Preparation of Ultrafine Silica by Supercritical Carbon Dioxide Technology

In this paper,sodium silicate was used as silica source and supercritical fluid technology was carried out to prepare ultrafine SiO2 particles.The effects of pressure and temperature on the particle size and zeta potential of ultrafine SiO2 particles were studied,respectively.Zeta potential and laser particle size analyzer,X-ray diffracmeter(XRD) and automatic adsorption instrument were employed to characterize the structure and properties of ultrafine SiO2 particles.The results showed that the minimum mean diameter of silica particles is 472.9 nm and the Zeta potential is-55.68 mV when the corresponding pressure and temperature is 8 MPa and 50 ℃,respectively.The ultrafine SiO2 particles exhibit amorphous state and compared with the purchased T36-5SiO2 particles,its pore structure is denser.