What are the functions of alumina
1.The main component of ruby and sapphire is alumina, because of other impurities and show different color, sapphire contains iron oxide and titanium oxide and show blue.
2.The content of alumina is the highest among the main components of alumina ore. In industry, ferric aluminium oxide is purified into alumina by Bayer process and then transformed into aluminium metal by Hall-Heroult process.
3.Aluminium reacts with oxygen in the air to form a dense aluminium oxide film covering the surface of aluminium exposed to the air.
Aluminum is a good conductor of electricity and heat. Because of its high hardness, alumina is suitable for grinding materials and cutting tools.
Alumina powder is often used as a medium for chromatographic analysis.
In August 2004, scientists at 3M IN the United States developed an alloy consisting of aluminum and rare earth elements to make a reinforced glass called Transparent Alumina.
Manufacture of reinforced glass
The hardness of corundum powder can be used as abrasive, polishing powder, high temperature sintered alumina, called artificial corundum or artificial gemstone, can be used to make mechanical bearings or clocks diamonds. Alumina is also used as high temperature refractory, refractory bricks, crucible, porcelain, artificial gems, etc. Alumina is also used as raw material for aluminum smelting. - can be obtained by calcining alumina hydroxide. Gamma-al2o3 has strong adsorption and catalytic activity, and can be used as adsorbent and catalyst. Corundum is mainly composed of -Al2O3. Trigonal crystals in the form of drums or cones. Have vitreous luster or diamond luster. The density is 3.9 ~ 4.1g/cm3, hardness is 9, melting point is 2000±15℃. Insoluble in water, neither in acids nor bases. Resistance to high temperature. Colorless transparent people called white jade, containing trace trivalent chromium red ruby; The bluish color containing divalent iron, trivalent iron or quaternary titanium is called sapphire; Dark gray and dark color with a small amount of ferric tetroxide is called corundum powder. Bearings for precision instruments, diamonds for clocks, grinding wheels, polishes, refractories and electrical insulators. Brightly colored gemstones can be used for decoration. Artificial ruby single crystal can be used as laser material
Alumina is the reason why the metal aluminum is not easy to corrode in the air. The pure metal reacts easily with the oxygen in the air, producing a thin film of alumina covering the surface of the aluminium exposed to the air. This thin film of alumina prevents further oxidation of aluminium. The thickness and properties of the oxide film can be enhanced by a process called anodic treatment (anodic preservative).
