Síntese de templates para aplicação em piezocerâmicas livre de chumbo
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Data
2008-02-22
Autores
Paula, Amauri Jardim de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
As piezocerâmicas de chumbo a base de Pb(Zr1-xTix)O3 (PZT) sempre tiveram destaque devido às suas excelentes propriedades piezoelétricas. Suas aplicações como sensores, atuadores e capacitores tornaram essas cerâmicas um alvo de incessantes estudos. Entretanto, cresce a necessidade de substituí-las devido ao impacto ambiental causado pelo chumbo. Com este objetivo, pesquisas em busca de materiais alternativos vêm ganhando destaque na comunidade científica internacional. Nesse contexto, os únicos materiais que apresentaram características equiparáveis ao PZT foram os niobatos alcalinos texturizados. Entretanto, para a obtenção dessas cerâmicas texturizadas foi necessária a produção de templates de niobato de sódio (NaNbO3) por complexos processos de síntese, uma vez que estes não estão disponíveis comercialmente. Nessa linha de estudo, o presente projeto de pesquisa buscou a síntese de moldes (templates) de niobato de sódio e de potássio para texturização de cerâmicas livres de chumbo a base de niobatos alcalinos (NaKLiNbO3) por método “Templated Grain Growth” (TGG) e “Reactive Templated Grain Growth” (RTGG). Os templates foram produzidos por síntese hidrotérmica assistida por microondas (H-M), a 200ºC, e com variações de tempo, tipo de precursor de nióbio e concentração de reagentes. Os templates de NaNbO3 e KNbO3 foram produzidos através da reação entre um precursor de nióbio (Nb2O5 ou NH4.NbO.(C2O4)2.(H2O)2.(H2O)n) e o hidróxido do respectivo metal alcalino (NaOH ou KOH). O NaNbO3 foi produzido com ambos os precursores de nióbio, embora o oxalato amoniacal favoreça a cristalização de partículas cúbicas de maior tamanho (>4μm). Durante a síntese do NaNbO3, as análises de difratometria de raios X (DRX) e de microscopia eletrônica de varredura (MEV) mostraram que as microfibras de Na2Nb2O6.nH2O formadas são uma fase intermediária...
PZT-based materials [Pb(Zr1-xTix)O3] are the most used piezoceramics around the world due to their excellent piezoelectric properties. Their applications as sensors, actuators and capacitors made these ceramics the center of unceasing studies. However, the necessity of substituting these materials has been increased mainly because of the environment impact caused by the lead element. With this objective, new researches aiming the discovery of alternative materials have been growth in the scientific community. In this context, the only materials which presented properties at the level of PZT were the texturized alkalines niobates. Nevertheless, to produce such texturized ceramics, the use of complexes methods of synthesis was necessary to create templates of sodium niobate (NaNbO3), once they are not commercially available. Therefore, this project attempted to produce templates of sodium and potassium niobates intending the texturization of alkaline niobate-based ceramics (NaKLiNbO3) by Templated Grain Growth (TGG) and Reactive Templated Grain Growth (RTGG) methods. The templates were produced by means of a microwave assisted hydrothermal synthesis (M-H), at 200ºC, by varying the time, type of niobium precursor and reactants concentrations. The templates of NaNbO3 e KNbO3 were produced through the reaction between a niobium precursor (Nb2O5 or NH4.NbO.(C2O4)2.(H2O)2.(H2O)n) and the hydroxide of the respective alkaline metal (NaOH or KOH). The NaNbO3 was synthesized by both niobium precursors, though the niobium ammoniacal oxalate promoted the formation of cubic particles of NaNbO3 with greater sizes (>4μm). During the synthesis of the NaNbO3, the analysis of X-ray diffratometry (XRD) and scanning electronic microscopy (SEM) indicated that the microfibers of Na2Nb2O6.nH2O are formed as an intermediary phase towards the NaNbO3 crystallization... (Complete abstract click electronic access below)
PZT-based materials [Pb(Zr1-xTix)O3] are the most used piezoceramics around the world due to their excellent piezoelectric properties. Their applications as sensors, actuators and capacitors made these ceramics the center of unceasing studies. However, the necessity of substituting these materials has been increased mainly because of the environment impact caused by the lead element. With this objective, new researches aiming the discovery of alternative materials have been growth in the scientific community. In this context, the only materials which presented properties at the level of PZT were the texturized alkalines niobates. Nevertheless, to produce such texturized ceramics, the use of complexes methods of synthesis was necessary to create templates of sodium niobate (NaNbO3), once they are not commercially available. Therefore, this project attempted to produce templates of sodium and potassium niobates intending the texturization of alkaline niobate-based ceramics (NaKLiNbO3) by Templated Grain Growth (TGG) and Reactive Templated Grain Growth (RTGG) methods. The templates were produced by means of a microwave assisted hydrothermal synthesis (M-H), at 200ºC, by varying the time, type of niobium precursor and reactants concentrations. The templates of NaNbO3 e KNbO3 were produced through the reaction between a niobium precursor (Nb2O5 or NH4.NbO.(C2O4)2.(H2O)2.(H2O)n) and the hydroxide of the respective alkaline metal (NaOH or KOH). The NaNbO3 was synthesized by both niobium precursors, though the niobium ammoniacal oxalate promoted the formation of cubic particles of NaNbO3 with greater sizes (>4μm). During the synthesis of the NaNbO3, the analysis of X-ray diffratometry (XRD) and scanning electronic microscopy (SEM) indicated that the microfibers of Na2Nb2O6.nH2O are formed as an intermediary phase towards the NaNbO3 crystallization... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Ceramica, Niobatos, Síntese hidrotérmica, Ceramics
Como citar
PAULA, Amauri Jardim de. Síntese de templates para aplicação em piezocerâmicas livre de chumbo. 2008. 115 f. Dissertação (mestrado) - Universidade Estadual Paulista, Instituto de Química, 2008.