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Sintering Behaviour of Mg(AlxFe1-x)2O4 Materials and their Corrosion in Na3AlF6-AlF3-K3AlF6 Electrolyte
Y.B. Xu, Y.W. Li, J.H. Yang, S.B. Sang, Q.W. Qin
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, 430081 Wuhan, PR China
received October 7, 2016, received in revised form November 7, 2016, accepted February 7, 2017
Vol. 8, No. 2, Pages 193-200 DOI: 10.4416/JCST2016-00081
Abstract
The development of new electrolysis technology in the aluminium industry calls for new sidewall materials since the frozen ledge would no longer exist. In the present paper, Mg(AlxFe1-x)2O4 materials were prepared and characterized, and corrosion tests in a Na3AlF6-AlF3-K3AlF6 bath were conducted. The results show that reaction sintering occurs in the MgAl2O4-MgO-Fe2O3 system in the range of 1000 to 1600 °C. Firstly, MgO reacts with Fe2O3 to produce MgFe2O4 phase at 1000 °C, which in turn reacts with MgAl2O4 to form Mg(AlxFe1-x)2O4 composite spinel at temperatures above 1200 °C. As a result, mass transfer and densification in the specimens are enhanced as the amount of the Fe2O3 increases. After being fired at temperatures above 1200 °C, all the specimens prepared are composed of single-phase Mg(AlxFe1-x)2O4 composite spinel, the lattice parameter of which increases with increasing Fe3+ ion concentration. The corrosion results show that corrosion resistance of the specimens increases progressively with the Fe2O3 content owing to the improved chemical stability of the Mg(AlxFe1-x)2O4 composite spinel and the enhanced densification of the specimens. And for the specimens with a Fe/(Al+Fe) mole fraction more than 0.5, a dense and stable ceramic layer forms on surface of the specimens during the corrosion test, which further improves their corrosion resistance.
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Keywords
Sidewalls, Mg(AlxFe1-x)2O4, dense layer, electrolyte, corrosion resistance
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