Navegando por Autor "Lima, Severino Jackson Guedes"

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Black and green pigments based on chromium–cobalt spinels
(Elsevier, 2011-09-15) Eliziário, Sayonara A.; Andrade, Jeferson M. de; Lima, Severino Jackson Guedes; Paskocimas, Carlos Alberto; Soledade, Luiz Edmundo Bastos; Hammer, Peter; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
Chromium and cobalt oxides are widely used in the manufacture of industrial pigments. In this work, the Co(Co2−xCrx)O4 powders with different chromium concentrations (x = 0, 0.25 and 1) were synthesized by the polymeric precursor method, heat treatment between 600 and 1000 °C. These powders were characterized by X-ray diffraction, infrared spectroscopy, colorimetry, UV–vis absorption and X-ray photoelectron spectroscopies. Even with the addition of chromium, the XRD patterns revealed that all powders crystallize in a single spinel cubic structure. The spinels with higher cobalt amount, Co(CoCr)O4 and Co(Co1.75Cr0.25)O4, displayed a dark color, without the Co3+ reduction observed in Co3O4 between 900 and 950 °C. The spinel with higher chromium amount, CoCr2O4, was green. The colors were directly related to the occupation of tetrahedral and octahedral sites by the chromophores, as well as to the different oxidation states of chromium and cobalt. The different optical band gap values estimated from UV–vis spectra suggested the existence of intermediary energy levels within the band gap. X-ray photoelectron spectroscopy confirmed an increasing presence of Co(III) and a decreasing amount of Cr(VI) with cobalt enrichment
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 dos
MoO3 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 observed
Influence of the network former on the properties of magnesium spinels
(Springer, 2007-03-07) Silva, Márcia R. S.; Miranda, Lydianne C. de O.; Santos, Maria Rita de Cássia; Lima, Severino Jackson Guedes; Soledade, Luiz Edmundo Bastos; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 andMg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has
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 de
In 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 SrWO4
Planejamento experimental aplicado à otimização de massas cerâmicas contendo matérias-primas naturais
(ABCERAM, 2007) Albuquerque, F. R.; Santos, Ieda Maria Garcia dos; Lima, Severino Jackson Guedes; Santos, Maria Rita de Cássia; Soledade, Luiz Edmundo Bastos; Souza, Antônio Gouveia de; Martinelli, Antonio Eduardo
A otimização da composição é uma etapa de fundamental importância no processamento cerâmico. Neste trabalho, planejamento experimental foi aplicado a fim de se avaliar a relação entre propriedade e a composição de um sistema obtido a partir de matérias-primas naturais extraídas no Pegmatito do Seridó, na região fronteiriça RN-PB. Para o estudo do sistema ternário foram combinadas variáveis de processo (temperatura: 1100 e 1200 oC; patamar de calcinação: 0 e 2 h), com a utilização de planejamento de misturas, de acordo com o planejamento simplex centróide. Os percentuais mínimos de cada componente na mistura foram de 10% v/v. Foram avaliadas as propriedades reológicas de suspensões aquosas das misturas com 50% v/v, otimizadas com PAA-Na. Determinou-se a porosidade aparente e massa específica aparente, além da retração de queima. A composição mineralógica das peças cerâmicas obtidas a 1200oC foi basicamente mulita e quartzo. O estudo permitiu especificar a região de composição que leva à maior densidade após sinterização, com um número relativamente pequeno de amostras
Synthesis and thermal characterization of zirconium titanate pigments
(Springer, 2004-02) Costa, C. E. F.; Crispim, Samara C. L.; Lima, Severino Jackson Guedes; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Fernandes Júnior, Valter José; Araújo, Antônio Souza de; Santos, Ieda Maria Garcia dos; Souza, Antônio Gouveia de
The objective of this work was to obtain modern pigments based on zirconium titanate doped with nickel and cobalt using polymeric precursor method. Thermal evolution of ZrTiO4 phase was determined. After primary calcination, the material still exhibits two thermal composition events. Calcination was done between 500 and 1000°C, to morphological and structural characterization. Surface area decreased exponentially with temperature increase, while crystallite size increased. ZTCo and ZTNi pigments were applied on ceramic tiles and the good quality of the pigment was observed
Thermal study of CoxZn7-xSb2O12 spinel obtained by pechini method using different alcohols
(Springer, 2004-02) Gouveia, Deiby Santos; Rosenhaim, R.; Maurera, M. A. M. A. de; Lima, Severino Jackson Guedes; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
With the aim of obtaining materials with applications in pigments, CoxZn7–xSb2O12 spinels were synthesized using the Pechini method. This method consists in the formation of a polymeric net, where the metallic cations are homogeneously distributed. In this work, two types of alcohol (ethyl glycol and ethylene glycol) were used for the synthesis of a zinc antimoniate spinel, CoxZn7–xSb2O12 (x=0–7). The materials were characterized by termogravimetry (TG) and differential thermal analysis (DTA). TG results indicated a decrease in total mass loss when cobalt was added to the solution substituting zinc, for samples prepared using the two different alcohols. Decomposition temperatures, obtained by TG and DTA, presented a decreasing behavior as cobalt was added to the material. In relation to the alcohols, all results indicated a better polymerization of the resin when ethylene glycol was used, being the most indicated one for cation immobilization. X-ray diffraction did not show differences between the two alcohols – both presented the spinel phase (Co, Zn)2.33Sb0.67O4. Samples with higher quantity of cobalt also presented ilmenite phase (Co, Zn)Sb2O6
Thermal transformations of tile clay before and after kaolin addition
(Springer, 2004-02) Albuquerque, F. R.; Parente, B.; Lima, Severino Jackson Guedes; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos; Fernandes Júnior, Valter José
The use of clays for ceramic filter processing may reduce its cost, leading to different applications, as water treatment. In this work, a low cost tile clay mixed with kaolin, for use in ceramic filters, were evaluated. Mineralogical and thermal changes occurring during sintering were characterized by differential thermal analysis, thermogravimetry, thermomechanical analysis and X-ray diffraction. An increase in the initial melting temperature of samples due to kaolin addition was observed. Mullite formation in kaolin was observed by DTA and in other samples by XRD. TMA analysis permitted the observation of pre-sintering step, around 850°C. This step is difficult to observe in other types of analysis
Thermogravimetric and UV–vis spectroscopic studies of chromium redox reactions in rutile pigments
(Springer, 2009-06-24) Vieira, Fagner Ticiano Gomes; Souza, Soraia C.; Oliveira, A. L. M.; Lima, Severino Jackson Guedes; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Soledade, Luiz Edmundo Bastos; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
In this study undoped and Cr, Sb or Mo doped TiO2 were synthesized by polymeric precursor method and characterized by X-ray diffraction, UV–VIS spectroscopy, infrared spectroscopy and thermogravimetry (TG). The TG curves showed a continuous mass loss assigned to the hydroxyl elimination and Cr6? reduction. Doped TiO2 samples showed a higher mass loss assigned to water and gas elimination at lower temperatures. In these doped materials a decrease in the anatase–rutile phase transition temperature was observed. After calcination at 1,000 C, rutile was obtained as a single phase material without the presence of Cr6?
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 dos
New 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

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Navegando por Autor "Lima, Severino Jackson Guedes"