LDPE基GNPs納米電介質(zhì)的陷阱特性和電導特性研究
發(fā)布時間：2018-07-14 07:16
【摘要】：聚合物基納米復合電介質(zhì)具有優(yōu)異的絕緣性能,其作為第三代絕緣材料一直是電氣絕緣領(lǐng)域的研究熱點�，F(xiàn)有研究表明陷阱對電介質(zhì)材料的電導、空間電荷和擊穿等特性都具有較大的影響。研究聚合物基納米電介質(zhì)的陷阱特性以及陷阱特性對材料的電性能的影響,有助于加速聚合物基納米電介質(zhì)的工業(yè)化進程。本論文選擇在電線電纜工業(yè)中被經(jīng)常使用的低密度聚乙烯(LDPE)作為基體材料,研究了填充石墨烯納米微片(GNPs)對LDPE的陷阱特性和電導特性的影響,并將實驗和理論計算相結(jié)合,從宏觀和微觀兩種角度探究了GNPs改善LDPE材料電性能的機理。利用混煉機制備了不同片徑尺寸,不同填充量的GNPs/LDPE納米電介質(zhì)。掃描電子顯微鏡(SEM)的觀測結(jié)果表明,GNPs在LDPE基體中分散較為均勻。XRD測試結(jié)果表明,填充GNPs提高了LDPE的結(jié)晶度。熱刺激退極化電流(TSDC)測試結(jié)果表明,GNPs摻雜使得LDPE中原有陷阱機制的陷阱能級密度增大,并引入了新的陷阱機制。光激放電(PSD)的測試結(jié)果顯示,在純LDPE出現(xiàn)光激放電峰的波長范圍內(nèi),GNPs/LDPE依然存在著光激放電峰,并且在更小的波長范圍內(nèi)出現(xiàn)了一個新的放電峰。電導電流試驗結(jié)果顯示GNPs可以有效降低LDPE的電導率,這與GNPs增大了LDPE的陷阱密度有關(guān)。利用理論化學計算軟件,將密度泛函(DFT)理論和非平衡格林(NEGF)公式相結(jié)合,計算了復合介質(zhì)模型的電子結(jié)構(gòu)和傳輸譜。該計算結(jié)果從實空間和希爾伯特空間雙重角度證明了GNPs在LDPE中能夠起到電荷陷阱的作用,其陷阱效力與GNPs的片徑尺寸有關(guān),片徑越小的GNPs的陷阱作用越明顯。理論計算結(jié)果與實驗結(jié)果相一致,因此,小尺寸的GNPs確實可以有效地提高聚合物基納米電介質(zhì)材料的絕緣性能,可以作為一種開發(fā)新型直流電纜用絕緣材料的有效策略。
[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.
【學位授予單位】：哈爾濱理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM21
[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.
【學位授予單位】：哈爾濱理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM21
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