US4083919A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Beta-alumina composites and methods for producing them
Assignee: Eastman Kodak Co
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Filing: 1976-08-04
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Granted: 1978-04-11
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Expires: 1996-08-04
Abstract
Abstract A hot-pressed beta-alumina composition is provided which consists essentially of M 2 O.nAl 2 O 3 , wherein n is a positive integer between about 3 and about 12 and M is selected from Na and K. The new beta-alumina composition features a flexural strength of at least about 45,000 psi as measured by ACMA Test No. 2, and high transmissability to light. Methods for preparing the above-described beta-alumina composition are also provided.
Inventors
- 👤 Donald Pearlman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 19:00
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/10; C04B35/111; C04B35/113; C04B35/622; C04B35/64; C04B35/645
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
88 words
A method for making a hot pressed beta-alumina composite which comprises: mixing and reacting together a solution of aluminum alcoholate and an aqueous solution of an alkali metal salt; coprecipitating as a gelatinous mass aluminum hydroxide and the alkali metal salt; drying the gelatinous mass coprecipitated in the previous step; heating the dried mass to a temperature between about 400° C to about 1200° C; cooling and grinding the dried gelatinous mass into a fine amorphous powder; and hot pressing the resulting powder to yield a beta-alumina composite.
Claim 2
Independent Claim
88 words
A method for making a hot pressed beta-alumina composite which comprises: mixing and reacting together a solution of aluminum alcoholate and an aqueous solution of an alkali metal salt; coprecipitating as a gelatinous mass aluminum hydroxide and the alkali metal salt; drying the gelatinous mass coprecipitated in the previous step; heating the dried mass to a temperature between about 400° C to about 1200° C; cooling and grinding the dried gelatinous mass into a fine amorphous powder; and hot pressing the resulting powder to yield a beta-alumina composite.
Claim 3
Dependent Claim
158 words
The method as defined in claim 1 wherein the hot pressing step includes the steps of: loading the powder into a pressing cylinder; and while maintaining the pressing cylinder under a vacuum, (1) gradually heating the powder to a first temperature; (2) applying an initial pressure to compress the powder after attaining the first temperature; (3) maintaining the compressed powder at at least the attained temperature and at the initial pressure for a first predetermined time period; (4) increasing the pressure to a holding pressure which is higher than the initial pressure; (5) holding the compressed powder at the attained values for a second predetermined time period; (6) cooling the compressed powder to a temperature which is lower than the first temperature whereupon the vacuum is released; (7) backfilling the pressing cylinder with an inert gas; and (8) cooling the compressed powder further to a temperature lower than that achieved by step (6), and thereafter removing the pressure.
Claim 4
Dependent Claim
23 words
The method of claim 2 wherein after the loading step, the powder is cold pressed under a pressure of at least 4000 psi.
Claim 5
Dependent Claim
52 words
The method of claim 2 wherein the first temperature is at least 1200° C and wherein, after applying the initial pressure on the compresssed powder, the method further comprises the step of heating the compressed powder to attain a higher temperature which is at least 100° C higher than said first temperature.
Claim 6
Dependent Claim
27 words
The method of claim 2 wherein the first predetermined time period is at least 5 minutes and the second predetermined time period is at least 10 minutes.
Claim 7
Dependent Claim
27 words
The method of claim 1 wherein said alkali metal salt is selected from the group consisting of bicarbonate, acetate, hydroxide, nitrate and carbonate of sodium or potassium.
Claim 8
Independent Claim
242 words
A method for making a hot pressed beta-alumina composite which comprises: mixing and reacting together a solution of aluminum alcoholate and an aqueous solution of an alkali metal salt; coprecipitating as a gelatinous mass aluminum hydroxide and the alkali metal salt; drying the gelatinous mass coprecipitated in the previous step; heating the dried mass to a temperature between about 400° C to about 1200° C; cooling and grinding the dried gelatinous mass into a fine amorphous powder; and hot pressing the resulting powder to yield a beta-alumina composite, wherein the hot pressing step includes the steps of: loading the powder into a pressing cylinder; cold pressing the powder by applying a pressure of at least 4000 psi; maintaining the pressure cylinder under a vacuum; gradually heating the powder to a first temperature of at least 1200° C; applying an initial pressure of at least 4000 psi to compress the powder after attaining the first temperature; maintaining the compressed powder at at least the first temperature and at the initial pressure for at least 10 minutes; increasing the pressure to a holding pressure of at least 20,000 psi; holding the compressed powder at at least the first temperature and the holding pressure for at least 20 minutes; cooling the compressed powder to about 1000° C whereupon the vacuum is released; backfilling the pressing cylinder with an inert gas; and cooling the compressed powder further to about 800° C whereupon the pressure is removed.
Claim 9
Independent Claim
242 words
A method for making a hot pressed beta-alumina composite which comprises: mixing and reacting together a solution of aluminum alcoholate and an aqueous solution of an alkali metal salt; coprecipitating as a gelatinous mass aluminum hydroxide and the alkali metal salt; drying the gelatinous mass coprecipitated in the previous step; heating the dried mass to a temperature between about 400° C to about 1200° C; cooling and grinding the dried gelatinous mass into a fine amorphous powder; and hot pressing the resulting powder to yield a beta-alumina composite, wherein the hot pressing step includes the steps of: loading the powder into a pressing cylinder; cold pressing the powder by applying a pressure of at least 4000 psi; maintaining the pressure cylinder under a vacuum; gradually heating the powder to a first temperature of at least 1200° C; applying an initial pressure of at least 4000 psi to compress the powder after attaining the first temperature; maintaining the compressed powder at at least the first temperature and at the initial pressure for at least 10 minutes; increasing the pressure to a holding pressure of at least 20,000 psi; holding the compressed powder at at least the first temperature and the holding pressure for at least 20 minutes; cooling the compressed powder to about 1000° C whereupon the vacuum is released; backfilling the pressing cylinder with an inert gas; and cooling the compressed powder further to about 800° C whereupon the pressure is removed.
References Cited (Backward Citations)
US3671324A
Cited
US3795723A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-04-10 | 1981-10-10 | 1982-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-10 | 1985-10-10 | 1986-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-10 | 1989-10-10 | 1990-04-11 | $7700.00 | Window Closed / Lapsed |