Navegando por Autor "Soledade, Luiz Edmundo Bastos"

Agora exibindo 1 - 15 de 15

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
Characterization of gypsum using TMDSC
(Springer, 2007-03-07) Dantas, H. F.; Mendes, R. A. S.; Pinho, R. D.; Soledade, Luiz Edmundo Bastos; Paskocimas, Carlos Alberto; Lira, B. B.; Schwartz, M. O. E.; Souza, A. G.; Santos, Ieda Maria Garcia dos
Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4⋅2H2O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles
Color and structural analysis of CoxZn7−xSb2O12 pigments
(Elsevier, 2006-11-09) Gouveia, Deiby Santos; Soledade, Luiz Edmundo Bastos; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
The polymeric precursor method was successfully used to synthesize CoxZn7−xSb2O12 (x = 0–7) powders. Pigments were evaluated using colorimetry, X-ray diffraction, UV–vis and infrared spectroscopy. The optical band gap values vary with the Co2+ substitution. These results suggest that the concomitant presence of Co and Zn in the spinel lattice leads to the rupture of the Végard law, as well as other properties of the studied system, such as unit cell volume. The Co-richer samples display a higher absorbance than the Co-lean samples. The high absorption of the Co7Sb2O12 sample at most of the visible region makes this compound a candidate for a black pigment. It was shown that color depends on the site where the chromophore ion is located, in agreement with the ligand field theory.
Efeito da adição de rejeito na redução de coração negro em cerâmicas vermelhas
(ABCERAM, 2005) Santos, Ieda Maria Garcia dos; Silva, J. M.; Trindade, M. F. S.; Soledade, Luiz Edmundo Bastos; Souza, Antônio Gouveia de; Paskocimas, Carlos Alberto; Silva, Elson Longo da
Um dos problemas que afeta a indústria cerâmica é a elevada perda de produtos acabados, decorrente do próprio processamento, levando a trincas e peças fora de conformidade. Deste modo, é necessário o reaproveitamento desses resíduos, como forma de reduzir o impacto ambiental. Neste trabalho, os resíduos de duas indústrias de cerâmica vermelha foram moídos e adicionados à própria massa, levando, também, a um ganho econômico. As porcentagens variaram de 10% a 30%, em peso. As peças foram conformadas por extrusão e sinterizadas a 950 ºC e 1000 ºC. Os resultados obtidos mostram que a adição levou a uma melhoria nas propriedades das amostras, pois diminuem a possibilidade de ocorrência de coração negro, levando a peças mais uniformes e menos porosas.
Effect of the modifier ion on the properties of MgFe2O4 and ZnFe2O4 pigments
(Springer, 2007-03-07) Xavier, Camila S.; Candeia, R. A.; Bernardi, M. I. B; Lima, S. J. G.; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Soledade, Luiz Edmundo Bastos; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dos
Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow-orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color
Foundry sand recycling in the troughs of blast furnaces: a technical note
(Elsevier, 2005-01-10) Andrade, Ricardo Magnani; Cava, Sérgio; Silva, Sidiney Nascimento; Soledade, Luiz Edmundo Bastos; Rossi, Cláudia C.; Leite, Edson Roberto; Paskocimas, Carlos Alberto; Varela, José A.; Silva, Elson Longo da
The foundry sand agglomerated with alkaline phenolic resin, used for the manufacture of molds, was found to be a residue which is able to be recycled, minimizing the costs of disposal and the environmental impact. This paper analyzes the thermomechanical regeneration and leaching processes and also assesses the influence of additives on the improvement of the mechanical properties of the sands. Besides, the industrial experiments carried out at CSN aiming at the foundry sand recycling in the covering of the blast furnace troughs are presentedThe foundry sand agglomerated with alkaline phenolic resin, used for the manufacture of molds, was found to be a residue which is able to be recycled, minimizing the costs of disposal and the environmental impact. This paper analyzes the thermomechanical regeneration and leaching processes and also assesses the influence of additives on the improvement of the mechanical properties of the sands. Besides, the industrial experiments carried out at CSN aiming at the foundry sand recycling in the covering of the blast furnace troughs are presented
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
Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC
(Springer, 2011-02-14) Bicudo, Tatiana de Campos; Candeia, R. A.; Sinfrônio, F. S. M.; Queiroz, N.; Barros Filho, A. K. D.; Soledade, Luiz Edmundo Bastos; Santos, I. M. G.; Souza, A. L.; Souza, A. G.
Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by basecatalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME
Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente
(Sociedade Brasileira de Química, 2006-08-22) Sales, Luciano Leal de Morais; Souza, Antonio Gouveia de; Soledade, Luiz Edmundo Bastos; Santos, Ieda Maria Garcia dos; Rodrigues Neto, João Batista; Silva, Elson Longo da; Paskocimas, Carlos Alberto
In this work, aqueous suspensions of aluminas with different particle sizes were evaluated. The effect of pH on the electrosteric stabilization using PMAA-NH4 (ammonium polymethacrylate) as deflocculant was studied. The amount of deflocculant was optimized and rheologic properties were determined at four different pH values. Sedimentation was also evaluated. For suspensions with pH 4, an electrostatic mechanism of stabilization was observed, probably due to a flat adsorption of PMMA- on the alumina surface, leading to a small efficiency in relation to steric stabilization. For a suspension with pH 12, the steric mechanism of stabilization prevails. Suspensions with pH 7 and 9 present a higher flocculation degree. In relation to particle size, A-1000 samples present a smaller particle size, leading to a smaller interparticle distance (IPS), making stabilization more difficult
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
Propiedades ópticas del pigmento α-Fe2 O3 /SiO2
(Sociedad Española de Cerámica y Vidrio, 2005) Spinelli, A.; Oliveira, A. P. N.; Soledade, Luiz Edmundo Bastos; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Souza, A. G.; Chicariano, C. A.; Flores, J. A.
En el presente trabajo describimos la síntesis del pigmento α-hematites/SiO2 según el método de mezcla de óxidos. El color rojo del pigmento corresponde a las transiciones electrónicas 6A1g→ 4T1g y 6A1g→ 4T2g del ion Fe+3 que presenta la configuración estructural d5 y está enlazado a seis oxígenos en la estructura de la hematites. Los cambios en el matiz del color rojo del pigmento están relacionados con la entropía del sistema y con la disminución consecuente del gap. El compuesto α-hematites/SiO2 se mostró como un pigmento cerámico promisorio para aplicación a la temperatura de 1100°C
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

SIGAA

Navegando por Autor "Soledade, Luiz Edmundo Bastos"