Common size of Green Silicon Carbide Used as Opacifiers
I. Particle Size (Mie Scattering Matching High-Temperature Infrared Radiation at 2.5~7 μm)
Optimal D50: 2.5～3.5 μm, overall applicable particle size range: 0.5～5 μm
This particle size matches the wavelength of high-temperature thermal radiation, delivering the highest efficiency in infrared scattering and absorption, making it the standard particle size range for aerogel opacifiers.
II. Conversion Table of Common Grit Size & Median Particle Size (D50, μm)
| Green Silicon Carbide Grit Grade | Median Particle Size D50 (μm) | Suitability for Opacifier | Application Description |
|---|---|---|---|
| 4000# | ≈2.5～3.0 | ✅ Preferred general grade | Mass-produced mainstream opacifier grade in the industry; balanced light extinction performance, good dispersibility and cost-effective |
| 3000# | ≈4.0～4.5 | ✅ Commonly used grade | Slightly lower opacifying efficiency, easier to suspend and disperse, convenient for feeding and processing |
| 5000# / 6000# | ≈1.5～2.0 | ✅ For high-precision formulations | Applied to ultra-thin aerogel and low-density thermal insulation boards; superior opacifying performance with higher milling cost |
| 2000# and coarser grades (＞6 μm) | ≥6.7 | ❌ Not recommended | Excessively large particle size mismatches infrared wavelength, resulting in drastically reduced opacifying efficiency |
III. Selection Recommendations for Different Working Conditions
Conventional aerogel & microporous thermal insulation boards (90% mass-production formulation)
Recommended grade: 4000# green silicon carbide with D50 ≈ 2.5~3 μm, typical dosage: 8%~15%
Low-density & ultra-thin aerogel formulations
Recommended grade: 5000~6000# (1.5~2 μm). Finer particles fill internal pores and enable uniform light shielding.
Low-cost general thermal insulation fiber boards
Optional grade: 3000# (4~4.5 μm), featuring lower difficulty in dispersion during processing.
IV. Mandatory Raw Material Specifications
- Purity: SiC ≥ 98.5%; low free carbon and iron oxide content to avoid discoloration at high temperatures
- Narrow particle size distribution, free of oversized coarse particles to prevent puncturing the pore structure of aerogel
- Surface modification is available to improve compatibility and dispersibility in silica-based systems
