Mullite


Also found in: Dictionary, Wikipedia.
Related to Mullite: kyanite, corundum, cordierite

mullite

[′mə‚līt]
(mineralogy)
Al6Si2O13 An orthorhombic mineral consisting of an aluminum silicate that is resistant to corrosion and heat; used as a refractory. Also known as porcelainite.

Mullite

 

a mineral from the silicate class, with a chemical composition that varies from Al6Si2O13 to Al4SiO8 (or from 3A12O3 • 2SiO2iO2 to 2Al2O3 • SiO2). Its structure is similar to that of sillimanite; however, mullite differs significantly in the irregularity of the Si and Al atoms. Mullite occurs in small prisms of the orthorhombic system. It has a hardness of 6–7 on Mohs’ scale and a density of 3,030 kg/m3; it melts at a temperature of about 1,810°C. Pure mullite is colorless; it is pinkish or bluish as a result of admixtures of iron or titanium oxides and exhibits pleochroism. Mullite is the only compound of Al2O3 and SiO2 that is stable at high temperatures.

Mullite is rarely found in nature. It was discovered in partially fused clayey enclosures in Quaternary lava on the island of Mull in Scotland. Mullite is an important component of such man-made industrial products as porcelain and fireclay (alumina-containing refractory). It is formed by heating kaolinite to 950°C and by heating such alumina silicates as andalusite, sillimanite, and kyanite at temperatures ranging from 1,300–1,550°C. Fused mullite refractory is obtained in electric furnaces from a mixture consisting of bauxite, alumina, kaolin, coke, and other substances.

References in periodicals archive ?
It is evident that there is a strong recrystallization from 1150[grados]C, especially the formation of cristobalite and mullite.
It is well known that the mineralogy of fly ash typically consists of a vitreous matrix containing various amounts of precipitated mullite (3[Al.
Above about 800[degrees]C, kaolin begins to convert to relatively inert ceramic materials such as spinel, silica and mullite.
Exothermic temperature peaks between 930 [degree]C and 1000 [degree]C were attributed to the temperature range for mullite formation from metakaolinite (Ekosse, 2008) as per the following equation:
al, "Influence of combustion aids on suspension combustion synthesis of mullite powders," Journal of European Ceramic Society, vol.
The formation of primary mullite at doses above four percent may be responsible for the increase in strength observed thereby.
The studies are carried out using the production waste of mineral or mullite wool, fly ash, crushed glass, waste of paper manufacturing, etc.
This could be due to the formation of mullite which protects the clay layers from further acid attack.
Among their topics are the chemical vapor deposition growth of graphene-encapsulated palladium nanoparticles, fabricating porous mullite by freeze casting and sintering of alumina-silica nanoparticles, the current status and prospects of nanotechnology in Arab states, the influence of substrate temperature and radio-frequency power on the formation of zinc oxide nanorods for solar driven hydrogen production, and fabricating porous material using ice particles as a pore-forming agent.
The phases in zeolitic materials were hydroxysodalite (JCPDS 31-1271) and NaX (JCPDS 38-0237) with peaks of quartz (JCPDS 85-0796) and mullite (JCPDS 74-4143) of ashes that remained after the treatment.
The toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high temperatures.
After thermal treatment at high temperature crystallization of the material took place with the formation of thermal and chemical resistant mullite phase.