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Calcinated Alumina

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Lowest calcinates

Calcinates in this product group are characterised by the fact that they have a lower Mohs hardness than corundum. They break more easily and differently than classical corundum. They are usually metastable but isolable phases of aluminium oxide with a very high specific surface area.

Low Calcinates

Lowest and low-calcined products are relatively close in their properties, but ultimately differ in BET (specific surface area) and oil absorption. The products have a different history. They are often used in polishes. Despite a lower Mohs hardness of the grain, the angularity of a grain can strongly influence the polishing process.

Medium calcinates

In the case of medium calcinates, the alpha phase of the Al₂O₃ - i.e. the corundum - is preferred. Here one finds low BET values and lower oil absorption. They are found in polishes for hard surfaces such as steel. Nevertheless, they still have a certain activity, which also makes them suitable for use in ceramics and glazes.

Medium-high and high calcinates

Medium-high and high calcinates consist practically only of alpha Al₂O₃ and thus also have the Mohs hardness of corundum. The BET is low here. They provide the highest abrasiveness on hard surfaces and are used in a wide variety of places in refractories, ceramics and sometimes also in polishing.

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