高温高压合成立方氮化硼的热力学分析

 从热力学角度计算出了以六角氮化硼为原料、用高压触媒法合成立方氮化硼时所形成稳定的临界晶粒半径r_k的大小，当p=6.0 GPa、T=1 600 ℃时，r_k≈15 nm。分析了r_k的大小与合成温度、压力的关系，以及在给定压力下立方氮化硼晶粒转化率与温度的关系。结果表明：在立方氮化硼稳定区，在相同压力下，r_k随温度的升高而增大；在相同温度下，r_k随压力的升高而减小，r_k越小立方氮化硼晶粒的转化率越高。计算结果与实际合成实验所得结果完全一致。

Thermodynamic Analysis of Cubic Boron Nitride Synthesized under HPHT

We analyzed the relationships between growth condition and phase transition probability, and critical crystal radius respectively by thermodynamics. Then we calculated the critical grain radius r_k for forming cBN crystal under high pressure and high temperature (HPHT). Under 6.0 GPa, 1 600℃ ,the r_k is around 15 nm. In the thermodynamically stable region of cBN, the results show that under the same pressure, r_k is increasing with the elevated temperature; under the same temperature, r_k is decreasing with increasing pressure,and the smaller r_k is,the higher phase transition probability is. These results are well consistent with experimental data.