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Preparation of cubic BN

Synthesis of c-BN uses the same methods as a diamond: cubic boron nitride is produced by treating hexagonal boron nitride at high pressure and temperature, much as synthetic diamond is produced from graphite. Direct conversion of hexagonal boron nitride to the cubic form has been observed at pressures between 5 and 18 GPa and temperatures between 1730 and 3230 °C, similar to direct graphite-diamond conversion. Adding a small amount of boron oxide can lower the required pressure to 4–7 GPa and temperature to 1500 °C. As in diamond synthesis, to further reduce the conversion pressures and temperatures, a catalyst is added, such as lithium, potassium, or magnesium, their nitrides, their fluoro nitrides, water with ammonium compounds, or hydrazine. Other industrial synthesis methods borrowed from diamond growth use crystal growth in a temperature gradient or explosive shock wave. 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. As in diamond growth, the major problem is suppressing the growth of hexagonal phases (h-BN or graphite, respectively). Whereas in diamond growth, this is achieved by adding hydrogen gas, boron trifluoride is used for c-BN. Ion beam deposition, plasma-enhanced chemical vapor deposition, pulsed laser deposition, reactive sputtering, and other physical vapor deposition methods are also used. Wurtzite BN can be obtained via static high-pressure or dynamic shock methods.

The limits of its stability are not well defined. Both c-BN and w-BN are formed by compressing h-BN, but the formation of w-BN occurs at much lower temperatures, close to 1700 °C. Whereas the production and consumption figures for the raw materials used for BN synthesis, namely boric acid and boron trioxide, are well known (see boron), the corresponding numbers for the boron nitride are not listed in statistical reports. An estimate for 1999 world production is 300 to 350 metric tons. The major producers and consumers of BN are located in the United States, Japan, China, and Germany. In 2000, prices varied from about $75–120/kg for standard industrial-quality h-BN and up to $200–400/kg for high-purity BN grades. 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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