高锆含量改性聚硼硅氮烷的合成与表征

Synthesis and characterization of high zirconium content modified polyborosilazane

摘要:

本文通过Cp₂Zr(CH₂CH=CH₂)₂与液态聚硼硅氮烷(LPBSZ)在过氧化二异丙苯的作用下发生自由基共聚反应,制备了锆含量大于10wt%的含锆聚硼硅氮烷(PZC-PBSZ)。采用红外光谱、核磁共振、光电子能谱等方法研究了PZC-PBSZ的分子结构及合成机理。结果表明在先驱体的合成过程中,Cp₂Zr(CH₂CH=CH₂)₂除了自身发生自由基聚合反应外,还会与LPBSZ中的Si-H发生硅氢加成和取代反应,生成Zr-C和Zr-Si。通过TG-MS和₂₉Si MAS NMR分析表明,PZC-PBSZ先驱体中Cp、(CH₃)₃Si和(CH₃)₂SiH等官能团的脱除主要发生在400~800℃。当温度升高到800~1200℃后,先驱体基本无机化,主要发生SiHN₂C和SiN₃C结构向SiN₄结构的转变。PZC-PBSZ经1000℃以上高温热解后可以转化为ZrC纳米颗粒分布均匀在SiBNC基体的ZrC/SiBNC纳米复相陶瓷。经1800℃高温处理后,ZrC/SiBNC陶瓷仍保持均匀和晶粒细化的纳米晶结构。

Abstract:

In this work, Zr-modified polyborosilazanes (PZC-PBSZ) with a high zirconium content over 10wt% were synthesized via radical reaction between Cp₂Zr(CH₂CH=CH₂)₂ and liquid polyborosilazane under the existence of dicumyl peroxide. The structure and reaction mechanism of PZC-PBSZ were studied using Fourier transforminfrared spectra, nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results shown that besides the self-polymerization, Cp₂Zr(CH₂CH=CH₂)₂ can also reacted with Si-H in LPBSZ via hydrosilylation reaction and substitution reaction to form Zr-C and Zr-Si, respectively. The thermogravimetric-mass spectrometry and ₂₉Si MAS NMR results shown that the escape of goups such as Cp, (CH₃)₃Si and (CH₃)₂SiH was ooccured at temperature range from 400 _oC to 800 _oC. As the temperature went up to 800~1200_oC, the polymer PZC-PBSZ converted into inorganic mineral, and the evolution of SiHN₂C and SiN₃C structure to SiN₄ structure was occurred at that temperature. After pyrolyzing at above 1000 _oC, PZC-PBSZ can convert into ZrC/SiBNC ceramic nanocomposites, with ZrC nanoparticles finely dispersed in SiBNC matrix. The obtained ZrC/SiBNC ceramic nanocomposites can remain fine and nanocrystalline microstructure after annealing at 1800 _oC.