共查询到20条相似文献,搜索用时 15 毫秒
1.
实验研究了聚四氟乙烯薄膜在重复频率纳秒脉冲下的击穿特性,选用脉冲上升时间约15 ns,脉宽30~40 ns,重复频率1~1 000 Hz。测量并计算了击穿前后的电压电流波形、重复频率耐受时间和施加脉冲个数与击穿特性密切相关的参数。结果表明,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿场强为MV/cm量级,重复频率耐受时间随施加场强和重复频率的增大而减小。薄膜本身性质及油浸时间使实验数据具有分散性,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿应考虑重复频率条件下的热积累效应和材料缺陷。 相似文献
2.
实验研究了聚四氟乙烯薄膜在重复频率纳秒脉冲下的击穿特性,选用脉冲上升时间约15 ns,脉宽30~40 ns,重复频率1~1 000 Hz。测量并计算了击穿前后的电压电流波形、重复频率耐受时间和施加脉冲个数与击穿特性密切相关的参数。结果表明,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿场强为MV/cm量级,重复频率耐受时间随施加场强和重复频率的增大而减小。薄膜本身性质及油浸时间使实验数据具有分散性,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿应考虑重复频率条件下的热积累效应和材料缺陷。 相似文献
3.
Pulsed breakdown of dry air at ambient pressure has been investigated
in the point-plane geometry, using repetitive nanosecond pulses with
10 ns risetime, 20--30 ns duration, and up to 100 kV amplitude. A
major concern in this paper is to study the dependence of breakdown
strength on the point-electrode polarity. Applied voltage, breakdown
current and repetitive stressing time are measured under the
experimental conditions of some variables including pulse voltage
peak, gap spacing and repetition rate. The results show that
increasing the E-field strength can decrease breakdown time lag,
repetitive stressing time and the number of applied pulses as
expected. However, compared with the traditional polarity dependence
it is weakened and not significant in the repetitive nanosecond-pulse
breakdown. The ambiguous polarity dependence in the experimental
study is involved with an accumulation effect of residual charges and
metastable states. Moreover, it is suggested that the reactions
associated with the detachment of negative ions and impact
deactivation of metastable species could provide a source of primary
initiating electrons for breakdown. 相似文献
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5.
实验研究了尖-板电极中,不同重复频率(10,100,500,1 000 Hz)、不同间隙(0.5,1 cm),不同气压(0.1~0.4 MPa)等条件下空气的绝缘特性。得到了击穿时延、重复频率耐受时间、施加脉冲个数等与施加电压、重复频率的关系。研究发现:在该实验条件下击穿时延随着场强与气压的比值减小而增加,但重频耐受时间和脉冲击穿个数并没有明显变化;随着重复频率的提高,击穿时延和重频耐受时间会减小,但脉冲击穿个数可能会增加;且重复频率条件下击穿的极性效应不明显;重复施加的脉冲产生大量的亚稳态粒子和残余电荷影响放电的发展过程;负离子的脱负或正离子碰撞阴极的过程,及亚稳态粒子的去激励作用给击穿提供了有效初始电子。 相似文献
6.
探索提高金属表面真空击穿阈值的方法,对脉冲功率技术的发展和应用具有重要意义。在金属表面电子发射理论分析的基础上,采用有限元法计算阴极杆表面电场随二极管电压的变化规律,设计了实验系统,并开展了实验研究。实验对比了在脉宽约30 ns、阴极杆与阳极筒间隙12 mm时,钛合金TC4阴极杆在不同种类高分子膜(膜厚30~60 μm)下真空击穿阈值的变化情况。在表面粗糙度Rz(轮廓最大高度)为0.8 μm的TC4阴极杆表面分别镀环氧树脂膜和丙烯酸膜,实验结果表明,镀丙烯酸膜阴极杆的击穿阈值约505 kV/cm,相对于不镀膜阴极杆,击穿场强提高了约20.6%;在表面粗糙度Rz为0.2 μm的TC4阴极杆表面分别镀聚酰亚胺膜和聚醚醚酮膜,实验结果表明,镀聚酰亚胺膜阴极杆的击穿阈值为584 kV/cm,相对于不镀膜阴极杆,击穿场强提高了约28.1%。因此,在金属表面镀丙烯酸膜、聚酰亚胺膜可以有效提高金属表面的真空击穿阈值。 相似文献
7.
Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD (PTFE) > EBD (PMMA) > EBD (Nylon) > EBD (PE). This result is consistent with the theoretical prediction. 相似文献
8.
Based on the concepts of fast polarization,effective electric field and electron impact ionization criterion,the effect of polymer type on electric breakdown strength(E BD) on a nanosecond time scale is investigated,and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived.According to this formula,it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers.By calculating the effective relative dielectric constants for different types of polymers,the theoretical relation for the electric breakdown strengths of common polymers is predicted.To verify the prediction,the polymers of PE(polyethylene),PTFE(polytetrafluoroethelene),PMMA(organic glass) and Nylon are tested with a nanosecond-pulse generator.The experimental result shows E BD(PTFE) > E BD(PMMA) > E BD(Nylon) > E BD(PE).This result is consistent with the theoretical prediction. 相似文献
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10.
Laser-induced breakdown spectroscopy: A versatile tool for monitoring traces in materials 总被引:1,自引:0,他引:1
Laser-induced breakdown spectroscopy (LIBS) is an emerging technique for simultaneous multi-elemental analysis of solids,
liquids and gases with minute or no sample preparation and thus revolutionized the area of on-line analysis technologies.
The foundation for LIBS is a solid state, short-pulsed laser that is focused on a sample to generate a high-temperature plasma,
and the emitted radiation from the excited atomic and ionic fragments produced within the plasma is characteristic of the
elemental composition of the sample that can be detected and analyzed using a suitable optical spectrograph. In the present
paper, the applicability of LIBS for different solid samples having homogeneous (silver ornament, aluminum plate) or heterogeneous
composition (soil) using nanosecond laser pulses is discussed. Nanosecond pulse laser makes plasma at the sample surface even
at very low pulse energies and also allows for precise ablation of the substrate material with little damage to the surrounding
area. We have also studied the penetration of different heavy metals inside the soil surface.
相似文献
11.
为了更好分析系统的放电特性和工作状态,优化脉冲功率源系统的设计,研制了一套1.2MV重复频率高功率微波驱动电源测试诊断系统。通过研究高电压、大电流测试技术和数据采集、信号处理、故障诊断技术,同时运用虚拟仪器和电磁兼容等技术,探索开发了一套重复频率脉冲电压电流测试诊断系统。结合系统的研制需求,通过分析各种数据采集设备的优缺点,硬件选用了凌华公司的PXI数据采集系统,软件采用LabVIEW,设计开发了重复频率快信号的采集诊断程序,研制出实时诊断系统,并在1.2MV重复频率脉冲电源系统中应用,实现了对重复频率电源关键点电压电流的测试以及数据的诊断、处理和远程在线监测,出现故障时报警、存储数据并自动断电等功能。 相似文献
12.
A novel transparent polymer neutron scintillation material poly[styrene-co-lithium maleate-co-2-phenyl-5-(4-vinylphenyl)oxazole] has been synthesized and characterized for thermal neutron detection and neutron/gamma-ray discrimination. The terpolymer was synthesized using solution-based free radical polymerization and had a composition by mass of 60.64% styrene, 31.64% maleic anhydride, and 7.72% 2-phenyl-5-(4-vinylphenyl)oxazole. The maleic anhydride groups were hydrolyzed and titrated with 6LiOH to form the lithiated terpolymer, resulting in a 6Li content of 2.96% by mass. Monomer and polymer synthesis, film fabrication protocols, photoluminescence, and scintillation responses of this new scintillation material are reported. This approach demonstrates a novel method by which mechanically robust and transparent 6Li-based polymer films can be produced. 相似文献
13.
为了更好分析系统的放电特性和工作状态,优化脉冲功率源系统的设计,研制了一套1.2 MV重复频率高功率微波驱动电源测试诊断系统。通过研究高电压、大电流测试技术和数据采集、信号处理、故障诊断技术,同时运用虚拟仪器和电磁兼容等技术,探索开发了一套重复频率脉冲电压电流测试诊断系统。结合系统的研制需求,通过分析各种数据采集设备的优缺点,硬件选用了凌华公司的PXI数据采集系统,软件采用LabVIEW,设计开发了重复频率快信号的采集诊断程序,研制出实时诊断系统,并在1.2 MV重复频率脉冲电源系统中应用,实现了对重复频率电源关键点电压电流的测试以及数据的诊断、处理和远程在线监测,出现故障时报警、存储数据并自动断电等功能。 相似文献
14.
研究了一种偶氮聚合物薄膜的光谱和二阶非线性光学特性.研究结果表明,聚合体中的偶氮发色团以反式异构体形式存在.加热可使分子之间的相互作用减弱,聚集体的聚集程度降低;温度低于70℃时聚集体的结构不会发生变化,分子间相互作用的改变能够完全恢复;高于70℃降温后聚集体聚集程度的降低不能完全恢复.在一定温度下极化可使发色团偶极子定向有序排列,形成J-聚集体.偶氮聚合物薄膜的二阶非线性光学特性起源于偶极子模型,极化温度是影响极化膜二次谐波强度的重要因素之一,该偶氮聚合物薄膜的最佳极化温度约为90℃. 相似文献
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16.
对孔洞聚丙烯(PP)驻极体膜系统的研究结果表明:孔洞PP膜中空间电荷的俘获特性随注入的空间电荷量或试样表面电位而变化,注入的电荷量较少时空间电荷主要被俘获在表面深陷阱和近表面次深陷阱中,较多的注入电荷量时空间电荷在进一步填充表层(表面和近表面)陷阱的同时,还将填充体内浅陷阱;这三类陷阱中心所对应的电荷脱阱温度分别约为160℃,138℃和92℃.而孔洞击穿电荷不仅被俘获在与试样表层空间电荷陷阱相似的孔洞表层陷阱中,还有相当的量穿过孔洞表层进入体内、成为浅阱俘获孔洞击穿电荷.
关键词:
孔洞聚丙烯膜
空间电荷
孔洞击穿电荷
俘获特性 相似文献
17.
Melissa A. Holmes Michael E. Mackay Rachel K. Giunta 《Journal of nanoparticle research》2007,9(5):753-763
Addition of fullerenes (C60 or buckyballs) to a linear polymer has been found to eliminate dewetting when a thin (∼50 nm) film is exposed to solvent
vapor. Based on neutron reflectivity measurements, it is found that the fullerenes form a coherent layer approximately 2 nm
thick at the substrate – polymer film interface during the spin-coating process. The thickness and relative fullerene concentration
(∼29 vol%) is not altered during solvent vapor annealing and it is thought this layer forms a solid-like buffer shielding
the adverse van der Waals forces promoted by the underlying substrate. Several polymer films produced by spin- or spray-coating
were tested on both silicon wafers and live surface acoustic wave sensors demonstrating fullerenes stabilize many different
polymer types, prepared by different procedures and on various surfaces. Further, the fullerenes drastically improve sensor
performance since dewetted films produce a sensor that is effectively inoperable. 相似文献
18.
采用磁控溅射法制备出透明导电氧化物NiO薄膜.椭偏(SE)测试表明NiO薄膜在可见光区域透光性良好,通过调节生长、退火温度可调控NiO的折射率.采用X射线衍射(XRD)、扫描电子显微镜(SEM)手段研究表明,通过退火、改变衬底温度等,可有效改变NiO薄膜的晶体结构以及表面形貌,实现对NiO导电性的调控. 采用优化后的NiO材料为阳极阻挡层制备出的聚合物太阳能电池器件的效率为2.26%,是同等条件下采用 PEDOT:PSS阻挡层的电池器件的3倍以上. 相似文献
19.
We reported a controlled architecture growth of layer-ordered multilayer film of poly(3,4-ethylene dioxythiophene) (PEDOT) via a modified Langmuir-Blodgett (LB) method. An in situ polymerization of 3,4-ethylene dioxythiophene (EDOT) monomer in multilayer LB film occurred for the formation of ordered conducting polymer embedded multilayer film. The well-distribution of conducting polymer particles was characterized by secondary-ion mass spectrometry (SIMS). The conducting film consisting of ordered PEDOT ultrathin layers was investigated as a hole injection layer for organic light-emitting diodes (OLEDs). The results showed that, compared to conventional spin-coating PEDOT film and electrostatic self-assembly (ESA) film, the improved performance of OLEDs was obtained after using ordered PEDOT LB film as hole injection layer. It also indicated that well-ordered structure of hole injection layer was attributed to the improvement of OLED performance, leading to the increase of charged carrier mobility in hole injection layer and the recombination rate of electrons and holes in the electroluminescent layer. 相似文献
20.
Laser-induced breakdown spectroscopy (LIBS) in the last decades has become a promising analytical technique for a broad variety of archeological objects with great results obtained either alone or in combination with complementary techniques. It is mainly advantageous due to no sample preparation, minimally destructive, rapid analysis and depth profiling analysis spur LIBS technique to become a significant attractive technique for the characterization and conservation of archeological samples or artworks. The present paper describes in brief the basic principles and instrumentation of LIBS, and reviews several case studies on metallic alloys, ceramic, glass, painted artworks, historical buildings and biomaterials in the most recent 7 years (2011–2017) that demonstrate the applicability and prospects of LIBS in the field of archeological science. 相似文献