Claims
- 1. A process for the preparation of substantially polycrystalline silicon carbide fibers comprising the steps of:
- a) forming fibers from a preceramic polymeric precursor consisting essentially of phenyl-containing polyorganosiloxane resins;
- b) infusibilizing said fibers; and
- c) pyrolyzing said fibers at a temperature in excess of 1600.degree. C. in a nonoxidizing atmosphere to form substantially polycrystalline silicon carbide fibers;
- said fibers having incorporated therein at least about 0.2% by weight boron during either or both of said infusibilizing and pyrolyzing steps.
- 2. The process of claim 1 in which said substantially polycrystalline silicon carbide fibers have at least 75% crystallinity.
- 3. The process of claim 1 in which said substantially polycrystalline silicon carbide fibers have a density of at least about 2.9 gm/cm.sup.3.
- 4. The process of claim 1 in which said fibers formed in step a) are formed by spinning.
- 5. The process of claim 4 in which said fibers formed in step a) are formed by melt spinning.
- 6. The process of claim 4 in which said fibers formed in step a) are formed by wet spinning.
- 7. The process of claim 4 in which said fibers formed in step a) are formed by dry spinning.
- 8. The process of claim 1 in which said phenyl-containing polyorganosiloxanes have a degree of substitution of between about 1.0 to 1.5.
- 9. The process of claim 8 in which said phenyl-containing polyorganosiloxanes have a softening temperature of less than about 100.degree. C.
- 10. The process of claim 1 in which said fibers are infusibilized by curing said fibers in air.
- 11. The process of claim 1 in which said fibers are infusibilized by curing said fibers in an atmosphere containing a mixture of boron trichloride and ammonia or amine.
- 12. The process of claim 1 in which said fibers are infusibilized by curing said fibers in an atmosphere containing diborane.
- 13. The process of claim 1 in which said fibers are infusibilized by curing said fibers with gamma irradiation.
- 14. The process of claim 1 in which said fibers are infusibilized by curing said fibers with ultraviolet light.
- 15. The process of claim 1 in which said fibers are infusibilized by curing said fibers first in an atmosphere containing nitric oxide followed by curing said fibers in an atmosphere containing boron trichloride or diborane.
- 16. The process of claim 1 in which said fibers are infusibilized by curing said fibers by heating said fibers in an atmosphere containing an acid or a base.
- 17. The process of claim 1 in which said fibers are infusibilized by curing said fibers by heating said fibers in an atmosphere containing hydrogen chloride.
- 18. The process of claim 1 in which said nonoxidizing atmosphere comprises a gas selected from the group consisting of argon, helium, and mixtures thereof.
- 19. The process of claim 1 in which said pyrolysis step includes heating said fibers to about 1800.degree. C. and maintaining that temperature for about one hour.
- 20. The process of claim 1 in which boron is incorporated into said fibers during said infusibilization step by exposing said polymeric precursor to a boron-containing gas.
- 21. The process of claim 1 in which boron is incorporated into said fibers during said pyrolyzing step by exposing said polymeric precursor to a boron-containing gas.
- 22. A process for the preparation of substantially polycrystalline silicon carbide fibers comprising the steps of:
- a) forming fibers from a preceramic polymeric precursor consisting essentially of phenyl-containing polyorganosiloxane resins which have incorporated therein at least about 0.2% by weight boron therein either prior to or during the formation of the fibers;
- b) infusibilizing said fibers; and
- c) pyrolyzing said fibers at a temperature in excess of 1600 degrees C. in a nonoxidizing atmosphere to form substantially polycrystalline silicon carbide fibers.
- 23. The process of claim 22 in which said substantially polycrystalline silicon carbide fibers have at least 75% crystallinity.
- 24. The process of claim 22 in which said substantially polycrystalline silicon carbide fibers have a density of at least about 2.9 gm/cm.sup.3.
- 25. The process of claim 22 in which said fibers formed in step a) are formed by spinning.
- 26. The process of claim 25 in which said fibers formed in step a) are formed by melt spinning.
- 27. The process of claim 25 in which said fibers formed in step a) are formed by wet spinning.
- 28. The process of claim 25 in which said fibers formed in step a) are formed by dry spinning.
- 29. The process of claim 22 in which said phenyl-containing polyorganosiloxanes have a degree of substitution of between about 1.0 to 1.5.
- 30. The process of claim 29 in which said phenyl-containing polyorganosiloxanes have a softening temperature of less than about 100 degrees C.
- 31. The process of claim 22 in which said fibers are infusibilized by curing said fibers in air.
- 32. The process of claim 22 in which said fibers are infusibilized by curing said fibers in an atmosphere containing a mixture of boron trichloride and ammonia or amine.
- 33. The process of claim 22 in which said fibers are infusibilized by curing said fibers in an atmosphere containing diborane.
- 34. The process of claim 22 in which said fibers are infusibilized by curing said fibers with gamma irradiation.
- 35. The process of claim 22 in which said fibers are infusibilized by curing said fibers with ultraviolet light.
- 36. The process of claim 22 in which said fibers are infusibilized by curing said fibers first in an atmosphere containing nitric oxide followed by curing said fibers in an atmosphere containing boron trichloride or diborane.
- 37. The process of claim 22 in which said fibers are infusibilized by curing said fibers by heating said fibers in an atmosphere containing an acid or a base.
- 38. The process of claim 22 in which said fibers are infusibilized by curing said fibers by heating said fibers in an atmosphere containing hydrogen chloride.
- 39. The process of claim 22 in which said nonoxidizing atmosphere comprises a gas selected from the group consisting of argon, helium, and mixtures thereof.
- 40. The process of claim 22 in which said pyrolysis step includes heating said fibers to about 1800 degrees C. and maintaining that temperature for about one hour.
Parent Case Info
This application is a continuation of U.S. application Ser. No. 449,709, filed Dec. 12, 1989, now abandoned.
US Referenced Citations (3)
Foreign Referenced Citations (2)
Number |
Date |
Country |
7077230 |
Oct 1980 |
JPX |
57-77320 |
May 1982 |
JPX |
Continuations (1)
|
Number |
Date |
Country |
Parent |
449709 |
Dec 1989 |
|