Microcrystalline alumina-based ceramic articles

Details Microcrystalline alumina-based ceramic articles Microcrystalline alumina-based ceramic articles

1990-07-09

1993-02-09

Bell, Mark L.

Compositions: ceramic

Ceramic compositions

Refractory

501127, 501128, 501153, C04B 3510

Patent

active

051852993

ABSTRACT:
Microcrystalline alpha-alumina based ceramic articles comprising at least 60% alumina by weight, and 0.1-7.0 percent by weight iron equivalence 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, and a surface roughness height of less than 100.0 nm, which is essential if a ceramic article such as an alpha alumina fiber is to have reasonable strength.

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