Compositions: ceramic – Ceramic compositions – Refractory
Patent
1989-03-01
1990-09-04
Lovering, Richard D.
Compositions: ceramic
Ceramic compositions
Refractory
2523157, 501 12, 501 33, 501 35, 501127, 501128, 428283, 428702, 1062865, C04B 3510, B01J 1300
Patent
active
049544624
ABSTRACT:
Microcrystalline alpha-alumina based ceramic articles comprising at least 60% alumina by weight in which substantially all the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites with an average crystallite size less than 0.5 micrometer and a density greater than 90% theoretical are disclosed. Ceramic articles particularly useful as high modulus refractory fibers, among other shaped bodies such as beads, flakes, coatings, and shaped or randomly-shaped abrasive particles, are produced from a unique sol-gel process wherein hydroxy iron polymers are utilized to nucleate the alpha alumina transformation. An inherent advantage of the unique process disclosed is the resulting fine grained microstructure which is essential if a ceramic article such as an alpha alumina fiber is to have reasonable strength.
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"PURAL.RTM., PURALOX.RTM., DISPERAL.RTM., HIGH PURITY ALUMINAS", Product Brochure from Condea Chemie, Pre 1988.
Kumagai and Messing Comm. Am. Ceram. Soc. C-230 (1984) and J. Am. Ceram. Soc. 69(1), 500 (1985).
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Synthesis of Alumina by Controlled Chemical Nucleation, J. L. McArdle, G. L. Messing; talk presented at the 89th Annual American Ceramic Society Meeting, Pittsburgh, Pa., Apr. 28, 1987. Alpha-Iron Oxide is disclosed as a seeding agent for boehmite-derived alumina. There is no disclosure to the use of hydroxy iron polymers as nucleating agents for basic aluminum salt-derived aluminas.
Wilson David M.
Wood Thomas E.
Geist Gary L.
Kirn Walter N.
Lovering Richard D.
Minnesota Mining and Manufacturing Company
Sell Donald M.
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