Silicon nitride

Description

Silicon nitride (molecular formula Si3N4) is a kind of chemical compound comprised of both silicon and nitrogen elements. It appears as a white solid with a high melting point. It is chemically stable upon the presence of dilute HF and hot H2SO4. It has a series of properties such as high strength among a wide temperature range, high fracture toughness, high hardness, outstanding wear resistance and chemical property. It has a strikingly high thermal shock resistance. It has a wide applications in various kinds of fields. In automobile industry, it is an important materials for engine parts. It can also be applied to the manufacturing of bearings due to its high shock resistance. For example, in spacecraft, silicon nitride ceramic is capable of surviving the severe thermal shock generated in the hydrogen/oxygen rocket engines. It can also be used as abrasive and cutting tools due to its harness and resistance to wear. In electronics, it can be used as an insulator and chemical barrier during the production of integrated circuits. There are several method for the manufacturing the silicon nitride. 1. The powdered silicon is subject to a heating reaction of 1300-1400 °C in the atmosphere of nitrogen. 2 Diimide route which involves the reaction of SiCl and NH3. 3 Silicon dioxide is subject to carbothemral reduction at 1300-1400 °C under the presence of nitrogen.

References

https://en.wikipedia.org/wiki/Silicon_nitride
http://accuratus.com/silinit.html

Chemical Properties

slightly beige powder

Physical properties

Gray amorphous powder or crystals. Resistant to thermal shock. Good oxidation resistance up to 1500°C but decomposes into nitrogen and silicon above 1850°C. Excellent corrosion resistance to molten nonferrous metals such as Al, Pb, Zn, Cd, Bi, Rb, and Sn, and molten salts like NaCl-KCl, NaF, and silicate glasses. However, corroded by molten Mg, Ti, V, Cr, Fe, and Co, cryolite, KOH, and Na₂ O.

Uses

As high tempereture engineering material for use in gas turbines, diesel engines.

Uses

Silicon Nitride is used in preparation of thermal conductive Poly(Me Methacrylate)/Silicon Nitride nanocomposites via click chemistry.

Uses

Silicon nitride (Si3N4), resistant to oxidation, is an excellent coating for metals, as well as an adhesive and abrasive, and it is used in high-temperature crucibles. It has proven useful as heat-resistant substance for the nozzles on rocket engines.

General Description

Silicon nitride based ceramics possess high fracture toughness, hardness and wear resistance, resistance to corrosion, thermal stability. Two known polymorphs of silicon nitride exist, alpha and beta Si₃N₄, both have hexagonal structure. A study shows that a third state, cubic spinel structure, has also been synthesized.

Flammability and Explosibility

Non flammable