两步沉淀法制备核壳型SiO_2颗粒

Preparation of SiO_2 by Two-Step Chemical Precipitation Method

以硅酸钠为硅源、硫酸为酸化剂、硫酸钠为分散剂,通过两步沉淀法制备内核致密、外部疏松的核壳型SiO_2颗粒,探讨酸化剂、反应温度和陈化时间以及硅酸钠用量对SiO_2比表面积的影响,并对产物的吸水性能和磨擦性能进行表征.结果表明:第一步沉淀反应过程中,反应温度越高,陈化时间越长,产物比表面积越小,nH2SO4:nNa2SiO_3达到1.05~1.1时,产物比表面积出现最小值;第二步沉淀反应中,反应温度越低,硅酸钠用量越大,核壳型SiO_2比表面积越大;核壳型SiO_2吸水值2.04 mL/g,铜片磨耗值180,可用作牙膏的磨擦剂兼增稠剂.

SiO2 particles with compact core and porous shell were made by two-step chemical precipitation method using sodium silicate as precursor, H2SO4 as acidifier and Na2SO4 as dispersant. Effects of the chemical precipitation conditions in two steps on the specific area of SiO2 were investigated, and the water-absorbing ability and the cleaning ability of product were also characterized in the paper. It was found that in the first chemical precipitation process, the higher the reaction temperature and the longer the aging time, the smaller the specific surface area of SiO2. When nH22SO4：nNa2SiO3 is 1.05-1.1, the specific surface area of SiO2 reaches to the minimum. In the second chemical precipitation process, the specific surface area of product increases with the decreasing of reaction temperature and amount of sodium silicate. The water absorption capacity of product is 2.04 mL/g, and the Copper abrasion value is 180, accounting for the product can be used both as thickening agent and abrasive in toothpaste.