High-temperature lubricant boron nitride
What is boron nitride?
Boron nitride was introduced more than 100 years ago, and its earliest application was hexagonal boron nitride as a high-temperature lubricant. Its structure and properties are very similar to graphite, and it is white, so it is commonly known as white graphite. Boron nitride (BN) ceramics were compounds discovered as early as 1842. Much research has been carried out on BN materials abroad since the Second World War, and it was not developed until the BN hot pressing method was solved in 1955. The American Diamond Company and United Carbon Company were the first to put into production, and in 1960, they produced more than 10 tons. CBN is usually a black, brown, or dark red crystal with a sphalerite structure and good thermal conductivity. The hardness is second only to diamond, a superhard material commonly used as a tool material and abrasive.
Material Properties of Boron Nitride
Boron nitride has chemical resistance and is not attacked by inorganic acids and water. The boron nitrogen bond is broken in hot concentrated alkali. Oxidation begins in the air at 1200 ℃. Decomposition begins at about 2700 ℃ in a vacuum—slightly soluble in hot acids, insoluble in cold water, relative density 2.29. The compressive strength is 170 MPa. The maximum operating temperature in an oxidizing atmosphere is 900 ℃, while it can reach 2800 ℃ in an inactive reducing atmosphere. However, the lubricating performance is poor at room temperature. Most properties of boron nitride are superior to carbon materials. For hexagonal boron nitride: low friction coefficient, high-temperature stability, good thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, microwave or infrared transmittance. "The hexagonal crystal system of boron nitride, commonly known as a graphite lattice, also has amorphous variants. In addition to the hexagonal crystal type, there are other crystal forms of boron nitride, including rhombohedral boron nitride (r-BN), cubic boron nitride (c-BN), and wurtzite type boron nitride (w-BN).". People have even found two-dimensional boron nitride crystals like graphite thin.
Synthesis of boron nitride at high temperature and pressure
In 1957, Wentorf first synthesized cubic BN. When the temperature is close to or above 1700 ℃, and the minimum pressure is between 11 and 12 GPa, the pure hexagonal boron nitride (HBN) is directly transformed into cubic boron nitride (CBN). Subsequently, it was found that catalysts can significantly reduce the transition temperature and pressure. Commonly used triggers include alkali and alkaline earth metals, alkali and alkaline earth nitrides, alkaline earth fluoro nitrides, ammonium borate salts, and inorganic fluorides. Using ammonium borate as a catalyst requires the lowest temperature and pressure, with a force of 5 GPa at 1500 ℃ and a temperature range of 600 to 700 ℃ at 6 GPa. It can be seen that although adding a catalyst can significantly reduce the transition temperature and pressure, the required temperature and pressure are still high. Therefore, the preparation equipment is complex and costly, and its industrial application is limited.
Price of boron nitride
Boron nitride particle size and purity will affect the product's Price, and the purchase volume can also affect the cost of molybdenum Silicide. A large amount of large amount will be lower. The Price of molybdenum silicide is on our company's official website.
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