The difference between silica sol and silica gel

Silica sol is a colloid solution, odorless and non-toxic, with a molecular formula that can be expressed as mSiO2·H2O. It appears as a milky white or light blue semi-transparent liquid. Silica sol is a sol with colloidal properties, nearly spherical particles, and a negative charge. However, the colloidal particles are metastable and always have a tendency to spontaneously aggregate. If any of the three major stabilizing factors is weakened, it will automatically aggregate, resulting in gelation or sedimentation. The characteristics of silica sol: Finished silica sol is generally divided into alkaline silica sol and acidic silica sol, among which alkaline silica sol is more stable and is used more frequently. The SiO2 mass fraction is generally 10% to 40%, with a particle size of 5 to 100 nm and a specific surface area of 50 to 400 m2/g. The wide application of silica sol in scientific research and various industrial fields is closely related to its performance characteristics. Silica sol has many excellent properties such as large specific surface area, high adsorption capacity, high dispersion (from several nanometers to tens of nanometers), and high refractory and insulating properties. From its properties, the following characteristics can be found:

① The silica gel particles attached to the solid surface can increase the friction coefficient; ② It can firmly adhere to the solid surface and form a strong film without a curing agent, and the film-forming temperature is very low;

③ It can form a solid gel through drying or sintering, thus having certain durability;

④ It can form a gel with a large and uniform surface area and fine pores, and can also uniformly disperse powder materials, increasing the stability of the suspension;

⑤ By uniformly mixing particles, the mechanical, optical, and electrical properties of organic resins can be enhanced;

⑥ As a liquid system, the sol can undergo homogeneous reactions. Using silica sol instead of silica as a raw material for reactions can increase the reaction rate. Silica gel is an amorphous substance with a chemical formula of mSiO2·nH2O. It is insoluble in water and any solvent, odorless and tasteless, and chemically stable. It does not react with any substance except strong alkali and hydrofluoric acid. Different types of silica gel have different microporous structures due to different manufacturing methods. The chemical composition and physical structure of silica gel determine that it has many characteristics that are difficult to be replaced by other similar materials: high adsorption capacity, good thermal stability, stable chemical properties, and high mechanical strength, etc. Due to its chemical properties, it is used to make many types of silica gel products, such as silica gel sealing rings, silica gel sealing strips, and silica gel kitchenware, etc. Silica gel is classified according to its pore size as: macroporous silica gel, coarse-pore silica gel, B-type silica gel, and fine-pore silica gel. Due to the different pore structures, their adsorption properties are different. Coarse-pore silica gel has a higher adsorption capacity under high relative humidity conditions, while fine-pore silica gel has a higher adsorption capacity under low relative humidity conditions. B-type silica gel, with a pore structure between coarse and fine pores, has an adsorption capacity between the two. Macroporous silica gel is generally used as a catalyst carrier, opacifier, and toothpaste abrasive, etc.