Aluminum Oxide

CAS：1344-28-1

Molecular formula：Al2O3

Molecular weight：101.96

Physicochemical properties: Alumina, commonly known as bauxite, is a kind of white powder which is difficult to melt and insoluble in water. The melting point is 2015 ℃, the boiling point is 2980 ℃, the relative density is 4.0, and the Mohs hardness is 8.8. It has different crystal forms, mainly including α and γ Two variants. Alumina can be obtained by heating and dehydration of aluminum hydroxide. Existing in nature α Type alumina, called corundum, whose hardness is second only to diamond. Mixed with a small amount of impurities, corundum can have various colors. It is called gem.

Purpose:

1. The diversity of alumina properties makes it widely used, but more than 90% of it is used to make metal aluminum, and the rest is used as fillers for plastics and other polymer products, adsorbents and catalysts, raw materials for medicine, cosmetics and chemical products, ceramics, abrasives and refractories. China is used to calling it special alumina or multi variety alumina. Its varieties and needs have an increasing trend.

2. Alumina is the main raw material for electrolytic production of metal aluminum. The purer the alumina used, the purer the aluminum will be. Since it is more difficult to purify aluminum than alumina, the purification of alumina before electrolysis is very important. Alumina is one of the main components of the earth's crust. Aluminum ores mainly include bauxite Al2O3 · 2H2O, alunite (alo) 2SO4 · 9h2o, aluminum clay h2al (SiO4) · H2O, etc. China is rich in aluminum resources, such as Taiwan, Shandong, Shanxi, Guizhou, Kunming, Hebei, Henan and Liaoning. Natural bauxite is the best raw material for preparing alumina, with a general content of 40% ~ 60%. The rest are mainly impurities such as silica, iron oxide and rare elements. Alumina can be separated from other impurities by using their commonness and individuality in chemical properties. There are two main purification methods: acid method and alkali method. Activated alumina γ Type alumina is a porous material with an internal surface area of hundreds of square meters per gram. It has high activity and can adsorb water vapor and many gas and liquid molecules. It is often used as adsorbent, catalyst carrier and desiccant.

3. The artificially prepared alumina fiber takes alumina as the main component and contains about 5% silica (used to stabilize the crystalline phase of alumina). It is often used as thermal insulation furnace lining of various heat treatment furnaces in iron and steel industry and cracking furnaces in petrochemical industry, thermal insulation materials of nuclear reactors and space shuttles, reinforcement materials of light alloys, etc. Alumina fiber is polycrystalline alumina fiber. It is made by colloid method or organic fiber impregnation method (organic fiber precursor method), and its structure is in microcrystalline form, which eliminates the disadvantage of recrystallization and pulverization of fibers made by melt blowing method. This kind of fiber has great strength at room temperature and high temperature, high service temperature resistance, small bulk density, good chemical stability, strong thermal insulation, excellent dielectric and sound-absorbing properties, etc.