Polycrystalline, sintered abrasive granules based on .alpha.-Al.sub.2 O.sub .

US5261930A · kind A · utility

Assignee

• Huels Aktiengesellschaft · DE

Inventors

• Christine Fliedner · Bonn, DE
• Gerhard Rehfeld · Aachen, DE
• Dietrich Maschmeyer · Recklinghausen, DE

Key dates

• Filing date: Apr 24, 1992
• Grant date: Nov 16, 1993
• Expiry date: Apr 24, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09K3/1418
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention relates to polycrystalline, sintered abrasive granules based on .alpha.-Al.sub.2 O.sub.3 with a density of >98% of the theoretical density of corundum, a Vickers hardness of 21 GPa and greater and a crystallite size of 0.05 to 1.3 micron, as well as abrasives made from these abrasive granules and the use of these abrasive granules for the production of ceramic, refractory products. The polycrystalline, sintered abrasive granules based on .alpha.-Al.sub.2 O.sub.3 are produced by .alpha.-Al.sub.2 O.sub.3 crystal nuclei being added to a boehmite dispersion, the mixture of the boehmite dispersion and the crystal nuclei being acidified and gelled and the gel being dried, crushed, and sintered. In doing so, 0.5 to 35% by weight of .alpha.-Al.sub.2 O.sub.3 crystal nuclei, relative to the sintered abrasive granules, is added and the mixture of the boehmite dispersion and of the crystal nuclei is refluxed, while the pH of the mixture is kept in a range of 2.5 to 3.5 by adding acid.