Minnesota Mining and Manufacturing Company

General Atomic Company

Harold G Sowman

Roger W Lange

David R Kaar

Thomas Edward Wood

Jerome W McAllister

James R Johnson

Lien-Huong T Pham

Melvin A Leitheiser

Kyung H Moh

David M Wilson

Tai T Tran

Karl A Karst

Soon-Kun Kang

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.

Microcrystalline alumina-based ceramic articles

Discrete, free-flowing, ceramic microbubbles consist essentially of at least one of a non-oxide component and an oxide component having diameters in the range of 1 to 300 micrometers and each having a wall thickness of less than 10 percent of the diameter of the bubble. In the process of the invention, a sol precursor and a suitable liquid, referred to as a bloating agent, when added to a bubble promoting medium under proper conditions, provide green gelled microbubbles which after firing are ceramic microbubbles having wall thicknesses less than 10 percent of the diameter of the bubbles. The microbubbles are non-vitreous, sol-gel derived, fine microstructured, uniform, hollow, smooth, and are either essentially all oxide or non-oxide or combinations of both.

Sol gel-derived ceramic bubbles

A multicomponent ceramic article which can be a fiber or particle comprises a continuous ceramic matrix phase and at least one in situ-generated discontinuous ceramic or metal phase. Particles can include shapes in the form of beads, flakes, granules, and microspheres.

Internally modified ceramic fiber

An amorphous organic-inorganic hybrid fiber consists essentially of 70 to 90 weight percent alumina and 10 to 30 weight percent of organic residue based on the total hybrid fiber composition. The organic residue can be derived, for example, from polyvinylpyrrolidone, polyvinyl alcohol, aluminum formoacetate or combinations thereof.

Refractory fibers of alumina and organic residue

A shaped article comprises a ceramic matrix and dispersed therein in the range of 5 to 30 weight percent mechanically added silicon carbide, said article having a modulus of elasticity (E) value of at least 10 percent greater than the inherent elastic modulus value of the fully dense host matrix. The articles are useful as high temperature stable reinforcement materials in composites requiring a high modulus of elasticity.

Ceramic articles containing silicon carbide

A coated article having a substrate coated with a layer of silica particles is provided. The coating is substantially uniform in thickness, adheres aggressively to the substrate, and provides excellent antireflection properties to the substrate.

Silica coating

Refractory fibers comprising a homogeneous mixture of 60 to 95 weight percent amorphous alumina and 40 to 5 weight percent amorphous phosphorus pentoxide. The fibers optionally can contain chloride, and up to 20 weight percent carbon derived from the alumina precursor material. Other organic residues can be present. The fibers are useful in the manufacture of fireproof consumer fabrics as well as reinforcement or polymeric composites.

Refractory fibers of alumina and amorphous phosphorus pentoxide

A shaped article is described comprising a ceramic matrix and dispersed therein in the range of 5 to 30 weight percent mechanically added silicon carbide, said article having a modulus of elasticity (E) value of at least 10 percent greater than the inherent elastic modulus value of the fully dense host matrix. The articles are useful as high temperature stable reinforcement materials in composites requiring a high modulus of elasticity.

Homogeneous, nonporous ceramic fibers containing at least one magnetically-unaligned, microcrystaline transition metal oxide spinel phase. The ceramic fibers may be used in polymeric, ceramic and metallic composites. Said ceramic spinel is produced by dispersing soluble inorganic and transition metal compounds in an aqueous mixture, concentrating to produce a viscous concentrate, shaping into the desired article, gelling the shaped article, and heating to produce the transition metal spinel article. Beads, bubbles, flakes, microspheres, films and granules may be made as well as fibers.

Microcrystalline transition metal oxide spinel articles

This invention provides a shaped, graded, cermet article comprising at least one continuous ceramic phase and at least one discontinuous metal phase, the ratio of ceramic/metal being controlled and varied over the thickness of the article. The ceramic phase preferably is microcrystalline.

Graded refractory cermet article

The invention relates to synthetic, non-fused, aluminum oxide-based abrasive mineral having a microcrystalline structure of randomly oriented crystallites comprising a dominant continuous phase of .alpha.-alumina and a secondary phase, to a method of making the same employing chemical ceramic technology, and to abrasive articles made with the abrasive mineral.

Articles containing non-fused aluminum oxide-based abrasive mineral

Shaped and fired, porous or impermeable nonvitreous ceramic microcapsules of metal oxide, preferably transparent and polycrystalline, are made by a non-melt process comprising the liquid-liquid extraction of aqueous metal oxide precursor with a dehydrating liquid having a limited water solubility, and drying and firing the resulting gelled microcapsules. For example, an aqueous titania sol is added to an agitated body of n-butanol to form a dispersion of droplets of said sol and water is rapidly extracted from the droplets to form gelled microcapsules; the latter are recovered by filtration, dried, and fired to convert them into transparent, sealed or heat-sealable, non-vitreous ceramic, spherical microcapsules of polycrystalline titania. The microcapsules can be used as fillers for plastic and other composites or filled with a selected solid, liquid or gas for purpose of storing, transporting, or facilitating the use of the same.

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Maplewood, MN, United States of America

Harold G Sowman