High-temperature And High-pressure Synthesis Of Boron Nitride

In 1957, Wentorf synthesized cubic BN for the first time. When the temperature is close to or higher than 1700°C and the minimum pressure is 11-12 GPa, pure hexagonal boron nitride (HBN) is directly transformed into cubic boron nitride (CBN). Subsequently, it was discovered that the use of catalysts can greatly reduce the transition temperature and pressure. Commonly used catalysts are: alkali and alkaline earth metals, alkali and alkaline earth nitrides, alkaline earth fluoronitrides, ammonium borate and inorganic fluorides. Among them, the temperature and pressure required for ammonium borate as the catalyst are the lowest. The required pressure is 5GPa at 1500℃, and the temperature range is 600～700℃ when the pressure is 6GPa. It can be seen that although the addition of a catalyst can greatly reduce the transition temperature and pressure, the required temperature and pressure are still relatively high. Therefore, its preparation equipment is complicated and costly, and its industrial application is limited.