Study On Dispersion Stability And The Surface Modification Of Ultra-fine Particles

The study on the dispersion stability and surface modification is the important part of the application of the ultra-fine powder, which relate directly to the ultra-fine powder performance and prospect in industry. There were many ways to surface modification of Ultra-fine powder up to now. But in application, the surface of ultra-fine powder was usually modified by physical adsorption or esterification for diversified conditions limit. Although many people have done in this subject, few influencing factors which study on surface modification completely and regularly, and the characterization of the surface modified ultra-fine is imperfect.The properties and applications of ultra-fine indium tin oxide and tin oxide have been presented in this thesis. Based on colloidal dispersion stabilization theory, the mechanism of stabilization of ultra-fine indium tin oxide dispersed in a liquid ethanol system is investigated. The purpose of the research is to provide theoretical guide and operation conditions for stabilized ultra-fine indium tin oxide dispersed in a liquid ethanol system in practical applications. The surface of the indium tin oxide powder was modified by several surfactants and the performances of the powder were tested. The preparation of heat insulation material made from the powder was studied.The dispersion behaviors of ultra-fine indium tin oxide in a liquid ethanol system were studied in this paper. The influence of pH value variety and content of dispersants and different dispersing methods on dispersion stability results were discussed, The dispersion stability and diameter of indium tin oxide were tested. The experimental results indicated that the equipotential point determined in liquid ethanol is pH=6. The dispersion stability improves when the pH value are higher or lower than that. The most effective dispersant in the dispersion system is KH570 and its optimum consumption is 1% of the weight of ultra-fine particles. The influences of high-speed dispersing method and ultrasonic dispersing method on the dispersion stability were discussed. High-speed dispersing way needs lots of time and the ultrasonic dispersing way can reach better effect in a short time. The ultra-fine powder whose average diameter is 0.85μm was made under the optimization conditions and its size distributing is narrow.The surface of ultra-fine tin oxide was respectively modified by coupling method with silane coupling agent KH570 and esterification reaction with stearic acid in this thesis. The technologic conditions of surface modification of ultra-fine tin oxide and the preparation of the heat insulation material made from the powder were discussed. The influences factors on heat insulation were studied. The results showed that the surface of the ultra-fine powder modified by KH570 or stearic acid was covered with surfactants and the chemical bond occurred between them. The powder which is lipophilicity was obtained. The effect of the surface modification was better modified by stearic acid than KH570. The hydrophobic value of the ultra-fine powder modified by KH570 was 0.37 under the following conditions: the dosage of modifier reagent is 2%,the modification temperature is 50℃, the time is 30min; The hydrophobic value of the ultra-fine powder modified by stearic acid was 0.56 under the following conditions: the dosage of modifier reagent is 10%, the concentration of the stearic acid is 2.67g/L, the modification temperature is 60℃, the time is one hour. The dispersion of the modified ultra-fine powder in the organic solvent was improved and the surface of the ultra-fine powder was changed from hydrophilicity to lipophilicity. The test results show the production has good obvious performance of heat insulation effect, which has a difference in temperature about 10℃between the heat insulating and ordinary glass under infrared radiation. From the experiment the optimization conditions was discovered: the mass ratio of acrylate resin and the powder is 200/3 and the glasses were sprinkled for four times. Although the production has good obvious performance of heat insulation, there is a bigger difference between the standard and heat insulating glass, So further studies on this should be made. The heat insulating glass has better diaphaneity than the standard glass. The study on the heat insulation production has great significance because of its better transparency.