What are the main components of silica sol used in precision casting? How is silica sol prepared?

Silica sol is a colloidal solution, odorless and non-toxic. Silica sol is a dispersion of nanometer-sized 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 SiO2.nH2O.

The ion exchange process of silica sol was developed by the American NALCO company in the 1940s, and was later perfected by the American DuPont Company in the 1950s and 1960s. It is currently the most mature and widely used process. This process has certain requirements for water glass, ion exchange resin and other materials as well as operating techniques, and these are the weaknesses of domestic products. Relatively speaking, the one-step hydrolysis process of silicon powder is relatively simple and is currently widely used in China. However, the silica sol prepared by this method usually has a particle size of about 10-20 nanometers, the interface between the particles is not clear, the morphology is non-spherical and cannot be controlled, and the interface between the particles is not clear, so it is usually only used in large quantities in castings. and other industries, but has not made any great achievements in many more demanding fields such as precision polishing and catalysts. Compared with internationally renowned silica sol brands, the main shortcomings of current domestic silica sol are high impurity content, lack of strict particle size control, particle specific surface area that is not strictly tested, low silica concentration, and poor stability under acidic or neutral conditions. , short service life, more or less colorful, few varieties, etc.