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1.
环氧纳米复合电介质具有抑制空间电荷积聚、高电阻率、高击穿强度等优异性能,对直流电力设备的发展具有重要的作用.但纳米粒子含量对纳米复合电介质陷阱、电导率和空间电荷的影响机理尚不清楚.本文在纳米复合电介质交互区结构模型的基础上提出了计算交互区浅陷阱和深陷阱密度的方法,得到了浅陷阱和深陷阱密度随纳米粒子含量的变化关系.随着纳米粒子含量的增加,浅陷阱密度逐渐增大,深陷阱先增加然后由于交互区重叠的影响而逐渐减少.研究了纳米粒子含量对浅陷阱控制载流子迁移率的影响,发现随着纳米粒子的增多,浅陷阱大幅增多,浅陷阱之间的平均间距迅速减小,导致载流子更容易在浅陷阱间跳跃迁移,浅陷阱控制载流子迁移率增大.建立了纳米复合电介质的电荷输运模型,采用电荷输运模型计算研究了环氧/二氧化钛纳米复合电介质的空间电荷分布、电场分布和电导率特性.发现在纳米粒子添加量较小时,交互区的深陷阱对电导的影响起主导作用;纳米粒子添加量进一步增加,浅陷阱对电导的影响将起到主要作用.  相似文献   

2.
A new preparation process for carbon nanotubes (CNTs) cold cathode was studied through the replacement of traditional organic or inorganic binder with Ag nano-particles. This method has the advantages of low preparation temperature and fine electrical contact between CNTs paste and substrate. A mixture paste of CNTs, Ag nano-particles and other organic solvents was spreaded on Si substrate. By melting and connecting of Ag nano-particles after sintered 30 min at 250 °C, a flat CNTs films with good field emission properties was obtained. The measurements reveal that the turn on electric field and the threshold electric field of as-prepared CNTs cathode are 2.1 and 3.9 V/μm respectively and the field emission current density is up to 41 mA/cm2 at an applied electric field of 4.7 V/μm.  相似文献   

3.
Polyethylene is widely used in electrical wires and power cables. The pre-stressing effect, which restricts the applications of polyethylene, has not yet been investigated in depth. We studied the breakdown of low-density polyethylene (LDPE) films pre-stressed by direct current (DC) electric field. The results showed some conformity, as reported in many other papers, that the DC breakdown strength EB+ with the same polarity to that of the pre-stressing field was higher than the DC breakdown strength EB of thin LDPE films without pre-stressing, while the DC breakdown strength EB? with the opposite polarity was lower than EB. Such phenomena could be explained by the hetero effects of accumulating space charges, which enhanced the electrical field when the polarity was reversed. However, as a further increase in pre-stressing electrical field, both EB+ and EB? were found higher than EB. We investigated the space charge behavior in LDPE films and found that when applied with a higher electrical field, space charge packet initialized and traveled through the specimen. The results suggest that the space charge packet behavior may contribute to the pre-stressing effects on electrical breakdown in LDPE films.  相似文献   

4.
碳纳米管场致发射中的空间电荷效应   总被引:1,自引:0,他引:1       下载免费PDF全文
采用微波等离子体化学气相沉积(MWPCVD)方法成功制备以碳纳米管束为单元的场致发射阵列,获得很好的场致发射电流发射特性,在电流密度较大时,发现I-V特性偏离由Fowler-Nordheim公式计算出的结果。采用Electron Beam Simulation(EBS)软件进行模拟分析发现:在电流密度较低时,I-V特性能很好与F-N公式吻合。但碳纳米管尖端电流密度大于106A/cm2时,碳纳米管尖端处的有效电场强度受空间电荷的影响比较明显,进而对碳纳米管的场致发射特性显现出不可忽略的影响,此时碳纳米管的发射电流密度开始受到空间电荷的限制。  相似文献   

5.
The effects of Ar microwave plasma treatment on field emission properties of the printed carbon nanotubes (CNTs) cathode films using Ag nano-particles as binder were investigated. The field emission J-E characteristics were measured at varied plasma treatment time. Significant improvement in emission current density, emission stability and uniformity were achieved for the Ar treated CNTs films, even though the plasma treatment increased the turn on electric field slightly. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy revealed the microstructural changes of CNTs after the plasma treatment. The improved field emission properties of CNTs film can be attributed to the generation of a high density of structural defects after treatment, which increased greatly the possible emission active sites. Besides, the formation of the sharpened and open-ended CNTs tips is all helpful for improving the field emission properties of the treated CNTs.  相似文献   

6.
7.
《Composite Interfaces》2013,20(6):427-433
Dielectric breakdown phenomena by electrical treeing deterioration was investigated in the new epoxy resin system DGEBA/MDA/SN filled with Al2O3. As the filler content increased, the maximum electric field at breakdown increased and then decreased with increase of defects such as voids, impurities and delamination or peeling between filler and matrix. As the electrode separation increased, the breakdown voltage increased, but the breakdown strength decreased and then saturated to 17 kV/mm. Also, the maximum electric field at the tip when the system was failed increased. The electrical tree initiated from the side of the needle electrode was not from the tip where the reinforced field is the highest. The electrical tree was blocked by the filler. The interface condition of filler and polymer matrix played an important role in the electrical treeing resistance. The final breakdown phenomena showed fan-type crack as observed in the non-filled system.  相似文献   

8.
A novel post-treatment method, including hard hairbrush and electrical treatment, is performed intentionally to improve the field emission capability and stability of screen-printed carbon nanotubes (CNTs). Compared with untreated films, the field emission properties of the treated ones are greatly enhanced. Scanning electron microscopy (SEM) and Raman spectrum studies reveal that field emission properties are enhanced by two factors. Firstly, the improved field emission properties of CNT films can be attributed to the more active CNT surface by removing the organic material cover on the CNTs. Secondly, the gener- ation of a high density of structural defects and the lower resistance contact to the topside CNT emitters after treatment are all helpful to improving the field emission properties of the treated CNTs.  相似文献   

9.
Data are presented on the dielectric strength of thin polymer films. The conclusion is drawn that the electron avalanche concept is inapplicable to the breakdown of thin films. It is proposed to consider electrical breakdown as a consequence of an abrupt local field enhancement induced by evolution of the space charge injected into the polymer from electrodes. It is shown that the lifetime of polymer films depends exponentially on electric field strength.  相似文献   

10.
The field emission properties of electrophoretic deposition(EPD) carbon nanotubes (CNTs) film have been improved by depositing CNTs onto the titanium (Ti)-coated Si substrate, followed by vacuum annealing at 900 °C for 2 h, and the enhanced emission mechanism has been studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy. Field emission measurements showed that the threshold electric field was decreased and the emission current stability was improved compared to that of EPD CNTs film on bare Si substrate. XRD and Raman spectroscopy investigations revealed that vacuum annealing treatment not only decreased the structural defects of CNTs but made a titanium carbide interfacial layer formed between CNTs and substrate. The field emission enhancement could be attributed to the improved graphitization of CNTs and the improved contact properties between CNTs and substrate including electrical conductivity and adhesive strength due to the formed conductive titanium carbide.  相似文献   

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