Amorphous diamond embedded in dense boron nitride with excellent mechanical properties

Diamond and cubic boron nitride (BN) are important materials with a variety of technological and industrial applications; however, overcoming the intrinsic brittleness of these materials is still a challenge. Here, we synthesize a compound of crystalline BN and amorphous diamond-like carbon through BN nanotubes and fullerene under high pressure and high temperature conditions. The obtained composite exhibits excellent combination of a measured Vickers’ hardness of 86.2 GPa and fracture toughness of 10.2 MPa m1/2. Morphological and structural characterizations reveal that the amorphous diamond-like carbon is homogeneously embedded in a matrix of dense BN. The formation of the amorphous diamond-like carbon particles within the polycrystalline BN can effectively impede the migration of crack tips when the compound is subjected to the plastic deformation, in which most of crack tips are forced to deflect or confined near the boundaries of dense BN and amorphous diamond particles. The crystalline-amorphous composite strengthening presented here may provide a promising strategy for the further improvement of mechanical properties of hard or superhard materials.