silika

Silika, also known as silicon dioxide, is a chemical compound with the formula SiO2. It occurs widely in nature as quartz and other minerals and is a major constituent of sand, rocks, and soils. Silica exists in several crystalline forms, including quartz, cristobalite, and tridymite, as well as amorphous hydrated forms such as opal, silica gel, and fused silica.

Structure and properties: Silica is a network covalent solid composed of interlinked SiO4 tetrahedra. Each silicon atom is fourfold coordinated to oxygen, creating a rigid framework that gives high hardness, a high melting point, and chemical inertness. It is largely insoluble in water and most acids, with dissolution occurring mainly in hydrofluoric acid or, under certain conditions, in hot alkali solutions to form silicates.

Occurrence and geology: Silica is among the most abundant oxides in Earth's crust and forms minerals such as quartz in igneous, metamorphic, and sedimentary rocks. It is the principal component of sand and clay minerals and serves as a key raw material in various industrial processes.

Uses: The largest use of silica is in glass production, followed by its role as a filler and processing aid in cement and ceramics. Other forms include fumed silica and silica gel, used as desiccants and thickening agents, while high-purity silica and silica coatings are important in electronics and optics. Silica aerogels provide low-density insulation, and silicon dioxide layers are fundamental in semiconductor devices.

Safety and environment: Inhalation of crystalline silica dust poses health risks, including lung diseases such as silicosis, making proper dust control and exposure management essential in mining, manufacturing, and construction.