界面可控纳米电介质空间电荷长期演化规律研究

Nanodielectrics is a significant basic insulation material, which has a broad application prospect in the fields of high voltage DC power cables, ultra-high voltage transmission and transformation equipments, and energy storage system. Currently, it is critically difficult to solve the agglomeration problem in the polymer-based nanodielectrics, which leads to the extreme limit of the specific surface area. Moreover, the introduction of polar groups, functionalizing the interfacial regions between nanoparticle (NP) and polymer matrix, brings in new challenges to well disperse NPs, which hits a real bottleneck of theories and technologies and greatly restricts the performance and application of nanodielectric materials. Injection and accumulation of space charge are the major causes of reliability problems of insulating materials in plastic DC power cables. The aim of the present project is to investigate the long-term behavior evolution of space charge in crosslinked polyethylene (XLPE) nanocomposites. The regulation mechanisms and methods of composition and structure of interfacial regions, the solution to the agglomeration problem of functionalized NPs based on the mixed bimodal grafting strategy, the distribution and formation mechanism of traps in the interfacial regions, and the short-term insulation performances were explored. Then, the correlation between the interfacial regions and the long-term evolution mechanism of space charge was established. Based on the above results, the composition and structure of the interfacial regions were further optimized in order to realize the development of high-performance XLPE nanocomposites. The investigation of the project can provide new insight on the design and regulation of interfacial regions of nanodielectrics in both basic and applied aspects.

纳米电介质是重要的基础绝缘材料，在高压直流电缆、特高压输变电设备和储能系统等领域具有广阔应用前景。目前，聚合物基纳米电介质难以解决纳米团聚问题，比表面积受到极大限制，而纳米粒子/聚合物基体界面的功能化所引入的极性基团与纳米粒子分散性间的矛盾，面临现实的理论及技术瓶颈，极大地限制了纳米电介质材料的性能和应用研究。空间电荷的注入和积聚是引起塑料直流电缆绝缘可靠性问题的主因，本课题拟以纳米复合交联聚乙烯材料的空间电荷长期演化为研究目标，通过研究界面组成结构的调控原理和方法、混合双峰接枝策略解决功能化纳米粒子团聚问题、界面陷阱分布及形成机制，以及短时绝缘性能，最终建立界面组成结构与空间电荷长期演化机制间的关联。在此基础上，优化界面的组成结构，实现高性能纳米复合交联聚乙烯材料的开发。课题研究有望在基础以及应用方面为纳米电介质界面的设计和调控提供新思路。

直流电缆已成为高压直流输电系统的关键组成，越来越多的高压直流电缆输电工程相继建成并投运。然而，实际运行中直流电缆面临着多物理场下空间电荷和电导问题，制约电缆有效载荷的提高，影响电缆的运行可靠性。本课题针对界面可控纳米复合交联聚乙烯（XLPE），并综合了化工、材料、高压测试等学科技术，围绕着交联聚乙烯空间电荷的抑制及其长期特性开展研究，并对基础电学性能、陷阱特性开展了测试，形成了直流电场下空间电荷抑制技术。研究成果为直流电缆绝缘料的研发和评价提供了重要参考。. 为制备界面可控纳米复合XLPE，基于可逆加成-断裂转移自由基聚合法（RAFT）对纳米粒子进行了表面接枝改性。选取了与聚乙烯具有相似结构的甲基丙烯酸十八烷基酯（SMA）合成表面接枝的聚合物刷，并实现了聚合物刷接枝密度和分子量的定量调控。提出了多峰混合接枝策略，实现了聚合物刷与电活性小分子功能基团的共同接枝。. 对纳米添加2 wt%的纳米复合XLPE材料进行了理化性能表征和显微结构观测，给出了纳米分散效果最好的优选接枝参数（0.04 ch/nm2和45 kg/mol）。研究了多峰混合接枝纳米复合XLPE试样空间电荷的1000 h长期演化特性，发现在-30 kV/mm下内部电场畸变率不超过20%。.针对界面可控纳米复合XLPE绝缘性能，开展了直流电导、直流击穿和短时空间电荷特性测试。发现了优选参数组别直流电导稳态最小，直流击穿强度较纯XLPE提高35%，且完全抑制短时强电场下（-100 kV/mm）空间电荷的注入和积聚。. 本课题来源于实际直流电缆绝缘所面临的空间电荷问题，采用了多学科交叉手段开展高性能纳米复合XLPE的研发，获得了空间电荷抑制效果良好的制样工艺参数，为有效抑制空间电荷的纳米复合技术提供了新思路。