Patent US3974249A successfully refreshed from Google Patents.
US3974249A
Expired / Lapsed
US
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Method for manufacturing a transparent ceramic body
Assignee: Coors Porcelain Co
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Filing: 1972-10-10
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Granted: 1976-08-10
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Expires: 1992-10-10
Abstract
Abstract The present invention provides a high heat resistant, light transmitting, thermal shock resistant and high strength sintered ceramic body containing at least about 98% by weight magnesia-alumina spinel and a method of manufacturing the same which comprises forming a uniform mixture containing approximately equal molar amounts of magnesia and alumina plus lithium fluoride in an amount of about 2% by weight of the mixture, the alumina in the mixture having an average particle size of less than 0.5 microns; calcining the mixture at such a temperature and under such conditions as will result in substantially less than total reaction to form spinel during calcining, i.e. less than 80% and preferably less than 50%; pressing the mixture into a self-sustaining compact having a density of at least about 2 grams per cubic centimeter; and then firing the compact, preferably in a wet hydrogen atmosphere, to a temperature of from about 1600° to 1900°C.
Inventors
- 👤 Donald W. Roy
- 👤 Franklin J. Stermole
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:04
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/44; C04B35/443; C04B35/622; C04B35/626; C04B35/62605; C04B35/6261; C04B35/62645; C04B35/62675; C04B35/63; C04B35/632; C30; C30B; C30B29/00; C30B29/10; C30B29/16; C30B29/22; C30B29/26; C04B2235/00; C04B2235/02; C04B2235/30; C04B2235/32; C04B2235/3201; C04B2235/3203; C04B2235/3217; C04B2235/44; C04B2235/444; C04B2235/445; C04B2235/50; C04B2235/54; C04B2235/5418; C04B2235/5445; C04B2235/65; C04B2235/652; C04B2235/656; C04B2235/6567; C04B2235/658; C04B2235/6582; C04B2235/6588; C04B2235/66; C04B2235/661; C04B2235/70; C04B2235/74; C04B2235/77; C04B2235/96; C04B2235/9607; C04B2235/9646; C04B2235/9653
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
125 words
A method for manufacturing a ceramic body comprising the steps of forming a uniform mixture containing approximately equal molar amounts of magnesia and alumina and from about 0.2% to 5% by weight lithium fluoride, the alumina in said mixture having a particle size of less than about 0.5 microns, calcining said mixture at a temperature of at least about 800°C for a time that there is less than about 80% reaction of the alumina and magnesia to form spinel, forming the calcined mixture into a self-sustaining compact and firing the compact in a reducing atmosphere to sintering temperature to cause the reaction of the magnesia and alumina in the calcined mixture to form spinel and thereby form a sintered body consisting predominately of magnesia-alumina spinel.
Claim 2
Independent Claim
125 words
A method for manufacturing a ceramic body comprising the steps of forming a uniform mixture containing approximately equal molar amounts of magnesia and alumina and from about 0.2% to 5% by weight lithium fluoride, the alumina in said mixture having a particle size of less than about 0.5 microns, calcining said mixture at a temperature of at least about 800°C for a time that there is less than about 80% reaction of the alumina and magnesia to form spinel, forming the calcined mixture into a self-sustaining compact and firing the compact in a reducing atmosphere to sintering temperature to cause the reaction of the magnesia and alumina in the calcined mixture to form spinel and thereby form a sintered body consisting predominately of magnesia-alumina spinel.
Claim 3
Dependent Claim
40 words
a method as set forth in claim 1 wherin the mixture is calcined at a temperature of at least about 800°C for a time that there is less than about 50% reaction of the alumina and magnesia to form spinel.
Claim 4
Dependent Claim
57 words
A method as set forth in claim 1, wherein mixture, after said calcining thereof, is milled in admixture with from about 2% to about 5% by weight of the mixture of an organic lubricant and wherein the mixture is formed into the self-sustaining compact by a pressing operation during which the organic lubricant remains in the mixture.
Claim 5
Dependent Claim
27 words
A method as set forth in claim 1, wherein said compact is fired in a wet reducing atmosphere to a temerature of from about 1600° to 1900°C.
Claim 6
Dependent Claim
56 words
A method as set forth in claim 1, wherein the compact is fired by first heating it to a temperature of from about 1000°C to about 1300°C in an oxidizing atmosphere and is then heated in a wet reducing atmosphere to a temperature of about 1800°C with a soak at that temperature of about 24 hours.
Claim 7
Dependent Claim
26 words
A method as set forth in claim 1, wherein the amount of lithium fluoride included in said mixture is approximately 2% by weight of the mixture.
Claim 8
Dependent Claim
29 words
A method as set forth in claim 1, wherein the aluminum oxide in the mixture wich is calcined has an average particle size of less than about 0.3 microns.
Claim 9
Dependent Claim
26 words
A method as set forth in claim 1, wherein said compact is formed so as to have a density greater than 2 grams per cubic centimeter.
Claim 10
Dependent Claim
60 words
A method as set forth in claim 1, wherein said mixture, prior to the calcining step, is formed into a self-sustaining compact and wherein said compact, after said calcining step is crushed and thereafter milled to a reduced particle size after from about 2% to about 5% by weight of the mixture of an organic lubricant has been added thereto.
Claim 11
Dependent Claim
22 words
A method as set forth in claim 1 wherein said mixture is calcined at a temperature of from about 800° to 1050°C.
Claim 12
Dependent Claim
26 words
A method as set forth in claim 1 wherein said mixture is calcined at a temperature of from about 900°C to 950°C for approximately 3 hours.
References Cited (Backward Citations)
US3212401A
Cited
US3026210A
Cited
US3530209A
Cited
US3531308A
Cited
US3862846A
Cited
US3768990A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-10 | 1980-02-09 | 1980-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-10 | 1984-02-09 | 1984-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-10 | 1988-02-09 | 1988-08-10 | $7700.00 | Window Closed / Lapsed |