Tecnologia em Metalurgia, Materiais e Mineração
https://tecnologiammm.com.br/article/doi/10.4322/tmm.2014.024
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

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

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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

Referências



1. Callister WD. Fundamentos da ciência e engenharia de materiais: uma abordagem integrada. 2. ed. Rio de Janeiro: LTC; 2006.

2. Qua R, Gao X, Cena K, Lib J. Relationship between structure and performance of a novelcerium-niobium binary oxide catalyst for selective catalytic reductionof NO with NH3. Appl Catal B, Environ. 2013;142-143:290-97. http:// dx.doi.org/10.1016/j.apcatb.2013.05.035

3. Sahner K, Tuller HL. Novel deposition techniques for metal oxide: Prospects for gas sensing. J Electroceram. 2010;24:177-99. http://dx.doi.org/10.1007/s10832-008-9554-7

4. Waser O, Hess M, Güntner A, Novák P, Pratsnis SE. Size controlled CuO nanoparticles for Li-ion batteries. J Power Sources. 2013;241:415-22. http://dx.doi.org/10.1016/j.jpowsour.2013.04.147

5. Daliya S. Mathew, Ruey-Shin J. An overview of the structure magnetism of spinel ferrite nanoparticles and their synthesis in microemulsions. Chem Eng J. 2007;129:51-65. http://dx.doi.org/10.1016/j.cej.2006.11.001

6. Navarro RCS. Estudo do sistema Al2O3 -MnO: propriedades termodinâmicas do óxido Al2MnO4 [tese de doutorado]. Rio de Janeiro: Pontifícia Universidade Católica do Rio de Janeiro; 2009.

7. Navarro RCS, Gomez MAS, Avillez RR. Heat capacity of stoichiometric Al2MnO4 spinel between 2 and 873 K. Calphad. 2012;37:11-17. http://dx.doi.org/10.1016/j.calphad.2011.12.008

8. Klemme S, Miltenburg JC. The heat capacities and thermodynamic properties of NiAl2O4 and CoAl2O4, measured by adiabatic calorimetry from T = 4 to 400 K. J Chem Thermodyn. 2009;41:842-48. http://dx.doi.org/10.1016/j. jct.2009.01.014

9. Bean CP, Livingston JD. Superparamagnetism. J Appl Physi. 1959;30(4):120-29. http://dx.doi.org/10.1063/1.2185850

10. Jena PK. Identification of a third phase in Cu-Al2O3 nanocomposites prepared by chemical routes. Mater Sci Eng, A Struct Mater: Prop Microstruct Process. 2002;371:72-78. http://dx.doi.org/10.1016/S0921-5093(03)00642-7

11. Brocchi EA, Motta MS, Jena PK. Preparation of Cu-Ni alloys through a new chemical route. Metall Mater Trans B Proc Metall Mater Proc Sci. 2004;35(6):1107-12. http://dx.doi.org/10.1007/s11663-004-0066-9

12. Brocchi, EA, Moura FJ, De Macedo DW. Synthesis and characterisation of nanostructured Ni-Co alloy part 3: NiO and Co3O4 co-formed reduction kinetics. Trans Inst Min Metall C, Miner Process Extr Metall. 2009;118(1):44-48.

13. Cullity BD. Elements of X-ray diffraction. 2. ed. London: Addison-Wesley-Publishing Company Inc.; 1978.

14. Halenius U, Bosi F, Skogby H. Galaxite, MnAl2O4, a spectroscopic standard for tetrahedrally coordinated Mn2+ in oxygen-based mineral structures. Am Mineral. 2007;92:1225-31. http://dx.doi.org/10.2138/am.2007.2481

15. Birks LS. Electron probe microanalysis. 2nd ed. Nova Iorque: Wiley Interscience Publication; 1971.
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