US4579699A
Expired / Lapsed
US
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Method for making α-Si3 N4 whiskers and articles therefrom
Assignee: Boeing Co
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Filing: 1983-09-29
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Granted: 1986-04-01
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Expires: 2003-09-29
Abstract
Abstract A method for producing α-silicon nitride whiskers. Silicon is blended with amorphous silicon nitride and a pore-forming composition particles able to be removed without leaving a residue, such as naphthalene particles. The mixture is compacted to a desired shape, after which the pore-forming particles are removed from the mixture to form a porous silicon precursor compact having the desired shape. The silicon precursor is reacted with a substance that releases free nitrogen, such as nitrogen or dry ammonia. The reaction is carried out at a temperature sufficiently high to form an identically shaped porous compact of α-silicon nitride whiskers but sufficiently low to avoid subliming substantially all of the formed whiskers. Preferably, the reaction is carried out in a range between about 1100° C. and 1500° C. The shaped porous compact of α-silicon nitride whiskers may be impregnated with a resin binder, a liquid metal, a colloidal suspension, an ionic solution or a gaseous material to form a composite. Alternatively, the compact of α-silicon nitride whiskers formed by the method described above may be broken down by crushing or grinding to form individual whiskers.
Inventors
- 👤 Juris Verzemnieks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 01:02
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/591; C04B35/71; C04B35/78; C04B35/80; C04B38/00; C04B38/06; C04B41/45; C30; C30B; C30B25/00; C30B25/005; C30B29/00; C30B29/10; C30B29/38; Y; Y10; Y10S; Y10S264/00; Y10S264/19
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
92 words
A method of making a low density α-silicon nitride article, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting the mixture to a desired shape; (c) removing the pore-forming composition to form a porous precursor; and (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride.
Claim 2
Independent Claim
92 words
A method of making a low density α-silicon nitride article, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting the mixture to a desired shape; (c) removing the pore-forming composition to form a porous precursor; and (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein said article has a density of less than 0.2 g/cm 3 .
Claim 4
Dependent Claim
18 words
The method of claim 1 wherein said article has a density of less than 0.6 g/cm 3 .
Claim 5
Dependent Claim
18 words
The method of claim 1 wherein said mixture comprises from 5 to 80% silicon and amorphous silicon nitride.
Claim 6
Dependent Claim
24 words
The method of claim 1 wherein the ratio of silicon powder to amorphous silicon nitride is in the range of from 95:5 to 50:50.
Claim 7
Dependent Claim
25 words
The method of claim 1 wherein said porous precursor is reacted with nitrogen at a temperature in the range of from 1100° to 1500° C.
Claim 8
Dependent Claim
46 words
The method of claim 1 wherein said gas is selected from the group consisting of nitrogen, dry ammonia, a mixture of hydrogen and dry ammonia, a mixture of nitrogen and dry ammonia, mixture of hydrogen and nitrogen, and a mixture of nitrogen, dry ammonia and hydrogen.
Claim 9
Dependent Claim
32 words
The method of claim 1 wherein said pore-forming composition is in the form of particles, said particles having a composition are selected from the group consisting of naphthalene, camphor and carbon dioxide.
Claim 10
Dependent Claim
18 words
The method of claim 1 wherein said silicon particles have a diameter of less than about 35 μm.
Claim 11
Independent Claim
125 words
A method of making a fiber reinforced composite, said composite being reinforced by whiskers of Δ-silicon nitride, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting the mixture to a desired shape; (c) removing the pore-forming composition to form a porous precursor; (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride to form a porous α-silicon nitride article; (e) impregnating said porous α-silicon nitride article with a matrix material; (f) solidifying said matrix material to form said composite.
Claim 12
Independent Claim
125 words
A method of making a fiber reinforced composite, said composite being reinforced by whiskers of Δ-silicon nitride, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting the mixture to a desired shape; (c) removing the pore-forming composition to form a porous precursor; (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride to form a porous α-silicon nitride article; (e) impregnating said porous α-silicon nitride article with a matrix material; (f) solidifying said matrix material to form said composite.
Claim 13
Dependent Claim
21 words
The method of claim 10 wherein said porous α-silicon nitride article has a density less than about 0.2 g/cm 3 .
Claim 14
Dependent Claim
21 words
The method of claim 10 wherein said porous α-silicon nitride article has a density less than about 0.6 g/cm 3 .
Claim 15
Dependent Claim
18 words
The method of claim 10 wherein said mixture comprises from 5 to 80% silicon and amorphous silicon nitride.
Claim 16
Dependent Claim
42 words
The method of claim 10 wherein said matrix material is selected from the group consisting of a resin binder, a liquid metal, a colloidal suspension, an ionic solution and at least one gaseous material capable of being solidified to form a matrix.
Claim 17
Dependent Claim
11 words
The method of claim 14 wherein said material is a resin.
Claim 18
Dependent Claim
18 words
The method of claim 15 further including the step of polymerizing the matrix material in said reinforced composite.
Claim 19
Dependent Claim
12 words
The method of claim 14 wherein said material is a liquid metal.
Claim 20
Dependent Claim
33 words
The method of claim 17 further including the step of treating said liquid metal with a wetting agent prior to said impregnating step to facilitate the wetting of said whiskers by said metal.
Claim 21
Independent Claim
96 words
A method of forming individual α-silicon nitride whiskers, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting said mixture; (c) removing the pore-forming composition to form a porous precursor; (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride; and (e) breaking the bond between the individual α-silicon nitride whiskers.
Claim 22
Independent Claim
96 words
A method of forming individual α-silicon nitride whiskers, said method comprising the steps of: (a) mixing particulate silicon with amorphous silicon nitride and a pore-forming composition to form a mixture, said pore-forming composition being capable of being removed without leaving a residue; (b) compacting said mixture; (c) removing the pore-forming composition to form a porous precursor; (d) reacting said porous precursor with a gas that releases free nitrogen to convert said silicon to α-silicon nitride while simultaneously converting said amorphous silicon nitride to α-silicon nitride; and (e) breaking the bond between the individual α-silicon nitride whiskers.
Claim 23
Dependent Claim
24 words
The method of claim 19 wherein the ratio of silicon powder to amorphous silicon nitride is in the range of from 95:5 to 50:50.
Claim 24
Dependent Claim
24 words
The method of claim 19 wherein said silicon is reacted with nitrogen at a temperature in the range of from 1100° to 1500° C.
Claim 25
Dependent Claim
46 words
The method of claim 19 wherein said gas is selected from the group consisting of nitrogen, dry ammonia, a mixture of hydrogen and dry ammonia, a mixture of nitrogen and dry ammonia, mixture of hydrogen and nitrogen, and a mixture of nitrogen, dry ammonia and hydrogen.
Claim 26
Dependent Claim
32 words
The method of claim 19 wherein said pore-forming composition are in the form of particles, said particles having a composition are selected from the group consisting of naphthalene, camphor and carbon dioxide.
Claim 27
Dependent Claim
20 words
The method of claim 19 wherein said individual α-silicon nitride whiskers have a diameter of about 0.2 μm or less.
Claim 28
Dependent Claim
17 words
The method of claim 19 wherein said mixture comprises from 5 to 80% silicon and silicon nitride.
References Cited (Backward Citations)
US2618565A
Cited
US3084998A
Cited
GB1274212A
Cited
DE2356921A1
Cited
GB1490543A
Cited
US4036653A
Cited
US4101616A
Cited
US4017319A
Cited
US4122152A
Cited
US4073845A
Cited
US4125592A
Cited
US4122155A
Cited
US4177230A
Cited
US4388255A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-03-31 | 1989-09-30 | 1990-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-03-31 | 1993-09-30 | 1994-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-03-31 | 1997-09-30 | 1998-04-01 | $7700.00 | Window Closed / Lapsed |