siliciumdioxide

Siliciumdioxide, commonly called silicon dioxide or silica, is a chemical compound with the formula SiO2. It occurs widely in nature as the mineral quartz and in numerous silicate minerals, making it one of the most abundant components of the Earth's crust. It is encountered in forms ranging from crystalline quartz to amorphous silica.

Structure and forms: Siliciumdioxide forms a three-dimensional network of SiO4 tetrahedra. In crystalline form it appears as quartz, cristobalite, and tridymite; in amorphous form it occurs as fused silica or glass. Quartz has a high hardness and a very high melting point (around 1713°C for the crystalline form), while amorphous silica melts to form silica glass at somewhat lower temperatures.

Properties: SiO2 is chemically inert and thermally stable. It is essentially insoluble in water and is an excellent electrical insulator. It reacts with hydrofluoric acid to produce silicon tetrafluoride and water and can dissolve in hot alkali to yield silicates.

Occurrence and production: Siliciumdioxide occurs naturally in sand, sandstone, and many rock types. Industrial silica is produced from quartz ore or sand through crushing, purification, and, for certain applications, fusion to make silica glass or processing to prepare silicon-containing materials.

Applications: The largest use is in glassmaking, including silica sand and fused silica for optics. It is also used as a filler or reinforcing agent in ceramics, concrete, paints, and plastics, and serves as a precursor for silicon production in the semiconductor industry after reduction.

Safety: Inhalation of crystalline silica dust poses health risks, including silicosis and other lung diseases. Proper controls and protective measures are essential during mining, processing, and handling.