Preparation and Characterization of Monodispersed and Spherical SiO_2 Particles

Monodispersed submicrospheres of silica in the size range of 300～500 nm were synthesized by Sol-Gel in the presence of ammonia.The effects of the concentrations of ammonia and silane coupling agent,the dosage of ethanol and the volume rate of tetra-ethoxysilane/water on the diameter,dispersion coefficient and the surface structure were studied.The stability properties and the formation mechanism of silica were also studied.The results show that the size of silica increases at first then decreases and the dispersion coefficient increases with increasing of concentration of ammonia.What's more,the size and the dispersion coefficient decrease with the increase of ethanol.The organic components of the surface increase and the hydrophobicity strengthen with adding of the silane coupling agent.The solution can't be placed for long time at the room temperature and with increasing the concentration of silane coupling agent,the particles will be conglutinated easily.