Preparation method of polycarbosilane ceramic precursor material

Abstract

The invention discloses a preparation method of a polycarbosilane ceramic precursor material. The method comprises the following steps: putting polydimethylsilane into a high-pressure synthesis kettle, repeatedly vacuumizing, replacing gas in the kettle with high-purity nitrogen, introducing nitrogen, controlling the temperature, cracking polycarbosilane under normal pressure, adding nitrogen to maintain the pressure, continuing heating to react, controlling a certain pressure, and cooling to obtain a polycarbosilane crude product; grinding and screening the polycarbosilane crude product to form polycarbosilane powder; soaking the screened polycarbosilane powder with absolute ethyl alcohol, fully stirring and filtering to collect polycarbosilane insoluble in the absolute ethyl alcohol; dissolving polycarbosilane which is insoluble in n-propanol by using xylene, introducing nitrogen during reaction, and fully stirring to obtain a mixed solution; heating the mixed solution under the protection of nitrogen, and cooling to obtain a polycarbosilane finished product of which the softening point is 200-210 DEG C, the high molecular weight part is 8-12% and the medium molecular weight partis more than 70%.

Description

technical field [0001] The invention relates to the technical field of ceramic precursor materials, in particular to a method for preparing a polycarbosilane ceramic precursor material. Background technique [0002] Polycarbosilane (PCS) is the key raw material for 3D printing of silicon carbide fibers and silicon carbide components. Melt spinning of silicon carbide fibers and 3D printing of silicon carbide components have high requirements on the molecular weight distribution and softening point of PCS. The increase of PCS softening point is basically linear with the increase of polymer content. With the increase of polymer content, the softening point of PCS increases, which is mainly due to the increase of PCS molecular weight due to the condensation between molecules. Since the PCS molecules are in the shape of oblate spheroids, the condensation between molecules will inevitably lead to the increase of branched and cross-linked structures in the molecules, resulting in t...

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Problems solved by technology

[0011] To sum up: Manufacture polycarbosilane according to the usual synthesis process to control the reaction temperature and holding time, it is difficult to ensure that the content of the middle molecular part (molecular weight 650 ~ 7000) in polycarbosilane > 70%, and the content of high molecular part (molecular weight greater than 7000) in polycarbosilane 8%~12%

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