Method for preparing SiBCN-containing thermally-polymerisable ceramic precursor

Abstract

The invention relates to a method for preparing a SiBCN-containing thermally-polymerisable ceramic precursor. The method comprises the steps of enabling vinyl dichlorosilane and hexamethyldisilazane, which are in a certain ratio, to react at a certain temperature, adding a certain amount of NaBH4 reducer into the reaction product for reduction after reaction is complete, then, adding dimethyl vinyl chlorosilane into the reduced reaction product to continue reaction, heating up the reaction product to distill off a solvent and some unreacted raw material molecules, finally, adding a solvent n-hexane into the reaction product to wash the reaction product, thereby obtaining a colorless viscous liquid product, i.e., the soluble and fusible SiBCN ceramic precursor. According to the synthesis method, the operation is simple and convenient, experimental conditions are easily controlled, experimental steps are reduced, the cost is low, the prepared SiBCN ceramic precursor is soluble and fusible, has good processability, is good in fluidity and can be subjected to thermal polymerization directly, the yield of the prepared product can reach 60% the input amount of chlorosilane, and the yield of sintered ceramics can reach 64%.

Description

technical field [0001] The invention belongs to a preparation method of a ceramic precursor, in particular to a preparation method of a thermally polymerizable ceramic precursor containing SiBCN, in which boron element is introduced in the preparation process, and the obtained ceramic precursor is soluble and fusible, and the experimental conditions are easy Control, good processability, can be directly heat-cured. Background technique [0002] The performance of ceramic materials is affected by the structure and properties of ceramic precursors, and different ceramic materials have very different requirements for precursors. Regarding how to choose ceramic precursors, Seyferth et al. proposed the following principles: (1) Monomer The raw materials are easy to obtain and the price is low; (2) the synthesis process is simple and the yield is high; (3) the polymer is liquid or soluble and meltable solid; (4) the polymer can exist stably at room temperature and does not interac...

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Problems solved by technology

[0003] However, it can be seen from the retrieved literature that many SiBCN ceramic precursors have some shortcomings in the preparation and obtained products: (1) The introduction of boron is through BH 3 ·S(CH 3 ) 2 , and the unreacted borane is difficult to remove, borane is very easy to spontaneously ignite in the air, so if there is unreacted borane in the final product, it is very dangerous; by adding BCl 3 Introduction of boron element, BCl 3 It is a gas at normal temperature and needs to be reacted at a lower temperature. The reaction conditions are harsh and the steps are complicated; (2) the NH produced by the ammonolysis reaction in the preparation process 4 Cl is difficult to remove; (3) the synthesized ceramic precursor contains oxygen, which greatly reduces the ceramic yield after sintering; (4) the prepared ceramic precursor SiBCN is insoluble in many solvents, which limits the processing performance of ceramic materials

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