Characteristics of PbO-BiO1.5-GaO1.5 glasses melted in SnO2 crucibles

PbO-BiO 1.5-GaO 1.5-based glasses are good candidates for optical applications, because of some of their interesting characteristics, such as high refraction indices and high transmission in the ultraviolet (UV), visible (VIS), and infrared (IR) regions. A limited stage in the processing of these glasses is the corrosion that is caused by the melt in all currently used conventional crucibles, such as noble metals (platinum or gold) and Al 2O 3. The absorption of crucible material by the glass composition may reduce the transmission level, the cutoff in the UV-VIS, and IR regions, and the thermal stability. In this study, a SnO 2 crucible has been tested for PbO-BiO 1.5-GaO 1.5 molten glass. Optical and thermal analyses show, in some cases, advantages over the use of platinum and Al 2O 3 crucibles. A visible cutoff value of 474 nm has been measured, and a longer melting time (850°C for 4 h) results in a significant reduction of the O-H absorption band at 3.2 μm.

Dielectric properties of Sr0.75Ba0.25Nb 2O6 thin films: Bias field, frequency and temperature dependence

Ferroelectric strontium barium niobate solid solutions had received great attention due to their excellent pyroelectric, electrooptic and photorefractive properties. Furthermore, they usually also present very interesting phase transition characteristics. In this work, polycrystalline single phase Sr 0.75 Ba 0.25 Nb 2 O 6 thin films were prepared by a hybrid chemical method and deposited on Pt/Ti/SiO 2 /Si substrates. The temperature dependence of dielectric constant was measured at different frequencies and bias field levels. The presence of two dielectric dispersion regions with relaxor characteristics was observed at distinct temperature ranges, corresponding to the ferro-paraelectric and to a structural phase transition at low temperatures, respectively. A specific dielectric dispersion region, associated with an incommensurate superstructure frequently observed in bulk samples, was not observed in this films probably due to their small grain sizes. © 2002 Taylor & Francis.

A technique for the determination of the available oxygen in living carp (Cyprinus carpio) muscle

1. 1. A polarographic method for the measurement of the available oxygen in the muscle of living carp by the use of a platinum microelectrode is proposed. 2. 2. The oxygen and the reference electrodes were assembled in a single insertion piece which was implanted in the muscle of a living carp maintained in a special experimental chamber. 3. 3. Curves for normal oxygen levels corresponding to air-saturated water, as well as to a carbogene-saturated water, were obtained. 4. 4. The method can be considered adequate for the measurement of tissue oxygen in living fishes. © 1984.

Eletro-oxidação de metanol e etanol sobre PtAu/C em meio alcalino

The development of electrocatalysts for the oxidation of methanol and ethanol is very important, because these alcohols may be used in the anode fuel cells which convert chemical energy directly into electrical energy with high efficiency, cleanly and with low noise. Thus, this study reports to the synthesis of nanocatalysts of PtAu supported on carbon by microemulsion method. The physical characterization of these catalysts is performed through the techniques of X-ray diffraction and transmission electron microscopy. The catalytic activity of the prepared materials was studied using conventional electrochemical techniques and also the technique of spectro-electrochemical in situ FTIR, which allows identification of intermediates and products of the reactions. From the x-ray diffraction, it was observed that the thermal treatment applied to catalysts favored incorporation of Au into the crystal lattice of Pt,that is, increased the formation of PtAu alloy. Micrographs indicated particle size about 3 nm to materials not heat treated and 9 nm to materials subjected to thermal treatment (heating at 150 ° C for 1h and 30 min in argon atmosphere). Current density oxidation of methanol on PtAu / C were superior to pure platinum. Spectroscopic results indicated the presence of formate in solution in 50:50 and the composition showed bands for CO2, indicating complete oxidation, in lower potential. During ethanol oxidation on the catalyst PtAu, the main product formed was acetate, product of incomplete oxidation. The good performance for methanol oxidation can be attributed to large amounts of oxygen species adsorbed on the catalyst surface, or an electronic effect.

Corrosion resistance of Ni-Cr alloys in different mouthwashes

Several alloys have been used for prosthodontics restorations in the last years. These alloys have a number of metals that include gold, palladium, silver, nickel, cobalt, chromium and titanium and they are used in oral cavity undergo several corrosion. Corrosion can lead to poor esthetics, compromise of physical properties, or increased biological irritation. The objective of this study was evaluated corrosion resistance of two alloys Ni-Cr and Ni-Cr-Ti in three types of mouthwashes with different active ingredients: 0.5g/l cetylpyridinium chloride + 0.05% sodium fluoride, 0.05% sodium fluoride + 0.03% triclosan (with fluor) and 0.12% chlorohexidine digluconate. The potentiodynamic curves were performed by means of an EG&G PAR 283 potentiostat/galvanostat. The counter electrode was a platinum wire and reference electrode was an Ag/AgCl, KCl saturated. Before each experiment, working electrodes were mechanically polished with 600 and 1200 grade papers, rinsed with distilled water and dried in air. All experiments were carried out at 37.0oC in conventional three-compartment double wall glass cell containing mouthwashes. The microstructures of two alloys were observed in optical microscopy. Analysis of curves showed that Ni-Cr alloy was less reactive in the presence of 0.12% chlorohexidine digluconate while Ni-Cr-Ti alloy was more sensitive for others two types of mouthwashes (0.5g/l cetylpyridinium chloride + 0.05% sodium fluoride  and 0.05% sodium fluoride + 0.03% triclosan). This occurred probably due presence of titanium in this alloy. Microstructural analysis reveals the presence of dendritic and eutectic microstructures for NiCr and Ni-Cr-Ti, respectively.

Al-doping effect on the surface morphology of zno films grown by reactive rf magnetron sputtering

Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZnO:Al) thin films were deposited onto glass and silicon substrates by RF magnetron sputtering using a zinc-aluminum target. Both films were deposited at a growth rate of 12.5 nm/min to a thickness of around 750 nm. In the visible region, the films exhibit optical transmittances which are greater than 80%. The optical energy gap of ZnO films increased from 3.28 eV to 3.36 eV upon doping with Al. This increase is related to the increase in carrier density from 5.9 × 1018 cm−3 to 2.6 × 1019 cm−3 . The RMS surface roughness of ZnO films grown on glass increased from 14 to 28 nm even with only 0.9% at Al content. XRD analysis revealed that the ZnO films are polycrystalline with preferential growth parallel to the (002) plane, which corresponds to the wurtzite structure of ZnO.

Effect of Zn Sputtering Rate on the Morphological and Optical Properties of ZnO Films

Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZnO:Al) thin films were deposited onto glass and silicon substrates by RF magnetron sputtering using a zinc-aluminum target. Both films were deposited at a growth rate of 12.5 nm/min to a thickness of around 750 nm. In the visible region, the films exhibit optical transmittances which are greater than 80%. The optical energy gap of ZnO films increased from 3.28 eV to 3.36 eV upon doping with Al. This increase is related to the increase in carrier density from 5.9 × 1018 cm-3 to 2.6 × 1019 cm-3. The RMS surface roughness of ZnO films grown on glass increased from 14 to 28 nm even with only 0.9% at Al content. XRD analysis revealed that the ZnO films are polycrystalline with preferential growth parallel to the (002) plane, which corresponds to the wurtzite structure of ZnO.

Modelamento matemático para otimização de perfuração em seções de pré-pal: um foco em operações no oceano Atlântico sul

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Método para controle da qualidade de medicamentos sólidos por difração de raios X

Pós-graduação em Química - IQ

Estudo da relação de ordem-desordem estrutural em nanopartículas de TiO2

Pós-graduação em Química - IQ

Estudo estrutural, morfológico, elétrico e óptico de cristais de a-Ag2WO4 dopados com Mo6+ via co-precipitação assistida por PVP

Pós-graduação em Química - IQ

Compostos de paládio(II) contendo ligantes N,S-quelantes: síntese, caracterização e investigação da atividade biológica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crescimento epitaxial e caracterização de filmes finos: óxidos condutores e ferroelétricos preparados por deposição de solução química

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito da radiação ionizante, simulando radioterapia, nas propriedades de cerâmicas Y-TZP e cimentos resinosos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de um sistema de controle para avaliação de fontes de energias renováveis no bombeamento de água

The use of alternative energy systems in the current days is an urgent necessity due to the problems that the planet is facing as the heating and loss of ozone layer. The scarcity of conventional energy is another problem that must be solved for the future of humanity. It must be considered that the people are inhabiting places moved away not always with available energy. The application of technologies as automation and control can help us to solve this problem. Therefore, this work aimed at apply an equipment of industrial usage, the Programmable Logical Controller, PLC, in alternative energies systems, as eolic generation and fotovoltaic generation used for water pumping, aiming the automatic control and the efficiency in the places where it has simultaneous availability of these sources, based in criterion of priority that previously established itself between them. It was made a hydraulic and energetic evaluation of the energy system, eolic and fotovoltaic, used in the automatic control system of pumping, in the place of accomplishment of the experiment, according to previously established physical conditions. The results have shown that the control system using the PLC is practicable and has trustworthiness. The program developed can be adapted for the use with several power plants in a specific application place. The fotovoltaic system of pumping, using a polycrystalline of 70 Watts connected to a pump Shurflo 8000, showed to be efficient with significant flows in almost all the months. The eolic system of pumping, using an eolic generator of 400 Watts assembled in place of experiment, did not demonstrate energetic capacity for use in this specific type of application.