Silica fume is a mineral composed of primary particles < 1 µm of amorphous, non-crystalline, silicon dioxide (SiO2), produced during the manufacture of silicon or ferrosilicon. This tightly controlled electro-metallurgical process involves the carbothermic reduction of quartz in the production of Silicon and FeSi alloys. Silica fume is formed when SiO gas, given off as the quartz is reduced, mixes with oxygen. Here SiO is oxidised to SiO2 condensing into the spherical particles of silica fume, forming the major part of the smoke or fume from the furnace.
At ambient temperature, silica fume is a fine odourless powder with a putrity range of 85-98 % depending on raw materials and furnace parameters. The colour varies from white to black, depending on the carbon content. In order to save on transport and storage costs and to avoid dust formation in the use of the product, silica fume is often densified.
EINECS 273-761-1 – fumes, silica: Amorphous silicon dioxide particles from the volatilization and vaporization of furnace feed materials in the manufacture of ferrosilicon and silicon.
CAS - 69012-64-2 - Silica. Amorphous – fume: Silica fume (by-product of electrometallurgical processes).
IUPAC-name: Silicon dioxide.
Other names: Silica fume, microsilica, condensed SiO2 (silica) fume, amorphous silica, silicon dioxide powder, silica powder, volatilized SiO2, thermally generated silica fume (TGSF), microfume.