The Effect of Amine Source on the Structure and Properties of Polyborosilazane Synthesized by"One Pot"Method
We used three different structures of disilazane,hexamethyldisilazane(MMN),tetramethyldivinyldisilazane(MMNVi)and tetramethyldisilazane(MMNH),as a source of amine,which then reacted with chlorosilanes and boron trichloride,to produce polyborosilazanes with different end-capped structures.Among the reactants,liquid state products were acquired when using MMN and MMNVi as the amine source.While gelatine products were acquired when using MMNH as the amine source,due to the excess crosslink of the active group during synthesis.We then used nuclear magnetic resonance spectrometer and infrared spectrometer to characterize the liquid precursor polymer and its pyrolysis products.The results showed that the liquid polyborosilazane backbone made by one pot method had more branches and cyclic structures.As the vinyl group in the end-capped structure increases,the curing temperature of the precursor dropped and the activation energy of the curing reaction lowered.When compared to the polyborosilazane which is made by using MMN and the capping agent,the ceramic production rate increased by 14.9％and 8.1％when MMNVi made precursor curation occurred.Furthermore,SiBCN ceramic,made by pyrolysis of the synthetic precursor polymers,has a crystallization temperature higher than 1700 ℃.This conclusion is reached by adjusting the element composition through changing the amine source type and ratio.
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