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Search Results: 1 - 10 of 167404 matches for " E.;Muccillo "
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Pesquisa e desenvolvimento em ceramicas eletro-eletr?nicas no IPEN
Muccillo, R.;Muccillo, E. N. S.;
Ceramica , 1999, DOI: 10.1590/S0366-69131999000400004
Abstract: the electroelectronic ceramics group at ipen perform r&d in advanced ceramic materials to be used in devices like sensors for gaseous species and solid electrolyte fuel cells. the main research areas are 1) synthesis, processing and electrical characterization of ceramic materials, 2) study of the dependence of the electrical properties on the microstructural aspects of ceramic materials, 3) design, development, setup and testing of electrochemical sensors for chemical species. the main materials being studied are ionic conductors (zro2 and tho2-based, and others), protonic conductors (baceo3), tin oxide based varistors, high-tc ceramic superconductors (y-ba-cu-o and bi-sr-ca-cu-o ceramic systems) and ceramic matrix composites (electrical insulators in an ionic conductor matrix and ionic conductor in a ceramic superconductor matrix). the experimental facilities are an impedance analyzer, an x-ray diffractometer, a simultaneous thermal analyzer, high temperature furnaces for sintering, and a chemical laboratory. the research work is sponsored by grants from fapesp, a state foundation and pronex.
Pesquisa e desenvolvimento em ceramicas eletro-eletr nicas no IPEN
Muccillo R.,Muccillo E. N. S.
Ceramica , 1999,
Abstract: O Grupo de Ceramicas Eletro-eletr nicas do IPEN desenvolve trabalhos de pesquisa em materiais ceramicos avan ados para utiliza o em dispositivos sensores de espécies químicas e em células de combustíveis a eletrólitos sólidos. As principais áreas de atua o do grupo s o em 1) síntese, processamento e caracteriza o elétrica de materiais ceramicos, 2) estudo de correla o microestrutura-propriedades elétricas de materiais ceramicos, 3) projeto, desenvolvimento, montagem e testes de sensores eletroquímicos de espécies químicas. Os principais materiais estudados s o condutores i nicos (à base de ZrO2, ThO2 e outros), prot nicos (à base de BaCeO3), varistores à base de SnO2, supercondutores ceramicos de alta temperatura crítica (das famílias Y-Ba-Cu-O e Bi-Sr-Ca-Cu-O) e compósitos de matriz ceramica (dos tipos isolante em matriz condutora i nica e condutor i nico em matriz supercondutora). A infra-estrutura experimental disp e de analisador de impedancia, difrat metro de raios X, equipamento de análise térmica simultanea, fornos para sinteriza o e laboratório químico. O trabalho de pesquisa do Grupo é financiado por projetos FAPESP e PRONEX.
Aplica??o da técnica de deposi??o eletroforética para a obten??o de tubos ceramicos de zirc?nia-ítria
Caproni, E.;Muccillo, R.;
Ceramica , 2012, DOI: 10.1590/S0366-69132012000100021
Abstract: the electrophoretic deposition (epd) is recognized as the most versatile technique for processing particulate materials, due to low cost, deposition in minutes and forming of pieces with complex geometry shapes. in this work an experimental setup for the simultaneous conformation of 16 ceramic tubes by epd was built. bimodal submicron yttria-stabilized zirconia particles were deposited into graphite electrodes, after suitably adjusting the rheological characteristics of the suspension in isopropanol. after graphite burning and ysz sintering at 1500 °c, the ceramic tubes were characterized by x-ray diffraction, scanning probe microscope, impedance spectroscopy and electrical response as a function of oxygen content. small dense one end-closed ceramic tubes, fully stabilized in the cubic phase, were successfully obtained by the epd technique, showing the ability of that technique for processing large quantities of tubular solid electrolytes with electrical response to different amounts of oxygen according to the nernst law.
Condutores de íons oxigênio: uma breve revis?o
Muccillo, E. N. S.;
Ceramica , 2008, DOI: 10.1590/S0366-69132008000200002
Abstract: the main characteristics related to transport properties of oxygen ion conductors are described in detail. the materials focused are those based on zirconia and ceria solid solutions, compounds with pyrochlore and perovskite-type structures, and the most recently reported ionic conductors based on apatite structure and those derived from la2mo2o9 composition. particular emphasis will be paid on recent results. the main purpose of this review is to summarize the most relevant aspects related to transport properties, allowing for a critical analysis of the potential of application of these ceramic solid electrolytes.
Microestrutura e condutividade elétrica em Ce0,85Y0,15-xRxO2-delta (R=Pr, Tb)
Tadokoro, S. K.;Muccillo, E. N. S.;
Ceramica , 2007, DOI: 10.1590/S0366-69132007000100014
Abstract: ce0.85y0.15-xrxo2-d (r=pr, tb) with x = 0.02 e 0.06 solid solutions were synthesized by the hydroxide coprecipitation technique to study the effect of pr and tb additions in the microstructure and electrical conductivity of yttria-doped ceria solid electrolyte. for comparison purposes, the solid solution ce0.85y0.13pr0.02o2-d was prepared by mixing pr6o11 to the precipitated gel of ceria-yttria. the solid electrolyte ce0.85y0.15o2-g was also synthesized by chemical route. the structural characterization of sintered specimens was carried out by conventional x-ray diffraction and raman spectroscopy experiments. the morphology of sintered materials was verified by scanning electron microscopy coupled to energy dispersive x-ray analysis. the electrical conductivity was measured by impedance spectroscopy. the overall results show the key role of the synthesis technique for obtaining chemically and structurally homogeneous solid solutions. reductions in the average grain size and in the full width at half maximum height of the grain size distribution curve were obtained with increasing praseodymium additions to ceria-yttria. in contrast, tb additions to yttria-doped ceria do not result in any significant microstructural change. both co-dopants, pr and tb, exert a deleterious effect on the electrical conductivity of yttria-doped ceria at temperatures of typical solid oxide fuel cells operation.
Efeito da temperatura de calcina??o e do teor de dopante nas propriedades físicas da céria-gadolínia preparada pela complexa??o de cátions com ácido cítrico
Rocha, R. A.;Muccillo, E. N. S.;
Ceramica , 2001, DOI: 10.1590/S0366-69132001000400010
Abstract: ceria-gadolinia solid solutions were prepared by the cation complexation technique using citric acid as complexant agent. the purposes of this work were to evaluate de calcining profile of the precursor resin in order to obtain nanosized powders with high sinterability; and to verify the effects of dopant content on densification and electrical resistivity of sintered specimens. the main results show that powders with less than 10 nm crystallite size may be obtained at relatively low temperatures. gadolinium oxide enhances the densification of pressed specimens reaching a relative density > 99% for the ce0.8gd0.2o1.9 composition sintered at 1500 oc for 3 h.
Zirc?nia tetragonal policristalina. Parte I: síntese e caracteriza??o
Tadokoro, S. K.;Muccillo, E. N. S.;
Ceramica , 2000, DOI: 10.1590/S0366-69132000000400011
Abstract: zro2: 3 mol% y2o3 and 12 mol% ceo2 nanosized powders have been prepared by the coprecipitation technique. the main purpose of this work is to optimize the synthesis and processing procedures to obtain nanosized powders with high reactivity and controlled physical properties. several characterization techniques were used: thermal analyses, laser scattering, nitrogen adsorption, x-ray diffraction, and scanning electron microscopy. the main results show that the precise control of synthesis and processing techniques allows for obtaining nanosized ceramic powders with reproducible and optimized properties.
Densifica??o, tamanho de gr?os e condutividade elétrica da céria-samária
Reis, S. L.;Muccillo, E. N. S.;
Ceramica , 2011, DOI: 10.1590/S0366-69132011000300018
Abstract: ceria containing 20 mol% samaria is a solid electrolyte with potential application in solid oxide fuel cells operating at intermediate temperatures (~500 to 700 oc) due to its high ionic conductivity. one of the main concerns related to this solid electrolyte is the relatively low sinterability. in this work, two alternative sintering methods were used to obtain ceramic samples with high density, homogeneous microstructure and controlled grain size. other purpose of this work was to correlate the observed effects in the microstructure and densification with the electrical conductivity of sintered samples. commercial ce0.8sm0.2o1.9 was used as starting material. the consolidation was accomplished by uniaxial and isopressing followed by sintering in air. several techniques were used for sample characterization. apparent density results revealed that both sintering methods were able to produce samples with relative density higher than 92%. the electrical conductivity of grains and grain boundaries were similar in these samples, although different grain sizes were obtained.
Zirc?nia tetragonal policristalina. Parte II: Microestrutura e resistividade elétrica
Tadokoro, S. K.;Muccillo, E. N. S.;
Ceramica , 2001, DOI: 10.1590/S0366-69132001000200007
Abstract: results on dense zro2: 3 mol% y2o3 (y-tzp) and 12 mol% ceo2 (ce-tzp) ceramics are shown in this second part. sintered specimens were analyzed by raman spectroscopy, scanning electron microscopy and impedance spectroscopy. the main results show that both types of solid solutions may attain a high densification (> 95% of the theoretical density) for sintering temperatures lower than 0.45 tf (tf = melting temperature). the rate of grain growth is governed by the stabilizing cation and is faster for ce-tzp than for y-tzp. raman spectra exhibit the six characteristic bands of the tetragonal phase for both specimens. impedance spectroscopy results for y-tzp do not differ from those obtained for nanophase ceramics. a reduction in the extrinsic conductivity due to the high purity of the crystallized precursor was observed for ce-tzp specimens.
Zirc nia tetragonal policristalina. Parte I: síntese e caracteriza o
Tadokoro S. K.,Muccillo E. N. S.
Ceramica , 2000,
Abstract: Solu es sólidas de zirc nia - 3% mol ítria e 12% mol céria com partículas nanométricas foram preparadas pela técnica da co-precipita o. O principal objetivo deste trabalho é a utiliza o de parametros otimizados de síntese e de processamento para a obten o de pós nanométricos, com alta reatividade e com características físicas controladas. As principais técnicas de caracteriza o utilizadas foram: análises térmicas, espalhamento laser, adsor o gasosa, difratometria de raios X e microscopia eletr nica de varredura. Os resultados mostram que a técnica de síntese das solu es sólidas e o controle das etapas de processamento s o decisivos para a obten o de pós ceramicos com propriedades desejadas e reprodutíveis.
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