METHOD FOR PRODUCING POLYSILANE-POLYCARBOSILANE HAVING REDUCED CARBON CONTENT AND FIBERS PRODUCED THEREFROM

摘要

The invention relates to a method for producing a polysilane-polycarbosilane copolymer solution from which a ceramic material having a ratio of silicon to carbon in the range of 0.8:1.0 to 1.1:1.0 can be obtained after removal of the solvent and pyrolysis, comprising the following steps: generating a chloric raw polysilane/oligosilane containing hydrocarbon groups by means of disproportioning a methylchlorodisilane or a mixture of a plurality of methylchlorodisilanes of the composition Si2MenCl6-n, where n = 1-4, wherein the disproportioning takes place by means of a Lewis base as a catalyst, thermally post-cross-linking the raw polysilane/oligosilane into a non-melting polysilane-polycarbosilane copolymer that is soluble in a neutral solvent, and producing said solution by means of dissolving the polysilane-polycarbosilane in a neutral solvent. The invention is characterized in that additional elementary silicon or titanium disilicide is added in one step of said method in a suitable quantity as a powder or in the form of a compound comprising alkyl groups bonded to silicon or to nitrogen, wherein said additive either (a) takes place in that the raw polysilane/oligosilane is generated in the presence of a cross-linking agent, selected from compounds of the formula CI2R1Si-R2, having a boiling point above 100°C and where R1 means chlorine, hydrogen, or an alkyl radical having 1 to 4 carbon atoms, and R2 is -SiR3 3, -NH-SiR3 3 or -N(SiR3 3)2, where -R3 has the same meaning as R1, or (b) takes place in that powdered silicon or titanium silicide is added to the polysilane-polycarbosilane solution. Green fibers or material in other forms can be produced from the copolymer solution, and can in turn be converted into ceramic silicon carbide materials. Said material can also be used for constructing ceramic matrices.