Abstract: An uncrosslinked polysilazane containing chemically bound peroxide groups is prepared by reacting a polysilazane and a hydroperoxide at a temperature below the decomposition temperature of the hydroperoxide. A thermoset polymer is formed by heating an uncrosslinked, peroxide-substituted silazane that is also substituted by alkenyl or alkynyl groups at temperatures sufficiently high to decompose the chemically bound peroxide groups to yield a free radical, thereby initiating crosslinking. The crosslinked polysilazanes can be pyrolyzed to form ceramic articles.

Abstract: The present invention relates to preceramic polymers incorporating boron and their application in the sintering of SiC ceramics. The present invention is also directed to a process for preparing a boron-substituted polysilazane which involves preparing a silazane ammonolysis product by reacting ammonia with a halogenated silicon compound selected from the group consisting of RSiX.sub.3, RR'SiX.sub.2, RR'R"SiX, SiX.sub.

Abstract: An uncrosslinked polysilazane containing chemically bound peroxide groups is prepared by reacting a polysilazane and a hydroperoxide at a temperature below the decomposition temperature of the hydroperoxide. A thermoset polymer is formed by heating an uncrosslinked, peroxide-substituted silazane that is also substituted by alkenyl or alkynyl groups at temperatures sufficiently high to decompose the chemically bound peroxide groups to yield a free radical, thereby initiating crosslinking. The crosslinked polysilazanes can be pyrolyzed to form ceramic articles.

Abstract: The present invention relates to preceramic polymers incorporating boron and their application in the sintering of SiC ceramics. The present invention is also directed to a process for preparing a boron-substituted polysilazane which involves preparing a silazane ammonolysis product by reacting ammonia with a halogenated silicon compound selected from the group consisting of RSiX.sub.3, RR'SiX.sub.2, RR'R"SiX, SiX.sub.

Abstract: A composition that comprises a (thio)amide-modified silazane polymer containing at least one alkenyl or alkynyl group and a free radical generator can be crosslinked by an energy input provided in the form of heat, ultraviolet radiation, or an electron beam. The crosslinked (thio)amide-modified silazane polymer composition can be pyrolyzed to form a silicon nitride-containing ceramic.

Abstract: Silazane polymers are prepared by (1) reacting ammonia with one or more halogenated organic silicon compounds containing an Si-H bond to produce a silazane ammonolysis product, (2) mixing the ammonolysis product with 0.1% to 30% by weight of an organic amide or thioamide, and (3) heating to a temperature of 30.degree. to 300.degree. C. Silazane polymers containing alkenyl or alkynyl groups can be cured by supplying energy to generate free radicals. The cured or uncured polymers can be pyrolyzed to produce silicon nitride-containing ceramic materials.

Abstract: A composition that comprises a poly(thio)ureasilazane having at least one alkenyl or alkynyl group and a free radical generator can be crosslinked by an energy input provided in the form of heat, ultraviolet radiation, or an electron beam. The crosslinked poly(thio)ureasilazane compositions can be pyrolyzed to form silicon nitride-containing ceramics.

Abstract: Polysilazane addition polymers are prepared by (1) reacting ammonia with one or more halogenated organic silicon compounds to produce a cyclic silazane ammonolysis product and (2) reacting the ammonolysis product with from 0.1% to 30% by weight of an isocyanate, isothiocyanate, ketene, thioketene, carbodiimide, or carbon disulfide. Polysilazane addition polymers containing alkenyl or alkynyl groups can be cured by supplying energy to generate free radicals. The cured or uncured polymers can be pyrolyzed to produce silicon nitride-containing ceramic materials.

Abstract: Polysilazane addition polymers are prepared by (1) reacting ammonia with one or more halogenated organic silicon compounds to produce a cyclic silazane ammonolysis product and (2) reacting the ammonolysis product with from 0.1% to 30% by weight of an isocyanate, isothiocyanate, ketene, thioketene, carbodiimide, or carbon disulfide. Polysilazane addition polymers containing alkenyl or alkynyl groups can be cured by supplying energy to generate free radicals. The cured or uncured polymers can be pyrolyzed to produce silicon nitride-containing ceramic materials.

Abstract: A method of forming preceramic polymers using an organosilicon polymer containing Si--H repeat units by reacting it with alkali metal amide or silylamide is disclosed. Preferably, the silylamide is a polymeric silylamide formed by reacting in solution anhydrous ammonia with a mixture of R.sup.1 SiHX.sub.2 (where R.sup.1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms; and X is a halogen) and R.sup.2 SiX.sub.3 (where R.sup.

Abstract: A method for preparing preceramic polymers is disclosed. This method includes the steps of(1) reacting in solution anhydrous ammonia with a mixture of R.sup.1 SiHX.sub.2 (where R.sup.1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and X is a halogen) and RSiX.sub.