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Silica, quartz and silicate materials include fused silica, quartz, kaolin or clay-based materials, cordierite, steatite, forsterite, sillimanite, zircon, porcelain, and fireclay. They are based on silicon dioxide and various chemical variations.
Processing and Production
Silica and silicate materials are fused or cast with aluminum, calcium, sodium, and magnesium oxide additions to modify specific properties and impart various processing characteristics. Quartz is a hard, crystalline mineral that is the second most abundant mineral in Earth’s crust. It is often colored by impurities, but also contains silicon dioxide.
Chemical variations and different processing techniques can be used to improve the clarity, transparency, and dielectric properties of silica and silicate materials. These various methods are used to produce aluminum silicate, calcium silicate, clay, cordierite, fireclay, forsterite, and kaolin.
The GlobalSpec SpecSearch database contains information about these and other types of silica and silicate materials.
- Aluminum silicate is insoluble and often used as a refractory in glassmaking. Categories include sillimanite, fibrolite, and mica (muscovite, biotite, and phlogopite). Mica is fireproof and non-fusing, has low heat conductivity, excellent thermal stability, and good dielectric or electrical insulation properties.
- Cordierite has a low coefficient of thermal expansion, high mechanical strength, low dielectric loss, and excellent thermal-shock resistance. It can withstand a red heat to ice water quench, and then be returned to red heat. Cordierite is often fabricated into an insulator or insulating substrate because of its good dielectric properties.
- Fireclay is a heat-resistant, secondary clay or clay-based mixture useful for elevated temperature or refractory bond applications. Fireclay-based refractories or ceramics use natural clay or a mixture of clay and other ceramics such as alumina, calcium aluminate, or silicon carbide.
- Forsterite is a stoichiometric magnesium orthosilicate (Mg2SiO4) used in applications that require a high coefficient of thermal expansion. Forsterite has desirable electrical insulation properties and is used as a layer on transformer steel sheets.
- Fused silica is a compound of silicon and oxygen. High purity, amorphous, fused silica is a high-performance ceramic with very low expansion, remarkable thermal shock resistance, low thermal conductivity, excellent electrical insulation up to 1000° C, and excellent resistance to corrosion from molten metal and glass.
- Steatite ceramics are used for high frequency, low loss, and high voltage insulation. Steatite has good mechanical properties and low loss electrical qualities. It is used in igniters, standoffs, surge arrestors, coil forms, spacers, and spark plugs. Steatite is easily fabricated to close tolerances and much less expensive than alumina ceramic insulators.
Silica, quartz and silicate materials are used in optical, thermal, chemical, and electrical and electronics applications.