Ultra Low Density Materials Synthesized via an Aerosol Gelation Process

We synthesized carbon and silica ultra low dense and high specific surface area solids via aggregation and gelation of nano-sized particles in the aerosol phase. We named such solids as Aerosol Gels. The process of formation of an Aerosol Gel starts with a collection of individual nano-sized monomers which undergo Brownian aggregation and finally gel quickly relatively to the gravitational settling when the monomers are small enough ($\sim $ 10 nm radius) and the monomer volume fraction is high enough ($\ge $ 10$^{-4})$. The Carbon Aerosol Gel was found to have high specific surface area (200 -- 350 m$^{2}$/g), an extremely low density (2.5 -- 5 mg/cc) and a high electrical conductivity, properties similar to conventional aerogels. The Silica Aerosol Gel was also extremely porous with high specific surface area ($\sim $ 450 m$^{2}$/g) and a very low density ($\sim $ 4mg/cc).