Basic knowledge of alumina

Aluminum oxide, chemical formula: Al2O3. It is a kind of high hardness compound, melting point 2054 ℃, boiling point 2980 ℃, ionizable ionic crystal at high temperature, commonly used in the manufacture of refractories.

Industrial alumina is prepared from bauxite (Al2O3 · 3H2O) and diaspore. For high purity alumina, it is usually prepared by chemical method. There are many isomorphic and heteromorphic crystals in alumina, of which more than 10 are known. There are mainly three crystal forms, namely α - Al2O3, β - Al2O3 and γ - Al2O3. The structure is different and the properties are different. It is almost completely transformed into α - Al2O3 at high temperature above 1300 ℃.

essential information

Alumina is a stable oxide of aluminum with the chemical formula of Al2O3. Bauxite is also called bauxite in mining, ceramics and materials science.

Properties: white solid insoluble in water, odorless, tasteless, extremely hard, easy to absorb moisture without deliquescence (burned without moisture absorption). Alumina is a typical amphoteric oxide (corundum is α - shaped, belongs to hexagonal most dense accumulation, is an inert compound, slightly soluble in acid and alkali, corrosion resistance), soluble in inorganic acid and alkaline solution, almost insoluble in water and non-polar organic solvents; relative density (d204) 4.0; melting point 2050 ℃.

Storage: sealed and dry.

Uses: used as analytical reagent, dehydration of organic solvent, adsorbent, organic reaction catalyst, abrasive, polishing agent, raw material for aluminum smelting and refractory.

Main components

Alumina contains elements aluminum and oxygen. If the raw material of bauxite is chemically treated to remove the oxides of silicon, iron and titanium, the product is alumina with high purity, and the content of alumina is generally more than 99%. The ore phase is composed of 40% ～ 76% γ - Al2O3 and 24% ～ 60% α - Al2O3. γ - Al 2O 3 can be transformed into α - Al 2O 3 at 950-1200 ℃, and the volume shrinkage is significant.