【作者】 张磊；

【导师】 李家俊；

【作者基本信息】 天津大学 ， 材料工程， 2012， 硕士

【摘要】 聚酰亚胺（PI）是一种重要的耐高温功能高分子材料,将多壁碳纳米管/铁氧体复合粉末与聚酰亚胺复合制备复合材料,对研制轻,薄,宽,强的耐高温吸波材料具有重要意义。本文采用氩等离子体修饰多壁碳纳米管,利用傅里叶红外,X光电子能谱仪,X射线衍射及拉曼光谱仪对修饰过的多壁碳纳米管（L-MWNTs）进行形貌及物相分析,并且解释了等离子体与碳管之间相互作用过程。采用化学共沉淀法制备了L-MWNTs/Co_0.5Ni_0.5Fe₂O₄复合粉末,利用透射电镜观察了铁氧体纳米颗粒在L-MWNTs上的分布,通过X射线衍射对铁氧体物相进行分析。采用溶胶—凝胶法制备了L-MWNTs/Co_0.5Ni_0.5Fe₂O₄/PI复合吸波材料,并对不同L-MWNTs含量的复合材料吸波性能进行了对比研究,利用扫描电镜观察了L-MWNTs在复合材料中分散性,利用透射电镜观察了碳管聚合前后的形貌变化,及对复合材料力学性能和热性能进行了表征分析。结果表明,在放电电压50V,放电电流0.3A,放电时间10min的处理条件下,经过氩等离子体修饰的多壁碳纳米管,其表面基团比例发生了改变,-COOH含量增多,提高其与聚酰亚胺的结合性。对比L-MWNTs/Co_0.5Ni_0.5Fe₂O₄/PI复合材料吸波性能发现,随L-MWNTs含量的增多,复合材料最大衰减增加,当L-MWNTs含量增加到0.75wt%时,最大衰减达到了-24.37dB,且衰减大于10dB的有效带宽变宽为5GHz,直到L-MWNTs含量增加到1 wt%时,有效带宽变窄,但是有向高频移动的趋势。复合材料的抗拉强度随L-MWNTs含量的增加而增加,当L-MWNTs含量增加到0.75wt%时,其抗拉强度达到了105MPa。同时,随L-MWMTs含量的增加,复合材料的玻璃化转变温度降低,但降低幅度较小,维持在260℃以上;相比于纯PI,复合材料的热分解温度有所降低,但也在500℃才开始分解。更多还原

【Abstract】 Polyimide （PI） functions as an important high temperature polymer materials. It is important to develop polyimide matrix composites combining carbon nanotubes/ferrite composite powder for meeting the demand of light, thin, wide, strong for microwave absorbing materials served at high temperatures.In this thesis, multiwalled carbon nanotubes （MWNTs） were surface-modified by Ar plasma. The morphologies and structure of plasma modified MWNTs （denoted as L-MWNTs） were characterized by Fourier transform infrared spectroscopy （FT-IR）,X-photoelectron spectrometer （XPS）, X-ray diffraction （XRD） and Raman spectroscopy. The reaction between the Ar plasma and the MWNTs was illustrated. L-MWNTs/Co_0.5Ni_0.5Fe₂O₄ composite powder was obtained via chemical coprecipitation, the distribution and phase of ferrite nano particles on the surface of L-MWNTs were investigated by transmission electron microscope （TEM） and XRD. L-MWNTs/Co_0.5Ni_0.5Fe₂O₄/PI composites were prepared by Sol-Gel method in different contents and the absorbing properties were compared. Dispersity and morphology of L-MWNTs in the composites was characterized by scanning electron microscope （SEM） and TEM. The thermal and mechanical properties of the obtained nancomposites were also investigated.The results show that the proportions of functional groups on L-MWNTs have changed after Ar plasma treatment, which was carried out at 50 V with a current of 0.3 A, lasted for 10 min. Increase of carboxyl group is help to improve interfacial bonding between the MWNTs and PI matrix. Meanwhile, the reflection loss （RL） of the nanocomposites increases with the content of L-MWNTs increasing. When the content of L-MWNTs increased to 0.75 wt%, the reflection loss value of L-MWNTs/Co_0.5Ni_0.5Fe₂O₄/PI nanocomposites increases to -24.37 dB, the frequency range of RL value （dB） less than -10 dB is 5 GHz. When the content of L-MWNTs is 1 wt%, the reflection loss value of nanocomposites drops to -12.23 dB, and moves to high frequency range. It is obvious that tensile strength of nanocomposite increases with the content of L-MWNTs increasing from 0.25 wt% to 0.75 wt%, and when the content of L-MWNTs increases to 0.75 wt%, the tensile strength reaches 105 MPa. Besides, the results show that the glass transition temperature of nanocomposites was 261℃,and the thermostability is preserved at 500℃.更多还原