Synthesis of boride and nitride ceramics in molten aluminium by reactive infiltration

The infiltration of solid powder mixtures with molten aluminium has been investigated as a potential route for the synthesis of ceramic/metal composites. Either titanium or tantalum powder was mixed with boron nitride flakes for the reaction powder mixture. The infiltration occurred spontaneously at 1473K for both [Ti + BN] and [Ta + BN] powder mixtures. Owing to reactions between the starting materials, both boride and nitride ceramics were produced in molten aluminium. TiB2 and AlN were produced from the [Ti + BN] powder mixture, and TaB2 and AlN were produced from the [Ta + BN] powder mixture. When the [Ti + BN] powder mixture was used, a reaction producing Al3Ti took place immediately after the infiltration of the molten aluminium, and a subsequent reaction producing TiB2 and AlN proceeded gradually. The time required to convert BN flakes to TiB2 and AlN particles at 1473K was in the range of 1800-3600 s. On the other hand, when the [Ta + BN] powder mixture was used, there was an initial incubation period to allow the tantalum and molten aluminium to react with each other. The reaction between tantalum, BN and aluminium took place after this incubation period.