Production Process of Black Silicon Carbide

1. Production Process of Black Silicon Carbide
1.1 Raw Material Selection and Formulation
The primary raw materials for black silicon carbide are quartz sand (SiO₂) and petroleum coke (C), supplemented with a small amount of wood chips (to adjust porosity). Extremely high purity is required:
Quartz sand: SiO₂ content ≥99.5%, Fe₂O₃ ≤0.1%
Petroleum coke: Fixed carbon ≥98%, ash content ≤0.5%
Wood chips: Regulate furnace permeability and prevent over-densification during sintering
The raw materials are mixed at a mass ratio of SiO₂:C = 3:2 to ensure complete reaction for SiC formation.
1.2 High-Temperature Smelting (Acheson Process)
The mixed materials are loaded into a resistance furnace and electrically heated to 2000-2500°C, where the following chemical reaction occurs:
SiO₂ + 3C → SiC + 2CO↑
The smelting process lasts 36-72 hours, with the furnace core temperature reaching up to 2700°C, producing α-SiC (hexagonal crystal system).
1.3 Crushing and Classification
The produced silicon carbide blocks undergo jaw crushing → cone crushing → ball milling, and are finally classified by air flow separation or vibrating screens to obtain products of different particle sizes (F-grade, P-grade, micro-powders, etc.).
1.4 Acid Washing and Surface Treatment
To remove metal impurities (Fe, Al, etc.), a mixed acid wash of hydrofluoric acid and nitric acid is used, achieving purity above 99.5%. For some high-end applications, silane coupling agent modification is additionally required to improve dispersion in resin or ceramic matrices.