Search and Characterization of Noval Superhard Phases in the B-C-N System Under Extreme Conditions

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0102215MingIn the proposed research, formation of the theoretically predicted new dense phases in the B-C-N composition triangle will be systematically examined over a wide pressure and temperature range using laser heated diamond anvil cell (up to 1x 106 atm or 14.7 x 106 psi and 2500oC) as well as large-volume high P-T apparatus (up to 3x 105 atm or 44.1 x 105 psi and 2000oC). The structures and properties of quenched samples will be analyzed by powder x-ray diffraction, electron microscopy, hardness measurements, and optical and acoustical methods. The overall scientific goals of the project are: (1) synthesis of novel superhard phases in the B-C-N system at high pressures and high temperatures by direct conversion of layered B-C-N phases, (2) investigation of physico-chemical and structural properties of the end-products at ambient conditions, and (3) characterization of elastic and vibrational properties of novel phase(s) at high pressures up to 1x 106 atm (14.7 x 106 psi) and at room temperature. %%%The proposed research will provide valuable data that will be used to identify main features of the phase transformations observed in the B-C-N system at high pressures and temperatures, and the factors responsible for formation of superhard B-C-N phases. These results will enhance our understanding of the fundamental problem in development of new superhard materials and will provide a sound basis of developing and producing new super-abrasives that are thermally and chemically more stable than diamond, and harder than cubic BN, enabling major advances in the cutting and polishing industries.