Silicon Carbide Production Process

Silicon carbide (SiC) is a high-performance semiconductor material widely used in power electronics, optoelectronics, and radio frequency devices due to its excellent high-temperature resistance, high-voltage resistance, and high-frequency characteristics. The production process of silicon carbide mainly includes the following steps:

Raw Material Preparation: The main raw materials for silicon carbide production are high-purity silicon powder and carbon powder. The purity of the silicon powder is typically required to be above 99.999%, while high-purity graphite or petroleum coke must be used for the carbon powder. The purity of the raw materials directly affects the performance of the final product.

Mixing and Molding: Silicon powder and carbon powder are mixed in a certain proportion, usually with a carbon-to-silicon molar ratio controlled at approximately 1:1. The mixed powder is then pressed into a green body. Molding can be done by cold pressing or hot pressing, depending on the requirements of subsequent processes.

High-Temperature Reaction Synthesis: The molded green body undergoes reaction synthesis in a high-temperature furnace, with the temperature typically controlled between 1600-2500℃. During this process, silicon and carbon react chemically to form silicon carbide. The reaction time varies from several hours to tens of hours, depending on the furnace type and process parameters.

Crushing and Grading: The synthesized silicon carbide blocks need to be crushed and graded to obtain silicon carbide powder of the required particle size. Crushing equipment typically includes jaw crushers or ball mills, while grading is achieved through sieving or air classification.

Purification Treatment: To remove impurities introduced during synthesis, silicon carbide powder requires acid washing or high-temperature purification. Acid washing usually uses hydrochloric acid or hydrofluoric acid, while high-temperature purification is carried out under an inert atmosphere at temperatures exceeding 2000℃.

Sintering and Densification: For applications requiring high-density silicon carbide, the powder must undergo sintering. Sintering methods include pressureless sintering, hot pressing, and hot isostatic pressing. Sintering temperatures are typically between 1800-2200℃, and the addition of sintering aids such as boron or aluminum can promote densification.

Processing and Testing: The sintered silicon carbide blank requires machining (such as cutting, grinding, and polishing) to achieve the final dimensional and surface precision requirements. After processing, rigorous performance testing is necessary, including density, hardness, thermal conductivity, and electrical properties.