The physical properties of ceramic materials undergo various changes in high-temperature environments. The following is a specific introduction:
Changes in thermal expansion performance
Ceramic materials usually have a low coefficient of thermal expansion, but their volume still expands with increasing temperature. The thermal expansion coefficient of different types of ceramics varies. For example, the thermal expansion coefficient of alumina ceramics is relatively low, and its expansion degree is relatively mild during the temperature rise process; The thermal expansion coefficient of silicon carbide ceramics is also relatively small, but observable volume increase phenomena will gradually occur at high temperatures. When the temperature change rate is fast or the thermal expansion coefficient of the ceramic material does not match that of the matrix material, this thermal expansion may generate thermal stress inside the material, leading to cracks or even ceramic fracture, affecting its performance and structural integrity.
Hardness change
Most ceramic materials have high hardness at room temperature, for example, silicon carbide ceramics have a hardness second only to diamond and perform well in wear resistance and other aspects. However, as the temperature increases, the hardness of ceramic materials tends to decrease. This is because high temperatures can affect the bonding force between atoms and ions inside ceramics, reducing the stability of the lattice structure. The originally tight structure becomes relatively relaxed, resulting in a weakened ability to resist external forces such as pressure and scratches. When performing operations involving external forces such as cutting and friction in high-temperature environments, the wear resistance of ceramic materials may not be as excellent as at room temperature due to a decrease in hardness.
Change in elastic modulus
The elastic modulus reflects the ability of a material to resist elastic deformation, and the elastic modulus of ceramic materials decreases in high temperature environments. At room temperature, ceramics generally have strong rigidity and limited elastic deformation ability. However, as the temperature increases, the thermal motion of atoms and ions intensifies, and the lattice structure inside the ceramic is more prone to deformation under external forces, resulting in a decrease in its elastic modulus. Externally, the material becomes relatively more prone to elastic deformation. For example, in some high-temperature structural component application scenarios, ceramics can originally maintain their shape and bear loads well, but may undergo significant deformation due to changes in elastic modulus at high temperatures, affecting the overall performance and stability of the components.
Changes in thermal conductivity
The thermal conductivity of ceramic materials also changes at high temperatures. Some ceramics, such as zirconia ceramics, have relatively stable thermal conductivity at room temperature, but as the temperature increases, the influence of internal lattice vibrations, defects, and other factors on thermal conductivity may change, and the thermal conductivity may fluctuate. Some ceramics have an increased thermal conductivity at high temperatures, which accelerates heat transfer; However, some ceramics may experience a decrease in thermal conductivity due to structural changes and other factors, which can affect the efficiency of heat dissipation and transfer, thereby affecting the thermal balance of the high-temperature system in which they are located.
Density variation
Overall, ceramic materials have relatively small density changes at high temperatures. However, high temperatures may cause some microstructural changes within ceramics, such as lattice vacancies and atomic diffusion, which can slightly alter the material content per unit volume at a microscopic level, resulting in a certain degree of density fluctuation. However, this change is usually more pronounced under extreme high temperatures and prolonged exposure, and its impact on its performance and effectiveness is relatively limited in conventional high-temperature application scenarios.
Color and appearance changes
Some ceramic materials may undergo color changes in high-temperature environments, such as some ceramics containing transition metal elements. As the temperature increases, the internal electronic transition changes, resulting in different colors. From the appearance, ceramic materials that are exposed to high temperatures for a long time may become rough on the surface, which may be caused by chemical reactions at high temperatures, grain boundary migration, or the detachment of small particles, affecting their surface smoothness and aesthetics.

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