What is silicon carbide used for?

Silicon carbide is a hard carbon-silicon compound that has been an important material in the abrasives industry since the 19th century. In recent years, due to its heat-resistant properties, it has also been used as a refractory material in industrial production. This article discusses the production process, characteristics, and applications of silicon carbide.

Application of Silicon Carbide

1. Abrasive Applications
   • Silicon carbide is widely used in the production of grinding wheels and cutting tools. These tools are essential for shaping and finishing hard materials such as metals, ceramics, and composites.
   • SiC-based abrasives are particularly effective in removing rust, paint, and other surface contaminants, making them valuable in industries such as automotive repair, metalworking, and construction.
2. Electronics and Semiconductors
   • Silicon carbide is used to manufacture semiconductor devices such as diodes, transistors, and thyristors, which are critical in power conversion systems.
   • SiC's wide bandgap enables the development of high-frequency electronic devices, essential in telecommunications, radar systems, and wireless communication technologies.
   • SiC substrates serve as the foundation for growing gallium nitride (GaN) layers, crucial for producing blue and green LEDs.
3. Ceramics and Refractories
   • Silicon carbide is used to produce high-performance ceramics and refractory materials, essential in processes involving extreme temperatures.
4. Heating Elements
   • SiC is widely used in the production of heating elements for industrial furnaces and kilns, designed to operate at high temperatures.

Production Process of Silicon Carbide

1. Raw Material Selection: The process begins with the selection of high-purity raw materials, such as silica sand (SiO2) and carbon sources.
2. Mixing: The selected silica and carbon materials are finely ground and thoroughly mixed in precise proportions.
3. Electric Furnace: The mixture is placed in a large electric furnace designed for high-temperature synthesis.
4. Heating and Carbothermal Reduction: An electric current is passed through the graphite core, generating extremely high temperatures.
5. Cooling and Solidification: After the reaction is complete, the furnace is allowed to cool gradually.
6. Crushing and Grading: The silicon carbide mass is extracted, crushed, and ground into different sizes based on the intended application.
7. Purification (if necessary): Additional purification steps may be employed for higher purity requirements, such as in the semiconductor industry.
8. Final Product Processing: The graded silicon carbide can be further processed depending on its end-use.

Characteristics

• Exceptional Hardness: Silicon carbide is one of the hardest materials known, ranking 9.2 to 9.8 on the Mohs scale.
• High Thermal Conductivity: SiC has excellent thermal conductivity, typically around 120-270 W/mK.
• Thermal Stability: Silicon carbide maintains its structural integrity at very high temperatures, with a melting point around 2,700°C.
• Chemical Inertness: SiC is chemically inert and resistant to oxidation, corrosion, and most acids and alkalis.
• Electrical Properties: SiC is a wide bandgap semiconductor, with a bandgap of around 3.26 eV.
• Low Thermal Expansion: SiC has a low coefficient of thermal expansion (CTE).
• High Fracture Toughness: SiC exhibits a degree of toughness, contributing to its resistance to cracking and fracture under mechanical stress.
• Lightweight: Silicon carbide has a relatively low density, around 3.2 g/cm³, making it lighter than many other materials with similar mechanical properties.

Conclusion

According to the different characteristics of silicon carbide, it can be used in various applications such as abrasives, electronics, ceramics, and refractory materials.