Aluminium silicate (or aluminum silicate) is a name commonly applied to chemical compounds which are derived from
aluminium oxide, Al
2O
3 and
silicon dioxide, SiO
2 which may be
anhydrous
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...
or hydrated, naturally occurring as
minerals or synthetic. Their chemical formulae are often expressed as xAl
2O
3·ySiO
2·zH
2O. It is known as
E number
E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...
E559.
Examples
* Al
2SiO
5, (Al
2O
3·SiO
2), which occurs naturally as the minerals
andalusite,
kyanite and
sillimanite which have different crystal structures.
* Al
2Si
2O
5(OH)
4, (Al
2O
3·2SiO
2·2H
2O), which occurs naturally as the mineral
kaolinite
Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral ...
and is also called aluminium silicate dihydrate.
[Handbook of Inorganic Compounds, Dale L. Perry, Taylor & Francis, 2011, ] It is a fine white powder and is used as a filler in paper and rubber and also used in paints.
* Al
2Si
2O
7, (Al
2O
3·2SiO
2), called metakaolinite, formed from kaolin by heating at .
* Al
6Si
2O
13, (3Al
2O
3·2SiO
2), the mineral
mullite, the only thermodynamically stable intermediate phase in the Al
2O
3-SiO
2 system at atmospheric pressure.
[Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford, R. H. Doremus, Springer, 2008, ] This also called '3:2 mullite' to distinguish it from 2Al
2O
3·SiO
2, Al
4SiO
8 '2:1 mullite'.
* 2Al
2O
3·SiO
2, Al
4SiO
8 '2:1 mullite'.
Aluminium silicate composite materials, fibres
Aluminium silicate is a type of fibrous material made of aluminium oxide and silicon dioxide, (such materials are also called aluminosilicate fibres). These are glassy solid solutions rather than chemical compounds. The compositions are often described in terms of % weight of
alumina, Al
2O
3 and
silica, SiO
2. Temperature resistance increases as the % alumina increases. These fibrous materials can be encountered as loose wool, blanket, felt, paper or boards.
[Concise Encyclopedia of Composite Materials, ed. Anthony Kelly, MIT Press, 1989, ]
References
External links
Aluminum silicatesat the University of Waterloo, Canada
{{Authority control
Silicates
Silicates
Orthorhombic minerals
E-number additives