Sample records for tungsten oxides
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Sample records 1 - 2 shown.



1

Estudo da adsorção de íons fosfato em matriz inorgânica/ Adsorption study of phosphate from aqueous solution in inorganic matrix

Rodrigues, L. A.; Silva, M. L. C. P. da
2008-03-01

Resumo em português Este trabalho visa a preparação, caracterização e estudo da adsorção de íons fosfato em óxido de tungstênio hidratado preparado pela lixiviação ácida do tungstato de sódio. Parte desse material (S1) foi tratado termicamente a 100 °C para a obtenção de um material com características diferenciadas (S1/delta). Os materiais obtidos foram caracterizados por difração de raios X, análise termogravimétrica, microscopia eletrônica de varredura e espectroscop (mais) ia de energia dispersiva. Através da constante Q0, relacionada com a capacidade de adsorção máxima, observou-se que o S1 possui maior capacidade de adsorção para íons fosfato que o S1/delta. Pelos resultados de deltaG, observou-se que os íons fosfato foram adsorvidos através de reações energeticamente favoráveis para toda a faixa de concentração estudada. Resumo em inglês This work reports the preparation, characterization and adsorption study of phosphate on hydrous tungsten oxides prepared by acid lixiviation of sodium tungstate. Part of this material (S1) was heated at 100 °C resulting in a material with differentiated characteristics (S1/delta). The materials prepared were characterized by X-ray diffraction, thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. Through the Q0 constant, related with the cap (mais) acity of maximum adsorption, it was observed that the S1 sample presented better adsorption capacity than the S1/delta. The deltaG values show that PO4-3 had been adsorbed through favorable reactions for all range of studied concentration.

Scientific Electronic Library Online (Portuguese)

2

Caracterização por XPS de filmes passivos formados sobre aços de baixa liga em meio de bicarbonato/ XPS characterization of passive films formed on mild steels in bicarbonate medium

Alves, Valéria Almeida; Brett, Christopher Michael Ashton; Montemor, Maria de Fátima
2005-03-01

Resumo em inglês Passive films formed in bicarbonate solutions on carbon steel, chromium steel and high speed steel have been characterized by XPS. The passive films formed on chromium and high speed steels showed superior protective properties than those formed on carbon steel. It was confirmed by XPS that the steel composition influences the passive film composition. Chromium oxide and hydroxide, as well as molybdenum and tungsten oxides and hydroxides are present in the passive film of (mais) chromium steel and high speed steel, respectively, besides iron oxide and hydroxide. The more complex composition of the oxide film on high speed steel explains its electrochemical behaviour and highest corrosion resistance.

Scientific Electronic Library Online (Portuguese)