What is Silicon Carbide Ceramic?
Silicon carbide ceramic (SiC) is a highly advanced material composed of silicon and carbon. It occurs naturally as the rare mineral moissanite, but it's typically manufactured synthetically. We've been producing synthetic SiC powder since 1893, initially for use as an abrasive. By sintering these SiC grains, we can create extremely hard ceramic materials,sucs as sintered silicon carbide and reaction bonded sic.
As technology advances in fields like national defense, nuclear energy, space exploration, automotive, and marine engineering, the demand for superior materials has increased. This has driven the development of high-performance structural materials, including silicon carbide ceramics.
SiC ceramic are known for their remarkable properties: high-temperature strength, excellent wear resistance, low thermal expansion, high hardness, and resistance to thermal shock and chemical corrosion. These characteristics make them invaluable in industries including automotive, mechanical, chemical, environmental protection, aerospace, electronics, and energy.
Applications of Silicon Carbide Ceramics
Silicon carbide ceramics find applications in a variety of industries. In the petrochemical sector, they are used for corrosion-resistant containers and pipelines. In the mechanical industry, you'll find them in bearings, cutting tools, and mechanical seal parts. The aerospace and automotive industries are exploring SiC for gas turbines, rocket nozzles, and engine components.
Basic Properties of Silicon Carbide Ceramics
Chemical Properties: At temperatures around 1300°C, SiC forms a protective silicon dioxide layer on its surface, which helps prevent further chemical reactions. This gives it excellent resistance to acids, though it is less resistant to alkalis due to the properties of the silica layer.
Physical Properties: SiC crystals have a density of about 3.20 g/cm³. With a Mohs hardness of 9.5 and a Knoop hardness ranging from 2670 to 2815 kg/mm², SiC is harder than corundum but softer than diamond, cubic boron nitride, and boron carbide. SiC also boasts high thermal conductivity and thermal shock resistance, along with a low thermal expansion coefficient, making it an ideal refractory material.
Electrical Properties: Industrial-grade SiC ceramics act as semiconductors at constant temperatures, with conductivity influenced by impurities. The internal resistance of pure SiC decreases as temperature increases.
Hydrophilicity: Known for its strong covalent bonds, SiC has an ionic character of about 12% in its Si-C bonds, resulting in high hardness, a significant elastic modulus, and good wear resistance. When oxidized, SiC forms a silicon dioxide layer that slows further oxidation.