VI. What are the fundamental differences between silica aerogel and fumed silica? How do their application fields differ?
1. Fundamental Differences
Silica Aerogel
路 Preparation: Produced by the sol??gel process followed by supercritical drying.
路 Structure: A three-dimensional, continuous nanoporous network with porosity as high as 80??99%.
路 Properties:
o Extremely low density (0.003??0.2 g/cm鲁)
o Very high surface area (500??1200 m虏/g)
o Ultra-low thermal conductivity (as low as 0.012??0.016 W/m路K)
o High optical transparency (up to >80% visible light transmittance)
Fumed Silica (Pyrogenic Silica)
路 Preparation: Produced mainly by hydrolysis of silicon tetrachloride (SiCl??) in a hydrogen-oxygen flame (chemical vapor process).
路 Structure: Amorphous nanoparticles (7??40 nm), loosely aggregated, not forming a continuous porous network.
路 Properties:
o White, lightweight powder
o High surface area (200??400 m虏/g)
o Strong rheological and thickening effects
o High adsorption capacity
2. Application Differences
Silica Aerogel
路 Building & Construction: Super-thin insulation for walls, roofs, curtain walls, and retrofitting of historical buildings
路 Energy & Batteries: Thermal management and fire protection for lithium-ion batteries and energy storage systems
路 Petrochemical/Industrial: High-temperature pipeline and equipment insulation
路 Aerospace: Spacecraft thermal insulation (famously used by NASA for Mars missions)
路 Optics & Acoustics: Transparent insulating glass, sound-absorbing and wave-absorbing materials
路 Environmental: Oil-spill sorbents, air-filtration materials
Fumed Silica
路 Rubber/Plastics: Reinforcing filler to improve strength and wear resistance (especially in silicone rubber)
路 Coatings/Inks: Thickener, anti-settling agent, rheology modifier
路 Adhesives/Sealants: Improves flow control and stability
路 Pharma/Food: Anti-caking agent, excipient, carrier
路 Cosmetics: Enhances texture, spreadability, and stabilit
3. Summary
Nature
路 Aerogel ?? A nanoporous 3D solid network (lightweight, super-insulating)
路 Fumed Silica ?? A nanoparticle powder (rheology modifier, reinforcing agent)
Applications
路 Aerogel ?? High-performance insulation, optics, aerospace, specialty uses (high-value functional material)
路 Fumed Silica ?? Commodity additive across many industries (cost-effective, broad usage)
You can think of fumed silica as a nano-powder ??additive?? to tune system performance, while silica aerogel is a nano-sponge ??structural material?? with unique functional properties.