Preparation Of Nanometer-sized SiO₂ Powders By Silica Sol

Nanometer-sized SiO₂ is amorphous and white powder which is non-toxic,tasteless, soilless and nonmetallic material.It has extensive applications in plastic,rubber,fine-ceramic, paint,bond industry etc.Presently main methods on preparation of Nanometer-sized SiO₂ Powders list as follows:gas method,arc welding method,deposited method,sol-gelmethod, micro-emulsion method,over-weighted reaction method,hydrothermal method etc.But these methods existed some defects,for example costly raw materials,complex operating sequence and crafts.Methods on preparation of Nanometer-sized SiO₂ Powders was by Silica sol in this paper, Si-sol was a kind of colloid liquor which Nanometer-sized SiO₂ powders was scattered in water,the size of colloid particles in it was from 5 to 20 nanometers commonly,some colloid particles attained 100 nanometers,structure of its three dimensions was exactly the same as Nanometer-sized SiO₂,the colloid particles consolidated and formed big particles irreversibly through hydrogen-bond when it was concentrated or gelled because its surface filled with hydroxyl group.We utilized colloid-protect reagent in this paper,let it combined with hydroxyl group preventing colloid particles condensing and attained intrinsic structure in Si-sol.Commonly concentrating sequences and crafts destroyed integrality of Silica sol colloid structure in some degree.We adopted inverse extraction method that is entered a kind of extraction liquid which didn't react with SiO₂,in addition this liquid possessed better absorbent character,it can extract water from Si-sol gently.Colloid-protecting reagent entered and method of inverse extraction prevented colloid particles concentrating keeping intrinsic structure and forming gel,while the extraction liquid can use circled through evaporation.This gel was calcined at high temperature after dehydrated absolutely,we can obtain pure Nanometer-sized SiO₂ and colloid-protect reagent can be volatilized and reused.