Preparation of Cubic Boron Nitride/Diamondo Nanocomposite from CVD Materials by Very High Pressure Treatment

the cubic,zincbiende from of boron nitride (cBN) is a very intriguing material with a high hardness，thermal conductivity，作为良好的反应，This work aimed at developing a cBN - diamond composite by combination ofCVD/high pressure techniques.Two CVD^. d samples, BN (97) - C (3) and BN (20) - C (80)，were subjested to high pressures to 10 GPa and high temperatures to 1700 C. From BN (97) - C (3)，cBN appeared above 6 GPa and 1600^゚C or above 8 GPa and 1400^゚C. No diamond was formed at anyconditions studied. From BN (20) - (80)，a coexistence of cBN and diamond was observed at 10 GPa and 1600^゚C. Lowering of pressure at thissame temperature. 1600^゚C，resulted in disappearance of diamond. Elevation of temperature to 1700^゚C at 8gpa could howeverrender sample partly convert into diamond.In reference to the存在的phase relations of boronnitride and carbon, the present study has clarified two important points：第一，diamond can be formed at 8gpa which is unexpectedly low for noncatalytic condition. Second，the temperature required for cBN formation exhibits upward shift with incorporation of carbon。

The cubic, zincbiende from of boron nitride (cBN) is a very intriguing material with a high hardness, thermal conductivity, as well as refractivity, all next ot diamond. This work aimed at developing a cBNーdiamond composite by combination of CVD/high pressure techniques.Two CVD^. d samples, BN (97) - C (3) and BN (20) - C (80), were subjested to high pressures to 10 GPa and high temperatures to 1700^ﾟC. From BN (97) - C (3), cBN appeared above 6 GPa and 1600^ﾟC or above 8 GPa and 1400^ﾟC. No diamond was formed at any conditions studied. From BN (20) - (80), a coexistence of cBN and diamond was observed at 10 GPa and 1600^ﾟC. Lowering of pressure at this same temperature. 1600^ﾟC, resulted in disappearance of diamond. Elevation of temperature to 1700^ﾟC at 8 GPa could however render sample partly convert into diamond.In reference to the existing phase relations of boron nitride and carbon, the present study has clarified two important points : First, diamond can be formed at 8 GPa which is unexpectedly low for noncatalytic condition. Second, the temperature required for cBN formation exhibits upward shift with incorporation of carbon.