Black silicon carbide is mainly added into nano‑insulation boards as an infrared opacifier. It addresses the infrared radiation penetration issue of the silica‑based matrix at high temperatures, while additionally improving the high‑temperature resistance and mechanical properties of boards.
- Core Function: Block High‑Temperature Infrared Radiation The nano‑porous silica matrix is semi‑transparent to mid‑infrared thermal radiation. As temperature rises, radiative heat transfer accounts for a larger proportion, which causes a sharp increase in the high‑temperature thermal conductivity of the board. Through absorption and Mie scattering, fine black silicon carbide powder intercepts high‑temperature infrared radiation within 2.5‑7 μm waveband, greatly reducing radiative heat flux and stabilizing thermal conductivity at high‑temperature ranges. This enables nano‑insulation boards to maintain excellent thermal‑insulating performance at 800‑1000 °C.
Simple explanation: Nano‑pores block conduction and convection at low temperatures; black silicon carbide blocks infrared rays at high temperatures.
- Improve High‑Temperature Resistance and Thermal Stability Black silicon carbide has an extremely high melting point (approx. 2730 °C) and good chemical inertness. A dense SiO₂ film forms on its surface under high‑temperature conditions to further retard oxidation. It inhibits shrinkage and softening of boards at high temperatures, preserves the integrity of nano‑pore structure, and raises the maximum long‑term service temperature.
- Reinforce mechanical properties and thermal‑shock resistance.
- Low‑thermal‑expansion black SiC particles disperse within the matrix.
- They suppress crack growth and boost flexural and compressive strength.
- Optimize Fire‑Resistance and Flame‑Retardant Performance It achieves Class‑A1 non‑combustibility and releases no toxic flue gas under high‑temperature conditions.
- Black silicon carbide exhibits relatively high solid thermal conductivity.
Manufacturers must precisely control its dosage.
Insufficient loading produces poor infrared opacifying performance.
Excessive loading increases solid heat conduction and board bulk density.
The industry widely uses super‑fine black silicon carbide powder with D50=1~4 μm.
