X-ray diffraction and mossbauer spectra of nickel ferrite prepared by combustion reaction

Nickel ferrite powders with a nominal NiFe2O4 composition were synthesized by combustion reaction using urea as fuel. The powder was obtained using a vitreous silica basin heated directly on a hot plate at 480 degrees C until self-ignition occurred. After combustion, the powder was calcined at 700 degrees C for 2 h. The formation of the spinel phase and the distribution of cations in the tetrahedral and octahedral sites of the crystal structure were investigated by the Rietveld method, using synchrotron X-ray diffraction data and Mossbauer spectroscopy. The material presented a crystallite size of 120 nm and magnetic properties. The resulting stoichiometry after the Rietveld refinement was (Fe-0.989(2) Ni-0.011(2)) [Fe-1.012(2) Ni-0.989(2)] O-4.

Structural and electrochemical properties of LiCoO2 prepared by combustion synthesis

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 degreesC for 12 h. The powders were characterized by X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and specific surface area values were obtained by BET isotherms. Composite electrodes were prepared using a mixture of LiCoO2, carbon black and poly(vinylidene fluoride) (PVDF) in the 85:10:5% w/w ratio. The electrochemical behavior of these composites was evaluated in ethylene carbonate/dimethylcarbonate solution, using lithium perchlorate as supporting electrolyte. Cyclic voltammograms showed one reversible redox process at 4.0/3.85 V and one irreversible redox process at 3.3 V for the LiCoO2 obtained after a post-heat treatment at 400 and 500 degreesC.Raman spectroscopy showed the possible presence of LiCoO2 with cubic structure for the material obtained at 400 and 500 degreesC. This result is in agreement with X-ray data with structural refinement for the LiCoO2 powders obtained at different temperatures using the Rietveld method. Data from this method showed the coexistence of cubic LiCoO2 (spinel) and rhombohedral (layered) structures when LiCoO2 was obtained at lower temperatures (400 and 500 degreesC). The single rhombohedral structure for LiCoO2 was obtained after post-heat treatment at 600 degreesC. The maximum energy capacity in the first discharge was 136 mA g(-1) for the composite electrode based on LiCoO2 obtained after heat treatment at 700 degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Analysis of oxy-fuel combustion as an alternative to combustion with air in metal reheating furnaces

Using oxygen instead of air in a burning process is at present being widely discussed as an option to reduce CO2 emissions. One of the possibilities is to maintain the combustion reaction at the same energy release level as burning with air, which reduces fuel consumption and the emission rates of CO2. A thermal simulation was made for metal reheating furnaces, which operate at a temperature in the range of 1150-1250 degrees C, using natural gas with a 5% excess of oxygen, maintaining fixed values for pressure and combustion temperature. The theoretical results show that it is possible to reduce the consumption of fuel, and this reduction depends on the amount of heat that can be recovered during the air pre-heating process. The analysis was further conducted by considering the 2012 costs of natural gas and oxygen in Brazil. The use of oxygen showed to be economically viable for large furnaces that operate with conventional heat recovering systems (those that provide pre-heated air at temperatures near 400 degrees C). (C) 2014 Elsevier Ltd. All rights reserved.

Cu0.5Zn0.5Fe2O4 ferrite for application as a soft magnetic material

This work involved the synthesis and characterization of Cu0.5Zn0.5Fe2O4 ferrite powders prepared by combustion reaction for use as soft magnetic materials. The powders were characterized by nitrogen adsorption (BET), XRD, Rietveld refinement, SEM, TEM and magnetic measures. The results indicate that the combustion reaction yielded crystalline powders containing spinel ferrite as the primary phase and traces of Fe2O3 as secondary phase. The crystallite size and lattice microdeformation calculated from Rietveld refinements were 36 and 0.24 nm, respectively. The micrographic analysis revealed particles smaller than 100 nm and fine particle agglomerates. The particles were approximately spherical and their size, calculated by TEM, was 29 nm. The magnetic parameters indicated that the Cu-Zn ferrite powders presented closed hysteresis loops and soft magnetic properties. © (2012) Trans Tech Publications, Switzerland.

Aplicação do Método de Rietveld em caracterização estrutural e nanoestrutural do espinélio 'Ni IND. 1'- 'delta' Co'delta''Fe IND.2''O IND.4' preparado por reação de combustão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise estrutural e morfológica de ferrita NiFe2O4 dopada com cromo

This paper reports on the effect of the substitution of Fe3+ for Cr3+ ions in the spinel lattice of the powders was investigated. Nickel ferrite powders with a NiFe2-xCrxO4 nominal composition (x = 0.0; 0.5; 1.0 and 1.5 mol of the chromium) were synthesized by combustion reaction using urea as fuel. The powders resulting were characterized by XRD, nitrogen adsorption by BET, SEM and Mössbauer spectroscopy (57Fe Mössbauer spectra). The results show that the substitution of the Fe3+ for Cr3+ions increased the crystalline degree of the phase, reduced the superficial area and consequently increased the particle size. The Mössbauer spectra of the samples also confirm the distribution of the particles size by the magnetic properties. Analyze of the spectra Mössbauer gives an estimate of the superparamagnetic and ferromagnetic particles behavior in each sample for several chromium concentrations.

COMBUSTION and PYROLYSIS of A SLUDGE FROM WASTEWATER TREATMENT PLANT

The possibility of thermal treatment plants of municipal wastewater is an alternative solution for the final disposition of the sludge produced on small cities as Barueri, a small town of São Paulo State, Brazil. Combustion and pyrolysis of that municipal waste, occurring respectively in air and nitrogen, have been studied by thermogravimetry (TG) and differential thermal analysis (DTA). The main steps of each case were analyzed and Kissinger plots were used to estimate respective activation energies. DTG peaks are more indicated to represent the condition of maximum reaction rates than DTA peaks.

Photoelectroactivity of Bismuth Vanadate Prepared by Combustion Synthesis: Effect of Different Fuels and Surfactants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pyrolysis, combustion and oxy-combustion studies of sugarcane industry wastes and its blends

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparison of DNA-extraction methods and Selective Enrichment broths on the detection of Salmonella Typhimurium in swine feces by polymerase chain reaction (PCR)

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

Evaluation of the counterimmunoelectrophoresis reaction as a serodiagnosis test for swine leptospirosis

Avaliou-se a reação de contraimunoeletroforese (CIE) como teste gênero-específico para diagnóstico da leptospirose suína, usando-se três extratos solúveis de Leptospira sp, sorovares pomona, icterohaemorrhagiae e patoc, obtidos pelo tratamento com Triton X-100 a quente e aplicados a amostras de soro de suínos subdivididos em três grupos: Grupo 1, 10 suínos experimentalmente infectados com estirpe Pomona; Grupo 2, 50 suínos naturalmente infectados e Grupo 3, controle. As amostras de soros foram submetidas à reação de CIE e os resultados comparados aos da Soroaglutinação Microscópica (SAM), técnica de referência pela WHO. Os Grupos 1 e 3 foram monitorados por 93 dias após a inoculação (p.i.). Pela SAM a soroconversão do Grupo 1 ocorreu por volta do 10º dia p.i., enquanto pela CIE, empregando-se qualquer extrato antigênico, foi anterior à SAM. Quando a CIE foi realizada frente a antigeno homólogo à infecção, seus resultados foram equivalentes aos da SAM, não se verificando o mesmo frente aos antígenos heterólogos. Neste aspecto, os Grupos 1 e 3 mostraram comportamento diferente pois não houve diferença significativa entre os resultados da CIE frente aos três antígenos, o que poderia significar serem independentes do sorovar responsável pelo surto ou infectante. Embora a CIE seja segura, rápida, de fácil execução, de baixo custo e ideal para análise em grande escala de amostras, revelou-se de limitada capacidade gênero-específica, o que não é desejavel para testes de triagem de campo; mas poderia ser útil na detecção precoce de resposta sorológica em relação à SAM.

Induction of the acrosome reaction test to in vitro estimate embryo production in Nelore cattle

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

Astrocytic reaction in the canine granulomatous meningoencephalomyelitis

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

Reaction of sugarcane genotypes to Pratylenchus brachyurus and P. zeae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Reaction of Bipolaris euphorbiae to environmental factors and its tolerance to solar and ultraviolet radiation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)