Silica sol is a colloidal solution with the following main characteristics and uses:
I. Characteristics:
Composition: Silica sol is a dispersion of nano-scale silica particles in water or solvent. Its molecular formula can be expressed as SiO2.nH2O, in which SiO2 contains a large amount of water and hydroxyl groups.
Physical properties: Silica sol is odorless and non-toxic. The colloidal particles are fine (10-20nm) and have a large specific surface area. The particles themselves are colorless and transparent and do not affect the original color of the covered object. In addition, the viscosity of silica sol is low, and water can penetrate wherever it can penetrate.
II. Preparation method:
There are many methods for preparing silica sol, including but not limited to the following:
Ion exchange method: This is a mature and widely used process developed by NALCO in the United States in the 1940s and later improved by DuPont in the United States. This method requires specific materials and operating processes.
One-step hydrolysis of silicon powder: This process is relatively simple and widely used in China, but the size of the silica sol particles prepared is about 10-20 nanometers, and the interface between the particles is not clear, the morphology is non-spherical and cannot be controlled.
Silicon dissolution method: Using inorganic or organic bases as catalysts, silica sol is prepared by reacting elemental silicon with pure water. The silica sol prepared by this method has a low impurity content, and the shape, size, viscosity, pH value, density and purity of the colloidal particles are easy to control.
Acid neutralization method: Using diluted sodium silicate as the starting material and dilute sulfuric acid and other inorganic acids as acidifiers, acidic or alkaline silica sol is prepared.
Electrolysis electrodialysis method: An electrochemical method that prepares silica sol by adjusting the pH value of the electrolyte solution and controlling the current density and temperature of the electrolysis electrodialysis reaction.
3. Application:
Since silica sol has excellent high temperature stability, adhesion, film-forming property, gel property, adsorption property, charge property, activity, large specific surface area, non-toxic, tasteless and odorless properties, it is widely used in many industries, such as electronics, catalysts, refractory materials, coatings, inks, textiles, food, etc. Specifically, silica sol can be used in precision casting, polishing, papermaking, coatings, refractory materials, textiles, food clarification, chemical catalysts, electronics industry and other fields.
In short, silica sol, as a multifunctional colloidal solution, has a wide range of applications in many fields