US4806333A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Finely divided oxide and its manufacture
Assignee: Tioxide Group Ltd
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Filing: 1986-10-22
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Granted: 1989-02-21
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Expires: 2006-10-22
Abstract
Abstract A product suitable as a ceramic comprises substantially nonaggregated alumina particles with 95% by number having an aspect ratio (i.e., the ratio of the longest dimension to the shortest dimension for any single particle) not greater than 1.1 and more than 80% having an aspect ratio not greater than 1.05 and having a geometric mean size of from 0.02 to 0.5 microns. Usually the product contains no more than 3% by weight as aggregates and preferably the product is as small as can conveniently be manufactured.
Inventors
- 👤 Terence A. Egerton
- 👤 Kevin A. Fothergill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 01:43
CPC Classifications
B; B82; B82Y; B82Y30/00; C; C01; C01F; C01F7/00; C01F7/02; C01F7/30; C01F7/302; C01P; C01P2004/00; C01P2004/30; C01P2004/32; C01P2004/54; C01P2004/60; C01P2004/62; C01P2004/64
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
83 words
In a ceramic material comprising a plurality of substantially non-aggregated spherical alumina particles having a geometric weight mean size between 0.02 and 0.5 microns, the improvement comprising: each of the particles consisting essentially of crystalline delta alumina; and each of the particles having a highly spherical shape wherein greater than 95% of said particles have an aspect ratio of less than or equal to 1.1 and greater than 80% of said particles have an aspect ratio of less than or equal to 1.05.
Claim 2
Dependent Claim
83 words
In a ceramic material comprising a plurality of substantially non-aggregated spherical alumina particles having a geometric weight mean size between 0.02 and 0.5 microns, the improvement comprising: each of the particles consisting essentially of crystalline delta alumina; and each of the particles having a highly spherical shape wherein greater than 95% of said particles have an aspect ratio of less than or equal to 1.1 and greater than 80% of said particles have an aspect ratio of less than or equal to 1.05.
Claim 3
Dependent Claim
23 words
A product according to claim 1 in which the particles contain no more than 300 ppm of a sodium compound expressed as Na.
Claim 4
Dependent Claim
20 words
A product according to claim 2 in which the amount of sodium compound is less than 100 ppm as Na.
Claim 5
Dependent Claim
23 words
A product according to claim 1 in which no more than 3% by weight of said particles are present in an aggregated form.
Claim 6
Dependent Claim
21 words
A product according to claim 1 in which the geometric weight mean size of the productis from 0.04 to 0.3 microns.
Claim 7
Dependent Claim
19 words
A product according to claim 5 in which the geometric weight mean size is from 0.05 to 0.2 microns.
Claim 8
Dependent Claim
72 words
A process for the manufacture of the crystalline delta alumina particles of claim 1, comprising oxidizing a gas consisting essentially of aluminum halide in an oxidation reactor at a temperature in a range of about 2050° C. to 2700° C.; and feeding the aluminum halide gas into the oxidation reactor to form said crystalline delta alumina particles having a geometric weight mean particle size in the range of 0.02 to 0.5 microns.
Claim 9
Dependent Claim
16 words
A process according to claim 7 in which the temperature attained is at least 2300° C.
Claim 10
Dependent Claim
20 words
A process according to claims 7 or 8 in which the oxidation is carried out at or about atmospheric pressure.
Claim 11
Dependent Claim
18 words
A process according to claims 7 or 8 in which the oxidation is carried out under superatmospheric pressure.
Claim 12
Dependent Claim
26 words
A process according to claim 7 in which an inert gas or oxygen is heated by an electrical plasma prior to mixing with said aluminium halide.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-02-21 | 1992-08-22 | 1993-02-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-02-21 | 1996-08-22 | 1997-02-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-02-21 | 2000-08-22 | 2001-02-21 | $7700.00 | Window Closed / Lapsed |