Preparation of cubic Boron nitride


Cubic boron nitride is produced by treating hexagonal boron nitride at high pressure and temperature, much as synthetic diamond is made from graphite. Direct conversion of hexagonal boron nitride to the cubic form occurs at pressures up to 18 GPa and temperatures between 1730-3230 °C; the addition of a small amount of boron oxide can lower the required force to 4-7 GPa and temperature to 1500 °C. Industrially, BN conversion using catalysts is used instead; the catalyst materials differ for different production methods, e.g., lithium, potassium, or magnesium, their nitrides, their fluoro nitrides, water with ammonium compounds, or hydrazine. Other industrial synthesis methods use crystal growth in a temperature gradient or explosive shock waves. The shock wave method produces hetero-diamond, superhard boron, carbon, and nitrogen compound. Low-pressure deposition of thin films of cubic boron nitride is possible. For selective etching of the deposited hexagonal phase during chemical vapor deposition, boron trifluoride is used (cf. use of atomic hydrogen for selective etching of graphite during deposition of diamond films). Ion beam deposition, Plasma Enhanced CVD, pulsed laser deposition, reactive sputtering, and other physical vapor deposition methods are also used. As w-BN, hexagonal boron nitride is a superhard phase at high pressures. This hexagonal phase differs from the layered graphitic material: it adopts the wurtzite structure. Rhombohedral boron nitride is similar to hexagonal boron nitride. It is formed transitionally during the conversion of cubic BN to hexagonal form. If you are looking for high quality, high purity, and cost-effective Boron nitride, or if you require the latest price of Boron nitride, please feel free to email contact mis-asia.

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