Electrodeposited TiB ₂ on graphite as wettable cathode for Al production

Abstract

Abstract Titanium diboride (TiB 2 ) is considered as a promising cathode material for Al production. However, the manufacture of TiB 2 cathodes is facing numerous challenges. In this study, electrodeposition of TiB 2 on graphite was performed in molten fluoride (FLiNaK) electrolyte at 600°C by using a periodically interrupted current technique for various electrodeposition times (from 10 to 75 minutes) and at two different current densities (−0.12 and −0.5 A/cm 2 ). It is shown that the TiB 2 coating morphology/microstructure strongly depends on the applied current density. Denser coatings were obtained at j on = −0.12 A/cm 2 with a growth rate of ca. 0.7 µm/min. The thicker films display a preferential crystallographic orientation along the [110] plan. At j on = −0.5 A/cm 2 , TiB 2 coatings are deposited at a growth rate of ca. 6 µm/min with no crystallographic texture. They present a porous and stratified morphology with numerous transversal macrocracks. All TiB 2 coatings show excellent wettability for molten Al as confirmed by sessile drop experiments. However, significant molten Al infiltration occurs in the TiB 2 coatings, which accumulates at the coating/graphite interface, inducing the coating delamination.