| Silicon dioxide spherical particles are widely used in many fields of advanced technology, such as photonic crystals, catalyst supports, accurate ceramic material, rubber, coating material, chromatogram packing materials and high polymer composite etc. In this article, micrometer and manometer Si02 spherical particles were synthesized by solid-state reaction, ion-exchange-sol-gel method and hydrolysis of silicon alcohol salt, respectively. Also the structures of microspheres and preparation conditions were detailed studied. The nanometer SiO2 powders were prepared using the ionic exchange -sol -gel method with the sodium silicate as the silicon source, the soluble starch as the dispersing agent and NH4NO3 as latent anti-aggregate agent. The factors that influent the silicon dioxide size, such as the silicon source density, the amount of starch and the ammonium nitrate, the pH value of sol and the aging time etc. were studied by SEM. The results indicated that the aggregation among the particles was inhibited effectively using the space obstruct of long molecular chain, the separation of the polymer network, the physical dispersion of soluble starch and potential anti-aggregate of NH4NO3. The ionic exchange process transferred the silicate to the silicic acid, got rid of the impurity ions and overcame the shortcoming which in the colloid impurities (Na+, Cl-) were not easy to be cleaned, so this step could guarantee the product purity and reduce the later process load to wash the impurities. Silicon dioxide powders were also prepared by solid-state reaction taking the sodium silicate and the ammonium nitrate as the raw materials under the room temperature condition. The result indicated that, the excessive ammonium nitrate not only was possible to reduce grinds viscosity of the product to make the response easier carry on, but also burn in the calcine process to reduce the aggregation. This function could help to decrease the silicon dioxide particle size and distribute the particles much evenly. But the use of ammonium chloride was easy to introduce the impurity ion to influence the product purity. Through the XRD phase analysis proof the product under the low temperature was the amorphous structure, the silicon dioxide would transfer to crystal gradually with the temperature elevated. |
