Superhard B–C–N materials synthesized in nanostructured bulks

We report here the high-pressure synthesis of well-sintered millimeter-sized bulks of superhard BC₂N and BC₄N materials in the form of a nanocrystalline composite with diamond-like amorphous carbon grain boundaries. The nanostructured superhard B–C–N material bulks were synthesized under high P–T conditions from amorphous phases of the ball-milled molar mixtures. The synthetic B–C–N samples were characterized by synchrotron x-ray diffraction, high-resolution transmission electron microscope, electron energy-loss spectra, and indentation hardness measurements. These new high-pressure phases of B–C–N compound have extreme hardnesses, second only to diamond. Comparative studies of the high P–T synthetic products of BC₂N, BC₄N, and segregated phases of diamond + cBN composite confirm the existence of the single B–C–N ternary phases.