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The main application fields of boron carbide

wallpapers News 2021-05-14

Boron Carbide, also known as Black Diamond, is usually a grayish-black powder. It is one of the three hardest materials known (the other two are diamond and cubic boron nitride) and is used in tank armor, bulletproof clothing and many industrial applications. It has a Mohs hardness of 9.3.

It was discovered in the 19th century as a by-product of research into metal borides and was not studied scientifically until the 1930s. Boron carbide can be prepared by reducing boron trioxide with carbon in an electric furnace. Boron carbide absorbs large amounts of neutrons without forming any radioactive isotopes, making it an ideal neutron absorber in nuclear power plants, where it controls the rate of nuclear fission. Boron carbide is used in nuclear reactors mainly as controllable rods, but sometimes in powder form to increase surface area.
Boron carbide has the characteristics of low density, high strength, high temperature stability and good chemical stability. It is used in wear-resistant materials, ceramic reinforcing phase, especially in light armor, reactor neutron absorbent, etc. In addition, compared to diamond and cubic boron nitride, boron carbide is easier and cheaper to manufacture and therefore more widely used. In some places, expensive diamonds can be obtained and are commonly used in grinding, grinding, drilling and other applications.
Application of boron carbide
Abrasive
B4C has a high hardness second only to diamond and CBN, so it can be used as a good wear-resisting material or anti-wear material, boron carbide instead of diamond abrasive, used for cemented carbide and engineering ceramics polishing, finishing or grinding process of grinding materials, can significantly reduce the cost of grinding process. B4C coating can also be coated on the substrate to form a layer of protective film to improve the wear resistance of the substrate. For example, B4C coating on the surface of the gearbox can effectively improve the wear resistance of the gear and improve the service life of the gear.
 
The field of bulletproof armor
The high hardness and low density of boron carbide make it an ideal choice for protective materials, especially for lightweight protective armor, which can effectively improve the protective ability of aircraft, military vehicles, ships, and the human body. However, the low toughness of boron carbide seriously affects its bulletproof performance. At present, material workers try to enhance it by adding the second phase, such as TiB2, SiC, TiC, WC, Si3N4 and carbon fiber, and have achieved certain results.
 
Nuclear industrial materials
Boron carbide has high neutron absorption capacity, high neutron capture cross section and wide capture energy spectrum. The thermal cross section of B10 is as high as 347 ×10-24cm2, second only to Gd, Sm, Cd and a few other elements. However, boron carbide has low cost, no radioactive isotopes, low secondary ray energy, corrosion resistance and good thermal stability. Therefore, it is increasingly favored in the nuclear industry. Its main applications include :(1) boron carbon brick is made by mixing B104C powder with graphite powder, which is used outside the reactor to prevent leakage of radioactive materials; (2) B104C powder is pressed into products at high temperature to do reactor control rods to control reactor reaction speed; (3) B104C powder is pressed into products at high temperature to be a shielding material for reactors to absorb radioactive substances; (4) The B104C powder was sintered into a block by atmospheric sintering process and used as shielding material for the reactor.
 
Thermocouple
The thermoelectric properties of B4C were sintered in Japan and Germany to produce a thermocouple which can measure 2200℃ for high temperature measurement and control. Its high thermoelectric property and stability make it reliable for long term use. A boron carbide/graphite thermocouple consists of a graphite tube, a boron carbide rod and a boron nitride bush between them. In inert gas and vacuum, the service temperature is up to 2200 ℃. In the range of 600~2200℃, the potential difference has a good linear relationship with temperature.
 
For other engineering ceramic materials:
Boron carbide for sand blasting machine nozzles, high pressure water cutting machine nozzles, sealing rings, ceramic mold, etc. Characteristics: Boron carbide nozzle with wear-resistant and high hardness will gradually replace the known carbide (tungsten steel) and silicon carbide, silicon nitride, alumina, zirconia and other materials of the sandblasting nozzle. In addition, applications of boron carbide in the field of composite ceramics: Boron carbide is a compound of covalent bond is very strong, and boron carbide plastic is very poor, the grain boundary migration resistance is very big, difficult to obtain the density of sintered body, except for some special occasions, such as microcrystalline boron carbide gas dynamic pressure bearing materials, used as a neutron absorption material of boron carbide in nuclear reactor block, usually use the method of adding sintering additives to improve the sintering behavior of boron carbide, Obtain cheaper and more practical boron carbide products. What is more noteworthy is that the B4C -- SiC composite ceramics can reduce the sintering conditions of boron carbide ceramics while maintaining the excellent physical and mechanical properties of boron carbide ceramics. B4C -- SiC ceramics are considered as a kind of high temperature corrosion and wear resistant materials with wide application prospects. They have been used in industrial nozzles, pump seals and hot extrusion dies, etc.
In recent decades, due to the rapid development of science and technology, especially the rapid development of electronic technology, space technology and computer technology, there is an urgent need for materials with special properties. Boron carbide is an important member of the special ceramic family because of its many excellent properties. At present, many problems concerning the preparation of boron carbide powder and the sintering of boron carbide ceramic materials have been solved. In the field of future materials, boron carbide will occupy an important position because of its excellent performance.
Application of electrical properties of boron carbide:
A boron carbide graphite thermocouple consists of a graphite tube, a boron carbide rod and a boron nitride bush between the two. In inert gas and vacuum, the service temperature is up to 2200℃. In the range of 600~2200℃, the potential difference has a good linear relationship with temperature.
Application of boron carbide as chemical raw material:
Boron carbide powder is activated by halogen and can be used as a boriding agent on the surface of steel and other alloys to produce thin layers of iron boride to enhance the strength and wear resistance of the material. Boron carbide can also be used as a nonmetallic additive in some metal-based friction materials. When boride powder is prepared by reduction and combination method, TiB2, ZrB2 and CrB2 powders can be prepared by using boron carbide as boron source, which is called "boron carbide method" for making powders.
Application of boron carbide in sapphire wafers (LED)
In recent years, the country's strong support and promotion for the LED industry makes the development situation of the LED industry better, thus bringing great business opportunities to the production and processing of sapphire crystal enterprises. Because of the high strength and hardness of sapphire crystal (Mohs hardness 9), it brings great difficulties to processing enterprises. From the point of view of materials and grinding academia, the best materials for processing and grinding sapphire crystals are artificial diamond, boron carbide and silicon dioxide. Due to the high hardness of artificial diamond (Mohs hardness 10), the surface of sapphire wafer will be scratched when grinding, affecting the transmittance of wafer, and the price is expensive. And silicon dioxide hardness is not enough (Mohs hardness 7), grinding force is poor in grinding engineering time - consuming, labor. Therefore, boron carbide abrasive (Mohs hardness 9.3) becomes the most ideal material for processing and grinding sapphire crystals. Boron carbide abrasives have excellent performance in double-sided grinding of sapphire wafers and back-thinning polishing of sapphire based LED epitaxial wafers. Some national key universities also have the main research on boron carbide grinding sapphire crystal. In short, with the rapid development of LED industry, boron carbide will also rise rapidly.

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