The material has the thermal properties of thermal stress and the mechanical properties of ceramic materials, and its geometric shape The size of the ceramic material and the size of the environmental medium also affect the thermal stress of the ceramic material. Therefore, thermal shock resistance represents the resistance of ceramic materials to temperature changes and must be a comprehensive reflection of its thermal and mechanical properties. Research on the thermal shock resistance of ceramic materials that began in the 1950s has resulted in many relevant evaluation theories regarding earthquake resistance, but they are all one-sided and limited to a certain extent.
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Thermal shock damage of ceramic materials includes: Cracking and peeling under the direct action of thermal shock; instantaneous rupture under the action of thermal shock. On this basis, for brittlenessCeramic materialsThe special thermal shock resistance evaluation theory puts forward two views. The first one is based on thermoelasticity theory. It is said that the original strength of the material cannot resist the thermal stress caused by thermal shock, resulting in "thermal shock fracture" of the material. The theory holds that ceramic materials need to have thermal conductivity, high strength, low thermal expansion coefficient, Poisson's ratio and Young's modulus of elasticity, viscosity andThermal radiation coefficient and other combinations have high thermal shock fracture ability. In addition, in order to improve the actual thermal shock resistance of ceramic materials, the heat capacity and density of the material can be appropriately reduced.
Another fracture mechanics based on the concept of concrete The theory is that thermoelastic strain energy in a material can nucleate and propagate as well as the new energy required to the surface, cracks form and begin to expand, thereby causing thermal shock damage to the material. According to this theory, materials with good thermal shock resistance should have higher elastic modulus and lower strength. By this approach, it can be seen that the above requirements are completely opposite to the ability of high thermal shock rupture. In addition, the actual fracture performance of ceramic materials can be improved and the actual fracture toughness of the material can be improved, which is obviously helpful in improving the damage capability of the material. In addition, having a certain number of micro-cracks is very helpful in improving the thermal shock damage performance. For example: in ceramics with a porosity between 10% and 20% density, the formation of thermal expansion cracks usually suffers from pore resistance, passivation cracks and The presence of pores can help reduce stress concentrations.
As a zirconia ceramic material, it has the characteristics of high temperature mechanical properties, high melting point, chemical stability and thermal stability. Therefore, it is often used under high temperature conditions. Therefore, its thermal shock performance is also a key indicator of its performance. Many zirconia have very special properties, such as: zirconia exists in a single material and in the form of square and cubic three crystals, which has its special phase change characteristics. So many functions can be used,Mingrui Ceramics is also improving its thermal expansion behavior and enhancing its thermal shock performance.
