In situ grown silicon carbide nanowires reinforced hexagonal boron nitride ceramics

One-dimensional (1D) structures, such as nanowires, whiskers and fibers, have attracted extensive attentions for their potential as reinforcements for advanced composite materials. To achieve uniform dispersion of 1D structures in the matrix and to materialize strong interface bonding between them and the matrix are the two most challenging tasks for preparing high-performance composite materials. For hexagonal boron nitride (h-BN) ceramics are naturally weak, in this work, SiC nanowires were introduced into BN powders via in-situ grown on a catalyst using chemical vapor deposition (CVD) technology and this technology ensured the uniform dispersion of SiC nanowires in later h-BN ceramics. High performance h-BN composite ceramics were fabricated by spark plasma sintering from as-prepared powder mixture of h-BN and SiC nanowires doped with cubic boron nitride (c-BN). The onion-like h-BN structures, freshly derived from c-BN, were activatory during the sintering process, facilitating the SiC nanowires firmly anchored onto the h-BN grains. These SiC nanowires were thus well distributed and strongly bonded with h-BN matrix, significantly improving the mechanical properties of h-BN ceramics by stopping and deflecting the extension of cracks. Optimal composite performance was achieved when SiC nanowires were grown with a catalyst mass ratio of 5.50 wt%, and the density, Young's modulus and flexural strength of the sample reached 2.29 g/cm³, 35 GPa, and 171 MPa, respectively. This study demonstrates a new combination strategy for the preparation of high-performance h-BN composite ceramics, and will further promote the development and application of h-BN ceramics.