Preparation Of Silica Sols And Its Application In Silicate Long Afterglow Materials

As a kind of important inorganic macromolecule material, silica sol is widely used in precision casting, coating, battery, adhesive and catalyst industry, etc, because of its good dispersion, good wear resistance, large specific surface area, good hydrophilicity and hydrophobicity, etc. At same time, requirements of different kinds of product is becoming more and more extensive at home and abroad. Also silicate long afterglow luminescent material has a strong water resistance, light color completment with aluminate system, so researchers are paying more and more attention to silicate. In this paper, the research is mainly divided into two parts:silica sol was prepared by combining ion exchange method with metal silicon powder dissolution method, technology parameters in the reaction process were analyzed and discussed in the the first part, long afterglow phosphors of strontium silicate SnMgSioO7 were prepared by combustion synthesis method with silica sol as silica source, phase composition and luorescence properties were analyzed in the second part. The conclusions were drawn as follows:(1)Solution concentration, amount of silicon powder, catalyst, reaction temperature, reaction time, and some other factors affect particle size and stability of the product in the prepration of silica sol. When the concentration was less than 2.5wt%, SiO2 content as same as average particle sizeincreased with the increase of concentration.When the concentration was more than 2.5 wt%, average particle size decreased with the increase of concentration.When addition of silicon powder was less than 26g in 200ml, average particle size increased with the increase of silicon powder, and increased rapidly in less than 20g, slowly between 20g-26g. When addition of silicon powder was more than 13g, average particle size decreased slowly with the increase of concentration, and eventually tended to be stable. Average particle size was different with different types of catalysts. Average particle size was maximum when ammonia and nine sodium silicate solution were used as composite catalyst. Average particle sizeincreased with the increase of the temperature. Average particle size increased first and then decreased with the increase of the reaction time.(2) Optimum technological conditions for preparation of acidic silica sol was obtained:solution concentration 2.5wt%(200ml), dosage of silicon powder 26g, stirring rate 200r/min, the reaction temperature 90?, the reaction time 8h, using ammonia water and nine sodium silicate solution as composite catalyst. Under these conditions, average particle size could reach 30nm or more,stability time could be up to about 200 days at room temperature.(3)The emission spectrum of Sr2MgSi2O7 was half broadband, and the main emission peak located at 568nm, which was the characteristic peak value of 5D?7F of Eu+,second emission peak located at 475 nm, which was the characteristic peak value of4f5d?4fof Eu2+. The material mainly emits yellow light.(4)Optimum technological parameters for the preparation of Sr2MgSi2O7 was: n(strontiumnitrate)/n(silica sol)=1:1.1, n(carbamide)/n(nitrate)=3:1, combustion temperature is 850?. It was found that the products made by silica sol were smaller and more easily to be crushed, and production cycle was short. This method was expected to be a newtechnical route in the preparation of silicate.