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Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO 2, commonly found in nature as quartz. [5] [6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product.
Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum.
Silicon carbide whiskers – Simazine: 122-34-9 Sodium dimethyldithiocarbamate: 128-04-1 Sodium fluoroacetate: 62-74-8 Soots, tars, and mineral oils (untreated and mildly treated oils and used engine oils) – Spirodiclofen: 148477-71-8 Spironolactone: 52-01-7 Stanozolol: 10418-03-8 Sterigmatocystin: 10048-13-2 Streptomycin sulfate: 3810-74-0
Silicon (Si) is the second most common element in the Earth's crust after oxygen. The compound silica, also known as silicon dioxide (SiO 2), is formed from silicon and oxygen atoms. Since oxygen and silicon make up about 75% of the Earth's crust, the compound silica is quite common.
Precipitated silica is an amorphous form of silica (silicon dioxide, SiO 2); it is a white, powdery material. Precipitated silica is produced by precipitation from a solution containing silicate salts. The three main classes of amorphous silica are pyrogenic silica, precipitated silica and silica gel.
Oxidation of organosilicon compounds, including siloxanes, gives silicon dioxide. This conversion is illustrated by the combustion of hexamethylcyclotrisiloxane: ((CH 3) 2 SiO) 3 + 12 O 2 → 3 SiO 2 + 6 CO 2 + 9 H 2 O. Strong base degrades siloxane group, often affording siloxide salts: ((CH 3) 3 Si) 2 O + 2 NaOH → 2 (CH 3) 3 SiONa + H 2 O
Silica fume, also known as microsilica, (CAS number 69012-64-2, EINECS number 273-761-1) is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm.
Fumed silica is made from flame pyrolysis of silicon tetrachloride or from quartz sand vaporized in a 3000 °C electric arc. [3] Major global producers are Evonik (who sells it under the name Aerosil), Cabot Corporation (Cab-O-Sil), Wacker Chemie (HDK), Dow Corning, Heraeus (Zandosil), Tokuyama Corporation (Reolosil), OCI (Konasil), Orisil (Orisil) and Xunyuchem(XYSIL).