Applications and Synthesis Methods of Cubic Boron Nitride

Cubic boron nitride (CBN) is a typical Ⅲ - Ⅴ group compound and a kind of synthetic inorganic crystal materials. In 1957, R.H. Wentorf from U.S. General Electric Company, used hexagonal boron nitride as raw materials, and alkali metal or alkaline earth metal and nitrides as catalyst under the condition of static high pressure high temperature to synthesize the first CBN crystal in the world.

CBN crystal has sphalerite structure, good thermal stability and chemical stability. Its hardness is second only to diamond, and resistant to high temperature above 1000 ℃. Under high temperature, it shows chemical inertness for iron group elements, and makes up for the deficiency of diamond. The two form a perfect family of superhard materials, which not only can be used as abrasive to process all materials, but also have wide functional uses.

At present, in the aspect of engineering materials, CBN is mainly used as superhard material, and is the first choice for processing all kinds of steel, cast iron, nickel base, cobalt base and alloy materials. Especially in the field of modern precision machining, such as automobile, aerospace, precision machinery, microelectronics and precision industries, CBN has become indispensable materials to realize high efficiency, super precision, save energy and automation operation; Secondly, in terms of functional materials, CBN is excellent semiconductor material, and can be used to make CBN-PN junction, light-emitting diodes, excellent oxidation resistance coatings and optical window materials. CBN crystals are electro-optic crystals and have broad application prospects.

The synthesis methods of CBN crystals include: high temperature and high pressure catalytic method, high temperature and high pressure direct phase transition method, high temperature and high pressure temperature gradient method, hydrothermal synthesis method, gas phase method. Catalytic method and temperature gradient method of the above methods are commonly used, and gas phase method is mainly used for thin film growth. At present, high temperature and high pressure catalytic method is a kind of CBN industrial synthesis method that has absolute advantage.