page_title: Aluminium
section_title: Compounds
hierarchical_section_title: Aluminium / Applications / Compounds
caption_attribution_description: English: Thin films of oxides are deposited with atomic layer precision using pulsed laser deposition. A high-intensity pulsed laser is shooting onto the rotating white target consisting of Al2O3 (alumina). The laser pulse creates a plasma explosion visible as the purple cloud. The plasma cloud expands towards the square substrate, consisting of SrTiO3 (strontium titanate), where it deposits thin layers of alumina, one atomic layer at a time. This results in a conducting interface between the two materials which are otherwise insulating. The substrate is mounted on a heating plate, glowing red from a temperature of 650 ºC, to improve the crystallinity of the alumina thin film.
context_page_description: Aluminium is a chemical element with the symbol Al and atomic number 13. It is a silvery-white, soft, non-magnetic and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust, where it is the third most abundant element and also the most abundant metal. Occurrence of aluminium decreases in the Earth's mantle below, however. The chief ore of aluminium is bauxite. Aluminium metal is highly reactive, such that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals.
  Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and building industries, such as building facades and window frames. The oxides and sulfates are the most useful compounds of aluminium.
  Despite its prevalence in the environment, no living organism is known to use aluminium salts metabolically, but aluminium is well tolerated by plants and animals.
context_section_description: The great majority (about 90%) of aluminium oxide is converted to metallic aluminium. Being a very hard material (Mohs hardness 9), alumina is widely used as an abrasive; being extraordinarily chemically inert, it is useful in highly reactive environments such as high pressure sodium lamps. Aluminium oxide is commonly used as a catalyst for industrial processes; e.g. the Claus process to convert hydrogen sulfide to sulfur in refineries and to alkylate amines. Many industrial catalysts are supported by alumina, meaning that the expensive catalyst material is dispersed over a surface of the inert alumina. Another principal use is as a drying agent or absorbent.
  Several sulfates of aluminium have industrial and commercial application. Aluminium sulfate (in its hydrate form) is produced on the annual scale of several millions of metric tons. About two-thirds is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordant in dyeing, in pickling seeds, deodorizing of mineral oils, in leather tanning, and in production of other aluminium compounds. Two kinds of alum, ammonium alum and potassium alum, were formerly used as mordants and in leather tanning, but their use has significantly declined following availability of high-purity aluminium sulfate. Anhydrous aluminium chloride is used as a catalyst in chemical and petrochemical industries, the dyeing industry, and in synthesis of various inorganic and organic compounds. Aluminium hydroxychlorides are used in purifying water, in the paper industry, and as antiperspirants. Sodium aluminate is used in treating water and as an accelerator of solidification of cement.
  Many aluminium compounds have niche applications, for example:
  Aluminium acetate in solution is used as an astringent.
  Aluminium phosphate is used in the manufacture of glass, ceramic, pulp and paper products, cosmetics, paints, varnishes, and in dental cement.
  Aluminium hydroxide is used as an antacid, and mordant; it is used also in water purification, the manufacture of glass and ceramics, and in the waterproofing of fabrics.
  Lithium aluminium hydride is a powerful reducing agent used in organic chemistry.
  Organoaluminiums are used as Lewis acids and cocatalysts.
  Methylaluminoxane is a cocatalyst for Ziegler–Natta olefin polymerization to produce vinyl polymers such as polyethene.
  Aqueous aluminium ions (such as aqueous aluminium sulfate) are used to treat against fish parasites such as Gyrodactylus salaris.
  In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.
caption: Laser deposition of alumina on a substrate
exif: {"Image XResolution": "240", "Image YResolution": "240", "Image ResolutionUnit": "Pixels/Inch", "Image Artist": "Adam Andersen L\u00e6ss\u00f8e", "Image Copyright": "Adam A. L\u00e6ss\u00f8e 2015", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "230", "Thumbnail JPEGInterchangeFormatLength": "9370"}