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AssigneeMinnesota Mining and Manufacturing Company
InventorsLarry D. Monroe, Thomas E. Wood
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An alpha alumina-based ceramic abrasive grain comprising, on a theoretical oxide basis, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3, and SiO.sub.2. The abrasive grain has a surface roughness height of greater than about 200 nanometers and a density of greater than about 3.50 g/cm.sup.3. Preferably, the alpha alumina-based ceramic abrasive grain has alpha alumina crystallites having an average crystallite size of less than about 0.5 micrometer (more preferably, less than about 0.3 micrometer). The presence of the SiO.sub.2 in combination with Fe.sub.2 O.sub.3 increases the amount of transgranular fracture of the abrasive grain, reduces the alpha alumina crystallite growth during sintering of the abrasive grain, dilates at least one of the unit cell dimensions of the abrasive grain, and generally improves the grinding performance of the abrasive grain.
Alpha alumina-based ceramic abrasive grain comprising, on a theoretical oxide basis, Al.sub.2 O.sub.3, SiO.sub.2, and at least about 0.25% by weight Fe.sub.2 O.sub.3, having alpha alumina crystallites with an average crystallite size of less than about 0.5 micrometer;
An alpha alumina-based ceramic abrasive grain comprising, on a theoretical oxide basis, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3, SiO.sub.2, and at least about 0.05% by weight of an alkali metal oxide, having alpha alumina crystallites with an average crystallite size of less than about 0.5 micrometer, and said abrasive grain having a density of greater than about 3.5 g/cm.sup.3.
A nontranslucent alpha alumina-based ceramic abrasive grain having a surface roughness height of greater than about 200 nanometers, a density of greater than about 3.5 g/cm.sup.3, and an average crystallite size of less than about 0.5 micrometer;
Alpha alumina-based ceramic abrasive grain consisting essentially of, on a theoretical oxide basis, Al.sub.2 O.sub.3, Fe.sub.2 O.sub.3, and SiO.sub.2, having alpha alumina crystallites with an average crystallite size of less than about 0.5 micrometer;
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