What factors affect the high thermal conductivity of Silicon Carbide Products

Silicon Carbide, SiC is widely used in various industrial fields due to its good physical and chemical properties, especially its high thermal conductivity makes it perform well in occasions where heat dissipation is required. Siliconized carbon materials have the advantages of high thermal conductivity, high temperature resistance, wear resistance and corrosion resistance, and are widely used in electronic devices, heat exchangers, semiconductor manufacturing and other fields. However, the thermal conductivity of siliconized carbon is not fixed, and it is affected by many factors. The following will analyze the factors that affect the high thermal conductivity of siliconized carbon products from the perspectives of crystal structure, material purity, temperature, doping elements and processing technology.

1. Influence of crystal structure
The high thermal conductivity of siliconized carbon is related to its unique crystal structure. There are mainly two crystal structures of siliconized carbon: α-type (hexagonal structure) and β-type (cubic structure). At room temperature, the thermal conductivity of β-type siliconized carbon is slightly higher than that of α-type siliconized carbon. The atomic arrangement of β-type siliconized carbon is more compact, the lattice vibration is more orderly, and the thermal resistance is reduced. Therefore, choosing a suitable crystal structure can improve the thermal conductivity of the material.
However, in high temperature environments, α-type silicified carbon gradually shows better thermal stability. Although its thermal conductivity is slightly lower at room temperature, it can maintain good thermal conductivity at high temperatures. This means that in specific application environments, it is crucial to choose the right crystal structure.

2. Influence of material purity
The thermal conductivity of silicified carbon materials is highly dependent on their purity. There are fewer impurities in silicified carbon crystals with higher purity, and the scattering of lattice vibrations during heat transfer is reduced, so the thermal conductivity is improved. On the contrary, impurities in the material will form lattice defects, hinder the transfer of heat flow, and reduce thermal conductivity efficiency. Therefore, maintaining the high purity of silicified carbon materials during production is crucial to ensure other high thermal conductivity.
Some residual impurities, such as metal oxides or other amorphous substances, will form thermal barriers at the grain boundaries of silicified carbon crystals, significantly reducing the thermal conductivity of the material. These impurities will cause the thermal resistance at the grain boundaries to increase, especially at higher temperatures. Therefore, strictly controlling the purity of raw materials and production processes is one of the key steps to improve the thermal conductivity of silicified carbon.

3. Effect of temperature on thermal conductivity
Temperature is one of the important factors affecting the thermal conductivity of carbon silicide. As the temperature increases, the lattice vibration in the material will be enhanced, resulting in increased phonon scattering, which will affect the conduction of heat. In low temperature environments, the thermal conductivity of carbon silicide materials is relatively high, but as the temperature increases, the thermal conductivity will gradually decrease.
The thermal conductivity of carbon silicide varies in different temperature ranges. Generally speaking, the thermal conductivity of carbon silicide is more prominent at low temperatures, but when the temperature exceeds 1000°C, its thermal conductivity will gradually weaken. Despite this, the thermal conductivity of carbon silicide in high temperature environments is still better than most other ceramic materials.

4. Effect of doping elements
In order to optimize the thermal conductivity of carbon silicide materials, some doping elements are usually introduced in the industry, which can change the crystal structure and electrical properties of the material, thereby affecting the thermal conductivity. For example, doping with elements such as nitrogen or aluminum can change the thermal conductivity of carbon silicide.
However, doping may also cause negative effects. If the doping concentration is too high, the defects in the crystal structure increase, and the doped atoms interact with the lattice atoms, resulting in enhanced lattice vibration, increased thermal resistance, and ultimately reduced thermal conductivity of the material. Therefore, the type and concentration of the doping element need to be precisely controlled to minimize the negative impact on thermal conductivity while enhancing other properties (such as electrical conductivity).

5. Influence of processing technology
The manufacturing process of siliconized carbon materials has a direct impact on their thermal conductivity. Different production methods such as sintering process, hot pressing molding, and vapor deposition will affect the grain size, density, and porosity of the material, all of which will affect thermal conductivity.
For example, siliconized carbon materials produced by hot pressing sintering usually have higher density and fewer pores, shorter heat conduction paths, and therefore better thermal conductivity. Siliconized carbon materials prepared using conventional sintering methods may have more pores and microscopic defects, resulting in increased thermal resistance and reduced thermal conductivity.