Silica sol is a dispersion of nano-silica particles in water or solvent. Since SiO2 in silica sol contains a large amount of water and hydroxyl groups, silica sol can also be expressed as mSiO2.nH2O. It is widely used in electronics, polishing, catalysts, papermaking, textiles, ceramics, refractory coatings and other industries.
Silica sol is a dispersion of nano-silica, so it gives people the impression that silica sol is a product with a relatively simple composition. Its components are nano-silica particles and dispersion medium. However, the quality of silica sol is mainly reflected in the following aspects:
(1) Particle size: For example, large-particle silica sol, such as silica sol with a particle size of more than 100nm, is more expensive because its manufacturing cost is much higher than that of silica sol with ordinary particle size.
(2) Particle size uniformity: Some silica sols have very uniform particle size distribution. For example, silica sol used to prepare CMP polishing liquid requires its particle size to be very uniform. Its manufacturing difficulty is relatively large, and its manufacturing cost is also relatively high, so the price is naturally higher. However, the particle size uniformity of some silica sols is very poor. For example, silica sols used in refractory materials, casting, concrete and other fields do not require strict particle size control during the manufacturing process, and the production process is simple and low-cost.
(3) Product purity: For example, there are no requirements for the purity of silica sol products used in casting and concrete fields. The metal impurity content can be as high as several thousand PPM. Therefore, most silica sols in these fields are made of low-purity silicon powder, cheap sodium silicate and other raw materials, and the raw material cost is relatively low. The silica sol used in chip CMP polishing liquid has very high purity requirements, and the metal impurity content must be controlled below 1 PPM. The production of this type of silica sol has very high requirements for the purity of raw materials, production equipment, and production environment. Product testing also uses expensive instruments such as ICPMASS, and the production cost is very high. The price of this type of silica sol can reach tens of thousands or even hundreds of thousands of yuan per ton.
(4) Special silica sol: Some silica sols require deep processing and modification of the basic silica sol to make special silica sols, such as surface-modified silica sol, organic silica sol, etc. The production process is much more complicated than that of ordinary silica sol, and the production cost naturally increases.