Aluminium oxide occurs in two different forms, the crystalline polymorphic phase α-Al2O3 as well as the metastable cubic γ-Al2O3. γ-Aluminium oxide is turned into α-Al2O3 when heated. Crystalline α-aluminium oxide is often used for ceramic insulators or as abrasives and has a Mohs hardness of 9 to 9.5. Due to this it is not economically feasible to grind crystalline aluminium oxide on Bauermeister mills.
The main application for γ-Aluminium oxide, also known as clay or alumina, is as a starting material for ceramic products or in aluminium production. It is a softer, hygroscopic, white powder that is often used in cosmetics, medicine and pigments for colours. For these applications a high surface area is essential, which can be achieved by grinding the alumina to the desired particle size on a Bauermeister Gap Mill or Universal Mill.
A high number of Bauermeister mills are in operation for the grinding of alumina all around the world. Depending on the required product fineness and output rate an optimal combination of milling parameters is available. These can be determined in trial grindings in our Technology Center. The decision for one of the many different grinding plant variations depends on the general conditions as well as the requirements of the customer. Bauermeister specialists will gladly assist you in the assessment of these characteristics and help chose the correct mill and plant type that matches your requirements.