Hexagonal-shaped tin glycolate particles: A preliminary study of their suitability as li-ion insertion electrodes

Tin glycolate particles were prepared by a simple, one-step, polyol-mediated synthesis in air in which tin oxalate precursor was added to ethylene glycol and heated at reflux. Hexagonal-shaped, micron-sized tin glycolate particles were formed when the solution had cooled. A series of tin oxides was produced by calcination of the synthesized tin glycolate at 600-800 degrees C. It was revealed that the micron-sized, hexagonal-shaped tin glycolate now consisted of nanosized tin-based particles (80-120 nm), encapsulated within a tin glycolate shell. XRD, TGA, and FT-IR measurements were conducted to account for the three-dimensional growth of the tin glycolate particles. When applied as an anode material for Li-ion batteries, the synthesized tin glycolate particles showed good electro-chemical reactivity in Li-ion insertion/ deinsertion, retaining a specific capacity of 416mAhg(-1) beyond 50cycles. Ibis performance was significantly better than those of all the other tin oxides nanoparticles (< 160mAhg(-1)) obtained after heat treatment in air. We strongly believe that the buffering of the volume expansion by the glycolate upon Li-Sn alloying is the main factor for the improved cycling of the electrode.

Bioactive coating on titanium implants modified by Nd:YVO4 laser

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Metallurgical evaluation of a copper-based alloy for dental castings.

The present study was designed to evaluate the metallurgical properties of an experimental, low-cost copper-zinc-aluminum-nickel alloy for dental castings. Some specimens were subjected to heat treatment after induction casting. The extent of corrosion was determined by measuring weight loss of specimens stored in a sodium sulfite solution. In the as-cast specimens, tests demonstrated the presence of three phases: the first consisted of copper-zinc-aluminum, the second was similar but lower in copper and aluminum, and the third consisted of an intermetallic compound of manganese-nickel-phosphorus. After heat treatment, the first phase remained relatively constant, the second was converted to Cu3Al, and the third increased in volume. The weight loss from the as-cast specimens was eight times that of the heat-treated specimens. It was concluded that the heat treatment substantially changed the microstructure and improved the corrosion resistance of the experimental alloy.

Hydrothermal treatment of gadolinium oxide in presence of silica

Hydrothermal and solvothermal (isopropanol) treatments of gadolinium oxide and silica were investigated under different pressure and temperature conditions. Products were examined by infrared vibrational spectroscopy (IR), x-ray powder diffraction (XRD) and thermal analysis (DTA, TG). Hexagonal gadolinium hydroxide was obtained in hydrothermal conditions, even in presence of silica, while no change was observed from isopropanolic medium treatment. Hydrothermally treated samples are more reactive as precursors for solid state reactions in inorganic synthesis.

Preparation and characterization of SrBi2Nb2O9 thin films made by polymeric precursors

A polymeric precursor solution was employed in preparing SrBi2Nb2O9 (SBN) powder and thin films dip coated onto Si(100) substrate. XRD results show that the SBN perovskite phase forms at temperatures as low as 600°C through an intermediate fluorite phase. This fluorite phase is observed for samples heat-treated at temperatures of 400 and 500°C. After heat treatment at temperatures ranging from 300 to 800°C, thin films were shown to be crack free. Grazing incident angle XRD characterization shows the occurrence of the fluorite intermediate phase for films also. The thickness of films, measured by MEV, was in the order of 80-100 nm.

Monolithic diphasic gels of mullite by sol-gel process under ultrasound stimulation

Diphasic gel in the mullite composition was prepared from a colloidal sol of boehmite mixed with a hydrolyzed tetraethoxisilane (TEOS) solution. The boehmite sol was obtained by peptization of a poorly crystallized or very small mean crystallite size (∼34 Å) precipitate, resulting from the reaction between solutions of aluminum sulfate and sodium hydroxide. Ultrasound was utilized in the processes of the TEOS hydrolysis and the boehmite peptization, and also for complete homogenization of the mixture to gel. The wet gel is almost clear and monolithic. The gel transparency is lost on drying, when syneresis has ended, so that the interlinked pore structure starts to empty and is recovered upon water re-absorption. Cracking closely accompanies this critical drying process. Differential thermal analysis (DTA) and X-ray diffraction (XRD) show that the solid structure of the gel is composed of an amorphous silica phase, as a matrix, and a colloidal sized crystalline phase of boehmite. Upon heat treatment, the boehmite phase within the gel closely follows the same transition sequence as in pure alumina shifted towards higher temperatures. Orthorhombic mullite formation was detected at 1300°C. © 1998 Elsevier Science B.V. All rights reserved.

Structural and surface morphology characterizations of oriented LiNbO3 thin films grown by polymeric precursor method

Polymeric precursor solution was used to deposit LiNbO3 thin films by dip coating on sapphire substrates. The effects of processing variables, such as heat treatment conditions and number of deposited layers, on crystallinity and morphology of the final films were investigated. X-ray diffraction patterns show the oriented growth of the films. The rocking curves, obtained around the (006) LiNbO3 peak, revealed that the shape peak and the FWHM value were influenced by the processing variables. According to these parameters, some films presented very homogeneous dense and smooth surfaces, as shown by the SEM and AFM studies.

Preparation and characterization of glass-ceramic materials in the BaO-Li2O-ZrO2-SiO2 system and their dependence on treatment temperatures

The preparation and characterization of transparent glass-ceramics in the composition of 30Li2O:5ZrO2:xBaO:(100-x) SiO2 with x = 0, 5, 10, 15, and 20 mol% are described. Glasses were melted in a platinum crucible at 1100°C for 2 h and then heat-treated at 900°C for 3 h. The characterizations were performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman and infrared spectroscopy, and scanning electron microscopy (SEM). The experimental results indicate that there was a structural change in the glass-ceramics as the BaO concentration in the mixture increased. In the XRD patterns of samples without heat treatment, only the halo was observed. After heat treatment, the appearance of the materials was verified by X-ray diffraction peaks. The reorganization of the amorphous solid was confirmed by Raman and IR spectroscopy along with XPS and SEM, with a more homogeneous phase formation being observed.

Thermal treatment effects on phase transitions in P(VDF-TrFE)

Differential scanning calorimetry (DSC) studies were performed for 60/40 P(VDF-TrFE). The results not only confirm the importance of thermal history but also show that the samples with various configurations in terms of ferroelectric phases can be obtained via thermal treatment.

Effects of thermal treatment on phase transitions and on the mechanical relaxation in poly(vinylidene fluoride)

This work reports on the effects from thermal treatment in poly(vinylidene fluoride), PVDF, obtained with differential scanning calorimetry (DSC) and dynamic thermal analysis (DMA) measurements. It is shown that in successive DMA measurements performed with one sample the α relaxation peak almost disappears while the γ′ peak appears. The α relaxation peak, at ∼100°C in DMA measurements, is attributed to the preferential orientation of chains in the amorphous phase while the γ′ relaxation peak, at ∼50°C, is related to the thermal treatment to which the sample was submitted.

Um estudo sobre a corrosão aquosa de ligas de alumínio 7xxx submetidas a diferentes tratamentos térmicos

This job aim has been to study the aqueous corrosion of the 7xxx heattreatable aluminium alloys, used in the aeronautical industry. The 7010, 7050 and 7475 alloys, have been supplied in the T7 condition and submitted to the annealed and aging thermal treatments of in order to study their behaviours front to corrosion in 5% NaCl pH 6,0, air-saturated and deaerated solutions. The electrochemical study has been accomplished through potential measures in open circuit, potentiodynamic polarisation curves and electrochemical impedance spectroscopy (EIS). The aged alloy resulted to be the most resistant to corrosion and annealed the less resistant ones. In spite of it they have different chemical compositions, in each mean, the alloy with the same thermal treatment has behaved in a similar way. In aerated solution, the process is controlled by oxygen diffusion and in oxygen absence for dissolution through a film. Hardness and mass loss measures, after corrosion test, have supported this research.

Cytotoxicity of denture base resins: Effect of water bath and microwave postpolymerization heat treatments

Purpose: This study compared the effect of two postpolymerization heat treatments on the cytotoxicity of three denture base resins on L929 cells using 3H-thymidine incorporation and MTT assays. Materials and Methods: Sample disks of Lucitone 550, QC 20, and Acron MC resins were fabricated under aseptic conditions and stored in distilled water at 37°C for 48 hours. Specimens were then divided into three groups: (1) heat treated in microwave oven for 3 minutes at 500 W; (2) heat treated in water bath at 55°C for 60 minutes; and (3) no heat treatment. Eluates were prepared by placing three disks into a sterile glass vial with 9 mL of Eagle's medium and incubating at 37°C for 24 hours. The cytotoxic effect from the eluates was evaluated using the 3H-thymidine incorporation and MTT assays, which reflect DNA synthesis levels and cell metabolism, respectively. Results: The components leached from the resins were cytotoxic to L929 cells when 3H- thymidine incorporation assay was employed. In contrast, eluates from all resins revealed noncytotoxic effects as measured by MTT assay. For both MTT assay and 3H-thymidine incorporation, the heat treatments did not decrease the cytotoxicity of the materials tested. Conclusion: Resins were graded by 3H-thymidine incorporation assay as slightly cytotoxic and by MTT assay as noncytotoxic. Cytotoxicity of the denture base materials was not influenced by microwave or water bath heat treatment.

Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)-deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2]. 13C NMR, 1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1. © 2005 NRC Canada.

Effect of disinfectants on the hardness and roughness of reline acrylic resins

Purpose: Potential effects on hardness and roughness of a necessary and effective disinfecting regimen (1% sodium hypocholorite and 4% chlorhexidine) were investigated for two hard chairside reline resins versus a heat-polymerizing denture base acrylic resin. Materials and Methods: Two standard hard chairside reliners (Kooliner and Duraliner II), one heat-treated chairside reliner (Duraliner II +10 minutes in water at 55°C), and one standard denture base material (Lucitone 550) were exposed to two disinfecting solutions (1% sodium hypochlorite; 4% chlorhexidine gluconate), and tested for two surface properties [Vickers hardness number (VHN, kg/mm2); Roughness (Ra, μm)] for different times and conditions (1 hour after production, after 48 hours at 37 ± 2°C in water, after two disinfection cycles, after 7 days in disinfection solutions, after 7 days in water only). For each experimental condition, eight specimens were made from each material. Data were analyzed by analysis of variance followed by Tukey's test, and Student's t-test (p= 0.05). Results: For Kooliner (from 6.2 ± 0.3 to 6.5 ± 0.5 VHN) and Lucitone 550 (from 16.5 ± 0.4 to 18.4 ± 1.7 VHN), no significant changes in hardness were observed either after the disinfection or after 7 days of immersion, regardless of the disinfectant solution used. For Duraliner II (from 4.0 ± 0.1 to 4.2 ± 0.1 VHN), with and without heat treatment, a small but significant increase in hardness was observed for the specimens immersed in the disinfectant solutions for 7 days (from 4.3 ± 0.2 to 4.8 ± 0.5 VHN). All materials showed no significant change in roughness (Kooliner: from 0.13 ± 0.05 to 0.48 ± 0.24 μm; Duraliner II, with and without heat treatment: from 0.15 ± 0.04 to 0.29 ± 0.07 μm; Lucitone 550: from 0.44 ± 0.19 to 0.49 ± 0.15 μm) after disinfection and after storage in water for 7 days. Conclusions: The disinfectant solutions, 1% sodium hypochlorite and 4% chlorhexidine gluconate, caused no apparent damage on hardness and roughness of the materials evaluated. Copyright © 2006 by The American College of Prosthodontists.

Effect of post-polymerization heat treatments on the cytotoxicity of two denture base acrylic resins

Introduction: Most denture base acrylic resins have polymethylmethacrylate in their composition. Several authors have discussed the polymerization process involved in converting monomer into polymer because adequate polymerization is a crucial factor in optimizing the physical properties and biocompatibility of denture base acrylic resins. To ensure the safety of these materials, in vitro cytotoxicity assays have been developed as preliminary screening tests to evaluate material biocompatibility. 3H-thymidine incorporation test, which measures the number of cells synthesizing DNA, is one of the biological assays suggested for cytotoxicity testing. Aim: The purpose of this study was to investigate, using 3H-thymidine incorporation test, the effect of microwave and water-bath post-polymerization heat treatments on the cytotoxicity of two denture base acrylic resins. Materials and Methods: Nine disc-shaped specimens (10 x 1 mm) of each denture base resin (Lucitone 550 and QC 20) were prepared according to the manufacturers' recommendations and stored in distilled water at 37°C for 48 h. The specimens were assigned to 3 groups: 1) post-polymerization in a microwave oven for 3 min at 500 W; 2) post-polymerization in water-bath at 55°C for 60 min; and 3) without post-polymerization. For preparation of eluates, 3 discs were placed into a sterile glass vial with 9 mL of Eagle's medium and incubated at 37°C for 24 h. The cytotoxic effect of the eluates was evaluated by 3H-thymidine incorporation. Results: The results showed that the components leached from the resins were cytotoxic to L929 cells, except for the specimens heat treated in water bath (p<0.05). Compared to the group with no heat treatment, water-bath decreased the cytotoxicity of the denture base acrylic resins. Conclusion: The in vitro cytotoxicity of the tested denture base materials was not influenced by microwave post-polymerization heat treatment.