【作者】 陈明华；

【导师】 殷景华；

【作者基本信息】 哈尔滨理工大学 ， 材料学， 2013， 博士

【摘要】 聚合物基新型纳米电介质材料因其优异的电气性能、热学性能和机械性能而广泛应用于电气绝缘、变频电机、集成电路、燃料电池和医疗卫生等领域，此类新型材料的设计与研制已成为材料科学研究的热点问题。本文利用成分、结构和电气绝缘性能与云母类似的层状MMT (蒙脱土)和球状AlN (氮化铝)纳米颗粒掺杂聚酰亚胺(PI)基体，制备具有较高耐电晕性能的纳米电介质材料。采用原位聚合法制备了不同组分单层、三层PI/AlN和PI/MMT+AlN四种类型聚酰亚胺基纳米复合薄膜。利用扫描电镜、透射电镜、X射线衍射、同步辐射小角X射线散射等方法研究复合薄膜微观结构。研究结果表明，AlN或MMT+AlN颗粒镶嵌在PI基体中，三层薄膜各层厚度均匀，层与层之间排列紧密。四种类型薄膜都存在相界面层，随着组分增加，相界面层厚度增加；三相纳米复合薄膜呈现多尺度的结构特征；PI/AlN单层与三层薄膜具有双分形特征，PI/MMT+AlN单层与三层薄膜存在三重分形特征。采用耐电晕测试方法研究不同结构复合薄膜电晕特性，结果表明，与单层PI/MMT+AlN薄膜相比，三层薄膜具有优异的耐电晕性能；组分为15wt%的薄膜耐电晕时间为242小时，是纯聚酰亚胺薄膜的80倍；单层薄膜的击穿场强普遍高于同组分的三层薄膜的击穿场强。利用小角X射线散射、X射线衍射、原子力显微镜、扫描电镜等测试手段，以准动态的方式研究不同电晕时间后薄膜微观结构演化；研究结果表明，随着电晕时间的增加，薄膜表面逐渐出现团簇现象，无机纳米颗粒聚集在薄膜表面，团簇数量增多，尺寸变大，形成有效放电阻挡层；同时，电晕老化引起聚合物高分子链结构变化，随着电晕时间的增加，聚合物高分子链间平均距离增加，电晕老化侵蚀改变了高分子链的柔顺性，导致聚合物分子链结构破坏并重新排列；随电晕时间的增加，薄膜界面层厚度增加，其中PI/MMT+AlN三相三层薄膜界面层厚度最大，层状MMT与球状AlN协同作用显著提高复合薄膜耐电晕性能。在分析大量实验结果基础上，提出了纳米颗粒、聚合物基体、界面层三者关系模型，阐明界面作用及电晕过程中微观结构演化机制，随电晕时间增加，纳米颗粒对高分子链的锚定作用减弱，内层（束缚层）厚度变小；高分子链之间平均距离变大，外层（过渡层）厚度增加，束缚层与过渡层厚度比例的变化，削弱放电阻挡层的作用，导致材料破坏。颗粒、基体、界面三者关系模型为深入研究纳米电介质耐电晕机理提供了新思路。更多还原

【Abstract】 Novel polymer matrix nanometer dielectric materials have been widely employedfor various contemporary applications such as insulation material, frequencyconversion motor, integrated circuit, fuel cells, and medical health for theiroutstanding electrical properties, thermal properties and mechanical properties. Designand development a kind of new materials have become a hot issue in the study ofmaterial science. The nanodielectric materials doping layered MMT (Montmorillonite)and spherical AlN (aluminum nitride) which have higher corona resistanceperformance have been prepared. MMT has similar composition, structure andelectrical insulating properties as mica, and spherical AlN (aluminum nitride) has highthermal conductivity characteristics. The mixture of MMT and AlN can generatecertain cooperative effect and improve the comprehensive electrical properties of PImatrix.Four types of composite films were prepared by in-situ method. The relationshipbetween material microstructure and macroscopic properties has been researched byusing scanning electron microscopy(SEM), transmission electron microscopy (TEM),small-angle X-ray scattering(SAXS), the corona resistant test. The experimentalresults showed that the four types of films have phase interfacial layer, the thickness ofthe interfacial layer increase with the components increase. The three-phasenano-composite film has multi-scale structural characteristics. The PI/AlN films havedual fractal characteristics, and the PI/MMT+AlN films had trebling fractalcharacteristics.The three-layer films have excellent corona resistance performance. The coronaresistance time of PI/MMT+AlN films with15%content is242hours, which is80times than that of the pure polyimide film. The breakdown strength of monolayer filmis generally higher than that of the three-layer films which have the same components.Microstructure evolution in the corona-progress has been studied using dynamictesting methods, such as SAXS, SEM AFM and XRD. The results show that theroughness of the surface changes and a large number of nano-particles gather in theprogress of corona with the corona aging increases. Meanwhile, the number of clustersincreases, and the effective blocking layer increases. Besides, the average distancesbetween the chains of the polymer increases, the flexibility of the chain changesbecause of the corona, the structural damagement and rearrangement of the polymermolecular chain occur. Furthermore, the chain transform from winding and spiral typeinto a linear type or transformed from regular coil gradually into ordered structure inthis condition. The thickness of the interfacial layer increase as the corona time increases, and PI/MMT+AlN films have the thicker interfacial layer. With the increaseof the corona aging time, more effective interfacial structures are caused by thecooperative effect of layered MMT and spherical AIN, which improve the coronaresistance performance of the composite films.The model based on the nano-particles, the polymer matrix and the interfaciallayer was established, interfacial effect and the evolutive mechanism of themicrostructure in the corona process was clarified, the evolutive rule of the interfacesis promoted. Compared with the increase of corona aging time, the anchoring effectbetween nanoparticles and the polymer chain reduces, the thickness of inner layer(bound layer) becomes thinner, the average distance between the polymer chainbecomes longer, the thickness of the outer layer (soil layer) becomes thicker. The ratioof layer thickness between bound layer and soil layer, leading to the effect ofdischarge blocking layer weaken, and the material damaged. The established modelprovides a new thought of corona resistance mechanism for nanodielectrics.更多还原