Preparation Of Nano-spherical Silica

This article prepares nano-SiO₂ spherical particle with the homo-precipitation method, the alkoxide hydrolysis method and the micro-emulsion method.The basic performance of powder has been characterized by means of SEM, TEM, XRD, TG and FTIR.First, this paper prepares SiO₂ with homo-precipitation method, used the water glass as one major raw material, polyethylene glycol (PEG) as the surface active agent, Glycerol for dispersant, the ethyl acetate as hide reagent. It was studied that the influence of silicon source density, ethyl acetate amount ,dispersing agent amount , reaction temperature, roasting temperature on the size and appearance. Later we carry out symptom with modern detection means for it. The results indicated that these powder SiO₂ is spherical approximately, the average particle size is 80 run and the specific area is 820m².g^-1, but the dispersion is bad.The alkoxide hydrolysis method is that using the strong ammonia water as the catalyst in the mellow water component solvent and the tetraethoxy-silicane (TEOS) as the silicon source, prepares the particle size is between 60nm and 130nm . Effects of the solvent, the amount of surface active agent, the concentration of ammonia and etc. on the particle size and morphology SiO₂ were investigated by SEM. The result showed the ammonia water density was the primary factor to affect the particle shape, with the increasing of ammonia water density the SiO₂ particle size increases slightly. The production had the close relation with the water volume so it must be controlled in the appropriate scope. The absolute alcohol as the co-solvent could promote hydrolytic reaction. However, the reunion problem remains, this paper also used micro emulsion in order to solve this problem.The micro emulsion method is that forming the W/O opposition micro emulsion taking cyclohexane /Span-80 and the Tween-80/ water (mass ratio as 12% ammonia spirit), uses the orthogonal test to prepare the monodispersed SiO₂ spherical particle with the size between 60 and 140 nm .The orthogonal test analysis indicated that the quantity of the surface active agent is primary factor which affects the SiO₂ pellet particle size and the appearance.Through the above three methods of analysis can be drawn: the first two methods exist samples from the uneven distribution of particle size, the reunion more serious, and product of a bad ball, but micro-emulsion can be a very good method to solve these problems.