Understanding Abrasive Raw Materials for Industrial Applications
Silicon Carbide, the chemical formula for SiC, belongs to the covalent bond material, C and Si belong to the same family, all have quadruvalent bond, Si also has metal properties, two elements of the material, its structure with mesh, shape characteristics, properties with high strength, So silicon carbide material performance is good high temperature strength, wear resistance, corrosion resistance, high thermal conductivity, high insulation.
Structure determines performance, the higher the performance, it requires the fine microstructure of silicon carbide material, so its preparation method becomes the key to obtain high-performance silicon carbide material.
The preparation methods of silicon carbide abrasive powder include the traditional solid phase reaction method, and the latest sol-gel method, laser method and plasma method. In this paper, according the gas, solid, and liquid three commonly used methods are classified as follows.
1.1. Carbothermic reduction
This method was invented by Acheson. The specific method is as follows: in Acheson electric furnace, silicon dioxide in quartz sand is reduced by carbon to produce silicon carbide. The silicon carbide particles obtained by this method are coarse and consume a large amount of electricity.
1.2. Direct carbon-silicon reaction method
1.2.1. Self-propagating High-Temperature Synthesis (SHS)
An external heat source ignites the reactant body, and the chemical reaction heat released by the material during the synthesis process is used to maintain the synthesis process by itself.
SiO2+C+2Mg-SiC+2MgO
The powder obtained by this method has high purity and small particle size, but Mg is removed by pickling and other processes.
1.2.2. Mechanical alloying
The carbon powder and silicon powder were prepared with a molar ratio of 1:1, and the grinding ball and powder were encapsulated in an argon tank with a mass ratio of 40:1. Mechanical ball milling was carried out on a ball mill for 25 hours, and silicon carbide powder with an average grain size of about 6nm was obtained.
2.1. Sol-gel method
The law as a liquid mixture Si alcohol salt precursor chemicals, will it dissolve in solvents to form a homogeneous solution at low temperature, add the appropriate solidifier makes alkoxide hydrolysis, polymerization reaction generated after the uniform and stable sol system, again after a long time to place or dry processing, condensed into a mixture of Si and C at the molecular level or polymers, A two-phase mixture of SiO2 and C with uniform composition and fine particle size was formed by heating, and the SiC fine powder was finally prepared by carbon reduction reaction at 1460~1600℃.
2.2. Polymer decomposition method
Silicon carbide ceramic material is prepared by the polymer pyrolysis method, which is composed of glass carbon immersed in liquid silicon. The mixture of trimethylene glycol, hydroxyethyl ether, and furfuryl alcohol resin is used for polymerization and furfuryl alcohol phase separation under the catalytic action of organic acid, and then the pyrolysis is performed to form microporous carbon. Finally, the liquid silicon is sintered and the free silicon is removed. Silicon carbide powder is prepared.
3.1. Gas reaction precipitation method
The sih4-c2h4-h2 system was studied at 1423~1673K, and the silicon carbide with an average particle size of 11nm was prepared.
3.2. Plasma method
Silicon carbide was prepared by plasma chemical vapor precipitation.
3.3. Laser-induced gas phase method
SiH4 and C2H4 were used as raw materials to prepare the average particle size of 20nm.
1. Abrasives - Tools
Using its high-temperature resistance and wear resistance, often used in the production of abrasion-grinding tools. In art, silicon carbide is a popular abrasive for modern gemstones due to its durability and low material cost. In manufacturing, it is used for hardness in abrasive processing such as grinding, honing, water jet cutting, and sandblasting. Silicon carbide particle composite paper manufacturing sandpaper and skateboard grip belt.
2. Structural materials
In high-temperature kilns, silicon carbide is used as a support and shelving material, such as firing ceramics, glass melting, or glass casting. And the production of a new strong plastic alloy for aerospace, automotive, and microelectronics.
3. Auto parts
Silicon permeated carbon-carbon composites are used in high-performance "ceramic" brake discs because of their ability to withstand extreme temperatures. Silicon carbide is also used in sintering to form diesel particulate filters. SiC is also used as a lubricant additive to reduce friction and exhaust emissions.
4. Cast crucible
The high-temperature resistance of silicon carbide is used to license the crucible of molten metal.
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