DETERMINAÇÃO DE ARSÊNIO, ANTIMÔNIO E BISMUTO EM ROCHAS POR ESPECTROMETRIA DE EMISSÃO ÓPTICA COM FONTE DE PLASMA ACOPLADO INDUTIVAMENTE (ICP-OES) E GERAÇÃO DE HIDRETOS

No presente trabalho descreve-se o método para determinação de arsênio, antimônio e bismuto em materiais geológicos, utilizando a geração de hidretos acoplado ao ICP-OES, que proporciona a determinação, com exatidão, dos elementos de interesse em concentrações abaixo de 1 ppm. O método é sensível e, por isso, está sujeito a interferências, como as causadas por elementos presentes na matriz. Desenvolveu-se uma técnica de dissolução eficiente e foram realizados diversos tratamentos com dopagens de soluções-padrão e testes com o uso de tiouréia e iodeto de potássio com ácido ascórbico em diferentes concentrações, com o objetivo de minimizar possíveis interferências presentes na matriz. Os resultados finais, mediante a dissolução de material geológico de referência internacional na determinação de arsênio, bismuto e antimônio, mostraram recuperações superiores à 97% em amostras com concentrações abaixo de 1 ppm.

Avaliação de propriedades físicas, químicas e biológicas de cimentos Portland associados a radiopacificadores micro e nanoparticulados

Pós-graduação em Odontologia - FOAR

Avaliação de propriedades físico-químicas, mecânicas e antimicrobianos do MTA e cimento Portland associado a solução de nanopartículas de prata

Pós-graduação em Odontologia - FOAR

Processamento e propriedades magnéticas de manganitas multiferróicas = Mise en forme et propriétés magnétiques de manganites multiferróïques

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Obtenção e caracterização de filmes finos de Bi3NbO7 pelo método dos precursores poliméricos

Pós-graduação em Engenharia Mecânica - FEG

Experimental evidence of enhanced ferroelectricity in Ca doped BiFeO3

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito do acréscimo de nano-hidroxiapatita nas propriedades físico-químicas, mecânicas e antibiofilnme do cimento portland com óxido de zircônio

Pós-graduação em Odontologia - FOAR

Microparticulated and nanoparticulated zirconium oxide added to calcium silicate cement: Evaluation of physicochemical and biological properties

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure and photocatalytic properties of Nb-doped Bi12TiO20 prepared by the oxidant peroxide method (OPM)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structure and properties of chemically synthesized BiFeO3. Influence of fuel and complexing agent

Perovskite, single multiferroic bismuth ferrite was prepared by two chemical methods: auto-combustion and soft chemical route. Influence of different fuels and complexing agents and thermal treatment on purity of bismuth ferrite powders and density of bismuth ferrite ceramics were investigated. X-ray diffraction technique (XRD) indicated that optimal temperatures and times for calcination and sintering are 600 degrees C for 2 h and 800 degrees C for 1 h with quenching, respectively. Scanning electron microscopy (SEM) analysis showed that soft route synthesized samples formed softer agglomerates and smaller grains with less secondary phases. Powders and pellets were characterized by Brunauer Emmett Teller (BET) specific surface area analysis, particle size distribution, Fourier transform infrared spectroscopy (FT-IR), dilatometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), dielectric and magnetic measurements. Resistivity and origin of electrical resistance were studied by means of impedance measurements. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Síntese e caracterização dielétrica de filmes finos de Bi3NbO7 obtidos pelo método dos precursores poliméricos

Bi3NbO7 thin films were prepared by the polymeric precursor method. The precursor solutions were prepared with excess of bismuth ranging from 0% to 10% and the pH was controlled to be maintained between 8 and 9. This control was done by adding to the solution niobium and ethylene glycol. The final solution was clear and free of precipitation. After obtaining the precursor solution, has begun the process of characterization of powders with thermogravimetry (TG), differential thermal analysis and X-ray analysis (XRD). The films were obtained by the polymeric precursors, the method is advantageous because it is simple, and low cost involves steps and controlled stoichiometry. The films were annealed and characterized by XRD and SEM and also characterized according to their dialectics properties. We observed that the best results were obtained when the film is thermally at 800 ° C for two hours and 860 ° C for two hour. Under these conditions we obtain Bi3NbO7 thin films with good homogeneity, uniform distribution of the grains, but with the formation of secondary phase, which does not occur in treatments with lower temperature. The dielectric characterization showed that the produced film showed good characteristics with high dielectric constant and low loss

Desenvolvimento de filmes finos de Bi3NbO7 pelo método dos precursores poliméricos em diferentes eletrodos óxidos

Technology always advances and thus the device miniaturization and improved performance, besides multifunctionality, they become extremely necessary. A wave of research on the area tends to grow in number and importance in today's market, it is necessary to search for new materials, new applicability of the existing ones and new processes for increasingly cheaper costs. Dielectric materials are considered a key element in this sector being the main electrical properties its high dielectric constant and low dielectric loss. The Polymeric Precursor Method appears as a good alternative because is a low cost, simple process with controlled stoichiometry. In this method, two steps were performed. In a first step, the precursor solution was decomposed into powders and in a second step the precursor solution was converted in thin films. In this work, was used the polymeric precursor methods to get thin films where they were heat treated and characterized by XRD, SEM and AFM. We have obtained Bi3NbO7 thin films with good homogeneity and uniform distribution of grains were noted. We observed that the best condition to obtain the tetragonal phase is annealing the film at high temperatures for a longer soaking time and with excess of bismuth. Several oxides electrodes were evaluated aiming to obtain textured dielectric thin films

Síntese e caracterização de filmes finos de ferrita de bismuto dopados com cálcio visando aplicação em memórias de múltiplos estados

The increasing demand for electro-electronic devices, with high performance and multi-functional and the rapid advances of the nanotechnology require the development of new methods and techniques for the production and characterization of nanostructure materials and phenomenological models to describe/to predict some of its properties. The demand for multifunctionality requires, at least, new materials, that can integrate ferroelectric and magnetic properties of high technological interest. Inside of this context, multiferroics material can be considered suitable to integrate two or more physical properties of high technological interest. It can also provides new challenges in the processes of synthesis of new materials, and development of new devices with controlling and simulation of its physical properties and modeling. For this Calcium (Ca)-doped bismuth ferrite (BiFeO3) thin films prepared by using the polymeric precursor method (PPM) were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), polarization and piezoelectric measurements.In order to study the behavior and determine which are the most important parameters to achieve the optimal property to be applied to a multiferroic materials

Avaliação da capacidade de vedamento e pH do tampão apical com cimento Portland branco acrescido de radiopacificadores convencionais

The Portland cement has shown similar biological properties to calcium hydroxide, but its radiopacity is lower. Therefore, the addition of materials that minimize this deficiency should be considered. OBJECTIVE: To evaluate the apical sealing ability and pH of a white Portland cement added of several radiopacifying agents. MATERIAL AND METHODS: Forty bovine roots with incomplete apices were selected, and the foraminal openings were standardized to PM 720G bur. After the external root sealing, an apical intracanal barrier 10.0 mm thick was executed with the white Portland cement powder, pure or added of a radiopacifying agent (iodoform, zinc oxide or bismuth subnitrate), and distilled water (0.37 mL). The apical roots were immersed 24h in water in humid atmosphere, and after that they were immersed 24h in 2% Rhodamine B, under vacuum. In sequence, the roots were longitudinally sectioned, the root fragments were photographed, the images were digitalized and the apical infiltration was measured by the Image Tool program. The pH solutions were also evaluated, in 24h and 48h and 7 and 30 days. Data were submitted to Anova test. RESULTS: The zinc oxide solution has the lowest apical infiltration in relation to the other groups (p < 0.05). The pH behavior varied during the analysis, and in the period of 24h all groups showed the highest values (p < 0.05). CONCLUSION: The type of radiopacifying agent used interferes in the sealing ability of the apical barrier, and zinc oxide showed to be the most beneficial one. The pH varies according to the period of analysis, and the highest values were obtained in the first 24h (p < 0.05).