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Synthesis of SiC Riley crystal

wallpapers News 2021-08-31
Since natural silica is rare, most silicon carbide is synthetic. Silicon carbide is used as an abrasive, as well as gem-grade semiconductors and diamond simulations. The easiest way to make silicon carbide is to mix silica sand and carbon in an Atchison graphite resistance furnace at high temperatures between 1600°C(2910°F) and 2500°C(4530°F). By heating the excess carbon in organic matter, fine SiO2 particles in plant matter such as rice husk can be converted to SiC. Silicon powder is a by-product of silicon metal and ferrosilicon alloy production. It can also be converted to SiC by heating with graphite at 1500°C(2730°F).
The purity of the material formed in the Atchison furnace depends on the distance from the graphite resistance heat source. Colorless, light yellow and green crystals have the highest purity and are found closest to resistance. The greater the distance from the resistor, the colors turn blue and black, and the purity of these dark crystals decreases. Nitrogen and aluminum are common impurities in silicon carbide, which affect the electrical conductivity of silicon carbide.
Synthesis of SiC Riley crystal
Pure silicon carbide can be prepared by the Lely method. The silicon carbide powder can be sublimated to high-temperature silicon, carbon, silicon carbide (SiC2) and silicon carbide (Si2C) in an atmosphere of 2500℃ argon. C, and redeposited on a slightly cooler substrate into lamellar single crystals with a maximum size of 2×2 cm. This process can produce high-quality single crystals, mainly 6H-sic phase (due to high growth temperature).
To form SiC with complex shapes, preceramic polymers can be used as precursors to generate ceramic products by pyrolysis at 1000-1100℃. The precursor materials for silicon carbide obtained in this way include polycarbosilane, poly (methylsilane), and polysiloxane. Silicon carbide materials obtained through the pyrolysis of the pre-ceramic polymer are called polymer-derived ceramics or PDC. The pyrolysis of ceramic precursor polymers is usually carried out at lower temperatures in an inert atmosphere. Pyrolysis is advantageous over THE CVD process because polymers can form a variety of shapes prior to their thermal transformation into ceramics.
Silicon carbide can also be made into silicon wafers by cutting single crystals with diamond wire saws or lasers. Silicon carbide is a useful semiconductor in power electronics.

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