US4632793A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of fabricating hot pressed silicon nitride billets
Assignee: Ford Motor Co
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Filing: 1986-04-03
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Granted: 1986-12-30
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Expires: 2006-04-03
Abstract
Abstract A method is disclosed of making a plurality of dimensionally accurate hot pressed ceramic bodies. A plurality of Si 3 N 4 plates having a thickness to width ratio of 1:3 to 1:40 are stacked in a hot pressing assembly (40-41-42-43). The plates are arranged in groups of progressively decreasing number so that (a) for a plate group (10-11-12-13-14) residing in a zone of compression (15) that will experience the least movement along the pressing direction the stacked number of plates is greatest within such group, and (b) for a plate group residing in a zone of compression (22) that will experience the most movement along the pressure direction the stacked number of plates (21) within such group is the lowest, each group being separated from adjacent groups by an inert rigid spacer.
Inventors
- 👤 Andre Ezis
- 👤 Elaine C. Beckwith
- 👤 Warren B. Copple
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:56
CPC Classifications
C; C07; C07D; C07D215/00; C07D215/02; C07D215/16; C07D215/20; C07D215/24; C07D215/26; C22; C22B; C22B3/00; C22B3/20; C22B3/26; C22B3/36; C22B3/362; C22B3/364; Y; Y02; Y02P; Y02P10/00; Y02P10/20
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
235 words
A method of hot pressing ceramic plates in a pressing assembly having a constraining side wall aligned with the direction of pressing, comprising: (a) preparing a plurality of said plates, each having a thickness to width ratio in the range of 1:3 to 1:40 and a density in the range of 50-80% of full theoretical; (b) stacking a multiple number of said plates directly on top of one another within groups, except for the interposition of a compliant release coating between plates, and stacking a plurality of said groups with rigid force transmitting spacer plates therebetween into a pressure assembly in such a manner that the groups and spacer plates are stacked in an alignment along the direction of pressure to be applied and in contact with said contraining side wall, said groups having a progressively decreasing number of constituent plates so that for a group residing in a zone of pressing that will experience the least movement along said pressure direction the number of plates in the group is greatest and for a group residing in a zone of pressing that will experience the most movement along said pressure direction the number of plates in the group is the smallest; and (c) hot pressing said stacked groups of plates under pressure and temperature to densify each of said plates to at least 95% of theoretical density with a compression ratio of 1.2:1 to 2:1.
Claim 2
Independent Claim
235 words
A method of hot pressing ceramic plates in a pressing assembly having a constraining side wall aligned with the direction of pressing, comprising: (a) preparing a plurality of said plates, each having a thickness to width ratio in the range of 1:3 to 1:40 and a density in the range of 50-80% of full theoretical; (b) stacking a multiple number of said plates directly on top of one another within groups, except for the interposition of a compliant release coating between plates, and stacking a plurality of said groups with rigid force transmitting spacer plates therebetween into a pressure assembly in such a manner that the groups and spacer plates are stacked in an alignment along the direction of pressure to be applied and in contact with said contraining side wall, said groups having a progressively decreasing number of constituent plates so that for a group residing in a zone of pressing that will experience the least movement along said pressure direction the number of plates in the group is greatest and for a group residing in a zone of pressing that will experience the most movement along said pressure direction the number of plates in the group is the smallest; and (c) hot pressing said stacked groups of plates under pressure and temperature to densify each of said plates to at least 95% of theoretical density with a compression ratio of 1.2:1 to 2:1.
Claim 3
Dependent Claim
51 words
The method as in claim 1, in which said hot pressing is carried out with uniaxial pressure and the number of plates in each of said groups proceeds from a maximum number of 5 to 3 to 2 to 1, the latter being for the group experiencing the most relative movement.
Claim 4
Dependent Claim
57 words
The method as in claim 1, in which said pressure is applied biaxially and the sequence of groups contains the following numbers in order: 1, 2, 3, 10, 3, 2, 1, with the group having the single number experiencing the highest movement during compression and the group with the number 10 experiencing the lowest movement during compression.
Claim 5
Independent Claim
185 words
A method of making a plurality of dimensionally accurate hot pressed silicon nitride plates, comprising: (a) preparing a plurality of silicon nitride comprising plates having a thickness to width ratio in the range of 1:3 to 1:40 and a density of 1.5-2.7 gm/cm 3 ; (b) stacking said plates into a pressure assembly having walls to support said plates normal to the direction of pressure, said stacking being in groups of progressively decreasing number so that for a plate group residing in a zone of said pressing that will experience the least movement along said pressure direction the stacked number of the plates is greatest within said group and for a plate group residing in a zone of pressing that will experience the most movement along said pressure direction the stacked number of plates within said group is the lowest, each group being separated from adjacent groups by an inert rigid spacer; and (c) hot pressing said stacked plate groups under pressure and temperature to densify each of said plates to at least 95% of theoretical density with a pressing ratio of 1.2:1 to 2:1.
Claim 6
Independent Claim
185 words
A method of making a plurality of dimensionally accurate hot pressed silicon nitride plates, comprising: (a) preparing a plurality of silicon nitride comprising plates having a thickness to width ratio in the range of 1:3 to 1:40 and a density of 1.5-2.7 gm/cm 3 ; (b) stacking said plates into a pressure assembly having walls to support said plates normal to the direction of pressure, said stacking being in groups of progressively decreasing number so that for a plate group residing in a zone of said pressing that will experience the least movement along said pressure direction the stacked number of the plates is greatest within said group and for a plate group residing in a zone of pressing that will experience the most movement along said pressure direction the stacked number of plates within said group is the lowest, each group being separated from adjacent groups by an inert rigid spacer; and (c) hot pressing said stacked plate groups under pressure and temperature to densify each of said plates to at least 95% of theoretical density with a pressing ratio of 1.2:1 to 2:1.
Claim 7
Dependent Claim
51 words
The method as in claim 4, in which said hot pressing is carried out with uniaxial pressure and the number of plates in each of said groups proceeds from a maximum number of 5 to 3 to 2 to 1, the latter being for the group experiencing the most relative movement.
Claim 8
Dependent Claim
57 words
The method as in claim 4, in which said pressure is applied biaxially and the sequence of groups contains the following numbers in order: 1, 2, 3, 10, 3, 2, 1, with the group having the single number experiencing the highest movement during compression and the group with the number 10 experiencing the lowest movement during compression.
Claim 9
Dependent Claim
69 words
The method as in claim 4, in which said plates are prepared by heating a mixture of silicon powder, Y 2 O 3 , and Al 2 O 3 in a nitrogen atmosphere for a period of time and at a temperature to agglomerate said mass to a density of about 2.3 gm/cm 3 and a chemical content comprised substantially of alpha phase silicon nitride and silicon yttrium oxynitrides.
Claim 10
Dependent Claim
52 words
The method as in claim 4, in which said hot pressing is carried out in increments by applying about 150 psi at room temperature, heating to 1800° C. accompanied by 500 psi pressure, then heating further to 2400° F. with 2500 psi pressure, and finally to 3000° F. with 3700 psi pressure.
Claim 11
Dependent Claim
65 words
The method as in claim 4, in which said plates are prepared by cold compacting a dry ball milled mixture of silicon, Y 2 O 3 , and Al 2 O 3 powder and then heating in a nitrogen atmosphere to convert said mixture to substantially silicon nitride and silicon yttrium oxynitrides, said cold compaction being carried out with a pressure of about 1400-1500 psi.
Claim 12
Dependent Claim
18 words
The method as in claim 4, in which each inert rigid spacer has a thickness of 0.25-1.5 inch.
Claim 13
Dependent Claim
55 words
The method as in claim 10, in which the thickness of said inert rigid spacer varies with the total overall thickness of the plate group immediately adjacent the inert spacer, said thickness being determined by the rule that in the zone of greatest axial movement for the plate, the spacer associated therewith is the thickest.
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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) | 1989-12-29 | 1990-06-30 | 1990-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-29 | 1994-06-30 | 1994-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-29 | 1998-06-30 | 1998-12-30 | $7700.00 | Window Closed / Lapsed |