Silicon carboxide composite reinforced with ceramic fibers having a surface enriched in boron nitride

A method of preparing fiber reinforced glass composites comprising:

• (a) preparing a polymer by either (a') reacting (1) a cyclosiloxane monomer having the formula ##STR10## where n is an integer from 3 to 30, R is hydrogen, and R' is an alkene of from 2 to 20 carbon atoms in which one vinyl carbon atom is directly bonded to silicon or (2) two or more different cyclosiloxane monomers having the formula of (1) where for at least one monomer R is hydrogen and R' is an alkyl group having from 1 to 10 carbon atoms and for the other monomers R is an alkene from 2 to 20 carbon atoms in which one vinyl carbon is directly bonded to silicon and R' is an alkyl group of from 1 to 20 carbon atoms or (3) cyclosiloxane monomers having the formula of (1) where R and R' are independently selected from hydrogen, an alkene of from 2 to about 20 carbon atoms in which one vinyl carbon atom is directly bonded to silicon, or an alkyl group of from 1 to 20 carbon atoms, and at least some of said monomers contain each of said hydrogen, alkene, and alkyl moieties, said reaction taking place in the presence of an effective amount of hydrosilylation catalyst;
• or (a") reacting (1') cyclosiloxanes of the formula ##STR11## where n is an integer from 3 to about 20, R and R' are independently selected from hydrogen, an unsubstituted vinyl group, a substituted vinyl group, an alkyl group have 1 to 20 carbon atoms, or aryl and where said siloxane contains at least two of either or both of hydrogen and substituted or unsubstituted vinyl groups and
• (2') non-cyclic siloxanes having the formula ##STR12## where R.sub.1, R.sub.2, and R.sub.3 are independently selected from hydrogen, an unsubstituted vinyl group, a substituted vinyl group, an alkyl group having I to 20 carbon atoms, or aryl and where said siloxane contains at least two of either or both of hydrogen and unsubstituted or substituted vinyl groups
• m is an integer from 0 to 1,000, the reaction of (1') and (2') taking place in the presence of an effective amount of a hydrosilylation catalyst,
• (b) applying the reaction product of (a) to at least one boron-containing refractory fiber having a surface enriched in boron nitride provided by nitriding said fibers at a temperature of about 1100.degree. C. to 1250.degree. C. with a gas containing 5-100% NH.sub.3 for 1 to 240 minutes to form a prepreg;
• (c) laying-up plies of the prepreg of (b) to form a green structure;
• (d) curing the green structure of (c) at a temperature not greater than 250.degree. C.;
• (e) pyrolyzing the cured structure of (d) at a temperature of about 800.degree. C. to about 1400.degree. C. in non-oxidizing atmosphere;
• (f) recovering the pyrolyzed product of (e) as the fiber reinforced glass composite;
• (g) impregnating the pyrolyzed product of (f) with the reaction product of (a);
• (h) pyrolyzing the impregnated product of (g) at 800.degree. C.-1400.degree. C.;
• (i) repeating steps (g) and (h) to achieve the desired density.

A method of preparing fiber reinforced glass composites comprising:

• (a) placing into a mold at least one boron-containing refractory fiber, having a surface enriched in boron nitride provided by nitriding said fibers at a temperature of about 1100.degree. C. to 1250.degree. C. with a gas containing 5-100% NH.sub.3 for 1 to 240 minutes;
• (b) filling the fiber-containing mold of (a) with either (b') (1) a cyclosiloxane monomer having the formula ##STR13## where n is an integer from 3 to 30, R is hydrogen, and R' is an alkene of from 2 to 20 carbon atoms in which one vinyl carbon atom is directly bonded to silicon or (2) two or more different cyclosiloxane monomers having the formula of (2) where for at least one monomer R is hydrogen and R' is an alkyl group having from 1 to 20 carbon atoms and for the other monomers R is an alkene from 2 to 20 carbon atoms in which one vinyl carbon is directly bonded to silicon and R' is an alkyl group of from 1 to 20 carbon atoms or (3) cyclosiloxane monomers having the formula of (1) where R and R' are independently selected from hydrogen, an alkene of from 2 to about 20 carbon atoms in which one vinyl carbon atom is directly bonded to silicon, or an alkyl group of from 1 to 20 carbon atoms and at least some of said monomers contain each of said hydrogen, alkene, and alkyl moieties, and an effective amount of hydrosilylation catalyst;
• or (b") (1') cyclosiloxanes of the formula ##STR14## where n is an integer from 3 to about 20, R and R' are independently selected from hydrogen, an unsubstituted vinyl group, a substituted vinyl group, an alkyl group have 1 to 20 carbon atoms, or aryl and where said siloxane contains at least two of either or both of hydrogen and substituted or unsubstituted vinyl groups and (2') non-cyclic siloxanes having the formula ##STR15## where R.sub.1, R.sub.2, and R.sub.3 are independently selected from hydrogen, an unsubstituted vinyl group, a substituted vinyl group, an alkyl group having 1 to 20 carbon atoms, or aryl and where said siloxane contains at least two of either or both of hydrogen and unsubstituted or substituted vinyl groups
• m is an integer from 0 to 1,000, the reaction of (1') and (2'), taking place in the presence of a effective amount of a hydrosilylation catalyst,
• (c) reacting the monomers of (b) at a temperature of about 30.degree. C. to 150.degree. C. to form a green composite;
• (d) pyrolyzing the green composite of (c) at a temperature of about 800.degree. C. to about 1400.degree. C. in non-oxidizing atmosphere;
• (e) recovering the pyrolyzed product of (d) as the fiber reinforced glass composite;
• (f) impregnating the pyrolyzed product of (e) with the reaction product of the monomers of (b);
• (g) pyrolyzing the impregnated product of (f) at 800.degree. C.-1400.degree. C.;
• (h) repeating steps (f) and (g) to achieve the desired density.