表面电荷积聚会导致局部电场畸变诱发闪络发生，造成绝缘失效和设备损坏。然而，目前针对这一问题的研究存在不足，尤其造成表面电荷积聚的根本原因，即深陷阱的成分仍不清楚，使得这一问题目前仍是制约绝缘材料在更高场强下安全稳定运行的瓶颈问题。因此，本文以几种常见的绝缘材料为切入点开展研究，如环氧树脂、聚四氟乙烯等。系统的对表面电荷积聚的微观机理及调控方式进行研究。本文首先基于表面改性和体相改性提出了多种抑制表面电荷积聚的材料改性方案。表面改性方面，本文通过自组装制备了各向异性的取向性氮化硼纳米片涂层，此外还研制了各向同性的电导非线性的涂层。在体改性方面，本文提出掺杂用表面接枝处理的SiO2纳米颗粒的方式来抑制表面电荷积聚，并发现通过掺杂微量金属纳米颗粒可抑制表面电荷积聚。通过开发和使用纳米尺度下表面电荷及陷阱参数的测量手段，发现环氧树脂等绝缘材料中自由基表现出深陷阱的特征。基于密度泛函理论计算，发现出现自由基后体系中出现了深能级缺陷态，且分子链中出现自由基的地方就会出现电荷局域。再分别通过微观和宏观的电荷测量手段，发现清除自由基后的环氧树脂等材料表面积聚的电荷量显著减少。即分别从理论计算和实验的角度验证了在环氧树脂等材料中自由基造成深陷阱的结论。在自由基造成深陷阱这一认识的基础上，本文提出直接调控深陷阱以抑制表面电荷积聚的思路及钝化深陷阱的概念，并发现RCl (R=Li, Na, K)和高能O2、O3及氧离子两种钝化自由基深陷阱的方法。通过实验结合理论计算分析了钝化深陷阱后的效果及微观机理。例如，通过实验发现高能O2、O3及氧离子处理后的材料表面电荷积聚减少，闪络电压和击穿强度都所有提升，且处理后长期稳定性良好。通过实验结合密度泛函理论计算，再次验证了自由基可造成深陷阱，发现该方法可以改善自由基造成的深陷阱所引发的电荷局域，并进一步分析了该方法可以钝化自由基深陷阱的物理机制。从轨道组成和杂化的角度发现其钝化自由基深陷阱的物理机制是将带隙深处的深能级缺陷态的杂化程度减弱，由能量较低的成键态变为能量更高的成键态，使得缺陷态能量变高并移至带隙之外。
The accumulation of surface charges can lead to local electric field distortion, inducing flashover, which causes insulation failure and equipment damage. However, current research on this issue is lacking, especially regarding the fundamental causes of surface charge accumulation, namely the components of deep traps are still unclear, making it a bottleneck issue that currently restricts the safe and stable operation of insulating materials under higher electric fields. Therefore, this article embarks on a study using several common insulating materials, such as epoxy resin and polytetrafluoroethylene, as starting points. The study systematically investigates the micro-mechanisms of surface charge accumulation and its control methods.This article first proposes various material modification schemes to suppress the accumulation of surface charges based on surface and bulk modification. In terms of surface modification, anisotropic oriented boron nitride nanosheet coatings were prepared through self-assembly. In addition, isotropic electrically conductive nonlinear coatings were developed. In terms of bulk modification, the approach of doping with surface-grafted SiO2 nanoparticles was proposed to inhibit the accumulation of surface charges. It was further discovered that doping with trace amounts of metal nanoparticles could suppress the accumulation of surface charges.Through developing and using methods to measure surface charge and trap parameters at the nanoscale, it was found that free radicals in insulating materials such as epoxy resin exhibit characteristics of deep traps. Based on density functional theory (DFT) calculations, it was discovered that deep-level defect states appear in the system after the formation of free radicals, and charge localization occurs at the sites of free radicals in the molecular chains. Then, by using both microscopic and macroscopic charge measurement methods, it was found that the amount of charge accumulated on the surfaces of materials such as epoxy resin significantly decreased after the clearance of free radicals. That is, the conclusion that free radicals cause deep traps in materials like epoxy resin was verified from both theoretical calculations and experimental perspectives. Based on the understanding that free radicals cause deep traps, this study proposes the concept of directly controlling deep traps to inhibit surface charge accumulation and passivating deep traps. It discovers methods of passivating free radical deep traps with RCl (R=Li, Na, K), high-energy O2, O3, and oxygen ions. The effects and microscopic mechanisms of passivating deep traps were analyzed through experiments combined with theoretical calculations. For example, it was found through experiments that the accumulation of surface charge on the materials treated with high-energy O2, O3, and oxygen ions decreased, flashover voltage and breakdown strength were improved, and the materials demonstrated good long-term stability after treatment. By combining experiments with DFT calculations, it was once again verified that free radicals could cause deep traps, and it was found that this method could improve charge localization caused by deep traps resulting from free radicals. Furthermore, the physical mechanism for passivating free radical deep traps was analyzed. From the perspective of orbital composition and hybridization, it was found that the physical mechanism of passivating free radical deep traps is to weaken the hybridization degree of deep-level defect states deep within the bandgap, transforming from a lower energy bonding state to a higher energy bonding state, thereby raising the energy of defect states and moving them out of the bandgap.
