Alumina ceramic applications and compositions
The main ingredient of corundum is alpha-al2o3. A pail or pyramidal trigonal crystal. It has a glass sheen or a diamond. Density is 3.9 ~ 4.1 g/cm3, 9 hardness, melting point 2000 + 15 ℃. Insoluble in water and insoluble in acids and bases. Resistance to high temperature. The colorless transparent person is called white jade, contains trace trivalent chromium red to call ruby; The blue, which contains divalent iron, trivalent iron or titanium, is called sapphire. The dark grey, dark color of a small amount of tetraoxide is called corundum powder. It can be used for the bearing of precision instruments, the diamond of the clock, the grinding wheel, the polishing agent, the refractory material and the electrical insulator. A colorful gem for decoration. Artificial ruby single crystal laser material. In addition to natural minerals, hydrogen oxide can be used to produce aluminum hydroxide.
Alumina is the reason that aluminum is not easily corroded in air. The pure metal aluminum reacts easily with oxygen in the air, creating a thin layer of alumina coated in exposed to the surface of the air. This aluminum oxide film prevents aluminum from being oxidized. The thickness and properties of this oxide film can be enhanced through a process known as anodizing.
Aluminium is a good conductor of electricity and heat. The crystal morphology of aluminum is high in hardness, suitable for grinding materials and cutting tools.
Alumina powder commonly used as a medium for the analysis of color layers.
High temperature sintered alumina, called artificial corundum or synthetic gemstone, which can be used to make a diamond in a mechanical bearing or clock. Alumina is also used as high temperature refractory material, making firebrick, crucible, porcelain, artificial gemstone, etc. Aluminum oxide is also the raw material of aluminum smelting. Calcinated aluminum hydroxide can be produced by gamma-al2o3. Gamma-al2o3 has strong adsorption and catalytic activity, which can be used as adsorbent and catalyst.