Articles
All articles | Recent articles
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.
Download Full Article (PDF)
Keywords
Sidewalls, Mg(AlxFe1-x)2O4, dense layer, electrolyte, corrosion resistance
References
1 Etzion, R., Metson, J.B., Depree, N.: Wear mechanism study of silicon nitride bonded silicon carbide refractory materials, Light Met., 955 – 958, (2008).
2 Brooks, G., Cooksey, M., Wellwood, G., Goodes, C.: Challenges in light metals production, Miner. Process. Extr. Metall., 116, 25 – 33, (2007).
3 Hang, E., Einarsrud, M., Grande, T.: Chemical stability of ceramic sidelinings in hall-herouh cells, Light Met., 257 – 263, (2001).
4 Gao, B.L., Wang, Z.W., Qiu, Z.X.: Corrosion tests and electrical resistivity measurement of SiC-Si3N4 refractory materials, Light Met., (2004).
5 Wang, Z., Skybakmoen, E., Grande, T.: Spent Si3N4 bonded SiC sidelining materials in aluminum electrolysis cells, Light Met., 353 – 358, (2009).
6 Pan, Y.H., Wright, S, Sun, S.Y: Review and applications of thermal conductivity models to aluminium cell sidewall refractories, Int. J. Mod. Phys. B, 23, 790 – 795, (2012).
7 Mukhlis, R.Z., Rhamdhani, M.A., Brooks, G.: Sidewall materials for Hall-Héroult process, Light Met., 883 – 888, (2010).
8 Yan, X.Y., Mukhlis, R.Z., Rhamdhani, M.A., Brooks, G.: Aluminate spinels as sidewall linings for aluminum smelters, Light Met., 1085 – 1090, (2011).
9 Nightingale, S.A., Longbottom, R.J., Monaghan, B.J.: Corrosion of nickel ferrite refractory by Na3AlF6-AlF3-CaF2-Al2O3 bath, J. Eur. Ceram. Soc., 33, 2761 – 2765, (2013).
10 Xu, Y.B., Li, Y.W., Sang, S.B., Ren, B., Qin. Q.W., Yang, J.H.: Preparation of MgO-SnO2-TiO2 materials and their corrosion in Na3AlF6-AlF3-K3AlF6 bath, Metall. Mater. Trans. B, 46, 1125 – 1132, (2015).
11 Xu, Y.B., Li, Y.W., Sang, S.B., Ren, B., Qin, Q.W., Yang, J.H.: Preparation of MgO-NiFe2O4-TiO2 materials and their corrosion in Na3AlF6-AlF3-K3AlF6 bath, Ceram. Int., 40, 13169 – 13177, (2014).
12 Downie, K.: NiFe2O4 as a sidewall material in Hall-Héroult cells, Wollongong, University of Wollongong, 2007.
13 Pawlek, R.P.: Inert anode: Research, development, and potential, Light Met., 50 – 55, (2002).
14 Yan, X.Y., Pownceby, M.I., Brooks, G.: Corrosion behaviour of nickel ferrite-based ceramics for aluminium electrolysis cells, Light Met., 909 – 913, (2007).
15 Olsen, E., Thonstad, J.: Nickel ferrite as inert anodes in aluminum electrolysis, Part I: Material fabrication and preliminary testing, J. Appl. Electrochem., 29, 293 – 299, (1999).
16 Zhou, K.C., Tao, Y.Q., Liu, B.G., Li, Z.Y.: Enhanced sintering and molten salt corrosion behavior of nickel ferrite based cermets, Chin. J. Nonferr. Met., 21, [6], 1348 – 1358, (2011).
17 Sadoway, D.R.: Inert anodes for the Hall-Héroult cell: the ultimate materials challenge, JOM, 53, 34 – 35, (2001).
18 Kvande, H.: Inert electrodes in aluminum electrolysis cells, Light Met., 369 – 376, (1999).
19 Jentoftsen, T.E., Lorentsen, O.A., Dewing, E.W., Haarberg, G.M., Thonstad, J.: Solubility of some transition metal oxides in cryolite-alumina melts: Part I. Solubility of FeO, FeAl2O4, NiO, and NiAl2O4, Metall. Mater. Trans. B, 3, 901 – 908, (2002).
20 Yu, X., Zhang, L., Dong, Y.: Corrosion of zinc ferrite based inert anodes in AlF3-NaF-Al2O3 melts under conditions of anodic polarization, J. Rare Earth., 24, 352 – 354, (2006).
21 Xu, Y.B., Li, Y.W., Yang, J.H., Sang, S.B., Qin, Q.W.: Reaction of magnesia and iron oxide in air and flowing nitrogen and its corrosion process by molten electrolyte, J. Ceram. Sci. Tech., 7, [3], 249 – 256, (2016).
22 Berchmans, L.J., Selvan, R.K., Augustin, C.O.: Evaluation of Mg2+-substituted NiFe2O4 as a green anode material, Mater. Lett., 58, 1928 – 1933, (2004).
23 Yan, W., Lin, X., Chen, J.: Effect of TiO2 addition on microstructure and strength of porous spinel (MgAl2O4) ceramics prepared from magnesite and Al(OH)3 J. Alloy. Compd., 618, 287 – 291, (2015).
24 Yan, W., Li, N., Li, Y.Y.: Effect of particle size on microstructure and strength of porous spinel ceramics prepared by pore-forming in situ technique B. Mater. Sci., 34, [34], 1109 – 1112, (2011).
25 Zou, Y., Gu, H.Z., Huang, A., Zhang, M.J., Lian, P.F.: Effect of particle distribution of matix on microstructure and slag resistance of lightweight Al2O3-MgO castables, Ceram. Int., 42, [1], 1964 – 1972, (2016).
26 Liang, Y.H., Huang, A., Zhu, X.W., Gu, H.Z., Fu, L.P.: Dynamic slag/refractory interaction of lightweight Al2O3-MgO castable for refining ladle, Ceram. Int., 42, [6], 8149 – 8154, (2015).
27 Hiromichi, A., Hideyuki, H., Takashi, N., Tsunehiro, M.: Surface study of fine MgFe2O4 ferrite powder prepared by chemical methods. Appl. Surf. Sci., 254, 2319 – 2324, (2008).
28 Liu, Y.L, Liu, Z.M., Yang, Y., Yang, H.F., Shen, G.L., Yu, R.Q.: Simple synthesis of MgFe2O4 nanoparticles as gas sensing materials, Sensor. Act. B, 107, 600 – 604, (2005).
29 Reddy, M.P., Shakoor, R.A., Mohamed, A.M.A.: Effect of sintering temperature on the structural and magnetic properties of MgFe2O4 ceramics prepared by spark plasma sintering, Ceram. Int., 42, [3], 4221 – 4227, (2015).
30 Liu, G.P., Li, N., Yan, W., Tao, G.H., Li, Y.Y.: Composition and structure of a composite spinel made from magnesia and hercynite, J. Ceram. Process. Res., 13, [4], 480 – 485, (2012).
31 Fawzi, A.S., Sheikh, A.D., Mathe, V.L.: Structural, dielectric properties and AC conductivity of Ni(1–x)ZnxFe2O4 spinel ferrites, J. Alloy. Compd., 502, 231 – 237, (2010).
32 Liu, B., Zhang, L., Zhou, K., Wang, H.: Electrical conductivity and molten salt corrosion behavior of spinel nickel ferrite, Solid State Sci., 13, [8], 1483 – 1487, (2011).
33 Luz, A.P., Braulio, M.A.L., Martinez, A.G.T., Pandolfelli, V.C.: Thermodynamic simulation models for predicting Al2O3-MgO castable chemical corrosion, Ceram. Int., 37, [8], 3109 – 3116, (2011).
34 Luz, A.P., Martinez, A.G.T., Braulio, M.A.L., Pandolfelli, V.C.: Thermodynamic evaluation of spinel containing refractory castables corrosion by secondary metallurgy slag, Ceram. Int., 37, [4], 1191 – 1201, (2011).
Copyright
Göller Verlag GmbH