silicon dioxide

silicon dioxide
LHcheM · CC BY-SA 3.0 · source
Name	silicon dioxide
Formula	SiO2
Molar mass	60.08 g·mol−1
Density	2.2–2.65 g·cm−3
Melting point	1710 °C (quartz)
Boiling point	2230 °C
Appearance	colorless transparent solid (crystalline or amorphous)

silicon dioxide is an inorganic compound composed of silicon and oxygen with the empirical formula SiO2. It is a major component of the Earth's crust and mantle and exists in multiple crystalline and amorphous forms used across Silicon Valley industry, European Union standards, and global materials science research. Its chemical stability, optical transparency, and mechanical hardness make it central to technologies developed by organizations such as Intel and Corning Incorporated and studied at institutions like Massachusetts Institute of Technology and Max Planck Society.

Properties

Silicon dioxide is a network covalent solid whose properties include high hardness, chemical inertness, wide optical transparency, and low electrical conductivity; these attributes underlie its roles in products from Apple Inc. displays to NASA instrumentation and are investigated at Stanford University, Harvard University, National Institute of Standards and Technology, and Fraunhofer Society. Room-temperature density varies by polymorph and glass content, with crystalline quartz (~2.65 g·cm−3) contrasted with lower-density amorphous silica produced by firms such as Evonik and Cabot Corporation. Thermal properties—high melting point and low thermal expansion—inform uses in Boeing components, Siemens furnaces, and CERN detectors. Optical refractive index and bandgap values guide applications in fiber optics pioneered by companies like Corning Incorporated and research groups at Bell Labs and University of Cambridge.

Structure and polymorphs

The atomic structure is based on tetrahedral coordination of silicon by oxygen; this network forms many polymorphs including low-temperature and high-temperature forms explored by researchers at California Institute of Technology and ETH Zurich. Notable crystalline polymorphs include quartz, tridymite, cristobalite, coesite, and stishovite—each associated with geologic settings studied by United States Geological Survey, Geological Survey of Japan, and universities such as University of California, Berkeley. Amorphous silica (silica glass) is produced industrially by companies like Schott AG and studied in laboratories at Imperial College London. High-pressure phases such as stishovite are of interest in planetary science work at Jet Propulsion Laboratory and Smithsonian Institution collections.

Occurrence and production

Silicon dioxide occurs naturally in sand, sandstone, quartz veins, and siliceous sediments; major mining and processing occur in regions like Western Australia, California, Sichuan, and Sahara Desert operations managed by corporations including Rio Tinto and BHP. Natural deposits supply silica for foundries, glassworks (e.g., Saint-Gobain), and construction materials used in projects by firms like Bechtel. Industrial production methods—pyrolysis of volatile silicon compounds, precipitation routes, and fumed silica synthesis—are practiced by chemical manufacturers such as DuPont and Wacker Chemie. Seawater and biogenic sources studied by researchers at Scripps Institution of Oceanography and Woods Hole Oceanographic Institution also contribute to global silica cycles.

Applications

Silica underpins glassmaking for architecture and consumer electronics produced by companies like Samsung Electronics and LG Corporation; optical fibers for telecommunications developed by AT&T and Verizon rely on high-purity silica from research at Nokia Bell Labs. In semiconductor fabrication, silica films and masks are integral to fabs operated by TSMC and GlobalFoundries, with process improvements driven by collaborations with SEMICON and academic groups at University of Texas at Austin. Silica fillers and thickeners are used in tires and composites by Michelin and Bridgestone; catalysts and chromatography supports employ silica from suppliers such as Thermo Fisher Scientific and Agilent Technologies. Specialty uses include silica aerogels in aerospace projects by Blue Origin and SpaceX and silica nanoparticles in cosmetics regulated in markets overseen by agencies like European Medicines Agency.

Health and safety

Respirable crystalline silica is a regulated occupational hazard monitored by agencies including Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, and European Agency for Safety and Health at Work. Chronic inhalation can cause silicosis and is linked to increased risks identified in studies from Centers for Disease Control and Prevention, World Health Organization, and academic medical centers such as Johns Hopkins University. Industrial hygiene practices—ventilation, wet cutting, and respiratory protection—are mandated in standards published by organizations like American National Standards Institute and enforced in jurisdictions by bodies such as Health and Safety Executive.

Environmental impact

Mining and processing of silica affect landscapes and biodiversity monitored by agencies such as United Nations Environment Programme and International Union for Conservation of Nature; dust emissions and energy use factor into life-cycle assessments conducted by Intergovernmental Panel on Climate Change-related research groups. Release of fine particulate silica contributes to air quality concerns regulated by Environmental Protection Agency and studied at environmental institutes like Environmental Defense Fund and The Nature Conservancy. Sustainable sourcing and recycling efforts are being pursued by manufacturers and coalitions including World Business Council for Sustainable Development.

History and discovery

The recognition of silica as a major mineral dates to early mineralogy and crystallography advances by figures associated with institutions such as Royal Society, Académie des Sciences, and scholars like Georgius Agricola and André-Marie Ampère; subsequent characterization of quartz and other polymorphs progressed through work at universities including University of Göttingen and University of Paris. Industrial-scale glassmaking and use of silica trace back to ancient civilizations recorded in artifacts preserved at museums such as British Museum and Louvre, while modern analytical techniques developed at Los Alamos National Laboratory and Argonne National Laboratory refined understanding of silica structure and behavior.

Category:Inorganic compounds