The market of ceramics is in constant growth. The employment of this class of materials is strongly encouraged in application involving highly aggressive environments that require resistance to corrosion and to high temperatures (i.e. over 900°C). In addition because of their high hardness and relatively high elastic modulus, they also find uses in high wear applications. Silicon Carbide (SiC) is the leader among various non-oxide ceramics for commercial application: it normally occurs in nature as the mineral moissanite but because of its scarce abundance in nature, SiC is commonly manufactured on a large scale either for use as an abrasive or as a high performance ceramics for semiconductor applications.
Due to different applications and production methods, the world production of SiC is difficult to evaluate. In 1994 the production amount to 500,000 t/y; today the the market is in constant growth.
Silicon carbide powders can be produced in three principal ways: pyrolysis of silane compounds, direct carbonisation of Si metal, and, of course, carbothermal reduction of SiO2.
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The first method, the so called Chemical Vapour Deposition (CVD) from silane, is expensive and hazardous for the nature of precursor employed, while the carbonisation uses a very high cost silicon source. These two methods produce high-purity SiC powders for specific technical applications and they are used for composite materials (i.e. Carbon Fibres) infiltration.
The third method is the cheapest one: it starts from inexpensive silicon dioxide and carbon (or carbon source) that usually react at temperature ranging from 1400-2100 °C to give SiC, which phase depends, as mentioned above, on the synthesis temperature.
Recent developments in technical applications emphasize the role of the starting materials: new applications in the field of ceramic reinforced composites show the improvements of the mechanical properties using nanometer range SiC particles (nanocomposites). Consequently, economical and efficient synthesis routes for nanometer-sized SiC powders are getting more and more important.
Silicon carbide is a high value added material used in a broad range of materials and products: once more cost-effective alternatives to produce it will be available, it could be used even in new markets, while its traditional application will continue to grow in future.
