Preparation And Characterization Of High Purity Spherical Nano-silica

The high purity spherical nano-silica is characterized with higher dielectric constants, higher heat resistance, higher wet resistant, higher fill quantity, lower dilatability, lower stress, lower impurity, lower friction modulus etc, so it is widely used in many fields of advanced technology, such as materials of electronic encapsulation, photonic crystals, catalyst supports, accurate ceramic material, rubber, coating material, chromatogram packing materials and high polymer composite etc. Now, the high purity spherical nano-silica which is used in our country, was almost importation. Study on the preparation parameters of the high purity spherical nano-silica, it play very important role in the upgrade of a lot of products in many fields. This will also change the condition of the high purity spherical nano-silica depend on importation. Consequently, the study of preparation and process condition of the high purity spherical nano-silica will become popular in the field of nanometer technology.In this paper, on the base of comprehensive Analysis of researching trends and preparation technique of the high purity spherical nano-silica, the new technic of preparation of the high purity spherical nano-silica was obtained. It was the preparation of the high purity spherical nano-silica from powder quartz by sol-gel method. The reaction system, spherical catalyst, surfactant and dispersing agent were added to the reaction system. The mechanism of preparation of the high purity spherical nano-silica by sol-gel method was discussed. The main factors contributing to the performance of products were studied. The results were characterized by modern testing technologies such as SEM, TEM, XRD etc. The best conditions was synthesizing temperature 25³5℃, the concentration of waterglass was 0.2mol/L, the dosage of ammonia was 1.0mol/L, synthesizing pH value is 9±0.2, ethanol is 2.4mol/L, drying temperature was 80℃, calcined at 450℃. In the course of preparation of precursor, the concentration of waterglass, the dosage of ammonia, surfactant and dispersing agent have greatly influenced on the performance of products. The gathering phenomenon could be reduced by supply the losing surfactant during washing.The XRD, SEM, TEM characterized results shows that the nano-silica products prepared by sol-gel method is non-crystalloid, uniformly dispersed spherical particles, the average particle size was 100nm, spheroidizing ratio was above ninety-five percent, good thermal stable, non-crstyal structure. The chemical compositions of 99.97wtï¼…SiO₂, 9ppmAl³⁺, no more than1.04ppm Fe³⁺, no more than 3.5ppm Na⁺, no more than 1ppm Cl^- and no more than 1ppm SO₄^2-. These indexes achieve or exceed the request of the materials of electronic encapsulation application to the large scale integrated circuit, super large-scale integration.