Abstract: Pyrogenically produced aluminum oxide, in which the BET specific surface area is greater than 115 m2/g and the Sears index is over 8 ml/2 g and the dibutyl phthalate absorption as a powder measured with a 16 g weighed portion is not measurable, is produced by means of flame oxidation or preferably flame hydrolysis, whereby a vaporizable aluminum compound is used as starting material. The aluminum oxide can be used as an ink-absorbing substance in inkjet media and also as a filler, as a substrate, as a catalytically active substance, as a starting material for the production of dispersions, as a polishing material (CMP applications), as a ceramic raw material, in the electronics industry, in the cosmetics industry, as an additive in the silicone and rubber industry, to adjust the rheology of liquid systems, as a heat stabilizer, in the paint industry.

Abstract: Pyrogenic oxides having a BET surface area of between 30 and 150 m.sup.2 /g have a viscosity of less than 2,500 mPas in an aqueous suspension. They are prepared by setting the hydrogen ratio gamma and the oxygen ratio lambda to less than one in a high-temperature flame hydrolysis. The pyrogenic oxides are employed in the CMP application in the electronics industry.