What is silicon carbide ceramic?

Silicon carbide ceramic (SiC) is an advanced ceramic material containing silicon and carbon. It occurs in nature as the extremely rare mineral moissanite. Synthetic silicon carbide powder has been produced in large quantities since 1893 for use as an abrasive. Silicon carbide particles can be bonded together by sintering to form a very hard ceramic.

Silicon carbide ceramic materials have excellent properties such as high temperature strength, good wear resistance, small thermal expansion coefficient, high hardness, thermal shock resistance, and chemical corrosion resistance. Therefore, they are widely used in automobile, machinery, chemical industry, environmental protection, space technology, information electronics and other industries. , energy and other fields. Silicon carbide has become an irreplaceable structural ceramic with excellent performance in many industrial fields.

chemical properties

When the oxygen reaction temperature reaches 1300°C, a silicon dioxide protective layer will form on the surface of the silicon carbide crystal. As the protective layer thickens, the internal silicon carbide resists continued bonding, giving silicon carbide good chemical resistance. In terms of resistance to acids, alkalis, and compounds, silicon carbide has strong acid resistance due to its silicon dioxide protective film, but poor alkali resistance.

Physical properties

The densities of various silicon carbide crystals are similar, usually 3.20g/mm3. The hardness of silicon carbide is 9.5 Mohs and the Knoop hardness is 2670-2815 kg/mm. It is higher than corundum in abrasives and second only to diamond, cubic boron nitride and boron carbide. Silicon carbide ceramics have high thermal conductivity and thermal shock resistance, and small thermal expansion parameters. Therefore, SiC ceramics are a high-quality refractory material.

Electrical properties

Constant-temperature industrial silicon carbide ceramic is a semiconductor with impurity conductivity. The internal resistance of high-purity silicon carbide decreases with increasing temperature. The conductivity of silicon carbide with different impurities is also different.

Good hydrophilicity

SiC is a compound with strong covalent bonds. According to Pauling electronegativity calculations, the ionicity of the Si-C bond in SiC is only about 12%. Therefore, SiC has high hardness, large elastic modulus, and good wear resistance. It is worth pointing out that when SiC is oxidized, the silicon dioxide layer formed on the surface will inhibit further diffusion of oxygen, so the oxidation rate is low.

Application fields of silicon carbide ceramics

There are four main application areas for silicon carbide ceramics: functional ceramics, advanced refractory materials, abrasives, and metallurgical raw materials. Silicon carbide raw materials can be supplied in large quantities and are not considered high-tech products, and the application of nano-silicon carbide powder with extremely high technical content cannot form economies of scale in a short period of time.

• 1.As an abrasive, it can be used as grinding tools, such as grinding wheels, whetstones, grinding heads, sand tiles, etc.
• 2.As metallurgical deoxidizer and high temperature resistant material.
• 3.High-purity single crystal, which can be used to make semiconductors and make silicon carbide fibers.

Main uses: used for wire cutting of 3-12 inch monocrystalline silicon, polycrystalline silicon, potassium arsenide, quartz crystal, etc. Engineering processing materials for solar photovoltaic industry, semiconductor industry, and piezoelectric crystal industry. Used in semiconductors, lightning rods, circuit components, high temperature applications, UV detectors, structural materials, astronomy, disc brakes, clutches, diesel particulate filters, filament pyrometers, ceramic membranes, cutting tools, heating elements, nuclear fuel, jewelry, steel , protective gear, catalyst carrier and other fields.