940 resultados para Ag addition
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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This work consists of preparation and characterization of glasses containing transition noble metals and the study of optical properties of such materials. The glasses were prepared by quenching of the glass melt followed by heat treatment and polishing of the monoliths. The structural characterization of glasses was made using differential thermal analysis, X-ray, Raman and infrared spectroscopies, while the optical properties were studied by UV-Vis and M-Lines spectroscopies. Preliminary results have shown that the color of the glasses is dependent on both concentration of silver and the melting temperature of the melt. Controlled heat treatments have been used to induce the crystallization of Ag nanoparticles within the glass. The study of crystallization was accompanied by electron microscopy and UV-Vis spectroscopy. Data from electron diffraction, as well as chemical analysis, EDX, were obtained using a transmission electron microscope. EDX data have shown that the atomic percentage of Ag is higher on the nanoparticle. X-ray diffraction was used in order to characterize the composition of the crystals and cubic AgCl was identified as the main crystallized nanophase obtained after annealing
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AgSIE was used for the direct analysis of folic acid (FA), with a detection limit and lower level of quantitation of 6.8 x10-10 mol L-1 and 2.3 x 10 8 mol L-1. The analysis in fresh and processed fruits was done without any sample pretreatment. In strawberry and acerola juices, FA concentration level values were below the method detection limit. FA was detectable in peach (77.7 0.4 mg L-1 and 64.4 0.5 mgL-1), Persian lime (45.4 0.7 mg L-1), pineapple Hawaii (66.2 0.4 mgL-1), pear pineapple (35.3 0.6 mgL-1), cashew (54.4 0.5 mgL-1) , passion fruit (73.2 0.3 mgL-1), and apple (84.4 0.5 mg L-1 ).
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The aim of this work was to evaluate the corrosion resistance of AuPdAgIn alloy, submitted to laser beam welding, in 0.9% NaCl solution, using electrochemical techniques. Measures of the open circuit potential (OCP) versus time were applied to electrochemical experiments, as well as potentiodynamic direct scanning (PDS) and electrochemical impedance spectroscopy (EIS) on AuPdAgIn alloy, submitted to laser beam welding in 0.9% NaCl solution. Some differences observed in the microstructure can explain the results obtained for corrosion potential, Ecorr, and corrosion resistance, Rp. EIS spectra have been characterized by distorted capacitive components, presenting linear impedance at low frequencies, including a non-uniform diffusion. The area of the laser weld presented corrosion potential slightly superior when compared to the one of the base metal. The impedance results suggest the best resistant corrosion behavior for laser weld than base metal region. This welding process is a promising alternative to dental prostheses casting.
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Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. It was investigated the barium (II) modification at 0.0, 0.2, 0.4 and 0.6 mol% in substitution to the lead (II) cation in A site of perovskite structure. The powder samples were characterized by XRD and the diffraction patterns were used to Rietveld refinement. The percentages of tetragonal and rhombohedral phases and a systematic study of the effect of barium (II) on the morphology and the dielectric properties of PZT were carried out. The results showed that the tetragonal phase is favored and the ceramic density is improved with the barium (II) insertion. The Curie temperature (Tc) is increased besides the slight reduction of dielectric constant (Kc).
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Nanotechnology, the science of minuscule, has developed products which are able t o manipulate atoms and molecules that could be applied in the sterilization process of dental instruments. Objetives: The objective of the present study was to evaluate the self-cleaning action of TiO2 and Ag nanoparticles coating on dental instruments by the photocataliys process under UV and visible light irradiation. Material and method: Microbiologic tests were done using dental cement spatulas coated with TiO2 and Ag nanoparticles (one or three layers), and contaminated with 10 mcrl of Pseudomonas aeruginosa and Enterococcus faecalis, respectively. After contamination, they were exposed to ultraviolet light and visible light for 120 minutes. Next, they were transferred to and stored in test tubes with BHI (Brain Heart Infusion) and incubated in 35 to 37 °C. Checking times for bacterial growth and for control and retrieval tests were done at: 24, 48, 72 and 96 hours. Result: The Pseudomonas aeruginosa was inactive after 120 minutes of ultraviolet light irradiation, thus confirming the heterogeneous photocatalytic activity of TiO2 and Ag. The Pseudomonas aeruginosa was not inactivated under visible light irradiation and the Enterococcus faecalis was not inactivated under UV and visible light irradiation of the dental cement spatulas coated with TiO2 and Ag nanoparticles in the readings to 96 hours, showing bacterial growth. Conclusion: There were no influence of one or three layers of TiO2 and Ag nanoparticles coating of the spatulas in the results. The heterogeneous photocatalysis activity of TiO2 and Ag under UV light irradiation was confirmed for Pseudomonas aeruginosa but not under visible light. Enterococcus faecalis did not confirmed the photocatalytics activity of TiO2 and Ag under UV light irradiation and visible lights irradiation.
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Objective: This study evaluated the flow, pH and calcium release of MTA Fillapex (G1) or Fillapex plus 10% in weight of calcium hydroxide powder (G2), compared to AH Plus (G3) and Sealapex (G4). Materials and methods:The flow test was performed according to ISO 6876:2001 requirements. The sealers were placed into plastic tubes and immersed in deionized water. After 24 hours, 7, 14 and 28 days, the water of each tube was removed and tested to evaluate the pH values and the level of released calcium. Calcium release values were analyzed statistically by Kruskal Wallis and Dunn tests and pH values analyzed by ANOVA and Tukey tests (? = 5%). Results:G1 presented higher flow among all sealers. The addition of 10% calcium hydroxide into MTA Fillapex reduced the flow (p < 0.05) but, in a level, that is lower than the one recommended for ISO norms. G2 and G4 presented pH values and calcium release higher than G3 (p < 0.05) in all periods. G1 presented pH value higher than G3 (p < 0.05), except in 7 days period (p > 0.05). G4 presented higher pH values than G1 and G2, but the calcium release was similar for all periods (p > 0.05). G3 presented lower calcium release among all groups (p < 0.05). Conclusion: The addition of 10% calcium hydroxide in MTA Fillapex caused reduction in flow and no negative interference in pH and/or calcium release. However, the obtained flow is different from ISO requirements. Clinical relevance: MTA Fillapex presents levels of flow above the ISO norms. The addition of calcium hydroxide is a suggestion for solving this problem, but the impact of these procedures should be carefully evaluated.
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Context: Calcium oxide (CaO) may be added to mineral trioxide aggregate (MTA) or Portland cement (PC) to improve physicochemical and biological properties. Aims: To evaluate the physicochemical properties of PC associated with radiopacifiers and CaO. Materials and Methods: MTA Angelus, PC + 30% zirconium oxide (Zr), or 30% niobium oxide (Nb) associated with 10 or 20% of CaO were evaluated. Gilmore needles were used to evaluate initial and final setting time. Compressive strength was evaluated after the periods of 24 hours and 21 days. pH was analyzed after 3, 12, 24 hours, 7, 14, 21 days. Solubility and flow tests were performed based on the ISO 6876. The data obtained were submitted to analysis of variance and Tukey tests (P ≤ 0.05). Results: The associations with 10% CaO showed greater strength that the associations with 20% CaO. The shortest initial setting time was observed for the association PC + Zr + 20% CaO and MTA. All the cements presented alkaline pH. The flow of all cements was similar. The highest solubility was found in the associations with 20% CaO. Conclusion: The addition of CaO to PC favored the alkaline property and the PC + Zr + 20% CaO presented setting time similar to MTA.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)