Development history of boron nitride

Boron nitride (BN) compound was first discovered in 1842. Research on BN materials began after the end of World War II, but the ceramic was not officially developed until 1955 when researchers solved the hot pressing method of BN. Since then, the American diamond company and United carbon company have first put into production, and more than 10 tons have been produced in 1960s. Japan began to import a large number of BN products from the United States and since then, three Japanese companies have also conducted research for several years, successfully trial produced in early 1969 and put into operation in 1970.Nowadays, the production technique has been applied worldwide by developed countries.

Physical and chemical properties of boron nitride ceramics

(1) Thermal performance: boron nitride products can be used in an oxidizing atmosphere of about 1000 ℃ and an inert atmosphere of nearly 3000 ℃. This property is higher than that of mullite, alumina and silicon carbide. At the same time, the heat resistance and impact are large, and the cracking will not occur in the environment of 1500 ℃ of quench and heat.

(2) Chemical stability: with the vast majority of metals such as solution iron, aluminum, copper, silicon, potassium arsenide, brass and cryolite, it does not work, and so does slag glass. Therefore, the container made of boron nitride material can be used as the vessel of the above substances. However, those containing B2O3 generally have hygroscopicity, which makes the rapid heating of the product in the process of use will infiltrate the absorbed water and produce cracks. One of the effective measures to improve this disadvantage can be to add some binders.

(3) Electrical properties: because the dielectric constant and dielectric loss of BN products are small, they can be widely used in high frequency range and low frequency range. Its dielectric strength is 4.5 times that of alumina, and its dielectric constant is half that of alumina. Its electrical properties are very different from that of graphite. Like oxide ceramics, it has no conductivity at high temperature. It is an electrical insulating material that can be used in a large temperature range.

(4) Machinability: the Mohs hardness of BN Ceramics is 2. It can be processed on lathe, milling machine, etc; It can also be processed into thin sheets, spiral bodies and various parts with complex shapes. BN has low mechanical strength. Although it is superior to graphite at room temperature, it is more brittle than oxide ceramics.

(5) Lubricity: BN powder is a hexagonal crystal system. It is a kind of white flake fine material, which is similar to graphite. It is commonly known as white graphite and has excellent lubrication.

(6) Light weight: BN is the material with smaller weight in ceramic materials.

(7) Nature of neutron absorption: BN has a large neutron absorption section.

Application of hexagonal boron nitride

Hexagonal boron nitride is a kind of material with high temperature resistance, corrosion resistance, high thermal conductivity, high insulation and excellent lubrication performance. At present, simplifying the manufacturing process, reducing the production cost and improving the service life of components are the active research directions of this kind of material.

(1) Due to the excellent chemical stability of hexagonal boron nitride, it can be used as crucible for melting and evaporating metal, boat dish, liquid metal delivery pipe, rocket nozzle, base of high-power device, pipe for melting metal, pump parts, mold of cast steel, etc.

(2) The heat resistance and corrosion resistance of hexagonal boron nitride can be used to manufacture high-temperature components, lining of rocket combustion chamber, heat shield of spacecraft, corrosion-resistant parts of magnetic current generator and so on.

(3) Using the insulation of hexagonal boron nitride, it is widely used in the insulators of high-voltage and high-frequency electricity and plasma arc, as well as the insulators of various heaters, heating pipe sleeves, high-temperature, high-frequency and high-voltage insulation and heat dissipation components, and the materials of high-frequency electric furnaces.

QSAM is a manufacturer with hot pressing euiqpment. As a major product line, QSAM's hBN has several type of material from pure BN99 and TPBN to composite materials such as ALNBN. These speciliased materials could be applied in all kinds of environment to fulfill customer's demand of boron nitride ceramics.