Macrocrystalline aluminum oxide and method for its manufacture
AssigneeGiulini Chemi GmbH
InventorsEgon Cherdron, Heinz Hellinghausen, Alois Kramer, Horst Pohland, Avraham Metzer
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Abstract
A method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, and a diameter to thickness ratio of about 3:1 to about 7:1. Aluminum hydroxide of particle size greater than 60 microns is calcined in the presence of a fluorine-containing mineralizer at a temperature of greater than 1200.degree. C. but no more than 1450.degree. C., and the desired grain size is separated from the calcinate.
Claims16
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al.sub.2 O.sub.3 and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 40.5% by weight of said monocrystals having a grain size of at least 60 microns.
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al.sub.2 O.sub.3, and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 56.5% by weight of said monocrystals having a grain size of at least 40 microns.
Method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, comprising:
- calcining aluminum hydroxide of a grain size greater than 60 microns at a temperature greater than 1200.degree. C. but no more than 1450.degree. C., in the presence of at least one fluorine-containing mineralizer compound, and separating a desired grain fraction from the resulting calcinate.
Dependencies are inferred from the claim text.