C-TiB2 Composite Inert Cathode Material by Spark Plasma Sintering
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TiB2 has been considered a potential inert, wettable cathode material for aluminum reduction cells for a long time. An important characteristic of TiB2 as a cathode material, is its excellent wetting properties towards molten aluminium. Because of the high cost and poor machining properties of TiB2, composites of C-TiB2 has been suggested as an alternative cathode material. In this work, nine C-TiB2 composites ranging from pure TiB2 to 85 wt% C were successfully sintered using Spark Plasma Sintering. Almost theoretical density of pure TiB2 was obtained with 97.1% relative density. Composites with 15 wt% C and 25 wt% C were sintered with relative high relative density of 91.3% and 79.8% respectively. The relative density of the composites ranging from 35 wt% C to 85 wt% C, were limited to just above 60%. The Sessile Drop method was used to test the wetting behaviour of molten aluminium on the sintered composites, including tests on pure TiB2 and graphite. Equilibrium contact angles were reached at 1100°C for three samples including pure TiB2, composite with 15 wt% C and graphite at 9.1°, 22.2° and 11.6° respectively. No stable contact angle were reached for the remaining composites. The dependence of carbon composition on the wetting angles were not discerned from the current measurements. The plausible reason and dynamic wetting behaviour at elevated temperatures were elaborated.