Alumina powder (Al2O3) is a white amorphous powder, belonging to inorganic oxide, insoluble in water, soluble in strong alkalis and strong acids, melting point 2054°C, boiling point 2980°C, with high purity and whiteness High, high specificity, good thermal stability, uniform particle size distribution and good fluidity; alumina has many isomers, and the alumina powder prepared by different preparation methods is quite different. The three most common crystal forms of alumina are: α-Al2O3, β-Al2O3, and γ-Al2O3.
(A) α-Al2O3, trigonal crystal system, exists in the form of corundum in nature, with compact structure, good thermal conductivity, is the most stable crystal type, and its hardness is second only to diamond and silicon carbide;
(B) β-Al2O3, cubic spinel structure, oxygen ions are arranged in face-centered cubic, and aluminum ions fill the gaps. β-Al2O3 is not a separate substance of Al2O3, but a polyaluminate mineral with high alumina content;
(C) γ-Al2O3 is an intermediate of the transformation from amorphous Al2O3 to α-Al2O3, and is the low temperature form of Al2O3. The structure is loose, the density is small, the activity is large, and it is easy to absorb water. It cannot exist stably under high temperature, and it does not exist in nature.
The output of alumina powder occupies a large proportion of the total output of artificial ceramic powder in the world. Of the total demand for alumina powder, more than 80% is used for aluminum smelting, and the rest can be directly used in the form of alumina powder as raw materials for the production of other products. The directly applied alumina powder is mainly used in refractory materials, fine ceramics, abrasives, etc. High-purity high-purity alumina powder is generally used to prepare artificial crystals, transparent alumina, precision electronic components, etc. In addition, artificial crystals have very high quality requirements for high-purity alumina, and most of their purity needs to reach 5N. China lags far behind foreign countries in the preparation of high-purity alumina, and the powder with particularly good quality still relies on imports.
