Navegando por Autor "Santos, Ieda Maria Garcia dos"

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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
Ceramic crucibles: a new alternative for melting of PbO–BiO1.5–GaO1.5 glasses
(Elsevier, 2002-07-10) Santos, Ieda Maria Garcia dos; Moreira, Rafael Carlos Martins; Souza, Antônio Gouveia de; Lebullenger, Ronan; Hernandes, Antônio Carlos; Leite, Edson Roberto; Paskocimas, Carlos Alberto; Silva, Elson Longo da
PbO–Bi2O3–Ga2O3 glasses present interesting properties such as good transmission in the mid-infrared region, high magnetic Verdet constant and non-linear properties. The processing of these heavy-metal-oxide (HMO) glasses is limited by the high corrosive nature of the melt, even in relation to noble metal crucibles. In this work, three kinds of ceramic crucibles (alumina, tin oxide and zirconia) were tested for melting HMO glasses. The main physical properties of the prepared glasses, such as the characteristic temperatures, optical transmission were studied in function of the crucible nature, time/temperature melting parameters. The incorporation of crucible material in the glasses was determined by ICP and atomic absorption. Themaximumglass contamination fromthe crucible was 2.9, 1.6 and 3.6mol% forAl2O3, SnO2 and ZrO2 crucibles, respectively, whenmelting was done at 900 C/240min, for zirconia crucibles and at 1000 C/60 min, for the other two crucibles. The evolution of the physical properties was discussed as a function of contamination degree
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
Gelatin synthesis of CuFe2O4 and CuFeCrO4 ceramic pigments
(Materials Letters, 2013) Melo, Marcus Antonio de Freitas; Costa, Asenete Frutuoso; Pimentel, Patrícia Mendonça; Aquino, Flávia de Medeiros; Melo, Dulce Maria de Araújo; Santos, Ieda Maria Garcia dos
In the present study, CuFe2O4 and CuFeCrO4 spinels were synthesized using a method, which makes use of gelatin as an organic precursor in order to assess the applicability as ceramic pigments. Powders resulting from the synthesis process were calcined between 500 and 900 °C and characterized by X-ray diffraction (XRD), infrared spectroscopy, scanning electron microscopy (SEM), UV–vis spectroscopy and Colorimetry analysis. Results showed brown color for the CuFeCrO4 spinel and darker colors, from brown to black, for CuFe2O4. This is an interesting finding due to the great importance of black pigments in the ceramic industry
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
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
Optimizing the synthesis of cobalt aluminate pigment using fractional factorial design
(Elsevier, 2015-01) Gomes, Yara Feliciano; Medeiros, P.N.; Delmonte, Maurício Roberto Bomio; Santos, Ieda Maria Garcia dos; Paskocimas, Carlos Alberto; Nascimento, Rubens Maribondo do; Motta, Fabiana Villela da
The increasing use of experimental design techniques comes from the growing need to optimize products and processes while minimizing costs and maximizing efficiency, productivity and quality of products. Ceramic pigments have wide application in ceramic industries in which the quality and advanced properties of materials are widely investigated. However, studies are required to improve the procedure for obtaining cobalt aluminate (CoAl2O4) using the Complex Polymerization Method (CPM). With the objective of optimizing this method, a 2(5-2) fractional factorial design was performed using data from UV–vis spectroscopy analysis as a response surface. To determine the best conditions for obtaining (CoAl2O4) in this study, five factors were chosen as input variables at levels determined for this study: citric acid concentration (stoichiometric), pyrolysis time (h), temperature (°C), calcination heating time and rate (°C/min). Through statistical application in the process of obtaining CoAl2O4, it was possible to study which of these factors may have greater influence in optimizing the synthesis. The precursor powders were characterized using TG/DSC thermogravimetric analysis, and the calcined powders were analyzed using X-ray diffraction (XRD) and energy dispersive scanning electron microscopy (SEM/EDS) to confirm the structural and morphological aspects of CoAl2O4. It was found that with increased calcination temperature 700 °C<800 °C<900 °C, the UV–vis bands decreased with increasing absorbance intensity, and with increasing pyrolysis time (h), there is a proportional increase in the UV–vis bands. The model was generated with the conditions proposed in this study due to the determination coefficient of 99.9%, variance (R2), and satisfactory response surfaces, thus obtaining optimization of the process according to the needs and applicability in the ceramic industry of pigments
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
Processamento de cerâmicas reticuladas a partir de matérias-primas naturais
(ABCERAM, 2006-04) Albuquerque, F. R.; Lima, S. J. G.; Paskocimas, Carlos Alberto; Silva, Elson Longo da; Souza, A. G.; Santos, Ieda Maria Garcia dos
Foram produzidas cerâmicas porosas reticuladas a partir de uma matéria-prima natural (AF) empregada na produção de telhas e tijolos, misturando-a com caulim (AC). A matéria-prima AF é constituída basicamente de quartzo e feldspatos. O método empregado para confecção das peças cerâmicas foi o da impregnação em espuma polimérica. Foram otimizadas as viscosidades de barbotinas contendo 70% m/m, utilizando poliacrilato de sódio (PAA-Na) como defloculante. As suspensões com 70% m/m de AF apresentaram viscosidade em torno de 600 mPa.s, reduzindo para 300 mPa.s após adição de 20% m/m de AC. O teor de PAA-Na empregado para a fabricação das cerâmicas porosas foi 2,0% m/m. A tixotropia e a pseudoplastia das barbotinas facilitaram a impregnação de espumas poliméricas com 5, 10 e 40 poros/cm. As cerâmicas reticuladas foram obtidas após sinterização a 1100 e 1200 oC. Os difratogramas de raios X indicaram a dissolução do quartzo a 1200 oC, com uma peça apresentando basicamente mulita e fase vítrea. As cerâmicas reticuladas com porosidade 10 poros/cm apresentaram estrutura suficientemente rígida com resistência mecânica superior a 1,70 MPa e com constante de permeabilidade darciana na ordem de 3,58.10-9 (±10,0%) m2
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 investigation of oil and biodiesel fromJatropha curcasL.
(Springer, 2009-06-19) Bicudo, Tatiana de Campos; Freire, L. M. S.; Rosenhaim, R.; Sinfrônio, F. S. M.; Botelho, J. R.; Carvalho Filho, J. R.; Santos, Ieda Maria Garcia dos; Fernandes Júnior., V. J.; Antoniosi Filho, N. R.; Souza, A. G.
Biodiesel is susceptible to autoxidation if exposed to air, light and temperature, during its storage. Physic nut (Jatropha curcas L.) seeds show potential application for biodiesel production since its oil yields high quality biodiesel. This work aims to evaluate the thermal behavior of the physic nut oil and biodiesel, from several Brazilian crops, by means of thermoanalytical techniques. Thermogravimetry (TG) and pressurized-ifferential scanning calorimetry (PDSC) were used in order to determine the applicability of physic nut biodiesel as fuel. Results suggest that physic nut biodiesel is a practical alternative as renewable and biodegradable fuel able to be used in diesel motors
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?
TiO2/PDMS nanocomposites for use on self-cleaning surfaces
(Elsevier, 2014-01-25) Tavares, Marileide L.A.; Santos, Amélia S.F.; Santos, Ieda Maria Garcia dos; Silva, Manoel Rincón S.; Delmonte, Maurício Roberto Bomio; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Motta, Fabiana Villela da
In this study, polydimethylsiloxane (PDMS)/TiO2 nanocomposite was processed by the spray method. TiO2 nanoparticles were synthesized by microwave-assisted hydrothermal method. Varying the proportion of nanoparticles in 0%, 0.5% and 1% by weight, commercial TiO2 (P25) was used for comparison purposes. The photocatalytic activity of nanocomposites impregnated with methylene blue was assessed by means of UV–visible spectroscopy. Changes in contact angle were analyzed before and after UV degradation tests. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by Fourier transform infrared spectroscopy (FTIR). The results indicated that the addition of TiO2 nanoparticles in PDMS provides good photocatalytic properties in the decomposition of methylene blue, which is an important characteristic for the development of coatings for self-cleaning. For comparison purposes, commercial P25 was also used to investigate the photocatalytic activity

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Navegando por Autor "Santos, Ieda Maria Garcia dos"