LDPE基GNPs纳米电介质的陷阱特性和电导特性研究

发布时间：2018-07-14 07:16

【摘要】：聚合物基纳米复合电介质具有优异的绝缘性能,其作为第三代绝缘材料一直是电气绝缘领域的研究热点。现有研究表明陷阱对电介质材料的电导、空间电荷和击穿等特性都具有较大的影响。研究聚合物基纳米电介质的陷阱特性以及陷阱特性对材料的电性能的影响,有助于加速聚合物基纳米电介质的工业化进程。本论文选择在电线电缆工业中被经常使用的低密度聚乙烯(LDPE)作为基体材料,研究了填充石墨烯纳米微片(GNPs)对LDPE的陷阱特性和电导特性的影响,并将实验和理论计算相结合,从宏观和微观两种角度探究了GNPs改善LDPE材料电性能的机理。利用混炼机制备了不同片径尺寸,不同填充量的GNPs/LDPE纳米电介质。扫描电子显微镜(SEM)的观测结果表明,GNPs在LDPE基体中分散较为均匀。XRD测试结果表明,填充GNPs提高了LDPE的结晶度。热刺激退极化电流(TSDC)测试结果表明,GNPs掺杂使得LDPE中原有陷阱机制的陷阱能级密度增大,并引入了新的陷阱机制。光激放电(PSD)的测试结果显示,在纯LDPE出现光激放电峰的波长范围内,GNPs/LDPE依然存在着光激放电峰,并且在更小的波长范围内出现了一个新的放电峰。电导电流试验结果显示GNPs可以有效降低LDPE的电导率,这与GNPs增大了LDPE的陷阱密度有关。利用理论化学计算软件,将密度泛函(DFT)理论和非平衡格林(NEGF)公式相结合,计算了复合介质模型的电子结构和传输谱。该计算结果从实空间和希尔伯特空间双重角度证明了GNPs在LDPE中能够起到电荷陷阱的作用,其陷阱效力与GNPs的片径尺寸有关,片径越小的GNPs的陷阱作用越明显。理论计算结果与实验结果相一致,因此,小尺寸的GNPs确实可以有效地提高聚合物基纳米电介质材料的绝缘性能,可以作为一种开发新型直流电缆用绝缘材料的有效策略。
[Abstract]:Polymer-based nano-composite dielectrics have excellent insulation properties. As the third generation of insulating materials, polymer-based nanocomposite dielectric has been a hot spot in the field of electrical insulation. It has been shown that traps have great influence on the conductivity, space charge and breakdown of dielectric materials. The study of the trap characteristics of polymer based nanocrystalline dielectrics and the influence of trap characteristics on the electrical properties of the materials are helpful to accelerate the industrialization process of polymer based nano dielectric materials. In this paper, low density polyethylene (LDPE), which is often used in wire and cable industry, is used as matrix material to study the effect of graphene filled nanocrystalline (GNPs) on the trap and conductance properties of LDPE, and to combine the experiment with theoretical calculation. The mechanism of improving the electrical properties of LDPE materials by GNPs was studied from macro and micro perspectives. GNPs / LDPE nanocrystalline dielectrics with different diameters and different filling amounts were prepared by a mixer. Scanning electron microscopy (SEM) showed that GNPs dispersed uniformly in LDPE matrix. XRD results showed that filling GNPs increased the crystallinity of LDPE. The results of thermally stimulated depolarization current (TSDC) measurements show that doping with GNPs increases the trap level density of the original trap mechanism in LDPE and introduces a new trap mechanism. The results of photodischarge (PSD) show that there is still a photodischarge peak in GNPs / LDPE, and a new discharge peak appears in a smaller wavelength range. The conductivity test results show that GNPs can effectively reduce the conductivity of LDPE, which is related to the increase of trap density of LDPE. The density functional (DFT) theory and the nonequilibrium Green's (NEGF) formula are combined to calculate the electronic structure and transmission spectrum of the composite medium model by using the theoretical chemical calculation software. The results show that GNPs can act as charge traps in LDPE from the view of real space and Hilbert space. The trapping effect of GNPs is related to the size of GNPs. The smaller the size of GNPs, the more obvious the trap effect of GNPs. The theoretical results are in agreement with the experimental results. Therefore, the small size GNPs can effectively improve the insulation properties of polymer-based nanocrystalline dielectric materials, and can be used as an effective strategy to develop new insulating materials for DC cables.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM21

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