Mechanical Property and Fracture Behavior of Borazine-Derived Bulk Boron Nitride Ceramics Reinforced with Chopped Si₃N₄ Fiber

Boron nitride (BN) ceramics are promising high-temperature structural and functional materials. Bulk BN ceramics are difficult to fabricate due to the covalent bond and flake grain structure. Polymer-derived ceramics (PDCs) method provides a feasible approach to prepare bulk BN ceramics at a relative low temperature while the mechanical properties remain insufficient for practical application. The present study reports the using of chopped silicon nitride (Si₃N₄) fibers as the reinforcement for the PDCs bulk BN ceramics, and the effects of content of Si₃N₄ fiber on the mechanical properties and fracture behaviors of the derived ceramics were studied. With 5.40 vol.% chopped Si₃N₄ fibers, the resulted bending strength, elastic modulus and fracture toughness of the obtained ceramics were improved by 93.4, 115.8 and 33.3% compared to the pure bulk BN ceramics. The good infiltration trait of borazine as well as the continuous interfacial structure contributed to improving the mechanical performance. The strengthening behaviors mainly include crack deflection and fiber pull-out.