Phase and Property Studies of Boron Carbide–Boron Nitride Composites

Boron carbide–boron nitride particulate composites were fabricated by vacuum hot-pressing. Near-theoretical densities of B₄C were obtained, but percent theoretical densities decreased with increasing amounts of BN. The grain size of B₄C and BN was not affected by composition, but the amount of twinning in B₄C decreased with increasing BN content. No third phase was found at the B₄C–BN interface by analytical STEM analysis. Lattice parameter measurements indicated slight solubility of B₄C in BN, but no solubility of BN in B₄C for samples hot-pressed at 2250°C. Room-temperature flexural strength measurements revealed a sharply decreasing strength with increasing BN content up to 40% BN, and then relatively constant values with greater amounts of BN.