Navegando por Autor "Ferreira, Jailson M."
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Artigo Influence of doping on the preferential growth of α-MoO3(Elsevier, 2008-07-14) Pereira, Luiza G.; Soledade, Luiz Edmundo Bastos; Ferreira, Jailson M.; Lima, Severino Jackson Guedes; Fernandes Júnior, Valter José; Araújo, Antônio Souza de; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Santos, Maria Rita de Cássia; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dosMoO3 is a lamellar material with applications in different areas, as solid lubricants, catalysis, solar cells, etc. In the present work, MoO3 powders, synthesized by the polymeric precursor method, were doped with nickel or cobalt. The powder precursors were characterized by TG/DTA. After calcination between 500 and 700 ◦C, the samples were characterized by X-ray diffraction, infrared and Raman spectroscopy and scanning electron microscopy. -MoO3 was obtained after calcination at low temperatures. With the temperature increase, -MoO3 is observed, with a preferential growth of the (0 2k 0) planes, when the material is doped and calcined at 700 ◦C. Doping with nickel increases five times the preferential growth. As a consequence, plate-like particles are observedArtigo Photoluminescence in the CaxSr1 xWO4 system at room temperature(Elsevier, 2008-08) Pôrto, S. L.; Silva, Elson Longo da; Pizani, Paulo Sérgio; Boschi, Tania M.; Simões, Luis Gustavo Pagotto; Lima, Severino Jackson Guedes; Ferreira, Jailson M.; Soledade, Luiz Edmundo Bastos; Espinoza, J. W. M.; Santos, Maria Rita de Cássia; Maurera, Maria Aldeiza M. A.; Paskocimas, Carlos Alberto; Santos, Ieda Maria Garcia dos; Souza, Antônio Gouveia deIn this work, a study was undertaken about the structural and photoluminescent properties, at room temperature, of powder samples from the CaxSr1 xWO4 (x ¼ 0–1.0) system, synthesized by a soft chemical method and heat treated between 400 and 700 1C. The material was characterized using Infrared, UV–vis and Raman spectroscopy and XRD. The most intense PL emission was obtained for the sample calcined at 600 1C, which is neither highly disordered (400–500 1C), nor completely ordered (700 1C). Corroborating the role of disorder in the PL phenomenon, the most intense PL response was not observed for pure CaWO4 or SrWO4, but for Ca0.6Sr0.4WO4. The PL emission spectra could be separated into two Gaussian curves. The lower wavelength peak is placed around 530 nm, and the higher wavelength peak at about 690 nm. Similar results were reported in the literature for both CaWO4 and SrWO4Artigo Yellow ZnxNi1−xWO4 pigments obtained using a polymeric precursor method(Elsevier, 2007-05-25) Oliveira, André Luiz M. de; Ferreira, Jailson M.; Silva, Maria Rita de Cássia; Braga, Glauco Soares; Soledade, Luiz Edmundo Bastos; Aldeiza, M. A. Maurera Maria; Paskocimas, Carlos Alberto; Lima, Severino Jackson Guedes; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dosNew tungstate-based ceramic pigments, displaying ZnxNi1 xWO4 stoichiometry, were obtained at low temperature using a polymeric precursor method. The powder precursors were milled in an attritor mill in an alcoholic medium and heat treated for 12 h, yielding homogeneous and crystalline powder pigments. Characterization (TG/DTA, XRD, IR and colorimetry) showed that mass loss increased with increasing Zn contents. Despite the presence of secondary phases and impurities, the wolframite phase was present in all samples. IR analysis revealed bands related to MeeO and [WO6]6 group stretching was observed. The intensity of the yellow color of the pigments increased with increasing amount of nickel