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US5185299A
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Microcrystalline alumina-based ceramic articles
Assignee: 3M Co
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Filing: 1990-07-09
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Granted: 1993-02-09
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Expires: 2010-07-09
Abstract
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.
Inventors
- 👤 Thomas E. Wood
- 👤 David M. Wilson
- 👤 Harold G. Sowman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 06:48
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/62227; C04B35/71; C01; C01F; C01F7/00; C01F7/02; C01F7/30; C04B35/01; C04B35/10; C04B35/111; C04B35/1115; C04B35/62231; C04B35/62236; C04B35/624; C09; C09K; C09K3/00; C09K3/14; C09K3/1409; C09K3/1418; C01P; C01P2002/00; C01P2002/60; C01P2004/00; C01P2004/01; C01P2004/03; C01P2004/10; C01P2004/51; C01P2004/60; C01P2004/62; C01P2006/00; C01P2006/10; C01P2006/12
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
93 words
A solid, fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is less than 0.5 micrometer and no grains are larger than 0.5 micrometer in diameter, the density of the article is greater than 90% of theoretical density, and the surface roughness height of said article is less than 100 nm.
Claim 2
Dependent Claim
93 words
A solid, fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is less than 0.5 micrometer and no grains are larger than 0.5 micrometer in diameter, the density of the article is greater than 90% of theoretical density, and the surface roughness height of said article is less than 100 nm.
Claim 3
Dependent Claim
18 words
The article according to claim 1 wherein the average alpha alumina crystallite diameter is less than 0.3 micrometer.
Claim 4
Dependent Claim
31 words
The article according to claim 1 further comprising an effective amount of at least one modifying additive to provide at least one of reduced grain size, improved elastic modulus, and color.
Claim 5
Dependent Claim
16 words
The article according to claim 3 wherein said modifying additive is silica or a precursor thereof.
Claim 6
Dependent Claim
14 words
The article according to claim 1 comprising at least 90 percent alumina by weight.
Claim 7
Dependent Claim
18 words
The article according to claim 1 which is a fiber, bead, flake, bubble, irregularly shaped particle, or coating.
Claim 8
Dependent Claim
9 words
The article according to claim 1 which is transparent.
Claim 9
Dependent Claim
33 words
The article according to claim 3 wherein said modifying additive is selected from the group consisting of a colloidal or particulate metal oxide, or a colloidal or particulate precursor to a metal oxide.
Claim 10
Dependent Claim
30 words
The article according to claim 1 which is selected from the class consisting of beads, flakes, bubbles, and randomly shaped particles, wherein the alpha alumina crystallites are substantially randomly oriented.
Claim 11
Dependent Claim
22 words
The article according to claim 3 wherein said additive is selected from the group consisting of zirconia, silica, magnesia, and precursors thereof.
Claim 12
Dependent Claim
10 words
The article according to claim 6 which is a fiber.
Claim 13
Dependent Claim
23 words
A fiber according to claim 11 wherein at least 95 percent of the alpha alumina crystallites are less than 0.25 micrometers in diameter.
Claim 14
Dependent Claim
26 words
The fiber according to claim 11 wherein at least 95 percent of the alpha alumina crystallites are uniformly oriented as determined by optical and X-ray analysis.
Claim 15
Dependent Claim
16 words
The fiber according to claim 11 wherein said fiber is a flexible, high modulus ceramic fiber.
Claim 16
Dependent Claim
12 words
The article of claim 6 wherein said article is a ceramic bead.
Claim 17
Dependent Claim
87 words
A solid, shaped and fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60 percent alumina by weight in which at least 99 percent of the alumina is in the alpha phase comprising alpha alumina crystallites wherein at least 99 percent of the alpha alumina crystallites are less than 0.2 micrometer in diameter and all are less than 0.7 micrometer in diameter, and the specific surface area of the article is greater than 15 m 2 /g.
Claim 18
Dependent Claim
87 words
A solid, shaped and fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60 percent alumina by weight in which at least 99 percent of the alumina is in the alpha phase comprising alpha alumina crystallites wherein at least 99 percent of the alpha alumina crystallites are less than 0.2 micrometer in diameter and all are less than 0.7 micrometer in diameter, and the specific surface area of the article is greater than 15 m 2 /g.
Claim 19
Dependent Claim
26 words
The article according to claim 16 having a microporous interior and having an alpha alumina sheath, said sheath having greater than 90 percent of theoretical density.
Claim 20
Dependent Claim
91 words
A ceramic fiber comprising in the range of 0.1 to 7.0 percent iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is less than 0.5 micrometer and at least 99 percent are less than 0.7 micrometer in diameter, said fiber having a density of at least 90% of theoretical density, and the surface roughness height of said fiber is less than 100.0 nm.
Claim 21
Dependent Claim
91 words
A ceramic fiber comprising in the range of 0.1 to 7.0 percent iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is less than 0.5 micrometer and at least 99 percent are less than 0.7 micrometer in diameter, said fiber having a density of at least 90% of theoretical density, and the surface roughness height of said fiber is less than 100.0 nm.
Claim 22
Dependent Claim
80 words
A solid, fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is in the range of 0.3-0.4 micrometer, and no grains are larger than 0.4 micrometer, the density of the article is greater than 90% of theoretical density.
Claim 23
Dependent Claim
80 words
A solid, fired refractory article comprising in the range of 0.1 to 7.0 percent by weight iron equivalence and at least 60% alumina by weight in which at least 99 percent of the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites wherein the average crystallite diameter is in the range of 0.3-0.4 micrometer, and no grains are larger than 0.4 micrometer, the density of the article is greater than 90% of theoretical density.
Claim 24
Dependent Claim
10 words
The article according to claim 4 which is a fiber.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1996-02-09 | 1996-08-10 | 1997-02-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-02-09 | 2000-08-10 | 2001-02-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-02-09 | 2004-08-10 | 2005-02-09 | $7700.00 | Window Closed / Lapsed |