高击穿场强有机包覆纳米粒子/聚丙烯复合电介质的制备与击穿机理

Research on polymer nanocomposite dielectrics with high electrical strength is attached great importance to the development of pulsed power technology. The key issues to develop nanocomposites with high electrical strength are controlling the bond strength between nanoparticles and polymer matrix as well as interfacial zone properties, and revealing the influence mechanism of interfacial zone on macroscopic dielectric properties. The present project will adopt chemical methods such as grafting-from method to form organic coating on inorganic nanoparticles. We will try to improve the compatibility and bond strength between nanoparticles and polypropylene matrix by altering the thickness of organic coating and the types of macromolecule. Then, polypropylene nanocomposites with uniform dispersion of nanoparticles can be obtained. Afterwards, energy dissipation spectra of atomic force microscope and complex conductivity spectra in Terahertz band are introduced to analyze the scattering effect of charge carriers and the trapping effect of defect traps in interfacial zones of nanocomposite. We will investigate the relation between the energy accumulation and dissipation of charge carriers and electrical breakdown. Accordingly, the influence mechanism of the scattering effect of charge carriers and the trapping effect of defect traps on electrical breakdown of nanocomposite can be depicted. Then, considering the impact of nanoparticle modification method on scattering centers and defect traps in interfacial zones, we can find the relation between nanoparticle surface modification method and electrical breakdown property. Therefore, we can obtain the method to enhance electrical strength and capacity density of polypropylene nanocomposite via selecting appropriate grafting macromolecule and grafting density. This research provides theoretical and practical support for the development of pulsed power equipment.

高击穿场强纳米复合电介质的研究对于脉冲功率技术的发展具有重要科学意义。调控纳米粒子/聚合物基体的键合强度与界面区特性，及揭示界面区对宏观介电特性的影响机制是开发高击穿场强纳米复合电介质的关键。本项目通过主链接枝法对纳米粒子进行有机包覆，改变接枝高分子类型和包覆厚度来改善纳米粒子与聚丙烯基体的相容性和键合强度，获得分散均匀的纳米复合电介质。采用原子力显微镜能量耗散谱和太赫兹频段复电导谱分析纳米复合电介质界面区载流子散射和界面缺陷陷阱捕获特性，探究纳米复合电介质内部载流子能量积累与耗散对击穿的作用机制，揭示界面区载流子散射和界面缺陷陷阱捕获对纳米复合电介质击穿性能的影响机理。结合纳米粒子表面改性方法对散射中心和界面缺陷陷阱的影响，建立表面改性方法与击穿性能的联系，获得通过合适的有机包覆方法提升聚丙烯纳米复合电介质击穿场强和储能密度的方法。为脉冲功率技术的发展提供理论和实验支撑。

脉冲功率技术广泛应用于激光武器、强脉冲X射线、高功率微波技术、Z箍缩等国防领域。脉冲电容器是脉冲功率系统中主要储能器件，发展脉冲功率技术对脉冲电容器储能密度提出了更高的要求。如何提升脉冲电容器薄膜电介质的击穿和储能性能是亟需解决的关键科学问题。本项目以聚丙烯纳米复合电介质为研究对象，研究了无机纳米填料原位聚合包覆方法和纳米复合电介质的制备方法，获得了分散均匀的聚丙烯纳米复合电介质。实验研究了不同表面改性纳米填料掺杂及不同掺杂浓度纳米复合电介质的极化、电导、击穿及储能性能，获得了击穿和储能性能优异的纳米复合电介质。仿真结合实验研究了复合电介质界面区极化和电导介观分布特性，揭示了聚丙烯纳米复合电介质的击穿机理。提出了聚合物纳米复合电介质的有序紧密凝聚低构象熵界面区模型，建立了界面区分子链运动特性和凝聚态结构与电荷输运和击穿性能的关联。建立了将不同掺杂试样以及界面区和基体作为整体、系统研究陷阱分布特性及其对电气绝缘性能影响机理的新方法。揭示了界面区深陷阱起源于分子链受束缚的新机制。提出了界面区极化和电导介观分布特性的高通量仿真结合实验的定量研究方法。开发了广义泊松方程的稳定高效高精度有限体积快速傅里叶变换迭代等计算方法，实现了十五个数量级电导率对比度的纳米复合电介质的电场稳定高精度高效数值求解。仿真分析了界面区的极化和电导介观分布特性，发现界面区强极化效应增强了载流子的散射，界面区的深陷阱增强了对载流子的捕获作用，界面区的强分子链相互作用降低了动态自由体积的扩张。建立了载流子输运与能量积累调制击穿模型，仿真计算了聚丙烯纳米复合电介质的击穿概率分布特性，揭示了纳米复合电介质击穿强度提升的界面区陷阱强捕获与分子链紧束缚协同作用新机理。界面区的散射效应、捕获效应、分子链束缚作用共同降低了载流子积累的能量，提升了聚丙烯纳米复合电介质的击穿强度。为脉冲功率技术的发展提供了理论和实验支撑。