High Strength - Toughness Hexagonal Boron Nitride Ceramics with Continuous Interface Structure

Hexagonal boron nitride ( h -BN) ceramics are attractive candidates for both structural and functional applications. However, the challenges in their inadequate deformability and inherent brittleness have not been significantly addressed. Herein, a type of h -BN ceramics (M2B-700-1300) with combined superior strength and toughness is fabricated via pre-pyrolysis, pressure molding, and high-temperature sintering in sequence. The key to the proposed strategy lies in proactively completing the intense gas-phase reaction of the precursor during the pre-pyrolysis stage, thereby forming a homogeneous boron oxynitride intermediate phase and then effectively alleviating structural collapse and pore defects during high-temperature sintering. The resulting ceramics, with densely stacked nanosheets framework bond-bridged by amorphous boron oxynitride structure, exhibit robust compressive strength of 439.2 MPa and large deformation of 10.18%. Impressively, it is as high as 5-8 times that of general h -BN ceramics in stress, and far exceeds 4% of traditional ceramics for strain, respectively. The successful synthesis of h -BN bulk ceramics with both superior strength and toughness provides potential opportunities for fabrication of other high deformability ceramics.