What are precipitated silica and white carbon black?
Introduction to white carbon black
White carbon black is the general name of white powdery X-ray amorphous silicic acid and silicate products, also called hydrated silica. Its English name is Silica, mainly referring to precipitated silica, fumed silica, ultrafine silica gel and aerogel. The appearance of precipitated white carbon black is micro bead, powder, blocky and ultra-fine, while that of fumed white carbon black is ultra-fine powder.
Structure of white carbon black
Structure of white carbon black: crystal white carbon black is a three-dimensional network crystal formed by silicon atoms and oxygen atoms with covalent bonds. There is no single white carbon black molecule in the crystal. The silicon atoms of white carbon black are in the center of the regular tetrahedron, and they are combined with four oxygen atoms at the top corner of the regular tetrahedron to form a regular tetrahedron respectively with covalent single bonds. Si-O bonds repeat in space, forming a "macromolecule". In the crystal, there are 6 silicon atoms and 6 oxygen atoms on the small ring, a total of 12 atoms. The number ratio of silicon to oxygen atoms is 1:2, so the simple formula of composition is SiO2. There is no single molecule in the crystal.
Physical properties of white carbon black
White carbon black crystal is a hard, brittle, non-conductive, refractory (melting point 1710 ℃) and water-insoluble colorless solid.
Chemical properties of white carbon black
White carbon black is an anhydride of silicic acid, but it cannot react with water to form silicic acid. Due to the strong silicon oxygen bond, the chemical properties are very stable. It is an acid oxide with some properties of acid oxide. For example, it can react with alkaline oxide, alkali, soda ash, etc. to form silicate under high temperature; White carbon black does not react with ordinary acids, and has good acid resistance, but can be corroded by hydrofluoric acid, so people often use hydrofluoric acid to carve glass; It can be reduced to coarse silicon by strong reducing agent (carbon) at high temperature.
Application of white carbon black
At present, the industrial production of white carbon black is mainly by precipitation method. The white carbon black produced contains a large number of polar groups such as hydroxyl groups on its surface, which leads to problems such as easy adsorption of water molecules, poor dispersion, and easy secondary aggregation, thus affecting the industrial application effect of white carbon black.
Precipitated silica is an indispensable fine additive in rubber, plastic, paint, ink, pesticide, toothpaste and other industries. Especially in the rubber industry, precipitated silica has become the best white reinforcing filler.