Silicon carburide also known by the names moissanite, emery or coal coke, is an organic substance with a formula of SiC. It is produced by a high-temperature resistive furnace using raw materials, such as wood chips, quartz sand or coal coke. Salt is needed for green silicon carbide. In nature, silicon carbide is found in the rare mineral moissanite. It is also called gold steel or refractory grit. In China, silicon carbide is made up of two types: green and black. They are both hexagonal crystals and have a specific gravity ranging between 3.20 and 3.25% and a microhardness range of 2840-3320kg/mm2.
Both black silicon carburide and green silica carbide belong to the aSiC. Black silicon carbide has a SiC content of 95% and is more durable than green silicon carbide. It is used for materials that have low tensile resistance, like glass, ceramics or stone. Also, it can be used on non-ferrous metals, cast iron, and refractory material. Green silicon carbide has a SiC content of over 97% and is self-sharpening. It is used primarily for the processing of cemented carbide (a titanium alloy), optical glass and optical glasses, as also for honing and fine grinding tools made from high-speed steel. There is also a cubic silicon-carbide, which is yellow-green crystals prepared through a special method. The abrasive tools used to make them are suitable for superfinishing of bearings. Surface roughness is processed between Ra320.16microns and Ra0.040.02 microns.
Aside from being an abrasive, silicon carbide can be used in many other ways. This is due to its chemical stability, high thermal conductivity (low thermal expansion coefficient), and wear resistance. The powder of silicon carbide can be used to coat a specific impeller, cylinder or other part of a turbine. It can also improve the abrasion resistance of its inner wall and increase its service life from 1 to 2x. High-grade refractory, made with it, has excellent heat shock resistance as well as being small, lightweight, strong and having a good energy-saving impact. Low-grade Silicon carbide (containing around 85% SiC), which is an excellent Deoxidizer and can improve steel quality, speed up the steelmaking process and ease chemical composition control. Silicon carbide can also be used to produce silicon carbide for electric heater elements.
It is the second hardest substance in the world, after diamonds (10). It has excellent thermal conduction, is a semi-conductor, and can resist corrosion at high temperatures.
There are at least 70 crystal forms of silicon carbide. Allomorphs of silicon carbide are the most common. It has a hexagonal crystalline structure and is formed above 2000 degC at high temperatures. Below 2000 degC b Silicon Carbide with cubic crystals, similar to a diamond, is produced. The network can be seen on the page. It is still eye-catching due to its larger surface area. A type of silicon carburide called m-silicon is more stable, and it produces a pleasing sound when colliding. However, until now these two types had not been used commercially.
Due to its high sublimation temp (approximately 27°C) and 3.2g/cm3 specific weight, silicon carbide makes a great raw material for bearings and high-temperature ovens. It does not melt at any pressure, and it has a very low chemical activity. Its high thermal conductivity and breakdown electric field strength as well as its high maximum current densities have led many to try to replace silicon when it comes to high-power semiconductor components. It has a high coupling effect to microwave radiation.
The color of pure silicon carbide, however, is black or brown when produced industrially. This is due to iron impurities. The silica coating on the surface of the crystal gives it a rainbow-like appearance. To
Pure silicon carbide is a transparent, colorless crystal. The impurities in industrial silicon carbide cause it to be yellow, light green, blue or black. Its clarity varies according to its purity. The cubic b-SiC is also known as cubic silicon carbide. The different stacking of silicon and carbon atoms creates a variety of a SiC variants. Over 70 types have been identified. Above 2100degC bSiC turns into aSiC. Industrial silicon carbide is produced by refining petroleum coke and high-quality sand in a resistance oven. The silicon carbide blocks that have been refined are crushed and then subjected to acid-base washing, magnetic separation, sieving, or water selection.
It is artificial because silicon carbide has a low natural content. Standard methods include mixing quartz sand, coke, silica and oil coke with wood chips and salt, heating it up to 2000degC in an electrical furnace, then adding the powdered silicon carbide after various chemical processing.
Its excellent hardness has made it an indispensable abrasive, but its range of applications goes beyond that of general abrasives. Due to its thermal conductivity and high-temperature resistance, it is a popular choice for kiln furniture in tunnel kilns. The electrical conductivity of this material makes it a vital electric heating element. SiC smelt pellets (or SiC blocks) are needed to make SiC products. It is not natural emery, also known as garnet. In the industrial production of SiC, quartz, petroleum coal, etc. is usually used. As raw materials, as auxiliary recovery material, or as spent materials. After grinding or other processes, the materials are blended to a charge that has a reasonable particle size and ratio to adjust its gas permeability. An appropriate amount must be added. To prepare green silicon carbide at high temperatures, you need to add the correct amount of sodium chloride. Special silicon carbide electric heaters are used for the thermal equipment to prepare SiC smelting at high temperature. It consists of a furnace bottom, an end wall with electrodes on its inner surface, a removable sidewall as well as the furnace core. Both ends of this furnace are electrode-connected. This electric heater uses what is known as buried-powder firing. As soon as you turn it on, the heating begins. The furnace core is at 2500degC (or even higher, between 2660-2700degC). SiC is produced when the charge reaches approximately 1450degC (although SiC forms mainly at temperatures >=1800degC). SiC decomposes when the temperature is >=2600. The decomposed si, however, will form SiC and C in the charged.
Each electric heater is equipped with transformers. Even so, during production only one electric heater is operated to maintain a constant voltage by adjusting the voltage in accordance with the electrical load characteristics. The high-power furnace must be heated for around 24 hours. After an interruption of power, the reaction that generates SiC is complete. After a cooling time, the sidewalls can be removed. The charge is then gradually removed. The products of silicon carbide can be categorized into different types and divided according to their use environment. Silicon carbide is used more on machines. Silicon carbide seal rings can, for example, be used to seal mechanical seals. These seal rings can be further divided into flat rings, moving bands, static rings and more. Our silicon carbide products can be made in different shapes according to the customer’s requirements. For example, we can produce silicon carbide plates and rings.
One of the silicon-carbide products is silicon carbide, a ceramic with high hardness. It also has high corrosion resistance and high temperature strength.
Silicon carbide ceramics are ideal for seal rings. They have a high level of chemical resistance, a high degree of strength, elasticity, hardness and wear resistance. The friction coefficient of silicon carbide ceramic is lower when combined with graphite than alumina and cemented carbide. Therefore, it can be used to produce PV values that are higher, particularly in conditions where strong acids or alkalis will be transported. Our company’s SIC-1 silicon carbid atmospheric sintered product line has high density and high hardness. It also produces large batches of products, and can produce products with complex shapes. These products are designed for sealing applications requiring high-performance, with high PV values. They also resist strong acids and Alkalis. Our company’s SIC-3 silicon-carbide ceramic works are made from graphite containing silicon carbide. When combined with other materials, the friction coefficient of silicon carbide is low because it contains fine dispersed graphite particles. It is self-lubricating and therefore ideal for air-tight, dry-friction sealings. It is used to increase the seals’ service life, and improve the reliability of the work.
The furnace charge is composed of unreacted material for heat preservation, silicon carbide and oxycarbide. Binder layer (for bonding Very Tight Material Layer, main elements are C, SiO2, 40-60% SiC and Fe Al Ca Mg Carbonate), amorphous layer (main component is 70-90 percent SiC; it’s Cubic SiC b-sic), second-grade SiC (main component is 90-95% SiC; the coating has formed hexagonal SiC (a coarse SiC crystal), first-class SiC (SiC content is less than 96%, and is hexagonal SiC) The unreacted and a small part of oxycarbide layers are collected and used as spent materials. The remaining oxycarbide layers, amorphous and second-grade products, and some of the bonding material are collected and recycled. Large lumps, tight bonds and impurities such as charges are discarded. The first-grade material is classified, then coarsely crushed or finely ground, treated chemically, dried, sieved, and magnetically separated into various size black and green SiC particles. It is necessary to go through the water selection process in order to produce silicon carbide.
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