Black Silicon Carbide: Properties and Applications
1. Overview
Black silicon carbide (SiC) is a synthetic ceramic material produced by heating a mixture of silica sand and petroleum coke in an electric resistance furnace at high temperatures (around 2200°C). It is harder than aluminum oxide but less tough than diamond or boron carbide.
2. Key Properties of Black Silicon Carbide
| Property | Description |
|---|---|
| Hardness | 9.0-9.5 on Mohs scale (close to diamond) |
| Melting Point | ~2700°C (decomposes, does not melt) |
| Thermal Conductivity | High (120-200 W/m·K) |
| Chemical Resistance | Resistant to acids, alkalis, and oxidation |
| Electrical Conductivity | Semi-conductive |
| Mechanical Strength | High compressive strength, brittle |
| Density | ~3.1 g/cm³ |
| Thermal Shock Resistance | Excellent |
| Color | Black/dark gray due to impurities (iron, carbon) |
3. Applications of Black Silicon Carbide
A. Abrasives & Grinding
Used in grinding wheels, sandpapers, and cutting tools.
Effective for non-ferrous metals (aluminum, brass), ceramics, and composites.
B. Refractories
High thermal stability makes it suitable for furnace linings, kiln furniture, and crucibles.
Used in steelmaking and glass manufacturing.
C. Metallurgical Applications
Acts as a deoxidizer in steel production.
Used in iron & steel refining to improve quality.
D. Wear-Resistant Components
Used in nozzles, seals, and blast media for sandblasting.
Applied in pump components subject to erosion.
E. Electronics & Semiconductors
Used in high-power, high-temperature electronic devices (diodes, LEDs).
Substrate material for certain semiconductor applications.
F. Automotive & Aerospace
Brake discs and ceramic brake pads (due to heat resistance).
Lightweight structural components in aerospace.
G. Ceramics & Composites
Reinforcing agent in ceramic matrix composites (CMCs).
Used in bulletproof armor materials.
H. Polishing & Lapping
Fine SiC powders are used for polishing glass, stone, and optical components.
4. Comparison with Green Silicon Carbide
Black SiC: Cheaper, slightly less pure (~97-98% SiC), used for general abrasive and refractory purposes.
Green SiC: Higher purity (>99%), used for precision grinding of hard materials like tungsten carbide.
5. Advantages & Limitations
✔ Advantages:
Extreme hardness and wear resistance.
Excellent thermal and chemical stability.
Cost-effective compared to diamond or boron carbide.