorbed water and OH surface groups. [Figure not available: see fulltext.].

© 2018 Elsevier B.V.This paper evaluates the feasibility of using niobium-based catalysts for the photodegradation of organic dyes. The metal oxides were prepared using niobium scraps and chips as precursors. The semiconductors were characterized by diffuse reflectance spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, infrared and Raman spectroscopy. The as-prepared anhydrous niobium oxide has a pseudohexagonal structure, whereas the hydrated niobium oxide is an amorphous material. The specific surface area of the hydrated niobium oxide is found to be double the area of its calcined counterpart. The photocatalytic efficiency of the materials was evaluated by methylene blue (MB) decomposition, measured by UV-visible spectroscopy. The effects of catalyst dosage and initial dye concentration were investigated in both the adsorption and photocatalysis processes. Increasing the initial MB concentration leads to increase the amount of adsorbed MB but to decrease the photocatalytic efficiency for all materials. In contrast, both the amount of adsorbed dye and the photocatalytic efficiency increase with increasing the catalyst dosage (0.5–2 g L−1). The highest photodegradation efficiency is achieved using UVC radiation. The specific surface area as well as the amount of acid sites, adsorbed water, and OH− surface groups on the catalyst surface demonstrates to be fundamental to the photocatalytic properties of the materials. Furthermore, the photocatalytic mechanism is controlled by superoxide and singlet oxygen species for the hydrated material, whereas the hydroxyl radical is the main active species in the photodegradation employing the anhydrous oxide. The hydrated material achieved a complete degradation of the methylene blue.

© 2018 Elsevier Ltd and Techna Group S.r.l.This work explores the development of hybrid Nb2O5/carbon xerogel photocatalysts. The precursor materials used, such as tannin and recycled niobium scraps, enhance the economic and environmental aspects of the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The photocatalytic action of the material was evaluated by methylene blue decomposition as determined by UV–visible spectroscopy. Anhydrous niobium oxide has a hexagonal structure. The X-ray profiles of the materials developed (XC-wNb) are similar to Nb2O5, confirming the presence of inorganic oxide in the matrix of these composites. The chemical elements that compose the samples are homogeneously distributed on the surface of the samples, confirming the dispersion of the oxide in the carbonaceous matrix. The XC-wNb absorbs radiation in a considerably wider range than inorganic oxides, in this case, for the entire wavelength range used in the experiments, thereby suggesting the synergistic effect of xerogel and niobium oxide on the optical properties of the XC-wNb samples. All XC-wNb presented photocatalytic activity under visible radiation, evidencing the beneficial coupling effect on the photocatalytic properties of the material. The XC-24Nb was the most effective photocatalyst at the wavelength used due its composition, morphological and photochemical properties. The methylene blue photodegradation is controlled to a greater extent by reaction with the OH• radical. The XC-24Nb also presents high stability and reusability, which are optimal properties for industrial application.

© 2017 Society of Plastics EngineersThis review describes the use of cellulose nanocrystals (CNC) as fillers in biodegradable polymer matrices over the past few years. The preparation and characterization of CNC-based nanocomposites are highlighted here with a focus on thermophysical and mechanical properties. The characterization and isolation of nanocellulose from different raw material sources are discussed in detail, as well as different surface modifications. The addition of CNC in biodegradable polymer, combined with nanocellulose surface engineering and driven by sustainability trends, has the potential to impact various industrial sectors. POLYM. COMPOS., 39:E9–E29, 2018. © 2017 Society of Plastics Engineers.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.Lately, nanomaterials have been largely studied as reinforcements for epoxy resin. Although their usage is highly promising, the literature has reported some drawbacks regarding the improvement of mechanical properties in nanocomposites. These difficulties are usually due to dispersion of nanomaterials and its adhesion to the polymeric matrix. One approach to this problem is the functionalization of nanomaterials such as carbon nanotubes (CNTs) and graphene. In this work, we have studied the synthesis and functionalization process of CNTs and graphene oxide (GO) to be used as reinforcements for epoxy resin nanocomposites. CNTs were synthesized at 850 °C in a quartz furnace, from hexane and ferrocene vapor, and functionalized by acids and ethylenediamine treatments. GO was obtained by graphite exfoliation through a modified Hummer’s method. The nanomaterials were characterized by Raman spectrum, FT-IR, XRD, and SEM images. Nanocomposites were prepared using these nanomaterials and evaluated by DMA. While both nanomaterials showed an improvement in mechanical properties, suggesting a chemical bond between nanomaterial and the epoxy matrix, it was clear that GO reinforced samples presented a higher storage modulus.

© 2017 Elsevier Ltd and Techna Group S.r.l.This work explores a new route for the synthesis of titanium dioxide using scraps and titanium chips, which are typically discarded as waste, as the precursor materials. The band-gap energy of the synthesised materials was determined using diffuse reflectance spectroscopy. The morphology, elemental analysis, crystallinity, and chemical structure of the synthesised materials were determined by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, and infrared and Raman spectroscopies, respectively. The X-ray and Raman analyses confirmed the formation of titanium dioxide in its tetragonal (anatase) crystalline form after heat treatment (400 °C, 2 h). Moreover, a mixture of (NH4)0,3TiO1,1F2,1 and anatase TiO2 was obtained as a by-product. After heat treatment, this by-product was converted into fluorine-doped titanium dioxide, also in anatase crystalline form. The apparent crystallite size (Lc) of anhydrous titanium dioxide was found to be smaller than that of the calcined by-product. The diffuse reflectance spectroscopy analysis revealed that the calcined by-product has a significantly higher absorption capacity at higher wavelengths, as well as a lower band-gap energy value. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) analyses showed large particulates on which smaller particles are deposited and good dispersion of the elemental components. The anhydrous titanium dioxide sample presents a smaller particle size than the calcined by-product.

© 2017 IOP Publishing Ltd.Carbon nanotube (CNT)-epoxy composites were prepared using carboxyl, amino and raw CNTs. The results of differential scanning calorimetry (DSC) showed that the effect of CNTs on the cure of epoxy resin is strongly dependent on the temperature and time. Raw and carboxyl CNTs accelerated the formation of branched chains (pre-cure at 80 °C), consuming the polymerization sites and leading to lower rates of crosslinking reaction (cure at 120 °C), resulting in lower storage modulus according to dynamic mechanical analysis (DMA). These results were explained by the catalysts of pre-cure (carboxylic groups and metallic residue of CNTs) and by CNT agglomerates, which could slow the crosslinking due to the consumption of epoxy sites. However, neat epoxy and amino-CNTs nanocomposites showed lower pre-cure rates and higher cure rates, resulting in higher storage modulus. Amino CNTs were the only nanotubes that increased the storage modulus of neat epoxy, due to the good homogeneity and adhesion of their composites.

© 2017 Taylor & Francis Group, LLC.Carbon nanotube (CNT) reinforced high-density polyethylene (HDPE) composites were prepared by a melt mixing procedure. The mechanical properties were analyzed using a central composite design where key factors were CNT concentration and sonication temperature during the sample preparation process. The results indicated that the optimum values were 0.8 wt% for the concentration of CNT and 55°C for the sonication temperature. The samples obtained at optimal conditions were systematically studied. Nanoindentation analysis showed an increase of 43% in Vickers hardness of the nanocomposite when compared to pure polymer. The improvement on the mechanical property is related to changes in the thermo-physical and viscoelastic properties of the nanocomposite.

© 2015 Society of Plastics EngineersCarbon nanotube-epoxy composites were prepared using amino-functionalized CNTs and sonication as a mixing process. Different times and sonication powers were used for preparing composites in order to study how the sonication process may influence the curing reaction of both systems: neat epoxy resin and amino-CNT/epoxy composite.The curing reaction was investigated with differential scanning calorimetry and the results were associated with analysis of gel permeation chromatography. The results showed that the effect of CNTs on the cure behavior of the epoxy resin depends on the sonication power. The sonication of neat resin with a 150 W powered device led to a molar mass reduction of the resin and an increase in the cure enthalpy. The CNT addition to this system reduced the cure enthalpy. However, when neat epoxy resin was sonicated with a 200 W powered device, the molar mass did not decrease (i.e., it was increased or was not changed) and the cure enthalpy did not increase (essentially it decreased or did not change). The CNT addition to such solutions did not reduce (i.e., it was increased or did not change) the cure enthalpy, which is a contrary result from that obtained with a 150 W powered device. POLYM. COMPOS., 38:1964–1973, 2017. © 2015 Society of Plastics Engineers.

© 2017 Elsevier B.V.This study presents the effect of dodecylamine (DDA) functionalization of carbon nanotubes (CNTs) on the thermo-physical and mechanical properties of high-density polyethylene (HDPE) based composites. Here, we showed that the functionalization with DDA improved the dispersion of the CNTs as well as the interfacial adhesion with the HDPE matrix via non-covalent interactions. The better dispersion and interaction of CNT in the HDPE matrix as a function of the surface chemistry was correlated with the improved thermo-physical and mechanical properties.

This paper investigates the application of the luminescence spectroscopy technique in steady-state to study the moisture influence in glass fiber/epoxy prepreg and their laminates. The studies were monitored by intrinsic luminescence comparing the results with gravimetric analysis and near infrared with Fourier transform. Samples are cured and submitted to humidity controlled at 60 and 80 °C until 90 days. It is verified that the decrease in the maximum emission of the samples is directly related to the material moisture content. However, for very short periods, there is an increase in the relative intensity and blue shift of the emission band for all samples treated at 60 °C, which is related to an increase of the rigidity of the polymeric matrix. The results in this paper have a great significance because it brings a wide discussion on the interaction of water in epoxy composites materials.

© 2016 Elsevier B.V. The effect of carbon nanotube treatment on the mechanical property of polyethylene/carbon nanotube composite (HDPE/CNT) was investigated. CNTs were initially treated with HCl and then with H 2 SO 4 /HNO 3 . Nanocomposites reinforced with untreated and treated CNTs were prepared by a mechanical mixture of the molten polymer. The results demonstrated a correlation among the surface treatment, dispersion and mechanical properties of HDPE/CNT composites. Raman spectroscopy and TGA analysis showed that both acid treatments removed efficiently amorphous carbon and residual metal catalysts of CNTs. However, these treatments not only removed impurities, they also decreased the crystallinity degree of CNTs due to the addition of oxygenated functional groups to the CNTs walls, as observed by XPS analysis. SEM micrographs revealed that the functional groups improved the CNTs dispersion in the polymeric matrix, resulting in an improvement of the mechanical properties of nanocomposites.

© 2016 Elsevier B.V. All rights reserved.Due to its high efficiency, low cost and a simple operation, the adsorption process is an important and widely used technique for industrial wastewater treatment. Recent studies on the removal of artificial dyes by adsorption include a large number of adsorbents, such as: activated carbon, silicates, carbon nanotube, graphene, fibers, titanates and doped titanates. The carbon insertion in the TiO2 structure promotes a synergistic effect on the adsorbent composite, improving the adsorption and the charge-transfer efficiency rates. However, there are few studies regarding the adsorption capacity of TiO2/Carbon composites with the carbon concentration. This study evaluates the effect of carbon (resorcinol/formaldehyde) insertion on TiO2 structure through the adsorption process. Adsorbents were prepared by varying the carbon weight percentages using the sol-gel method. The physicochemical properties of the catalysts prepared, such as crystallinity, particle size, surface morphology, specific surface area and pore volume were investigated. The kinetic study, adsorption isotherm, pH effect and thermodynamic study were examined in batch experiments using methylene blue as organic molecule. In addition, the effect of carbon phase on the adsorption capacity of TiO2-carbon composite was deeply investigated. SEM micrographs showed that TiO2 phase grows along the carbon phase and FT-IR results showed the presence of Ti-O-C chemical bonding. The experiments indicate that the carbon phase acted as a nucleation agent for the growth of TiO2 during the sol-gel step, with a TiO2 structure suitable for blue methylene adsorption, resulting in a material with large surface area and slit-like or wedge-shaped pores. Further experiments will show the best carbon concentration for methylene blue adsorption using a TiO2 based material.

Nanostructures based on ZnO have been widely studied due to their electronic and piezoelectric properties. Experimental studies have shown that thin films based on ZnO can be used as chemical and optoelectronic sensors. The great goal of this work is to study of the role of the number of graphene-like layers in the physical properties of the ZnO. Therefore, the geometrical and electronic properties of graphene-like structures will be compared with the wurtzite one. In this work, the pn-type semiconducting behavior of the graphene-like structures and its relationship with the number of layers will be also analyzed.

© 2015 Elsevier B.V. All rights reserved. The adsorption of H 2 O molecules on metal surfaces is important to understand the early process of water corrosion. This process can be described by computational simulation using molecular dynamics and Monte Carlo. However, this simulation demands an efficient description of the surface interactions between the water molecule and the metallic surface. In this study, an effective force field to describe the iron-water surface interactions was developed and it was used in a molecular dynamics simulation. The results showed a very good agreement between the simulated vibrational-DOS spectrum and the experimental vibrational spectrum of the iron-water interface. The water density profile revealed the presence of a water double layer in the metal interface. Furthermore, the horizontal mapping combined with the angular distribution of the molecular plane allowed the analysis of the water structure above the surface, which in turn agrees with the model of the double layer on metal surfaces.

© The Author(s) 2016.Graphene is a new member of the nanocarbon family that has revolutionized the field of materials science and has attracted much attention due to its exceptional properties. Recent progress has shown that graphene-based nanocomposites can be used in nanoelectronics, touch screens, optics, catalysis, supercapacitors, fuel cell transistors, flexible electronics, H2 storage, and polymer nanocomposites. The functionalization is a surface modification much used to reduce the cohesive force between the graphene sheets and also to manipulate the physical and chemical properties. The aim of this book was to provide a comprehensive scientific progress of graphene, containing topics such as synthesis, characterization, and application of functionalized graphene. The characterization of the functionalized graphene is extremely important for determining the physicochemical properties of the material obtained after the functionalization treatments. However, this characterization is rarely addressed in books or in review articles. Generally, the functionalization reviews are too wide-ranging, discussing the functionalization of various materials (e.g., nanomaterials) or too specific, analyzing only one functionalization agent (with some specific chemical group, for example). This book, however, proposes to discuss the functionalization of one of the most widely used nanomaterials in recent years: graphene. Thus, the reader will find information on graphene functionalization, using several functionalization agents, in the same book.

© The Author(s) 2016.Carbon nanotubes (CNTs) have unique structures, comprising diameters of few nanometers and length of several hundred nanometers, which provides outstanding mechanical, electrical, and thermal properties. Since their discovery in 1991, CNTs have received much attention and are a worldwide research subject due to their wide range of applications as biosensors, drug delivery, electrochemistry, nanoelectronics, superconductors, nanowires, graphene nanoribbons, nanocomposite materials, and so on. The functionalization treatments can enhance the usual CNT poor dispersion in solvents and improve their interactions with other materials, improving their technological application. Then, carbon nanotube is an extremely hot topic, and every day new research papers are published on this subject. This book contains complete and current reviews on CNT topics, such as synthesis, characterization, and application of functionalized CNTs. The characterization of functionalized CNTs is extremely important for determining the real physicochemical properties of the material obtained after functionalization treatments. However, this characterization is rarely addressed in books or review articles. Generally, the functionalization reviews are too wide-ranging, discussing the functionalization of various materials (e.g., nanomaterials), or too specific, analyzing only one functionalization agent (with some specific chemical group, e.g.). This book, however, proposes to discuss the functionalization of one of the most widely used nanomaterials in recent years: carbon nanotube. Thus, the reader will find information on CNT functionalization, using several functionalization agents, in the same book.

© 2015 Elsevier B.V. All rights reserved. In this work, it was performed a dispersion study of carbon nanotubes (CNTs) functionalized with carboxylic and alkane groups in various solvents. CNT was functionalized using H 2 SO 4 /HNO 3 and subsequently functionalized by dodecylamine (DDA). Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy were used to characterize the CNTs at each step of the surface modification. The dispersion state of CNTs in the solvents was evaluated by Optical microscopy and visual observations. The evaluation of the solvent influence itself was also made. Results confirmed the presence of oxygen-containing and alkane groups on CNTs surfaces. The dispersion stability was strongly dependent on the solvent and carbon nanotubes surface interactions, which can vary with the chemical nature of the solvent. The study of the surface modifications and the degree of carbon nanotubes dispersion is relevant to enhance the full understanding of its applications.

© 2014 SAGE Publications.Carbon nanotube-epoxy nanocomposite was obtained using amino-carbon nanotube and its thermal stability was compared with neat resin. The results showed that at lower temperatures (below 360°C), nanocomposite is more stable than neat resin. However, at higher temperatures (above 380°C), the contrary was observed: neat resin is more stable. In order to understand this anomalous behavior, a complete kinetic study of the cure process was performed. The precure degree of the nanocomposite was higher than that of the neat resin. However, both samples showed virtually the same final cure degree. The cure heat and activation energy were very similar for both samples. Nevertheless, the difference in thermal stability between nanocomposite and neat resin is not related to the cure process. This behavior must be associated with the good adhesion of amino-carbon nanotube-epoxy and to the presence of the functional groups linked to the carbon nanotube surface, especially oxygen molecules.

© 2014 Taylor and Francis Group, LLC.The main objective of this work was to evaluate nanocomposites formed by TiO2-CNT (carbon nanotube) and TiO2-C (resorcinol/formaldehyde) via a sonocatalytic process. The synthesis of composites was performed by the sol-gel method using titanium isopropoxide (Ti(OPr)4-TTIP), acetic acid and ethylene glycol as dispersing medium. Ultrasound was used as the irradiation source and methylene blue was chosen as a model substance. In addition, the adsorption capacity was studied in an attempt to achieve greater ratio degradation/adsorption. The methylene blue concentration after adsorption and sonocatalysis was investigated by UV-vis spectroscopy. It was found that adsorption was an important factor to achieve high degradation capacity. However, the sonocatalytic activity decreased when adsorption was too intense.

© 2015, Journal of Aerospace Technology and Management. All rights reserved.The focus of this study is to evaluate the effect of carboxyl and amino functionalization of multiwalled carbon nanotubes on the mechanical property of the epoxy resin filled with modified carbon nanotubes. The carbon nanotubes were treated with sulfuric and nitric acids and also with hexamethylenediamine. The presence of acid and amine chemical groups on the carbon nanotube surface was confirmed by X-ray photoelectron spectroscopy. The composites were produced with epoxy resin and modified carbon nanotubes. Vickers hardness tests were carried out on the composites and neat resin. The results showed an increase of hardness in the composite prepared with functionalized carbon nanotubes. This phenomenon is due to the fact that the chemical interaction between modified carbon nanotube and epoxy resin is much stronger than between pristine carbon nanotube and epoxy resin. This stronger interaction is related to the presence of functionalized carbon nanotubes.

© 2015 Elsevier Ltd. and Techna Group S.r.l. All rights reserved.A series of metakaolinite-based geopolymer was prepared at several curing temperatures and its relationship with porosity, infrared spectrometry (FT-IR) and mechanical properties was investigated. The samples were cured at the following temperatures: 55, 65 and 80 °C for 1 h. After a post cure of 28 days, the samples were investigated by using the following techniques: compressive strength, mercury intrusion porosimetry (MIP), helium pycnometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectrometry (FT-IR). All samples were amorphous by XRD. The sample thermally treated at 65 °C (C65) presented the highest values of compressive strength and relative integrated area of peak at 792 cm-1. This peak was attributed to a higher concentration of tetra-coordinated aluminum, indicating a higher efficiency of the geopolymeric reaction. The C65 also presented the lowest volume of closed pores. The values of the skeletal and the true densities for C65 were very similar and consistent with the volume of the closed pores. On the other hand, this sample showed the highest bulk density obtained by MIP and the greatest difference between the open and closed porosity measured by MIP and helium pycnometry, respectively. All these results are coherent and clearly indicate that the amount of open pores is directly related to a better mechanical performance of the geopolymeric sample.

© 2015 Elsevier Ltd.TFC was used for chromium ions (III and VI) adsorption from aqueous solution. The total chromium removal was strongly affected by pH changes and reached a maximum value at pH 1. The adsorption process was well described by the Langmuir model. The thermodynamic parameters exhibited the feasibility and the spontaneous nature of the adsorption. The optimum adsorbent dose obtained for chromium adsorption onto TFC was 0.1 g. The optimum contact time for chromium removal and treatment efficiency was 10 and 14 h, respectively. The kinetic studies showed that the adsorption process could fit into a pseudo-second-order model and the particle diffusion process was the rate-limiting step of the adsorption process. The desorbing agents studied did not show any promising result for the TFC regeneration process. The FT-IR results showed that the Cr(VI) removal onto TFC occurs through an indirect reduction mechanism. According to XPS spectrum, the majority of the adsorbed Cr is Cr(III), only a small quantity of Cr(VI) remains loaded on the TFC surface.

© 2013 Society of Plastics Engineers.The results regarding the effect of carbon nanotubes (CNTs) on the cure process of epoxy resin are widespread and contradictory. Therefore, this article aims to review the key studies on the effect of carbon nanotubes related to the curing process of epoxy resin, separating them according to analysis technique. Many articles have shown that nanocomposite homogeneity and medium viscosity have great influence on the cure process. Some of them have shown that heterogeneity and high viscosity slow down the epoxy resin cure, reducing the cure reaction heat. Furthermore, the presence of chemical groups such as amine and hydroxyl can catalyze this reaction, especially in the case of homogeneous composites. This review describes briefly and straightforwardly the value of using several techniques for studying and monitoring the nanocomposite cure, among them: DSC, rheometry, DMA, Raman, FT-IR, and luminescence spectroscopy. That importance is remarkably noticeable for studying a particular temporal reaction step, where a particular technique is more suitable than another. In this sense, one could say that luminescence spectroscopy is appropriate for studying the ending step of the cure reaction. Moreover, a great amount of information is also provided for supporting further research.

© 2014, Springer Science+Business Media New York.Mullite is an aluminosilicate widely used as a structural material for high temperature applications. This paper studies the effect of the gelation temperature on the synthesis of two mullite precursors: polymeric and colloidal silica, using both in fully-hydrolyzed silica sol, derived from sodium silicate. The gels were synthesized using aqueous silicic acid and aluminum nitrate. Ethylene glycol was added into polymeric gels. Two gelation temperatures were used: 80 and 100 °C. In the polymeric precursor, the increasing of the gelation temperature caused an increase in the silica incorporation inside the mullite crystalline lattice at 1,000 °C, and it also generated an increase in the reaction extent at all calcination temperatures. In the colloidal precursors, these effects were more intense than in the polymeric precursors in terms of yield. Colloidal samples calcined at 1,250 °C crystallized cristobalite and alpha alumina in addition to mullite when they were previously gelled at 80 °C. On the other hand, the same sample gelled at 100 °C led to only crystallized mullite. The reaction extent increased by more than 20 % for colloidal samples gelled at 100 °C compared to colloidal samples gelled at 80 °C (calcined at 1,250 °C). This increase was due to the almost total incorporation of alumina and silica in the crystalline lattice of mullite.

Tannin-formaldehyde cryogels (TFC) were synthesized by sol-gel polycondensation of low molecular weight and highly reactive modified tannin with formaldehyde using HCl as a catalyst. Carbon cryogels (CC) were obtained by the TFC pyrolysis at an inert atmosphere at 800 C. Pyrolysis caused significant changes in the physical and chemical properties of the material. The pyrolysis induced the decomposition of acid superficial groups and the development of basic ones. Pyrolysis also provoked significant change in the pore volume, forming a great amount of micropores. TFC and CC showed amorphous and turbostratic structures, respectively. Unpurified samples had inorganic impurities in their compositions. © 2013 Springer Science+Business Media New York.

In this study, activated carbon based on the waste macadamia nut shells (MAC) was investigated for potential use as an adsorbent for phenol removal. The pseudo second-order kinetic model best described the adsorption process. The extent of the phenol adsorption was affected by the pH solution and the adsorbent dosage. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 341 mg g-1. The calculated thermodynamic parameters suggested that the phenol adsorption onto MAC was physisorptive, spontaneous and exothermic in nature. Phenol desorption from loaded adsorbent was achieved by using 0.1 mol L-1 NaOH, ethanol (100 %) and deionized water. © 2012 Springer Science+Business Media New York.

Carbon nanotubes (CNTs) were annealed at high temperature under vacuum, followed by a chemical treatment using acids and ethylenediamine. The presence of acid and amine chemical groups on CNT surface was confirmed by infrared spectra. The amount of iron remaining in the CNTs after the treatments was evaluated by thermogravimetry and by energy dispersion spectroscopy. The crystalline property of CNTs was evaluated by Raman spectroscopy, showing that the acid treatment performed after the thermal treatment did not damage the nanotubes walls. Micrographs showed that the most dispersed CNTs were obtained after the amine functionalization step. The curing process of the neat resin and composites was studied by Raman and Luminescence spectroscopies and both techniques showed similar results. The presence of CNTs, functionalized or not, increased the cure degree of the epoxy resin when the same cure time was used in the comparison. Nanocomposites synthesized with annealed CNT and acid-treated CNT had cure rates considerably higher at the beginning of the reaction. The difference in the cure rate was explained by means of the sample's homogeneity and the presence of chemical groups. Copyright © 2012 Wiley Periodicals, Inc.

Mullite is an excellent structural material due to its high temperature stability, high electrical insulation capabilities and creep resistance. This material has a number of technological applications, such as rocket nozzles used in the aerospace industry. In this work, mullite was obtained by sol-gel process, using silicic sol, aluminum nitrate and ethylene glycol, besides the following volume ratios of silica sol dispersion to ethylene glycol: 1/0; 1/1; 1/2; and 1/3. After drying, the samples were thermal treated at temperatures of 1,000; 1,100; 1,200 and 1,250°C. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and specific surface area (Bruner-Emmett-Teller - BET). SEM showed that mullite particles are fine and nearly equiaxed. The sample without ethylene glycol showed 3/2 mullite after heat treatment at 1,250°C. The sample with intermediate ethylene glycol concentration presented two crystallization processes: the first at 1,000°C forming mullite and spinel phases, and the second at 1,250°C forming only 3/2 mullite. However, the sample with the highest ethylene glycol concentration crystallized directly to mullite at 1,000°C with the highest yield. There is a strong dependence on the specific surface area with temperature. The Rietveld refinement showed that the a cell lattice of mullite and the Al/Si molar ratio in the mullite formula depend on the ethylene glycol presence and on the calcination temperature. The lattice parameters b and c are not dependent on the alumina content, but the parameter a increases with the increase in the alumina content. Samples prepared with higher ethylene glycol concentrations reached higher mullite yields at lower temperatures.

Carbon xerogel (CX) was used for phenol adsorption from aqueous solution. CX was synthesized by sol-gel polycondensation of resorcinol with formaldehyde using sodium carbonate (Na 2CO 3) as catalyst. Then, it was dried by convective drying technique and pyrolyzed under inert atmosphere. Phenol adsorption kinetics was very fast, what was attributed to the presence of open pore structure. The kinetic studies showed that the adsorption process could be fitted to a pseudo-second-order model and the particle diffusion process is the rate-limiting step of the adsorption. The phenol removal was maximum and unaffected by pH changes when the initial pH of the phenol solution was in the range of 3-8. The optimum adsorbent dose obtained for phenol adsorption onto CX was 0.075 g/50 cm 3 solution. The Langmuir model described the adsorption process better than the Freundlich isotherm model and the monolayer adsorption capacity is 32 mg g -1. Among the desorbing solutions used in this study, the most efficient desorbent was EtOH (100 %) which released about 87 % of phenol bound with the CX. © Springer Science+Business Media, LLC 2012.

Synthetic ZrO2 · nH2O was used for phosphate removal from aqueous solution. The optimum adsorbent dose obtained for phosphate adsorption on to hydrous zirconium oxide was 0.1 g. The kinetic process was described very well by a pseudo-second-order rate model. The phosphate adsorption tended to increase with the decrease in pH. The adsorption capacity increased from 61 to 66 mg g-1 when the temperature was increased from 298 to 338 K. A phosphate desorption of approximately 74% was obtained using water at pH 12. © 2012 Taylor & Francis.

Mullite is one of the most important aluminosilicate due to its unique thermal properties. In this work, mullite was obtained by sol-gel process at low temperature using sodium metasilicate, water, aluminum nitrate and ethylene glycol. The samples were prepared with a volume ratio of ethylene glycol/water equal to 0/1, 1/1, 2/1 and 3/1. The ethylene glycol effect on mullite crystallization was studied by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). The sample prepared without ethylene glycol, the less homogeneous one, formed amorphous silica, spinel-phase and α-alumina at 1000. °C, and then crystallized mullite at 1200. °C, with an alumina molar fraction of 0.58. The other samples formed amorphous silica at 900. °C and crystallized mullite as the only crystalline phase at 1000. °C. However, the alumina content in mullite formula depends on the thermal treatment, reaching 0.58 at 1250. °C. © 2011 Elsevier Ltd.

Cd2+ is a highly toxic heavy metallic ion, which is found in mineral rocks and contaminated areas. Several different methods have been developed for the Cd2+ removal from contaminated water. Low cost adsorbents have been recommended as cadmium ions removers for aqueous effluents, replacing conventional materials of higher cost. In this review, an extensive list of the low cost adsorbent materials, such as agro-industrial wastes and biosorbents were compiled. The potential of various low cost adsorbents, for removing Cd2+ from water systems, was analyzed. ©2012 Nova Science Publishers, Inc. All rights reserved.

Mullite is an excellent structural material due to its physical and mechanical properties. In this study, mullite was obtained by the sol-gel process, using silicic acid, aluminum nitrate, and urea. The urea effect was studied by evaluating samples obtained from urea/Al3+ ratio equal to 0, 1, and 3. The kinetic study was conducted using the isoconversional, non-isothermal, Flynn-Wall- Ozawa method. The sample prepared without urea, which is the least homogeneous one, formed spinel and α-alumina at 1150 °C, and Al-poor mullite together with α-alumina, at 1200 °C. The Al-poor mullite crystallization process from this sample showed the lowest yield. The sample prepared with urea/Al3+ ratio equal to 1, which has an intermediate behavior, formed spinel at 1100 °C, Al-poor mullite at 1150 °C, and α-alumina together with Al-poor mullite at 1250 °C. However, the sample prepared with urea/Al3+ ratio equal to 3, the most homogeneous, formed spinel and Al-rich mullite at 1100 °C. This sample formed Al-poor mullite at 1200 °C with the highest yield. Moreover, the sample synthesized without urea showed a higher porosity and a greater amount of hexacoordinated aluminum at 350 °C. All samples showed the same kinetic model, Sesták and Berggren (SB) for Al-poor mullite crystallization. The samples synthesized with urea crystallized mullite through the same kinetic parameters and constant values of the activation energy, but the sample prepared without urea followed different kinetic parameters and values of activation energy which changed over the course of the crystallization. © Springer Science+Business Media, LLC 2011.

Activated carbon derived from avocado kernels (AAC) was evaluated for its ability to remove phenol. The Brunauer-Emmett-Teller (BET) surface area of the AAC was 206m2g-1 and the total pore volume was 0.100cm3g-1. The kinetic of the adsorption process was described by a pseudo-second-order rate model. The maximum uptake was obtained at pH values between 4 and 8.5. The optimum adsorbent dose obtained was 0.1g. The thermodynamic parameters exhibited the feasibility and the spontaneous nature of the adsorption process. Adsorption isotherms showed that the interaction of phenol with AAC surface was described by a localized monolayer adsorption. The adsorption mechanism was discussed based on experimental results, and the π-π interactions were considered to be an important parameter in the adsorption process. The adsorbent regeneration was investigated using several types of desorbing agents, but no agent show any promising result. The results showed that the prepared activated carbon was an effective adsorbent for phenol removal from aqueous solution. © 2011 Elsevier B.V.

This article investigates the application of the luminescence spectroscopy technique in steady-state conditions to study the glass fiber-epoxy F155 prepreg. The study was conducted by comparing the results obtained from the intrinsic fluorescence with the data obtained by application of Fourier Transform Near Infrared spectroscopy (FT-NIR) and photoacoustic spectroscopy in the medium infrared spectroscopy (PAS) to the same material. Extrinsic fluorescence of 9-anthroic acid (9-AA) was also used. Infrared spectroscopy with Fourier transform the medium region (FT-IR) was also used to characterize the epoxy resin. Prepregs containing 9-AA or not were heat treated at 121 °C (F-155) for 360 min at a 2 °C/min heating rate. The results obtained by both methods indicated that the cross-linking reaction can be monitored by analyzing the spectrometric changes of the emission bands of the prepreg and 9-AA. The intrinsic emission at 368 nm was used to calculate the conversion degree. The photophysical behavior of 9-AA probe indicated a reduction of free volume of the polymeric matrix with curing process. © Springer Science+Business Media, LLC 2010.

The kinetic of mullite crystallization from sol-gel method, with different water content, was investigated under non-isothermal conditions using DTA. The sols were obtained from Al(NO3)3.9H2O (ANN) and Si(OC2H5)4 (TEOS) mixtures by varying the water-alcohol content of the system. The crystalline phase changes were verified by X-ray diffraction (XRD). For a sample prepared using ethanol-based alkoxide solution (M0), only Al-poor mullite (p-mullite) crystallizes at 1000 °C; for the one synthesized with low water concentration (M6) Al-rich mullite (r-mullite) and spinel crystallize together; and for a sample prepared using a water-based alkoxide solution only spinel is formed. Thus, the variation of water contents during the synthesis caused great variations in the course of mullitization process. The average value of the apparent activation energy determined for p-mullite, r-mullite and spinel phase crystallization were found to be E = (899 ± 61) kJ mol-1, E = (1015 ± 272) kJ mol-1 and E = (980 ± 196) kJ mol-1, respectively. These results showed that sample M(0) was a monophasic gel, where aluminum and silicon atoms are mixed at a molecular level while sample M(100) was a diphasic gel, where silicon and aluminum atoms are distributed in a nanometric level. The fast reaction between TEOS and water molecules is responsible for this great difference in the sample's homogeneity. The kinetic model of the crystallization process was determined using Malek's procedure. It was established that the crystallization of p-mullite, r-mullite and spinel phase can be described by Šesták-Berggren autocatalytic model. © 2010 Elsevier B.V. All rights reserved.

Due to its chemical, physical and mechanical properties, mullite has been used in equipments subjected to extreme mechanical strain and high temperatures. This paper reports the study of the effect of urea on the mullite crystallization, synthesized through the colloidal and polymeric sol-gel processes, using XRD and FT-IR. The colloidal precursors were obtained from silicic acid, water, aluminum nitrate nonahydrate (ANN) and urea. The polymeric precursors were obtained from TEOS, ethanol, ANN and urea. For both methods, urea was used in the molar ratio urea/Al3+ equal to 0/1, 1/1 and 3/1. The urea addition in colloidal gels led to materials with higher concentrations of orthorhombic mullite, besides they crystallized mullite at lower temperatures (positive effect). However, a negative effect was observed when urea was added to polymeric gels. In addition, the amount of crystallized mullite increased with the urea content in the colloidal gels. The colloidal sample with the highest urea content proved to form mullite at a lower temperature. Moreover, this sample did not segregate the α-alumina phase. The positive effect of urea in the colloidal gels is related to its participation in the hydrolysis and condensation steps of aluminum and silicon, avoiding the extensive phase segregation of silica and alumina. The negative effect observed in the polymeric samples may have occurred due to a competition between the silanol, the ANN and urea by water molecules. The only water molecules that are present in the polymeric gel are those that are part of the ANN. © 2010 Elsevier B.V. All rights reserved.

In this study, we investigated the application of the luminescence spectroscopy technique in steady-state conditions to study glass fiber-epoxy F161 prepregs. We conducted this study by comparing the results obtained from the intrinsic fluorescence with Fourier transform near infrared spectroscopy. The extrinsic fluorescence of 9-anthroic acid (9-AA) was also used. Fourier transform infrared spectroscopy was also used to characterize the epoxide resin. The prepregs containing 9-AA and those that did not were heat-treated at 177°C (F161) for 1100 min at a 2°C/min heating rate. The results obtained by both methods indicated that the crosslinking reaction could be monitored by analysis of the spectral changes of the emission bands of the prepreg and 9-AA. The intrinsic emission at 320 nm was attributed to the fluorophore group containing the epoxy ring and was used to calculate the conversion degree. The photophysical behavior of the 9-AA probe indicated a reduction of free volume of the polymeric matrix with curing process. © 2010 Wiley Periodicals, Inc.

The sol-gel method for the mullite synthesis is reviewed, with particular emphasis on the characterization of monophasic and diphasic gels at low, intermediate and high temperatures and the factors that influence the hydrolysis and condensation rate of the sol-gel process, which in turn determine the properties of the final material. A wide range of studies about mullite precursors synthesized via sol-gel is discussed here. © 2010 Springer Science+Business Media, LLC.

We developed a simple pair-additive Lennard-Jones plus Coulomb potential for molecular simulations of the trivalent cation Al3+ in water which accounts reasonably well for the behavior of aluminum aqueous solutions. The model predicts an octahedral first hydration shell containing 6 water molecules and a trigonal second shell with 12 molecules on average, in good agreement with the available experimentally determined structure. The peak positions of the cation-oxygen radial distribution function are only slightly compressed compared to the x-ray structure, the hydration enthalpy is 10% too low, and the cation self-diffusion coefficient and the single-particle second rank reorientational time are in excellent agreement with inelastic neutron scattering and NMR spectroscopy data, respectively. The model also captures the essential vibrational features of the hydrated [Al (H2 O) 6] 3+ complex. It predicts the main O-Al-O bending mode frequency to within ∼5%, but significantly overestimates the frequency of the totally symmetric Al-O stretching mode. Overall, the accuracy of the proposed model is as good as the best available classical potentials, if not better in some aspects, with a much simpler functional form, which makes it an attractive alternative for computer simulations of Al3+ in more complex aqueous and biomolecular systems. © 2010 American Institute of Physics.

The influence of starch content and sintering temperature on the preparation of alumina bodies were studied. The process was water-based and cassava starch was used as consolidator, binder and pore former. Colloidal suspensions were prepared with three different starch concentrations and the ideal dispersant content and gel point were determined by rheological analysis. The wet samples were demolded after consolidation in silicone mold at 60 °C for 2 h. After the drying step the samples were sintered at 1200, 1400 and 1600 °C, showing open porosities between 13 and 55%, depending on the starch content on the precursor suspensions and sintering temperature. The pore structures were analyzed by SEM (scanning electron microscopy) and Hg porosimetry. Basically, the pore structures are dominated by large spherically shaped pores left by the starch particles, which are connected through small pore channels. © 2008 Elsevier Ltd. All rights reserved.

This paper describes the preparation of a reticulated ceramic that combines the morphology of vegetal sponge with ceramic properties, such as thermal stability, resistance to chemical attack, elevated porous degree and reticulation. In this method sponge samples are dipped into a colloidal suspension of 50% clay, 35% feldspar and 15% sand (w/w), followed by drying and heat treatment at 1175 °C for 120 min. Thermogravimetric analysis (TGA) of the vegetal sponge showed that the organic material is completely eliminated at temperatures around 515 °C. X-ray diffraction (XRD) analysis of the reticulated ceramic indicated the presence of mullite and cordierite. Scanning electron microscopy (SEM) of the reticulated ceramic showed the presence of two groups of porous ceramics, one in the range of 5-10 μm which was formed along the wall of the filaments, and another formed as a negative structure of the sponge filaments, measuring approximately 300 μm of diameter. © 2008 Elsevier Ltd and Techna Group S.r.l.

Diphasic cordierite gels were prepared from colloidal silica, aluminum and magnesium nitrates and citric acid. The mechanism of xerogel decomposition was studied by infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The thermal decomposition of the xerogel forms a solid mixture of MgO, Al 2O3 and SiO2 at around 250°C. Cordierite crystallization was studied by X-ray diffraction (XRD) and differential thermal analysis (DTA). Xerogels were initially thermally treated, and this sample crystallized to μ-cordierite at 850°C, at 900°C α-cordierite crystallizes and at 1150°C α-cordierite is the major phase and μ-cordierite is totally consumed. The apparent activation energy for cordierite crystallization process was determined based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, Ligero methods and the Arrhenius law for dependence of activation energy with temperature. The apparent activation energy was (466.8 ± 34.3) kJ/mol, the exponent of Avrami was (1.9 ± 0.2) and the frequency factor was (1.55 × 1020) s-1. The Avrami value indicates a nucleation controlled process, which can be a consequence of the high xerogel homogeneity, a consequence of the early and simultaneous formation of the MgO, Al2O3 and SiO2 mixture. © 2008 Springer Science+Business Media, LLC.

The crystallization kinetics of ceramics composed by Bi2O3-ZnO-Nb2O5 (BZN) was studied using non-isothermal method. The BZN samples were prepared by the polymeric precursors method. Phase evolution was evaluated by X ray diffraction and the thermal events were evaluated by differential scanning calorimetry (DSC). The crystallization of BZN occurs from 500 to 700 °C, which corresponds to a secondary event in DSC curves. The principal exothermic event in these curves is related to the decomposition of organic material and was isolated from the crystallization peak by deconvolution into two Gaussian curves. Those related to crystallization processes were evaluated in terms of crystallized fraction. Kinetic parameters were determined from Ligero (E = 242 ± 7) kJ.mol-1 and Kissinger (E = 241 ± 24) kJ.mol-1 methodologies and they are very close. The activation energy Ea = (241 ± 24) kJ.mol-1 and (242 ± 7) kJ.mol-1 (by the Kissinger and Ligero methodology, respectively), frequency factor k0 =1013.s-1 and exponent of Avrami n = (1.3 ± 0.1) were determined. The n value indicates that the crystallization is diffusion controlled, with decreasing nucleation rate. Scanning electronic microscopy showed the presence of nanoparticulated powder.

Mullite crystallization kinetics was studied using a non-isothermal method. The mullite crystallization parameters obtained from seeded gels were compared with those obtained from non-seeded gels. The phase evolution was studied by X-ray diffraction (XRD) and the thermal events associated to heating treatment by differential thermal analysis (DTA). The crystallization kinetic parameters were obtained using the methodology developed by R.A. Ligero, which is based on Johnson-Mehl-Avrami (JMA) kinetic model. The Avrami exponent (1.9), the apparent activation energy (980 kJ/mol) and the rate constant (3.68 × 10 30 s-1) were determined by this model, for both seeded and non-seeded processes, resulting in similar values for each parameter. Based on the apparent activation energy and rate constant values, one should conclude that mullite crystallization is not controlled by nucleation. On the other hand, Avrami exponent ∼2 is an indicative that the process is controlled by the nucleation step. These controversies are discussed in this paper, based on experimental procedure, model limitation and literature information. © 2005 Elsevier B.V. All rights reserved.

PZT powders were synthesized by a chemical method using the conventional Pechini method and a urea-modified Pechini method, where the smooth pH increase, by the decomposition of urea, allows a better control of the pH. The FTIR spectra revealed that the precursor gel in conventional Pechini method is formed by a mixture of unidentade- and bridged-bonded complexes between the metallic cations and the citric acid. On the other hand, the precursor gel in the modified Pechini method is formed essentially by unidentade complexes. The modified Pechini method leads to homogeneous sub-micrometric spherical particles of 0.1 μm and a 7.4 m2g-1surface area. © 2004 Elsevier Ltd. All rights reserved.

Cubic bismuth zinc niobate pyrochlore (base composition (Bi 1.5Zn 0.5)(Zn 0.5Nb 1.5)O 7) powders were successfully prepared by a chemical method. The formation mechanism of the pyrochlore phase was investigated by TG-DSC, FT-IR, Raman, and X-ray diffraction (XRD). The optical bandgap for the powders treated at temperatures ranging from 500 to 700°C is 3.0-3.1 eV, indicating low crystallization temperature for the pyrochlore phase. No detectable intermediary phases as BiNbO 4 or a pseudo-orthorhombic pyrochlore were observed at any time and the cubic-BZN phase was already formed after thermal treatment at temperatures as low as 500°C. The phase formation study reveals that a well-crystallized single-phased nanopowder is obtained after calcination at 700°C, indicating that the chemical synthesis conferred a higher chemical homogeneity and reactivity on the powder, modifying the crystallization mechanism. XRD results for cubic-BZN powders treated at 400, 500, 600 and 700°C. Zoomed 2θ range (25-35°) including BiNbO 4 and orthorhombic-BZN powders, also treated at 700°C. © 2004 Elsevier Inc. All rights reserved.

AA2024-T3-aluminum alloy surfaces were coated using non-chromate and chromate conversion coatings. All coatings were painted with the 10P4-2-primer epoxy resin. Independent on the film formation process, films passed on the substrate/conversion coating wet tape adhesion test. However, only the chromate conversion coating passed on the conversion coating/primer epoxy resin adhesion test. Electrochemical corrosion measurements showed that non-chromate conversion coated surfaces present lower corrosion current density, bigger polarization resistance and less negative corrosion potential than chromate conversion coated surfaces. © 2003 Elsevier B.V. All rights reserved.

The photoluminescence properties of the Eu3+ ion doped into α-cordierite were studied based on the excitation and emission spectra and lifetime measurements. These samples were prepared by the sol-gel method and calcined by heating the xerogel at different temperatures: 873, 1133, 1223 and 1473K. X-ray diffraction patterns were used to characterize the luminescent material. The 5D0→7F0 transition of the samples exhibits only one broad peak arising from the inhomogeneous linewidth of the amorphous phase, except for the ceramic material obtained at 1473K that presents two peaks. Also, in the latter case the luminescence decay lifetime exhibits a bi-exponential fit when excited at 280nm, corroborating that the Eu3+ ion exists in two sites of symmetry. The experimental intensity parameter Ω2 (10.0×10-20cm2) indicates a moderately polarizable chemical environment around the Eu3+ ion. The emission spectra of the Mg2Al4Si5O18:Eu3+ samples calcined at 873, 1133 and 1223K also presented inhomogeneous profiles for the 5D0→7FJ transitions suggesting disorder of the material. On the other hand, the sample calcined at 1473K shows narrow bands indicating the crystalline form. The emission quantum efficiency (η) of the α-cordierite system is also discussed. © 2003 Elsevier Science (USA). All rights reserved.

α-Cordierite (Mg2Al4Si5O18) was obtained, by a sol-gel aqueous route, from aqueous solutions containing Si:Al:Mg in a molar ratio equal to 5:2.15:2.25 and citric (Lcit samples), or oxalic (Lox samples), or tartaric acid (Ltart samples), in such amount that the molar ratio organic acid/aluminum ion was equal to 1. The effect of each organic chelating upon the quantity of crystallized α-cordierite was investigated. The influence of a heating treatment time, to eliminate the organic material from the xerogels containing citric acid, on the quantity of α-cordierite formed was also investigated. Thermal gravimetric analysis was used to investigate the thermal decomposition process of each sample. Based on thermal gravimetric results we suggest that the thermal decomposition of the Lcit, Lox and Ltart xerogels takes place in three major steps and little difference was observed for each case. X-ray diffraction (XRD) measurements were carried out to determine the crystalline phases present after heat treatment of each sample at 1000 °C. X-ray diffraction results showed that the sequence for the quantity of crystallized α-cordierite from each sample is: Lcit > Lox > Ltart. XRD results also indicate that the quantity of crystallized α-cordierite from samples containing citric acid (Lcit) increased with the time of the heating treatment used to eliminate the organic material. © 2002 Elsevier Science B.V. All rights reserved.

The kinetics parameters of orthorhombic mullite (o-mullite) crystallization from a diphasic gel were measured using a non-isothermal differential thermal analysis method. The diphasic gel was obtained from aqueous solutions containing silic acid and aluminum nitrate, in amount to keep the silicon and aluminum molar present in mullite (Si:Al equals 1:3). Urea in the molar ratio Al:urea equal to 1:3 was used as drying control chemical agent. The phase changes were verified using dynamic X-ray diffraction. The mullite morphology was analyzed by scanning electron microscopy (SEM). It was observed that mullite might be formed from the amorphous materials or from the spinel phase, since it was not observed the formation of tetragonal mullite and spinel phase disappeared before o-mullite crystallization. The apparent activation energy for the o-mullite crystallization was determined by a non-isothermal method based on Johnson-Mehl-Avrami-Kolmogorov (JMAK) and Arrhenius law for the chemical rate dependence on temperature. The apparent activation energy was equal to (730 ± 150) kJ mol-1, the Avrami's exponent was equal to 1.6 ± 0.1, the frequency factor was (1.8 ± 0.1) × 1021 s-1, and the ratio t0.75/t0.25 was equal to (1.9 ± 0.1). The SEM analysis showed that mullite growth is plate-like which agreed with JMAK model. © 2002 Elsevier Science B.V. All rights reserved.

Ti6Al4 V substrates were coated by diamond-like-carbon (DLC) films of various thickness (0 to 285 nm). The DLC films were deposited by an electrical discharge using a magnetron cathode and a 99.999 w/o graphite target in an argon/hydrogen atmosphere. The DLC films were characterized by Roman spectroscopy and optical microscopy. It was found that thick films present higher size of micro crystallites and higher order degree of the graphite crystalline reticule than thin films. After the corrosion tests, the order degree of the graphite crystalline reticule of thick films did not suffer significant variation. Thicker films present better adhesion on the Ti6Al4V alloy than thinner films. Potentiodynamic polarization of uncoated and DLC coated Ti6Al4V alloy was carried out in 0.5 mol L-1 NaCl aqueous solution, pH 5.9. The corrosion potential of surfaces coated with DLC film shifts to less negative values and the polarization resistance increases as the thickness of the DLC film increases.

Mullite was synthesized by a sol-gel process employing aqueous solution of silicic acid, aluminum nitrate and urea in high concentration (9 mol/l). t-Mullite crystallizes at temperatures around 1050°C, the fraction of the spinel phase formed was small and the apparent activation energy obtained by fitting the XRD results with the JMAK model was (770±4) kJ mol-1. Monte Carlo simulations were performed to investigate the site-site correlation function for ion (I)-urea (Ou) and ion (I)-water (Ow) interactions, g(rlOu) and g(rlOw,), respectively. The integration of these two correlation functions indicated the presence of four water and two urea molecules in the first Al3+ coordination shell. The 27Al nuclear magnetic resonance (NMR) results also indicate the presence of species like [Al(H2O)4(urea)2]3+. © 2001 Elsevier Science Ltd. All rights reserved.

Cordierite was synthesized by a simple aqueous sol-gel route. Citric acid action as a chelant for the Al3+ ion, and for controlling phase segregation during the drying and initial thermal treatment of the gel, results in an amorphous precursor that crystallizes to μ-cordierite and spinel. The changes in the ratios of the crystalline phases, formed during dry gel calcination at 1000°C for 12 h were dependent on the ratio (L/M) of citric acid/Al3+ (mol/mol). For L/M3 and L/M5 samples, the ratio between the amount of μ-cordierite phase and the amount of spinel phase was the same, while, for the sample L/M1, the amount of μ-cordierite was larger than that found in the other samples. © 2000 Elsevier Science B.V. All rights reserved.

SiO2 coatings were deposited on aluminum (98% Al) surfaces by dip-coating in silicic acid aqueous solutions containing urea as dry chemical control agent (DCCA). These films are of special interest for protection of metals against oxidation and acid corrosion at elevated temperature. In this work, we investigate the effect of two different treatments of aluminum surfaces on the adhesivity of the silica films. The optimum urea/silanol ratio in the precursor gel solution and the number of dips were also investigated. The corrosion protection afforded by the silica film was determined by anodic polarization of the coated surfaces in 0.5 mol/l sodium chloride aqueous solution exposed to air at room temperature. The best performance was obtained for surfaces anodized prior to dip coating, and for urea/silanol ratio and number of dips equal to, respectively, 7 and 5. © 2000 Elsevier Science B.V. All rights reserved.

Multicomponent ceramics are mainly synthesized by conventional solid-state reaction route and sol-gel routes. In the sol-gel route, colloidal or polymeric gel are envolved. In this work, some principles of the chemistry of theses routes are discused and it is ilustrated a variety of strategies for obtaining a homogeneous multicomponent precursors.

The mechanism of photoelectrochemical porous silicon formation in fluoride solutions under laser illumination and dark conditions has been investigated. Experiments were performed in a PTFE cell with a plastic window to allow the laser path to be horizontal and the silicon electrode to be in a vertical position inside the cell. Dark and illuminated anodic and cathodic current-voltage (I-V) curves were both measured in real time by chopping the laser beam. N-type wafers of resistivities 0.001 to 22 Ω · cm have been investigated for various conditions of illumination intensity and polarization. We focused our attention on relatively low illumination intensities ∼ 10-5-10-8 W/mm2 and high HF concentration. By measuring the dissolution rate and the photogenerated current we estimated that the main reaction path requires two holes for each Si atom as: S i + 2 H F + 2 h+ over(→, h v) S i F2 + 2 H+. The utilization of this technique for direct projection printing of porous Si images of 10 μm resolution was demonstrated. © 1995 Elsevier Science B.V. All rights reserved.

© 1990 SPIE. All rights reserved.We have studied the mechanisms of the copper metallization on P-silicon wafers immersed in CuCN solutions, using photoelectrochemical measurements and optical /electron microscopy. In this process the electroplating is enhanced by the minority carries in illuminated areas of the silicon cathode. The photo -selective deposition with high resolution have been obtained only on low doped Psilicon. The kinectics of the film growth is strongly dependent on the film thickness, and two mechanisms have been identified. Patterns of resolution of ∼4 microns can be realized only with thickness bellow ∼20 nm. Further investigation is needed for prevent the oxidation of the as-deposited film.

Summary form only given, as follows. The mechanisms responsible for latent image formation in lithographic high-resolution plates of Ag salts were studied using laboratory experiments with coherent laser absorption. An exposure model for optical density evalution was derived for feature-dependent analysis. The results of statistical Gaussian spot sensibilization show a quadratic dependence with impinging intensity before the initiation of the saturation process. To extend the analysis to the dynamic scanning condition 2-D modeling was made in an attempt to compare it with the printing of micrometer-line gratings. The general solution is a kinetic expression which shows an erfc dependence in the direction of the movement. The conditions for edge sharpening and feature dependence were identified. By appropriate selection of the band gap of the salts and the laser wavelength, the occurrence of n-photon absorption can be predicted, and unresolved lines can be printed without the common halo of linear laser lithography.