Thermal shock behavior of boron nitride/boron carbide composite ceramics

The thermal shock behaviour of hot-pressed B4C-BN composites was investigated. A computer controlled laser beam was used to produce sharp, axissymmetric temperature profiles in thin circular disks, and the time-dependent temperature profile was measured by a high speed pyrometer. Experimentally, as the BN was added to B 4 C, the figure of merit decreased to a minimum at about 20% BN, and then steadily increased with increasing amounts of BN. A similar curve was found when the figures of merit were calculated using strength thermal expansion and Young's modulus data, except that the minimum was at about 25% BN.