SÍNTESE DO ESPINÉLIO Al2MnO4 VIA REDUÇÃO COM H2
SYNTHESIS OF THE Al2MnO4 SPINEL THROUGH H2 REDUCTION
Siqueira, Rogério Navarro C. de; Oliveira, Pâmela Fernandes de
http://dx.doi.org/10.4322/tmm.2014.024
Tecnol. Metal. Mater. Min., vol.11, n2, p.163-170, 2014
Resumo
Óxidos nanoestruturados com propriedades magnéticas relevantes, como o espinélio Al2MnO4, podem ser sintetizados a partir da decomposição térmica de soluções de nitratos e posterior tratamento térmico em atmosfera redutora. O presente trabalho tem como objetivo principal a síntese do espinélio Al2MnO4 via redução com H2 de misturas de óxidos de Al e Mn, e o estudo de variáveis de processo relevantes - temperatura e tempo de tratamento térmico. Na faixa de temperatura entre 1.073 K e 1.173 K, tanto a redução dos óxidos de manganês inicias a MnO quanto a formação do espinélio Al2MnO4 foram comprovadas, apresentando o material final significativo conteúdo nanoestruturado. Nos momentos iniciais, o espinélio formado apresenta considerável desordem catiônica (estrutura não estequiométrica), aproximando-se a mesma da forma estequiométrica (estrutura de equilíbrio), uma vez elevando-se o tempo e temperatura de processo.
Palavras-chave
Espinélios, Al2MnO4, Nitratos, Redução com H2
Abstract
Nanostructured oxides with interesting magnetic properties, such as the spinel Al2MnO4, can be synthesized through thermal decomposition of nitrate solution followed by thermal treatment under a reducing atmosphere. The present work can be understood as a study of the synthesis of Al2MnO4 samples based on the H2 reduction of Al and Mn oxide mixtures, including a discussion of the effect of some important process variables over the kinetic behavior of the system, such as temperature and thermal treatment time. For the temperature range considered (1,073 K to 1,173 K) both the total reduction of manganese oxides to MnO, as well as the formation of spinel structures could be verified. At the beginning of the formation process, the spinel shows considerable cationic disorder (non-stoichiometric structure). The structure then evolves to the equilibrium stoichiometric form for higher process temperature and time.
Keywords
Spinel, Al2MnO4, Nitrates, H2 reduction
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