磁控直流辉光等离子体放电特性

本文利用单探针诊断等离子体参数来研究自行设计的磁控直流辉光等离子体实验装置的放电特性, 从而得出电子密度与气体压强、电子密度分布与磁场位型以及磁场强度等的关系. 另外, 用有限元的方法对线圈通电产生的磁场进行数值计算, 模拟出不同接线方式的两种磁场位型分布. 通过实验得出这两种不同的位型的磁场均对等离子体的状态有一定的“控制”作用, 而且这种“控制”作用与现有理论相符合.     

高气压直流辉光CH4/H2等离子体的气相过程诊断

对高气压(约100 Torr) 直流辉光碳氢等离子体的气相过程进行了光谱和质谱原位诊断. 在高气压下, 等离子体不同区域光发射特性存在明显差异. 正柱区存在着以C₂和CH为主的多个带状谱和分立谱线, 阳极区粒子发射谱线明显减少, 而在阴极区则出现大量复杂的光谱成分, 表明高气压情形下等离子体与阴极间强烈的相互作用将导致复杂的原子分子过程. 从低气压到高气压演变过程中, 电子激发温度降低而气体分子转动温度升高. 在高气压下, 高甲烷浓度导致C₂, C₂H₂及C₂H₄增多而C₂H₆减少. 表明在高气压条件下, 气体温度对气相过程的影响作用显著增强. 关键词： 高气压直流等离子体 光发射谱 质谱     

直流等离子体炬放电特性研究

对于磁约束直流等离子体炬,用氩－氢等离子体的放电体系,研究了等离子体炬几何结构、真空室气压、弧电流、外磁场与比变化等对等离子体炬放电特性的影响。得到了影响等离子体炬宏观和微观参数变化的一些基本规律。     

常压均匀辉光放电等离子体的杀菌作用

讨论了常压均匀辉光放电等离子体的形成和杀菌机理，提出了等离子体杀菌技术，并通过实例介绍了常压均匀辉光放电等离子体在空气过滤杀菌中的效果和实际使用价值。     

高气压氩气辉光放电条纹等离子体的形成和演化

辉光放电等离子体正柱区内的自组织条纹现象是气体放电物理中的基础性问题,涉及电子动力学、输运过程、放电不稳定性、非线性现象等丰富的物理内容,是基础物理及其应用中备受关注的重要课题.本文报道了一种在千帕量级气压下产生的氩气辉光放电条纹等离子体,重点关注了条纹等离子体的电学、光学及电离波传播特征,从物理上分析了氩气条纹等离子体的产生及消除机制.研究结果表明,在此气压下产生的氩气条纹等离子体,其条纹长度约为1.5 mm,且随气压减小;电离波波速为1.87 m/s,频率为1.25 kHz.发射光谱诊断证实,条纹等离子体的产生与丰富的亚稳态原子密切相关,亚稳态原子导致的分步电离过程会引起电离不稳定性,这种不稳定性以电离波的形式传播,使得等离子体参数发生纵向调幅,从而形成明暗相间的条纹等离子体.加入氮气可有效猝灭亚稳态氩原子,调整电子能量分布函数,这使得等离子体的不稳定性条件被破坏,因此,条纹等离子体消失.本工作可为人们进一步认识和理解高气压下辉光放电条纹等离子体的形成及消除机制提供新的思路和实验依据.     

直流辉光放电等离子体轴向动力学过程的研究

采用磁流体动力学理论,考虑了电子与中性粒子的非弹性碰撞,应用有限差分法研究了直流辉光放电氩等离子体的轴向动力学过程,得到了氩等离子体密度、输运速度、温度以及电位的轴向分布,发现了气体压强和电极间距的变化对阴极区的电子密度有较大的影响,而对阴极区的离子密度的影响甚微。 关键词：     

直流辉光放电等离子体激发光源自动调节控制系统

直流辉光放电过程中需要控制的三个重要工作参数为放电电流、放电电压和放电室内氩气气压.该文介绍了一种应用于直流辉光放电等离子体激发光源的自动调节控制系统,该控制系统在放电电流恒定的情况下调节放电室内氩气气压,实现了对放电电压的信号采集和自动控制.文卷阐述了该控制系统的设计思路、电路原理及控制方案.该自动调节控制系统改善了以往用手动调节时精度低且操作复杂的情况,提高了放电电压的控制精度,缩短了放电电压的稳定时间.文中给出了自动控制方式下激发源放电电压的稳定性测试结果,控制精度由手动调节时的4%FS改善为小于1%FS,放电电压稳定时间由手动时的大于90s缩短到30 s以内.采用该控制系统对中低合金钢和锡肯铜标准样品进行了样品精密度实验.元素含量分析精密度比手动调节方式显著提高,各元素含量测试结果的相对标准偏差(RSD)均优于3.5%.中低合金钢标准样品中Ti,Co,Mn元素含量测试结果的RSD范围由手动时的3.0%～4.3%减小到1.7%～2.4%,S和Mo元素RSD范围由5.2%～5.9%减小到3.3%～3.5%.锡青铜标准样品中Sn,Zn,Al元素RSD范围由2.6%～4.4%减小到1.0%～2.4%,Si,Ni,Fe元素的RSD范围由6.6%～13.9%降低到2.6%～3.5%,并给出了实测数据.     

高气压下交流旋转滑动弧放电特性实验研究

本文针对恶劣条件下滑动弧等离子体放电稳定性问题,搭建了高气压交流旋转滑动弧放电实验系统,开展了高气压下交流旋转滑动弧放电特性实验,并对其放电特性、电弧运动特性、光谱特性进行了分析.研究结果表明:随着介质气体压力的升高,滑动弧放电的电压、电流、能量均呈现增大趋势,当介质气体压力升高到0.52 MPa时,滑动弧放电的能量从常压下的84.74 J增大到147.13 J;且随着介质气体压力的升高,电弧的击穿频率并不是单调变化,而是在0.2 MPa时达到最大为26.55 kHz;高气压下电弧运动过程中会出现“弧道骤变”现象;随着介质气体压力的升高,滑动弧放电的整体光谱发射强度呈现变强趋势;通过两谱线法对滑动弧放电的电子激发温度进行了计算,常压下滑动弧放电的电子激发温度为0.8153 eV,随着介质气体压力的升高,电子激发温度呈现升高趋势,当介质气体压力达到0.4 MPa时,滑动弧放电的电子激发温度升高至5.3165 eV.     

高气压微波氢等离子体发射光谱诊断

在2.45 GHz,800 W级的高气压微波等离子体放电系统中,通过测量不同微波功率和放电气压下氢等离子体的Balmer线系的发射光谱,从测量的谱线总展宽中卷积去掉具有高斯线形的Doppler展宽和仪器展宽得到谱线的Stark展宽,并通过Stark展宽测量氢等离子体的电子数密度和电场强度。结果表明：等离子体的电子数密度和电场强度随着放电气压的升高都是先增大后减小,随着微波功率的增加呈现逐渐增大的趋势。微波功率为800 W时,气压在25 kPa时电子数密度和电场强度都达到最大值,等离子体的电子数密度和内部的电场强度分别为3.55×1012 cm-3及4.01 kV/cm。     

热处理对制备辉光放电聚合物薄膜结构及光学性能的影响

利用低压等离子体聚合技术制备了约5 μm的辉光放电聚合物薄膜, 将所制备的样品放入热处理炉中通入氩气保护, 分别在280 ℃, 300 ℃, 320 ℃, 340 ℃进行热处理. 对热处理后的样品采用傅里叶变换红外吸收光谱(FT-IR)分析了不同热处理温度对薄膜结构的影响. 对CH振动区进行了分峰高斯拟合, 定量的分析了个官能团的变化. 利用紫外可见光谱仪分析了热处理前后薄膜在紫外–可见光区域内光学透过率及光学带隙的变化. 结果表明: 随着热处理温度的升高,薄膜中H含量减少, 薄膜中甲基相对含量减少, 而双键、芳香环结构相对含量增加, 在600 nm以后的可见光区, 薄膜的透过率减小. 薄膜光透过率的截止波长红移, 光学带隙减小. 关键词： 热处理 薄膜结构 等离子体聚合 光学性能     

Optical properties of methanol at high pressures

The pressure dependence of the refractive index of methanol has been measured in a diamond-anvil cell up to 5·6 GPa at room temperature. These experiments cover the liquid phase of methanol (below 3·6 GPa) as well as the ‘superpressed fluid’ phase above 3·6 GPa. We have extracted the polarizability of methanol from our experimental data and the equation of state by using the Lorentz-Lorenz equation.     

Elastic and thermodynamic properties in CdO at high pressures from first-principles calculations

In this study, we report first-principles calculations of the elastic and thermodynamic properties for CdO in both the B1 (rocksalt) phase and B2 (cesium chloride) phase. The calculations are performed within the framework of density functional theory, using the pseudopotential plane-wave method. From the theoretical results, we find that the high pressure structural phase transition of CdO from B1 structure to B2 structure is 90.31 GPa. The calculated values are, generally speaking, in good agreement with experiments and with similar theoretical calculations. According to the quasi-harmonic Debye model, we investigate the sound velocity and Debye temperature of CdO under pressures in the range of 0<P<150 GPa.     

介质阻挡均匀大气压辉光放电数值模拟研究

通过数值求解一维电子、离子连续性方程和动量方程，以及电流连续性方程，计算了氦气介 质阻挡大气压辉光放电电子、离子密度和电场在放电空间的时空分布，以及放电电流密度和 绝缘介质板充电电荷密度随时间的变化. 分析讨论所加电压频率、幅值及介质板性质等对均 匀大气压辉光放电性质的影响. 当外加电压频率足够高时，大量离子被俘获在放电空间，空 间电荷场又引起足够多的电子滞留在放电空间. 这些种子电子使得在大气压下发生汤森放电 ，放电空间结构类似于低气压辉光放电，即存在明显的阴极位降区、负辉区、法拉第暗区和 等离子体正柱 关键词： 大气压辉光放电 介质阻挡 数值模拟 等离子体     

Thermoelectric power of cerium at high pressures

The electronic phase transition in cerium occurring near 7 kbar pressure at room temperature which is attributed to the 4f–5d electron promotion has been studied using thermoelectric power as a tool. The important results that have emerged out of this work are: (a) the relatively large variation in the absolute thermoelectric power ofγ-cerium (normal fcc phase) with pressure prior to the phase transition (in contrast to the rather small resistivity change with pressure in this region); (b) a sharp decrease in the thermoelectric power accompanying the iso-structuralγ-α phase transition; and (c) the continuous decrease in the thermoelectric power ofα-cerium (collapsed fcc phase) with pressure, ultimately changing sign at higher pressures. An explanation based on the “virtual bound state” model is proposed to account for these results.     

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空气中的大气压辉光放电通常因放电易过渡到火花状态而难以产生。在静态大气压空气针-板等离子体发生器中，采用阻容耦合负反馈方法控制等离子体放电发展过程，成功地抑制了辉光放电向火花放电的过渡，产生了稳定的交流辉光放电。研究了电压、电极间距等参数变化对放电的影响。     

Synthesis of nanoparticles in an atmospheric pressure glow discharge

Nanopowders are produced in a low temperature, non-equilibrium plasma jet (APPJ), which produces a glow discharge at atmospheric pressure, for the first time. Amorphous carbon and iron nanoparticles have been synthesized from Acetylene and Ferrocene/H₂, respectively. High generation rates are achieved from the glow discharge at near-ambient temperature (40–80°C), and rise with increasing plasma power and precursor concentration. Fairly narrow particle size distributions are measured with a differential mobility analyzer (DMA) and an aerosol electrometer (AEM), and are centered around 30–35 nm for carbon and 20–25 nm for iron. Particle characteristics analyzed by TEM and EDX reveal amorphous carbon and iron nanoparticles. The Fe particles are highly oxidized on exposure to air. Comparison of the mobility and micrograph diameters reveal that the particles are hardly agglomerated or unagglomerated. This is ascribed to the unipolar charge on particles in the plasma. The generated particle distributions are examined as a function of process parameters.     

Simulation of radio-frequency atmospheric pressure glow discharge in γ mode

The existence of two diffe1：ent discharge modes has been verified in an rf （radio-frequency） atmospheric pressure glow discharge （APGD） by Shi [J. Appl. Phys. 97, 023306 （2005）]. In the first mode, referred to as a mode, the discharge current density is relatively low and the bulk plasma electrons acquire the energy due to the sheath expansion. In the second mode, termed γ mode, the discharge current density is relatively high, the secondary electrons emitted by cathodc under ion bombardment in the cathode sheath region play an important role in sustaining the discharge. In this paper, a one-dimensional self-consistent fluid model for rf APGDs is used to simulate the discharge mechanisms in the mode in helium discharge between two parallel metallic planar electrodes. The results show that as the applied voltage increases, the discharge current becomes greater and the plasma density correspondingly increases, consequentially the discharge transits from the a mode into the γ mode. The high collisionality of the APGD plasma results in significant drop of discharge potential across the sheath region, and the electron Joule heating and the electron collisional energy loss reach their maxima in the region. The validity of the simulation is checked with the available experimental and numerical data.     

First-principles study of structural and elastic properties of CrO2 at high pressure

The structural and elastic properties of CrO₂ in the rutile phase under high pressures have been investigated using pseudopotential plane-wave method based on density functional theory. The optimized lattice parameters and the bulk modulus at zero pressure agree well with available experimental and theoretical data. The elastic constants C ₁₁, C ₁₂, C ₄₄, C ₃₃, C ₁₃, and C ₆₆ at zero pressure are calculated to be 359.91, 264.69, 143.28, 309.45, 218.45, and 260.74 GPa, respectively. Elastic constants, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio under pressures are obtained. Our results indicate that the rutile phase is mechanically stable below 11.99 GPa. The elastic anisotropy of rutile phase under pressures has also been predicted.     

Phase transition of ZnS at high pressures and temperatures

The high-pressure behaviour of zinc sulphide, ZnS, has been investigated, using an in situ X-ray powder diffraction technique in a diamond anvil cell, at pressures and temperatures up to 35 GPa and 1000 K, respectively. The pressure-induced phase transition from a zincblende (B3) to a rocksalt (B1) structure was observed. This transition occurred at 13.4 GPa and at room temperature, and a negative dependence on temperature for this transition was confirmed. The transition boundary was determined to be P (GPa) = 14.4 ? 0.0033 × T (K).