What is silicon carbide？

1. Introduction to Silicon Carbide (SiC)

Silicon Carbide (SiC), also known as carborundum, is a synthetic ceramic compound of silicon and carbon. With exceptional hardness (Mohs 9.5), thermal conductivity (120-270 W/m·K), and chemical inertness, it is a cornerstone material for high-performance abrasives, semiconductors, and refractory industries.

Key Characteristics:

• Types: Black SiC (cruder, cost-effective) vs. Green SiC (high-purity, premium).

• Crystal Structure: Hexagonal α-SiC (most common) vs. cubic β-SiC (specialized applications).

• Synthesis: Acheson process (2200–2500°C) or chemical vapor deposition (CVD).

2. Manufacturing Process

2.1 Acheson Method:

• Raw Materials: Silica sand (SiO₂) + Petroleum coke (C) + Sawdust (porosity control).

• Process: Electric resistance heating at 2400°C for 36+ hours.

• Output: Crushed, graded into grits (F8–F2000).

2.2 Green SiC Refinement:

• Purification: Acid leaching (HCl/HF) to reduce impurities (Fe₂O₃ <0.2%).

• Applications: Precision optics, semiconductor wafers.

The typical SiC purity of Black SiC is ≥ 98%, and the free carbon content is ≤ 0.3%. It is mainly suitable for processing scenes of coarse to medium fine particle size of F8-F220. Green SiC, through acid washing purification process, can increase its SiC purity to ≥ 99.5%, with a strictly controlled free carbon content of ≤ 0.1%. The particle size range is concentrated in the ultrafine particle size range of F240-F2000, designed specifically for precision polishing and high-purity requirements.

3. Technical Properties & Advantages

• Hardness: Mohs 9.5 (second only to diamond and boron nitride).

• Thermal Shock Resistance: Withstands rapid temperature changes (ΔT >1000°C).

• Electrical Conductivity: Semi-conductive properties enable use in power electronics.

Performance Comparison between Silicon Carbide and Aluminum Oxide (Al ₂ O3)

Silicon carbide is superior to traditional alumina materials in several key properties:

Hardness: The Mohs hardness of silicon carbide reaches 9.5, significantly higher than the 9.0 of aluminum oxide, second only to diamond and cubic boron nitride.

Thermal conductivity: The thermal conductivity of silicon carbide is 120-270 W/m · K, which is more than 6 times that of aluminum oxide (20-30 W/m · K). It can quickly dissipate heat and avoid thermal damage.

Cost: Alumina has a price advantage due to its simple raw materials and processes, while silicon carbide's high performance makes it irreplaceable in precision industry and semiconductor fields.

4. Industrial Applications

4.1 Abrasives & Grinding:

• Black SiC: Deburring metals, stone cutting (e.g., granite, marble).

• Green SiC: Polishing sapphire lenses, silicon wafers (Ra ≤0.05μm).

4.2 Refractories:

• Kiln furniture, blast furnace linings (thermal stability >1600°C).

4.3 Advanced Technologies:

• Semiconductors: SiC wafers for EVs and 5G devices (lower energy loss).

• Body Armor: Lightweight ceramic plates with high ballistic resistance.

Case Study:
A solar panel manufacturer reduced slicing time by 30% using Yumo’s Green SiC F1500 slurry for monocrystalline silicon ingots.

5. How to Choose the Right Silicon Carbide

5.1 Type Selection:

• Black SiC: Economical choice for rough grinding (e.g., cast iron, glass).

• Green SiC: Precision applications (e.g., LED substrates, optical coatings).

5.2 Grit Size Guidelines:

Select appropriate particle size according to processing requirements:

Coarse grained (F24-F60): Used for efficient material removal scenarios such as casting deburring and stone cutting, such as rough grinding of granite or cleaning of metal castings.

Medium to fine particle size (F80-F220): suitable for precision grinding of tool edges and semi precision machining of ceramic surfaces, balancing efficiency and surface quality.

Ultra fine grained (F240 and above): Specializing in nanometer level precision requirements such as semiconductor wafer slicing and optical lens polishing, it can achieve a surface smoothness of Ra ≤ 0.05 μ m.

5.3 Supplier Criteria:

• Certifications (ISO 9001, FEPA compliance).

• Custom grit sizing and batch consistency reports.

6. FAQs About Silicon Carbide

Q1: Is silicon carbide toxic?
No. SiC is chemically inert and safe for industrial use.

Q2: Can SiC replace diamond abrasives?
Yes, for non-ferrous metals and ceramics, offering better cost efficiency.

Q3: What’s the difference between bonded and coated SiC abrasives?

• Bonded: For grinding wheels (vitrified/resin bonds).

• Coated: For sandpaper and belts.