Chemical vapor infiltration of TiB[sub 2]-matrix composites

The efficiency of the Hall-Heroult electrolytic reduction of aluminum can be substantially improved by the use of a TiB[sub 2] cathode. The use of TiB[sub 2] 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, TiB[sub 2] is toughened through the use of reinforcing fibers, with chemical vapor infiltration used to produce the TiB[sub 2] matrix. In early efforts it was observed that the formation of TiB[sub 2] from chloride precursors at fabrication temperatures below 900--1,000 C may have allowed the retention of destructive levels of chlorine. At higher fabrication conditions as determined from the use of a process model, TiB[sub 2]/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.