Claims
- 1. A method for preparing ceramic fibers comprising:
- i) shaping into green fibers a blend comprising:
- a) 90 to 99.9 weight percent of a siloxane resin comprising units with a general formula R.sub.x R.sup.1.sub.y R.sup.2.sub.z SiO.sub.(4-x-y-z)/2, wherein each R is independently selected from unsaturated monovalent hydrocarbon groups, each R.sup.1 is independently selected from aryl groups of 6 to about 10 carbon atoms, and each R.sup.2 is independently selected from saturated monovalent hydrocarbon groups, x has a value of 1 or 2, y has a value of 0, 1, or 2, and z has a value of 0, 1, or 2 with the proviso that x+y+z=1, 2, or 3, and
- b) 0.1 to 10 weight percent of a carborane-siloxane oligomer having the formula ##STR6## where R.sup.3 is selected from the group consisting of a hydroxyl group, an alkyl group having from 1 to 4 carbon atoms, an alkenyl group having from 1 to 4 carbon atoms, and a vinyl carborane group having the formula ##STR7## x is has a value of 10, 7, or 5; and q has a value of 1 or 2; ii) curing the green fibers to cured fibers; and
- iii) pyrolyzing the cured fibers to ceramic fibers by heating to a temperature of 800 to 2,200.degree. C.
- 2. The method of claim 1, wherein the siloxane resin has the formula (R.sup.1 SiO.sub.3/2).sub.e (R.sup.2 SiO.sub.3/2).sub.f (RR.sup.2.sub.2 SiO.sub.1/2).sub.g, where 0.ltoreq.e.ltoreq.0.98, 0.ltoreq.f.ltoreq.0.98, 0<g.ltoreq.1, and e+f+g=1.
- 3. The method of claim 2, wherein R represents a vinyl group, R.sup.1 represents a phenyl group, R.sup.2 represents a methyl group, e has a value of 0.3 to 0.5, f has a value of 0.3 to 0.5, and g has a value of 0.15 to 0.3.
- 4. The method as claimed in claim 1 wherein the carborane-siloxane oligomer is ##STR8##
- 5. The method of claim 1, wherein the carborane-siloxane oligomer is present at 0.5 to 5 weight percent of the blend.
- 6. The method of claim 1, wherein the green fibers are produced by melt-spinning.
- 7. The method of claim 6, wherein the melt-spinning takes place at 200 to 240.degree. C.
- 8. The method of claim 1, wherein curing the green fibers occurs by exposing them to high energy radiation.
- 9. The method of claim 8, wherein curing the green fibers occurs by exposing them to electron beam radiation.
- 10. The method of claim 1, wherein the ceramic fibers are boron silicon oxycarbide fibers and the pyrolyzing is carried out at a temperature of 800 to 1,400.degree. C.
- 11. The method of claim 10, wherein the boron silicon oxycarbide fibers are further pyrolyzed to boron-doped silicon carbide fibers by heating to a temperature of 1,500 to 2,200.degree. C.
- 12. The method of claim 1, wherein the ceramic fibers are boron-doped silicon carbide fibers, and the pyrolyzing is carried out at a temperature of 1,600 to 2,200 .degree. C.
- 13. A method of preparing a ceramic material, comprising pyrolyzing a blend, comprising: a) 90 to 99.9 weight percent of a siloxane resin comprising units with a general formula R.sub.x R.sup.1.sub.y R.sup.2.sub.z SiO.sub.(4-x-y-z)/2, wherein each R is independently selected from unsaturated monovalent hydrocarbon groups, each R.sup.1 is independently selected from aryl groups of 6 to about 10 carbon atoms, and each R.sup.2 is independently selected from saturated monovalent hydrocarbon groups, x has a value of 1 or 2, y has a value of 0, 1, or 2, and z has a value of 0, 1, or 2 with the proviso that x+y+z=1, 2, or 3, and
- b) 0.1 to 10 weight percent of carborane-siloxane oligomer having the formula ##STR9## where R.sup.3 is selected from the group consisting of a hydroxyl group, an alkyl group having from 1 to 4 carbon atoms, an alkenyl group having from 1 to 4 carbon atoms, and a vinyl carborane group having the formula ##STR10## x is has a value of 10, 7, or 5; and q has a value of 1 or 2; wherein pyrolyzing is carried out by heating the blend to a temperature of 800 to 2,200.degree. C.
Parent Case Info
This application is a continuation-in part of U.S. patent application Ser. No. 09/019,577 filed on Feb. 6, 1998, now U.S. Pat. No. 5,958,324.
US Referenced Citations (17)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0873980A2 |
Oct 1998 |
EPX |
Continuation in Parts (1)
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Number |
Date |
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Parent |
019577 |
Feb 1998 |
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