Claims
- 1. A method for the production of polycrystalline ceramic fibers wherein the method comprises:
- heating an amorphous ceramic fiber comprised of silicon and carbon in an environment to which a boron oxide and carbon monoxide have been added at a temperature sufficient to convert the ceramic fiber to a polycrystalline ceramic fiber, said carbon monoxide being added by purging said environment with a purge gas comprising carbon monoxide.
- 2. The method as claimed in claim 1 wherein the amorphous ceramic fiber additionally comprises an element selected from the group consisting of oxygen, nitrogen, titanium, zirconium, chlorine and boron.
- 3. The method as claimed in claim 1 wherein the amorphous ceramic fiber comprises a material selected from the group consisting of SiC, SiCO, SiCN, SiCON, and SiCOTi.
- 4. The method as claimed in claim 3 wherein the amorphous ceramic fiber comprises SiCOTi.
- 5. The method as claimed in claim 2 wherein the amorphous ceramic fiber comprises silicon, carbon and oxygen.
- 6. The method as claimed in claim 1 wherein the boron oxide is B.sub.2 O.sub.3.
- 7. A The method as claimed in claim 1 wherein the carbon monoxide is present in an amount of 20 to 70 mole % of the purge gas.
- 8. The method as claimed in claim 1 wherein the amorphous ceramic fiber is heated to a temperature of 1400.degree. C. to 2200.degree. C.
- 9. The method as claimed in claim 8 wherein the amorphous ceramic fiber is heated to a temperature of 1500.degree. C. to 2000.degree. C.
- 10. A method for the production of polycrystalline ceramic fibers wherein the method comprises
- heating an amorphous ceramic fiber comprised of silicon and carbon in an environment to which a boron oxide and carbon monoxide have been added at a temperature of 1400.degree. C. to 2200.degree. C. for a time sufficient to incorporate boron oxide into the ceramic fiber and substantially remove any volatile elements from the fiber, said carbon monoxide being added by purging said environment with a purge gas comprising carbon monoxide; and
- thereafter heating the ceramic fiber with the boron oxide incorporated therein at a temperature of 1800.degree. C. to 2200.degree. C. in an inert environment to convert the ceramic fiber to a polycrystalline ceramic fiber.
- 11. The method as claimed in claim 10 wherein the amorphous ceramic fiber is heated to a temperature of 1500.degree. C. to 1600.degree. C. and the ceramic fiber with the boron oxide incorporated therein is heated at a temperature of 1900.degree. C. to 2000.degree. C.
- 12. A process for preparing a polycrystalline ceramic fiber comprising spinning a preceramic polymer comprising silicon and carbon to form a green fiber, curing the green fiber, and pyrolyzing the green fiber in a manner which incorporates boron into the fiber by diffusion wherein the improvement comprises
- purging said pyrolysis environment with a purge gas comprising carbon monoxide in an amount sufficient to reduce the time necessary for the boron to diffuse into the fiber.
- 13. A method for the production of polycrystalline ceramic fibers wherein the method comprises:
- heating an amorphous ceramic fiber comprised of silicon and carbon in an environment to which a boron oxide and carbon monoxide have been added at a temperature sufficient to convert the ceramic fiber to a polycrystalline ceramic fiber, said carbon monoxide being added by purging said environment with a purge gas comprising carbon monoxide.
- 14. The method as claimed in claim 13 wherein the carbon monoxide is present in the purge gas in an amount of 20 to 100 mole % of the purge gas.
Government Interests
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of NAS3-26385 awarded by NASA.
US Referenced Citations (15)
Foreign Referenced Citations (2)
Number |
Date |
Country |
53-81727 |
Jul 1978 |
JPX |
9402430 |
Feb 1994 |
WOX |