Ceramics based bismuth vanadate are conductors of oxygen ions and they are used as solid electrolytes in pressure sensors and fuel cells. The g-phase of Bi4V2O11 can be stabilized at T0 by partial substitution of V5+ ion by Cu2+ and Zn2+ ions to provide high electrical conductivity values between 100 and 400oC. Polycrystalline samples of Bi4V1.8Cu0.1Zn0.1O10.7 were obtained after 4h sintering at 800 °C. Investigations were made about densification process and electrical conductivity related to the effect of addition of Zr0.88Y0.12O1.94.
Na última semana, entre os dias 30 de março e 02 de abril, ocorreu no Instituto de Física de São Carlos, Universidade de São Paulo, a 1a Escola Brasileira de Espectroscopia de Absorção de raios-x (EBARX), organizada pelo coordenador do Grupo de Pesquisa Crescimento de Cristais e Materiais Cerâmicos, Prof. Valmor Roberto Mastelaro. O evento contou com apoio do Centro para o Desenvolvimento de Materiais Funcionais (CDMF), da CAPES e do Instituto de Física de São Carlos (IFSC) e recebeu 67 pesquisadores de Instituições de todo Brasil os quais participaram de aulas teóricas e práticas de análise durante a EBARX.
Influence of noble metals on the structural and catalytic properties of Ce-doped SnO2 systems
This paper discusses the influence of the presence of a second dopant (Pt or Pd) on the SnO2·Ce matrix. The characteristics of the material and the catalytic activity of oxidizing methanol were evaluated. Two routes were used to prepare the SnO2·5mol% Ce·1mol% NM (NM = Pt or Pd). Transmission electronic microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and chromatographic assays were used to study the samples. Almost no changes in the morphology were detected when the samples were
prepared by the impregnation route. In contrast, preparation by the chemical route (modified polymeric precursor (MPP) route) revealed crystallite growth and CeO2 segregation. No sample showed any metallic cluster, but all the samples containing noble metal displayed a very marked catalytic property, suggesting significant activity even at room temperature. The products formed were CO2 and water,
representing a competitive advantage from the standpoint of environmental protection.
Ingrid Távora Weber, Antoninho Valentini, Luiz Fernando Dias Probst, Elson Longo, Edson Roberto Leite
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