Quasi-static and dynamic compressive behavior of BN-BAS composite ceramic at room temperature and 1000 °C

Boron nitride-barium aluminosilicate (BN-BAS) composite ceramic specimens were prepared by using hot-press sintering at 1700 degrees C and 20 MPa from composite powders prepared by employing the sol-gel method. The dynamic compressive behaviors of these BN-BAS composite ceramic specimens were investigated by using split-Hopkinson-pressure-bar set-ups at room temperature and 1000 degrees C. The effects of the strain rate on the dynamic compressive strength, fragment size, and microstructure were investigated. The quasi-static mechanical properties of the composite ceramics were also tested. The results indicated that the quasi-static and dynamic mechanical properties of BN-BAS composite ceramics at 1000 degrees C were lower than those at room temperature, and this was caused by the crack propagation in the ceramic specimens at high temperatures owing to the high thermal expansion coefficient of hexacelsian. The dynamic compressive strength of the composite ceramic increased linearly with an increasing strain rate. Flake-like h-BN particles absorbed a large amount of energy through bridging and pull-out, which prevented macroscopic breakage of specimens at strain rates lower than 850 s(-1) at the initial failure stage at room temperature. As the strain rate increased, the cracks changed from long and sparse to small and dense reticularly distributed ones, and the fragment size decreased accordingly.