氢氧化铝/环氧树脂复合材料的电荷衰减特性

环氧树脂电气绝缘性能优良, 但是其在脉冲功率设备中充当绝缘子时, 表面容易带电且不易衰减, 当表面电荷集聚到一定的程度会造成局部放电甚至发展为沿面闪络。为了提高环氧树脂的沿面闪络性能, 用中心粒径为1 m的氢氧化铝(ATH)无机填料来改善环氧树脂复合材料的表面性能。分别制备了ATH填料质量分数为0%(纯环氧) , 20%, 40%, 60%, 80%和100%的ATH/环氧树脂复合材料试样。用电声脉冲法研究了ATH填料对环氧树脂复合材料电荷衰减性能的影响, 对比了试样直流极化场强为10 kV/mm和30 kV/mm的试验结果。结果表明：ATH/环氧树脂复合材料电荷的衰减常数不仅与填料的质量分数有关, 而且与试样的带电量有关。     

Evaluation of laser ablation threshold in polymer samples using pulsed photoacoustic technique

The acoustic signals generated in solids due to interaction with pulsed laser beam is used to determine the ablation threshold of bulk polymer samples of teflon (polytetrafluoroethylene) and nylon under the irradiation from a Q-switched Nd:YAG laser at 1.06μm wavelength. A suitably designed piezoelectric transducer is employed for the detection of photoacoustic (PA) signals generated in this process. It has been observed that an abrupt increase in the amplitude of the PA signal occurs at the ablation threshold. Also there exist distinct values for the threshold corresponding to different mechanisms operative in producing damages like surface morphology, bond breaking and melting processes at different laser energy densities.     

2D Simulations of Short‐Pulsed Dielectric Barrier Discharge Xenon Excimer Lamp

Self‐consistent two‐dimensional (2D) simulations of short‐pulsed dielectric barrier discharge (DBD) in pure xenon have been performed. It is shown that during short current pulse the traversal inhomogeneity of the plasma parameters can be important only at the end of the current pulse as an edge effect close to the side walls. During the current pulse, the gap voltage drops until the ionization wave reaches the cathode so the current in the cathode sheath is the displacement current. This means that almost all of the absorbed power is deposited into excitation of xenon atoms and not to the ion heating in the cathode sheath as in the traditional glow discharges. This fact is one of the reasons of high efficiency of short‐pulsed DBD. The developed model allows one to estimate the temporal position of the plasma‐sheath boundary. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

真空获得与测量实验装置的改进

本文分析了原真空获得与测量实验装置结构上的不足之处．介绍了对原装置所进行的改进工作──主要用于取代感应圈的专用电源的制作。     

Space- and direction-resolved Langmuir probe diagnostic in rf planar discharges

To consider the anisotropy of the plasma in the sheath regions, Langmuir probe characteristics are measured using a direction-resolving technique. The operation frequency, related to the neutral gas density (/p₀), is chosen in such a way that the electron velocity distribution function (VDF) may be regarded as frozen and the probe diagnostic may be performed without time resolution. In order to prevent convolution of the VDF from the effect of the time-dependent plasma potential, the rf component of the probe bias voltage is compensated to a minimum. The plasma potential, the mean energy of the electrons, and the electron density, averaged over the discharge bulk, are presented as functions of the discharge current and the neutral gas pressure for the O₂ gas. By means of a reactor model based on the theory of plane probes and using the plasma parameter measured, the sheath and bulk portions of the maintaining voltage are separated. In this procedure the thickness of the sheaths in front of the electrodes and the phase difference between discharge current and maintaining voltage are also obtained.     

Conversion of Methane to Hydrogen via Pulsed Corona Discharge

Experiments are performed to develop a pulsed corona discharge system for the conversion ofmethane to hydrogen at atmospheric pressure (≌760 Torr) without using a catalyst. The corona dischargewas energized by 10-12 μs wide voltage pulses (≤7 kV) at a repetition rate of about 1.0-1.5 kHz. Theresidual gases were characterized by mass spectrometry. The conversion of methane is as high as 50.8% producing the 70% yield of hydrogen. The influences of argon on the discharge of methane were studied.This result could be useful for the mass production of hydrogen in both academic and industrial point ofview.