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US3666851A
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Preparing high density magnesia refractories
Assignee: Canadian Patents and Development Ltd
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Filing: 1969-11-10
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Granted: 1972-05-30
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Expires: 1989-11-10
Abstract
Abstract A method of preparing high density refractories of magnesia by one of (a) partially calcining magnesium carbonate and/or magnesium hydroxide, and hot pressing the partially calcined raw materials while dehydroxylation and/or decarbonation is occurring; (b) calcining magnesium carbonate and/or magnesium hydroxide, partially hydrating (or rehydrating) the calcined raw materials and hot-pressing while the dehydroxylation is occurring; or (c) mixing sinterable magnesia and/or partially hydrated material from (b) with the hydroxide or carbonate and not pressing while decomposition is occurring : followed in each case by a short stabilizing heat treatment at sintering temperatures.
Inventors
- 👤 Asoke C D Chaklader
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 20:15
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/03
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
16 words
The method of claim 1 wherein partially calcined magnesium hydroxide is hot-pressed at about 400*-700* C.
Claim 2
Dependent Claim
16 words
The method of claim 1 wherein partially calcined magnesium carbonate is hot-pressed at about 700*-800* C.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein a magnesium compound selected from the group consisting of magnesium hydroxide, magnesium carbonate and mixtures thereof is calcined, cooled, partially hydrated to hydroxide and hot-pressed at about 400*-700* C.
Claim 4
Dependent Claim
23 words
The method of claim 1 wherein magnesium hydroxide is mixed with calcined partially hydrated material and the mixture hot-pressed at about 400*-700* C.
Claim 5
Dependent Claim
24 words
The method of claim 1 wherein magnesium hydroxide is mixed with a low temperature calcined magnesia and the mixture hot-pressed at about 400*-700* C.
Claim 6
Dependent Claim
13 words
The method of claim 6 wherein said magnesia is still hot from calcination.
Claim 7
Dependent Claim
22 words
The method of claim 1 wherein about 5-80 percent wt. of the magnesium compounds in the charge is the hydroxide or carbonate.
Claim 8
Dependent Claim
26 words
The method of claim 1 wherein magnesium hydroxide in about 10-50 percent wt. of the magnesium compounds in the charge is the compound decomposed on hot-pressing.
Claim 9
Dependent Claim
21 words
The method of claim 1 wherein the hot-pressing is carried out at about 5,000-25,000 psi for up to about 10 minutes.
Claim 10
Dependent Claim
16 words
The method of claim 1 wherein the heat stabilization is carried out at about 1,500*-1,750* C.
Claim 11
Dependent Claim
22 words
The method of claim 1 wherein the heat stabilization is carried out for a time within about 10 minutes to 5 hours.
Claim 12
Dependent Claim
25 words
The method of claim 1 wherein the charge is preheated to below decomposition temperature and then introduced into the die which is at hot-pressing temperature.
Claim 13
Dependent Claim
19 words
The method of claim 1 wherein low temperature calcination of magnesium hydroxide is carried out within about 400*-700* C.
Claim 14
Dependent Claim
26 words
The method of claim 1 wherein said composite particulate charge includes at least one additive selected from the group consisting of reinforcing fillers and cerment-forming metals.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-30 | 1975-11-29 | 1976-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-30 | 1979-11-29 | 1980-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-30 | 1983-11-29 | 1984-05-30 | $7700.00 | Window Closed / Lapsed |