Characteristics and Structure of Silicon Carbide Ceramic Tubes
2023-09-13
Silicon carbide ceramic tubes are resistant to high temperatures and maintain high strength in high-temperature environments. They are widely used in national economic and people's livelihood fields. Silicon carbide ceramic tubes are compounds with very strong covalent bonds, with the ionic character of the Si--C bond being only about 12%. Therefore, they also have excellent mechanical properties, excellent oxidation resistance, high wear resistance, and low friction coefficient.
The main feature of silicon carbide ceramic tubes is their high strength at high temperatures. Ordinary ceramic materials significantly lose strength at 1200~1400 degrees Celsius, while silicon carbide maintains a flexural strength of 500~600 MPa at 1400 degrees Celsius, so its operating temperature can reach 1600~1700 degrees Celsius.
Silicon carbide ceramic tubes have excellent mechanical properties, excellent oxidation resistance, high wear resistance, and low friction coefficient.
Crystal structure of silicon carbide ceramic tubes:
Silicon carbide mainly has two crystal structures, namely cubic β-SiC and hexagonal α-SiC.
The basic structural units of silicon carbide crystals are interpenetrating SiC and CSi tetrahedra. The tetrahedra share edges to form planar layers and connect at vertices with tetrahedra in the next stacking layer to form a three-dimensional structure. Different stacking sequences of tetrahedra can form different structures, with hundreds of variants discovered. The lattice types are generally denoted by letters C (cubic), H (hexagonal), and R (rhombohedral), and distinguished by the number of layers in the unit cell, for example, nH indicates a hexagonal structure with n layers repeating along the c-axis, while mR indicates a rhombohedral structure with m layers repeating along the c-axis.
Silicon carbide is synthesized at high temperatures, so silicon carbide ceramic tubes are mostly prepared or used at high temperatures.
For rough calculations, the average thermal expansion coefficient of silicon carbide in the range of 25~1400℃ can be taken as 4.4×10-6/℃. Measurements of silicon carbide's thermal expansion coefficient show that its value is much smaller compared to other abrasives and high-temperature materials, such as corundum, whose thermal expansion coefficient can reach (7~8)×10-6/℃. SiC has a very high thermal conductivity, which is another important physical property of silicon carbide ceramic tubes.
Its thermal conductivity is much higher than other refractory materials and abrasives, about four times that of corundum. Therefore, due to silicon carbide's low thermal expansion coefficient and high thermal conductivity, silicon carbide ceramic tubes experience less thermal stress during heating and cooling processes, which is why they have particularly good thermal shock resistance.
Recommended News
Service Hotline:
Address: Economic Industrial Park, East Street, Anyuan District, Pingxiang City, Jiangxi Province
Email: rk18307098991@163.com
