Study On Surface Modification Of Alumina Powder

Alumina powder is widely used in fine ceramics,microelectronics,polymer composites,paint and other fields for its high melting point,high hardness,good thermal conductivity,insulation and wear resistance,corrosion resistance and other properties.Application problems such as easy agglomeration,poor dispersion stability in an aqueous system,poor compatibility with an organic polymer matrix and so on,can affect the application performance of alumina powder.Alumina powder surface modification is an effective technique to solve these problems in alumina powder application.At present,alumina powder surface modification is mainly divided into inorganic coating and organic modification.In this paper,aiming at the problem that the alumina powder is easy to agglomerate and the dispersion stability of the aqueous system is poor,the inorganic silica modified coating method is used to modify it to improve its dispersion stability in aqueous system.And aiming at the poor compatibility of organic polymer matrix problem,the mechanochemical modification of organic modification was used to improve the affinity of alumina powder and organic polymer matrix.The influence of dispersion method on the dispersion of alumina powder in water and the influence of different modification process conditions on the modification effect were studied emphatically.A variety of testing methods were used to characterize and evaluate the modification effect of the modified powder.The study results show:1.The results of alumina powder dispersed in water indicate that the dispersibility of aluminum oxide powder in water can be improved by the dispersing of ultrasonic dispersion,the dispersing agent of sodium hexaphosphate and the method of regulating the pH of suspension.When the ultrasonic dispersion time is 4 min and the concentration of sodium hexametaphosphate dispersant is 1.25%,the absolute value of Zeta potential of alumina powder in aqueous suspension is the highest,and the dispersion stability is good.In the range of pH values 7-12,the more alkaline the suspension,the better the dispersion of powder.2.The results of silica-coated alumina powder modification indicate that hydrolytic coating method,using sodium silicate as the silicon source to coat the alumina powder,can form a silica film on the surface of the alumina powder particles to modify the microscopic morphology of the alumina particles.This method can improve the dispersion stability of alumina powder in aqueous systems.When the coating temperature is 70??80?,the aging time is 4h,the pH value of the system is 9.3 and the mass ratio of sodium silicate to alumina is 0.04:1,the modified powder has good modification effect and the dispersion stability in aqueous suspension is significantly improved.When 5g powder was precipitated in a l0mL colorimetric tube for 24 hours,the cumulative sedimentation volume was 0.8mL.3.The results of the mechanochemical surface modification of alumina powder indicate that sodium stearate,sodium laurate and TSG-0901 titanate coupling agent can all be used for effective surface organic modification of alumina powder by wet mechanochemical modification method.The modification effect of sodium stearate was better than the other two modifiers.When sodium stearate was used as the modifier,increasing modifier dosage and the modification time can improve the modified effect of alumina powder.When the modified agent is added in an amount of 5%of the mass of the alumina powder and the modified time is 90 min,the powder particles are almost all modified,and the powder activation index reaches 99.8%.When the amount of modifier continues to increase or the modification time continues to increase,the oil absorption of the modified powder and the viscosity of the paraffin oil suspension continue to decrease and the compatibility of the powder particles with the organic material becomes better.