Chemical Vapor Infiltration of TiB2-Matrix Composites

The efficiency of the Hall–Heroult electrolytic reduction of aluminum can be substantially improved by the use of a TiB₂ cathode. The use of TiB₂ components, however, has been hampered by the brittle nature of the material and the grain boundary attack of sintering-aid phases by molten aluminum. In the current work, TiB₂ is toughened through the use of reinforcing fibers, with chemical vapor infiltration used to produce the TiB₂ matrix. In early efforts it was observed that the formation of TiB₂ from chloride precursors at fabrication temperatures below 900–1000°C may have allowed the retention of destructive levels of chlorine. At higher fabrication temperatures (>1000°C), using appropriate infiltration conditions as determined from the use of a process model, TiB₂/THORNEL P-25 fiber composites have been fabricated in 20 h. The improved composite material has been demonstrated to be stable in molten aluminum in short-duration (24 h) tests.