Effect of TiB₂ content on resistance to sodium penetration of TiB₂/C cathode composites for aluminium electrolysis

Abstract

TiB₂/C cathode composites with various contents of TiB₂ were prepared and their characterizations were observed and compared. The expansion of samples due to sodium and bath penetration was tested with a modified laboratory Rapoport apparatus and the appearances of the cut sections of specimens after electrolysis were studied. The results show that the mass of TiB₂/C cathode composites with mass fraction of TiB₂ less than 70% appreciably increases, but that of the composites with mass fraction of TiB₂ more than 70% decreases slightly after being baked. The resistance to sodium and bath penetration of TiB₂/C cathode composites increases with the increase of TiB₂ content, especially in the composites with high TiB₂ content. TiB₂/C cathode composites have high resistance to the penetration of sodium and bath as well as good wettability by molten aluminum, and keep integrality and have little change of appearance after electrolysis, which indicates that TiB₂/C cathode composites can be used as inert wettable cathode for aluminum electrolysis.

Keywords

aluminium electrolysis / TiB₂ / cathode / composite material / sodium penetration

References

[1] WelchB J. Future materials requirements for the highenergy-intensity production of aluminum [J]. JOM, 2001, 53(2): 13-18

[2] BillehaugK, OyeH A. Inert cathodes for aluminium electrolysis in Hall-Heroult cells(1)[J]. Aluminium, 1980, 56(10): 642-648

[3] BillehaugK, OyeH A. Inert cathodes for aluminium electrolysis in Hall-Heroult cells(II)[J]. Aluminium, 1980, 56(10): 713-718

[4] McMinnC J. A review of RHM cathode development [A]. Light Metals 1992[C], 1992, Warrendale, TMS: 419-425

[5] DionneM, LesperanceG, MirtchiA. Wetting of TiB₂-carbon material composite [A]. Light Metals 1999[C], 1999, Warrendale, TMS: 389-394

[6] PawlekR P. Aluminium wettable cathodes: an update [A]. Light Metals 2000 [C], 2000, Warrendale, TMS: 449-454

[7] BrownC W. Wettability of TiB₂-based cathodes in low-temperature slurry-electrolyte reduction cells[J]. JOM, 1998, 50(2): 38-40

[8] SekharJ A, de NoraV, LiuJ, et al.. TiB₂/colloidal alumina carbon cathode coating in Hall-Heroult and drained cells[A]. Light Metals 1998[C], 1998, Warrendale, TMS: 605-615

[9] TabereauxA, BrownJ, EldridgeI, et al.. The operational performance of 70 kA prebake cells retrofitted with TiB₂-G cathode elements[A]. Light Metals 1998 [C], 1998, Warrendale, TMS: 257-264

[10] XueJi-lai, OyeH A. Sodium and bath penetration into TiB₂-carbon cathodes during laboratory aluminium electrolysis[A]. Light Metals 1992[C], 1992, Warrendale, TMS: 773-778

[11] XueJi-lai, OyeH A. Investigating carbon/TiB₂ materials for aluminum reduction cathodes [J]. JOM, 1992, 44(11): 28-34

[12] FengNai-xiang. Pentration of cryolite metal and sodium into cathode carbon blocks during electrolysis [J]. Acta Metallurgica Sinica, 1999, 35(6): 611-617(in Chinese)

[13] SorlieM, OyeH A. Laboratory testing of carbon cathode materials at operational temperatures [A]. Light Metals 1989 [C], 1988, Warrendale, TMS: 625-631

[14] LiaoXian-an, OyeH A. Increased sodium expansion in cryolite-based alumina slurries [A]. Light Metals 1998 [C], 1998, Warrendale, TMS: 659-666

[15] BrilloitP, lassiusL P, OyeH A. Melt penetration and chemical reaction in carbon cathodes during aluminium electrolysis: I. laboratory experiment [A]. Light Metals 1993 [C], 1993, Warrendale, TMS: 321-330

[16] SorlieM, OyeH ACathode in Aluminium Electrolysis(2nd ed) [M], 1994, Dusseldorf, Aluminium-Verlag

[17] SekharJ A, BelloV, de NoraV, et al.. Cathodic coating for improved cell performance [A]. Light Metals 1995 [C], 1995, Warrendale, TMS: 507-513

[18] LiaoXian-an, LiuYie-xiang, MaoZheng-ping. Development and application of TiB₂-C composite coated cathodes[J]. Material Review, 1995, 9(2): 17-19(in Chinese)

[19] XueJi-lai, OyeH A. Wetting of graphite and carbon/TiB₂ composites by liquid aluminium[A]. Light Metals 1993 [C], 1993, Warrendale, TMS: 631-637