Among modern ceramic materials, silicon carbide (SiC) and silicon nitride (Si3N4) has been successfully used in a variety of high-tech applications. SiC provides the effective combination of mechanical properties. It is widely used as an abrasive material and structure. It has high hardness, chemical inertness, than the melting temperature of the steel wear and oxidation of it for serious conditions such as high temperature sealing valve, rocket nozzle and wire drawing die and extrusion die for bearing applications because of its good wear resistance and corrosion resistance. In the tube by SiC to find its thermal properties and creep resistance of high temperature and hot electron exchange. The heating element from SiC. They can produce a high temperature of 1650 DEG C and medium in the air or inert considerable life. However, with any contact with water or hydrocarbon gas, can influence their age.
Silicon nitride has comparatively lower oxidation resistance and higher thermal conductivity than SiC. Major applications of silicon nitride are as automotive and gas turbine engine parts. It has high strength, fracture toughness and refractoriness which are required properties for ball bearings, anti-friction rollers. It performs remarkably when exposed to molten metal and/or slag.
A combined form of silicon carbide and nitride has been developed as silicon carbide grains bonded in silicon nitride matrix. This Si3N4-bonded silicon carbide is used for some critical applications where very high thermal shock resistance is required. For instance, in particular case of flame-out engine start-up, temperature reaches from ambient to 1600 °C in few seconds followed by an abrupt decrement to 900 °C in less than one second. Si3N4-bonded silicon carbide exclusively endures these conditions.
Traditional methods to produce these ceramic materials are energy intensive and hence expensive. For example, the Acheson process, which is the most widely adapted method to produce commercial-grade SiC, essentially takes 6 – 12 kWh to yield one kg of SiC. An inexpensive method, that uses low cost agro-industrial byproduct, is the pyrolysis of rice husks, first carried out by Lee and Cutler in 1975. Since then many researchers have discussed and used various process routes and modifications to obtain Silicon Carbide Nanopowders and/or silicon nitride, either in particulate or in whisker form, from rice husks.
Morphological studies on RH reveal that micron size silica particles are distributed in cellulosic part of RH. When these silica particles are made to react with carbon in biomass part of RH under specific experimental conditions, silicon carbide can result. Moreover, besides silicon carbide, modifications in process mechanism lead to formation of some other industrially useful products, viz. silicon nitride, silicon oxynitride (Si2N2O), ultra-fine silica, and solar-cell grade silicon.
Related reading: nano particles nano oxides