Process for gelling a sol in fiberformed ceramic insulation
AssigneeThe Boeing Company
InventorsPatrice K. Ackerman, Anna L. Baker
Life of this patent
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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.degree. F.
Claims24
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.
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.degree. F. for preventing rehydration of the sol.
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.degree. F. to prevent rehydration of the sol-gel binder.
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.
Dependencies are inferred from the claim text.