Study Of The Size Control Technology Of Silica Sol Prepared By Silicon Power Method

The size control technology of silica sol prepared by silicon powder method was investigated in this paper; size-controllable silica sol was obtained by controlling the hydrolysis reaction conditions to promote the growth of seeds and to suppress the formation of secondary particles. Gel-solving, silicon powder method and ion exchange method was employed to prepare the seeds and the best seeds were selected by growth performance experiments. The influence of feeding mode of silicon powder, concentration of seed, dosage of catalyst, reaction temperature and dosage of silicon powder, reaction time and additives on particle size and size distribution was investigated. TEOS was used to improve the activity of the seeds, promoting the growth degree in unit time and delaying the activity decrease and the modification mechanism was studied. The pH value, the silica concentration and viscosity of the products were measured and the average sizes were determined by alkaline titrimetric method. Transmission electron microscope (TEM) was employed to observe the morphology and size of the products and the laser particle size analyzer was used to determine the size distribution. The optimal preparation conditions were that the concentration of seeds, TEOS and KCl were 1.5%wt, 0.15mol/L and 0.001mol/L respectively, the ratio of catalyst and deionized water was 3:500, the dosage of silico powder was 45g and reacted at 90℃for 5 hours. The size of the product was comparatively even and the average size determined by alkaline titrimetric method was 42.3nm.The macro and microscopic process model were established and core/shell model of model was introduced. The influence of size controlling factors on the size and size distribution were analyzed. The formula of secondary particles was deduced, through which the silica consumed by the formation of secondary particles could be estimated to illustrate the inhibitory efficiency of secondary particles and the degree of evenness of the silica sol. The growth process of the seeds was investigated in depth and the secondary particle formation was analyzed from many aspects. The controlling methods were put forward and the preliminary interpretation of the growth kinetics of seeds was given on that base.