US5021369A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for gelling a sol in fiberformed ceramic insulation
Assignee: Boeing Co
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Filing: 1988-08-01
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Granted: 1991-06-04
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Expires: 2008-08-01
Abstract
Abstract A felted mat of ceramic fibers is impregnated with a sol-gel glass binder and is exposed to a low voltage direct current to catalytically gel the binder at ambient temperature and ambient pressure without pH conversion catalysts. The gelled binder can be easily converted to a ceramic thereafter and stabilized by firing above about 525° F.
Inventors
- 👤 Patrice K. Ackerman
- 👤 Anna L. Baker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 10:03
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B30/00; C04B30/02; C04B41/45; C04B41/4505; C04B41/4535; C04B41/4537
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
52 words
A method for gelling a sol to strengthen a felted mat of ceramic fibers, comprising the steps of: (a) impregnating the mat with a sol-gel binder; and (b) exposing the impregnated mat at ambient temperature and ambient pressure to a low voltage, direct current for a sufficient time to gel the binder.
Claim 2
Independent Claim
52 words
A method for gelling a sol to strengthen a felted mat of ceramic fibers, comprising the steps of: (a) impregnating the mat with a sol-gel binder; and (b) exposing the impregnated mat at ambient temperature and ambient pressure to a low voltage, direct current for a sufficient time to gel the binder.
Claim 3
Dependent Claim
12 words
The method of claim 1 wherein the binder is an alumina sol.
Claim 4
Dependent Claim
20 words
The method of claim 1 further comprising heat treating the mat at a temperature of at least about 525° F.
Claim 5
Dependent Claim
16 words
The method of claim 1 wherein the voltage is in the range of about 10-100 V.
Claim 6
Dependent Claim
8 words
The product of the process of claim 1.
Claim 7
Dependent Claim
17 words
The method of claim 1 further comprising the step of converting the gelled binder to a ceramic.
Claim 8
Dependent Claim
14 words
The method of claim 6 wherein the converting step includes drying the gelled binder.
Claim 9
Dependent Claim
12 words
The method of claim 6 wherein impregnating saturates the mat with sol.
Claim 10
Dependent Claim
19 words
The method of claim 8 wherein the sol is an alumina sol made from alkoxides in a water/ethanol carrier.
Claim 11
Dependent Claim
8 words
The product of the process of claim 9.
Claim 12
Dependent Claim
60 words
The method of claim 9 wherein the exposing step includes positioning a first electrode along a first surface of the mat, positioning a second electrode along a second surface of the mat to define a circuit path comprising the two electrodes and the saturated mat, and connecting the electrodes to establish direct current of a first polarity across the electrodes.
Claim 13
Dependent Claim
40 words
The method of claim 11 further comprising the step of reversing the polarity of the direct current after a period of time so that the mat develops gelled layers of high strength and density adjacent the first and second surfaces.
Claim 14
Dependent Claim
8 words
The product of the process of claim 12.
Claim 15
Dependent Claim
29 words
The method of claim 1 further comprising the step of adding additional sol-gel binder to the mat after a predetermined time as the initial amount of sol-gel binder decreases.
Claim 16
Dependent Claim
25 words
The method of claim 9 further comprising heat treating the mat after gelling of the binder at a temperature of at least about 525° F.
Claim 17
Dependent Claim
8 words
The product of the process of claim 15.
Claim 18
Dependent Claim
25 words
The method of claim 1 comprising the step of repeating steps (a) and (b) to increase the density of the mat by gelling additional binder.
Claim 19
Dependent Claim
18 words
The method of claim 1 wherein the mat initially includes gelled sol bridges between the felted ceramic fibers.
Claim 20
Independent Claim
109 words
A method for forming a rigid fiberform ceramic comprising the steps of: (a) preparing at least one slurry of ceramic fibers; (b) felting the fibers from the slurry to form a mat; (c) impregnating the mat with a sol-gel binder; (d) gelling the sol-gel binder by exposing the impregnated mat to a low voltage direct current for a 1-180 minutes; (e) repeating steps (c) and (d) to produce a preform composite of a predetermined density; (f) drying the preform composite to form the fiberform ceramic body; and (g) heat treating the dried ceramic body at a temperature above at least about 525° F. for preventing rehydration of the sol.
Claim 21
Independent Claim
109 words
A method for forming a rigid fiberform ceramic comprising the steps of: (a) preparing at least one slurry of ceramic fibers; (b) felting the fibers from the slurry to form a mat; (c) impregnating the mat with a sol-gel binder; (d) gelling the sol-gel binder by exposing the impregnated mat to a low voltage direct current for a 1-180 minutes; (e) repeating steps (c) and (d) to produce a preform composite of a predetermined density; (f) drying the preform composite to form the fiberform ceramic body; and (g) heat treating the dried ceramic body at a temperature above at least about 525° F. for preventing rehydration of the sol.
Claim 22
Dependent Claim
8 words
The product of the process of claim 19.
Claim 23
Dependent Claim
46 words
The method of claim 1 wherein the binder is an alumina sol and the voltage is in the range of about 10-100 V and further comprising heat treating the mat, after exposing the mat to the voltage, at a temperature of a least about 525° F.
Claim 24
Dependent Claim
17 words
The method of claim 21 wherein the exposing step involves using about 0.1 amp for 1-180 minutes.
Claim 25
Independent Claim
107 words
A method for forming fiberform composites having controlled areas of differing density comprising the steps of: (a) forming a preform ceramic fiber mat; (b) applying an anode and a cathode to the surfaces of the mat; (c) infiltrating a sol-gel binder into the mat; (d) defining areas of differing density in the mat by gelling the sol-gel binder by applying a low voltage, direct current to the anode and cathode at ambient temperature, to form a region of higher density adjacent the cathode; and (e) firing the mat after step (d) at a temperature of at least about 525° F. to prevent rehydration of the sol-gel binder.
Claim 26
Independent Claim
107 words
A method for forming fiberform composites having controlled areas of differing density comprising the steps of: (a) forming a preform ceramic fiber mat; (b) applying an anode and a cathode to the surfaces of the mat; (c) infiltrating a sol-gel binder into the mat; (d) defining areas of differing density in the mat by gelling the sol-gel binder by applying a low voltage, direct current to the anode and cathode at ambient temperature, to form a region of higher density adjacent the cathode; and (e) firing the mat after step (d) at a temperature of at least about 525° F. to prevent rehydration of the sol-gel binder.
Claim 27
Independent Claim
60 words
A method for controlling the density of a fiberform ceramic composite having a felted mat of fibers bound with a sol-gel binder, comprising the step of controlling the duration of exposure of a saturated mat of the felted fibers and ungelled binder to a low voltage, direct current at ambient temperature to gel the binder to achieve a high density.
Claim 28
Independent Claim
60 words
A method for controlling the density of a fiberform ceramic composite having a felted mat of fibers bound with a sol-gel binder, comprising the step of controlling the duration of exposure of a saturated mat of the felted fibers and ungelled binder to a low voltage, direct current at ambient temperature to gel the binder to achieve a high density.
References Cited (Backward Citations)
US4324576A
Cited
US4828774A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-03 | 1994-12-03 | 1995-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-03 | 1998-12-03 | 1999-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-03 | 2002-12-03 | 2003-06-04 | $7700.00 | Window Closed / Lapsed |