局部热力学平衡状态下的等离子体电导率计算

在Zollweg & Liebermann模型（Z&L模型）的基础上,结合高温条件下的量子机理作用,考虑了电子与中性粒子的碰撞关系,最终得出修正后的电导率模型,并对局部热力学平衡状态下的水中放电等离子体的粒子数密度及电导率进行了模拟计算.计算结果表明压力为定值的情况下,水中放电等离子体的总粒子数密度随温度变化呈下降趋势,温度达到15000 K时,一次电离达最大值.电导率随温度增加总体呈上升趋势,温度低于12000 K时,电子与中性粒子的碰撞起主导作用,而温度高于25000 K时,电子与离子的碰撞起主导作用.     

真空弧Ti-H等离子体热力学参数的原子发射光谱双温度研究北大核心CSCD

金属氢化物作阴极的真空弧离子源,假设其放电产生双温度的非平衡态Ti-H等离子体,其内部的气体解离过程和粒子电离过程分别由Culdberg-Waage解离方程和Saha电离方程进行描述,结合原子发射光谱以及电荷准中性条件,求出Ti-H等离子体的电子温度Te、重粒子温度Th和粒子数密度之后,可更进一步对等离子体的质量密度、焓、比热容等热力学参数进行描述。在不同的电子数密度下,研究各参数随变量θ(电子温度Te与重粒子温度Th的比值)变化的情况。计算结果显示:电子数密度已知,随θ值升高,除氢气分子数密度外,等离子体温度和单原子粒子数密度的计算结果均变化甚微。高电子数密度时,等离子体中单原子粒子占绝对优势,热力学参数由其控制;低电子数密度下,随θ值的升高,等离子体逐步由单原子粒子占优势转为氢气分子占绝对优势,热力学参数的变化情况表现出相同的规律。     

等离子体金属表面氮化中放电温度对氮原子态粒子的影响

采用快电子和重粒子(N₂⁺,N⁺,N_f)混合的Monte Carlo模型,研究了氮直流辉光放电等离子体金属表面氮化过程中.e-N_2s及N₂⁺-N_2s两种碰撞离解过程产生的原子态粒子(N⁺,N)的产生率和氮化粒子(N⁺,N_f)轰击靶表面的能量、粒子数密度及入射角分布随气体温度的变化规律.结果表明,使阴极靶处活性粒子(N⁺,N_f)的能量高且粒子数密度大,存在一个最佳放电温度;粒子(N⁺,N)的产生率及在靶表面的密度数都随着放电气体温度的升高而减少;有大量中性快原子N_f在工件表面小角入射,且粒子(N⁺,N_f)角分布受温度的影响很小.     

空气放电非平衡等离子体的模拟计算

 基于空气放电非平衡等离子体动力学,对空气放电进行了数值计算,分析了放电后等离子体中的主要粒子（N₂(v6),N₂(A3),O₂(a1),O和O₃）数密度随起始温度、电子数密度和约化场强的变化趋势。计算结果表明,随着初始温度的升高,空气放电产生的粒子数密度增加。温度为300 K时,放电产生的O原子数密度最大值约为4.90×⁷ cm^-3,而当温度升高到400 K和500 K时,O原子数密度的最大值则相应地增加到5.2×10¹⁰ cm^-3和5.51×10¹⁰ cm^-3。约化场强的影响与温度类似,其中氮气的振动激发态N₂(v6)数密度随约化场强的变化幅度不明显。电子数密度增加,粒子数密度大幅增加,氮分子的激发态N₂(A3)粒子数密度与电子数密度保持严格的线性关系。     

不同电离度下大气等离子体粒子行为的数值模拟

利用一个空间零维大气等离子体模型对其中的主要粒子在不同电离度情况下的变化规律进行了研究.得到放电后不同初始电子密度下的电子寿命,同时给出了主要带电粒子和中性粒子密度随时间的演化.结果表明,电子密度随时间快速衰减,电子寿命随电离度的增大而减小.对一些重要的中性粒子(如O,N,O₃和NO)随电离度增大的行为进行了分析. 关键词： 电离度 大气等离子体 数值模拟     

等离子体科学技术应用专题系列介绍——第七讲 低温等离子体及其在材料表面改性中的应用

一、低温等离子体概述 等离子体是一种电离的气态物质,称为物质第四态,宇宙中99.9%的物质都处于等离子体态.它由带电的电子、离子和中性粒子组成.粒子之间不断碰撞发生能量交换,同类粒子之间容易通过碰撞交换能量达到热力学平衡,因而有电子温度Tc,离子温度T1气体温度Ts按照研究的不同目的,等离子体可以作不同的分类.根据温度分为高温等离子体和低温等离子体.当电子温度105-108K时,称为高温等离子体,属于热力学平衡或局部热力学平衡等离子体,如太阳上的等离子体和核聚变等离子体等.当电子温度为3×102-105K时称为低温等离子体.低温等离子体…     

大气压He-Ar射频容性放电Ar亚稳态粒子数密度

利用发射光谱法测量大气压He-Ar混合气体射频容性放电中的Ar亚稳态1s5(3s23p54s［3/2］2)粒子数密度。在不同的放电功率和气体组分下测量放电等离子体中的重要参数:气体转动温度、电子激发温度和Ar亚稳态1s5粒子数密度。结果表明:气体温度在不同放电功率及Ar气压在5103 Pa以内时变化不大,范围为300~350 K;电子激发温度随着放电功率的增加而增加,并且在Ar气压为4103 Pa时最大,在放电功率为70 W时达到0.58 eV;1s5粒子数密度随着放电功率以及电子激发温度的增加而增加,在放电功率为70 W、Ar气压为4103 Pa时达到1.53109 cm-3。     

螺旋波等离子体放电三维直接数值模拟

在详细考虑电化学反应和粒子碰撞关系的基础上,建立了螺旋波放电三维直接数值计算模型,舍弃以往模型小扰动假设,对Maxwell方程组直接求解以计算电磁场能量沉积份额,扩展了螺旋波等离子体计算模型的精度和适用范围.以Ar为工质气体的仿真结果显示:密度跃升效应和电子温度与放电压力的关系与Toki等和Chen的实验结果符合较好;与经典鞘层理论对比,在粒子数密度、德拜长度、电势以及电子温度的分布上取得高度一致,验证了模型的有效性和精度.利用本文模型研究了低场螺旋波放电过程中的磁场峰值现象,验证了放电室端面的波干涉机理,并发现波干涉的本质是螺旋波分量与其端面回波叠加形成的驻波.     

磁场对直流辉光放电阴极鞘层中电子输运过程的影响

采用MonteCarlo模拟方法研究了磁场对直流辉光放电阴极鞘层中电子输运过程的影响.磁场垂直于阴极鞘层中电场的方问.模型中,电子与中性粒子的碰撞过程有三种(弹性碰撞;激发碰撞和电离碰撞).电子的自由飞行步长由电子与中性粒子的碰撞频率来决定.计算了电子的密度分布,电子与中性粒子的非弹性碰撞速率,以及电子能量和电子通量分布等.结果表明,横向磁场能在一定程度上改变直流放电中电子的输运过程.磁场中电子与中性粒于的非弹性碰撞速率被增强,这一结果与实验结果符合较好.     

基于发射光谱研究多针-板式水中He介质阻挡放电

采用多针-板式介质阻挡放电电极结构,并利用发射光谱研究了水中氦气等离子体的放电特性.实验结果表明:He等离子体中富含He*,Hα*,Hβ*,O*,OH*,N2*以及N2+等多种活性粒子,并且有效功率、气体温度、电子激发温度随峰值电压的增大几乎线性地增大,传导电流远大于位移电流.当峰值电压从7kV增大到10kV时,有效功率最大值约65W,气体温度从414K增大到498K,而电子激发温度从4 489K增大到4 635K.     

颗粒线度和非谐效应对传感器电极材料导电性能及其热稳定性的影响

本文考虑到原子的非简谐振动,应用固体物理理论和方法,研究了氧传感器多孔电极材料导电性能及热稳定性随温度和颗粒线度的变化规律,探讨原子非简谐振动和材料颗粒线度的影响.结果表明:(1)多孔Pt电极材料的电导率随温度的升高而非线性减小;电导率随颗粒半径的增大而非线性增大;电导率随时间增长而减小,但变化极小;(2)多孔Pt电极材料的电导率远小于Pt纳米材料的电导率,也小于块状Pt电极材料的电导率,且颗粒越小,颗粒线度效应越显著;(3)电导率的温度稳定性系数随温度的升高和颗粒线度的减小以及表面层参数的增大而非线性减小,即温度越高、颗粒线度越小、表面层参数越大,电极材料导电性的热稳定性越好;(4)表面层的存在使电导率降低,且降低情况与温度和颗粒线度有关,即颗粒越小,温度越低,电导率下降越明显;非简谐效应对电极材料的电导率几乎没有影响.     

Theoretical analysis for transmission of Gaussian and sine time irradiance of electromagnetic beam in collisional dusty plasmas

A theoretical model of propagation of Gaussian and Sine time irradiance of an electromagnetic beam in collisional dusty plasma has been done in the present analysis. It contains equilibrium of dust charge, particle density, and energy of plasma ingredients having charge neutrality. Ionization of neutral particles, recombination of free electrons with ions, adsorption and emission of electrons from dust grain surface, and binary collisions between plasma components are also considered in this treatment. Time varying behaviour of modified electron temperature and collision frequency has been illustrated numerically as a function of dust densities. Also, the comparative analyses of variation of beam waist parameter with the dimensionless length of transmission for both the Gaussian and Sine time irradiance are involved in this model as a function of distinguishable time width, collision frequencies, and dust densities under the condition that the size of dust nebulous is greater than the electrons mean free path for the adsorption on the dust grain surface. The observed results are significant for the applications in industry and astrophysics.     

Electronic and ionic conductivity in CaTiO3

The present work describes the electrical conductivity of undoped CaTiO₃ in terms of the electrical conductivity components corresponding to electrons, electron holes and ionic charge carriers in the temperature range 973 K — 1323 K and under controlled oxygen partial pressure (10 Pa — 72 kPa). These data are considered in terms of the transference numbers of the respective charge carriers. It appears that the ionic conductivity component assumes maximum at the n-p transition when the ionic transfer number reaches 50% of the total conductivity value at 1323 K. The present study also includes the determination of the activation energy of the conductivity component related to ions (162.1 kJ/mol), electrons (134.2 kJ/mol) and electron holes (86.2 kJ/mol). The data obtained in this work indicate that undoped CaTiO₃ exhibits a substantial level of ionic conduction that cannot be ignored in a quantitative analysis of electrical conductivity data.     

Hybrid computer simulations: electrical charging of dust particles in low-temperature plasma

This paper is focused on the study of the electrical charging process of micron-sized particles immersed into low-temperature argon plasma by the methods of computer modelling. The hybrid computer simulations are performed for a set of particles with the radius up to in order to determine the dependence of the electric charge on the surface of the particulate on its radius. This dependence seems to be linear. The distribution of the electric potential in the vicinity of the particulate is obtained from the fluid model. Afterwards, the non self-consistent particle simulation is performed in order to determine both the reaction rates and the electric charge on the surface of the particulate. The most important collision processes of charged particles in plasma and the appropriate dependence of the collision cross-section on the particle energy are considered (elastic scattering of electrons on neutrals, excitation of neutrals into all important energetic states, ionisation of Argon atoms by fast electrons, elastic scattering of positively charged ions etc.). The presented algorithm provides an effective way, how the key quantity in dusty plasma physics – electric charge on the surface of the particulate – can be determined.     

温稠密钛电导率计算

温稠密物质是惯性约束核聚变、重离子聚变、Z箍缩动作过程中物质发展和存在的重要阶段. 其热力学性质和辐射输运参数在聚变实验和内爆驱动力学模拟过程中有至关重要的作用. 本文通过建立非理想Saha方程, 结合线性混合规则的理论方法模拟了温稠密钛从10^-5-10 g·cm^-3, 10⁴ K到3×10⁴ K区间的粒子组分分布和电导率随温度密度的变化, 其中粒子组分分布由非理想Saha方程求解得到. 线性混合规则模型计算温稠密钛的电导率时考虑了包括电子、原子和离子之间的多种相互作用. 钛的电导率的计算结果与已有的爆炸丝实验数据相符. 通过电导率随温度密度变化趋势判断, 钛在整个温度区间, 密度0.56 g·cm^-3时发生非金属相到金属相相变. 对于简并系数和耦合系数的计算分析, 钛等离子体在整个温度和密度区间逐渐从弱耦合、非简并状态过渡到强耦合部分简并态.     

Physicochemical properties of ionic liquid mixtures containing choline chloride,chromium (III) chloride and water: effects of temperature and water content

The effects of water addition and temperature on some physicochemical properties of room temperature ionic liquids containing chromium chloride, choline chloride and water in the molar ratio of 1:2.5:x (where x = 6, 9, 12, 15 or 18) have been studied. The density, viscosity, surface tension and conductivity of the liquid mixtures were measured for the temperature range of 25 to 80 °C. Increasing both water content and temperature resulted in decreasing density, surface tension and viscosity and increasing electrical conductivity. The average void radii (hole sizes) for the liquid systems under study were calculated; they were in the range of 1.21 to 1.82 Å. The average hole size was stated to grow with increasing both temperature and water content in the mixture. The variation of the average void radii correlates with the change in viscosity and conductivity. The activation energies of viscous flow and conductivity diminishes with increasing water content in the liquid mixture. There is a strong linear correlation between conductivity and fluidity which indicates that the conductivity of the ionic liquid mixtures is generally controlled by the ionic mobility. A moderate viscosity and higher conductivity of the Cr(III)-containing ionic liquids with extra-water addition (at x > 9) make them suitable for the development of chromium electrodeposition processes.     

碰撞对尘埃等离子体鞘层中尘埃颗粒影响

在一维平板鞘层中应用流体模型研究了尘埃等离子体鞘层中碰撞对尘埃颗粒密度和带电量的影响。 研究所涉及的碰撞主要有电离碰撞,电子、离子分别与中性粒子的碰撞,以及电子、离子分别与尘埃颗粒的碰撞。通过采用四阶龙格库塔法,得到了数值解。结果表明,随着电离碰撞或者电子、离子分别与中性粒子碰撞的频率 增加,都将导致鞘层中尘埃颗粒的数密度增大,数密度的极值位置向鞘边位置靠近,尘埃颗粒带电量增多。电子、离子与尘埃颗粒的碰撞,使得尘埃带电量减小。此外,从研究的结果来看,由离子产生的碰撞要比电子产生的碰 撞对尘埃颗粒的影响明显得多。     

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The fluid dynamics model was used to study the influence of the existence of the collisions on the dust particles in a dusty plasma sheath. The main collisions in this study consist of the ionization collision, the collision between electron and neutral particle, the collision between ion and neutral particle, the collision between electron and dust particle, the collision between ion and dust particle. Numerical calculation results are obtained by the fourth-order-Rung-Kutta method. It is shown that both the dust particles’ density and corresponding electricity quantity increase as the following collisions’ frequency enhances, such as ionization collision, the collision between electron and neutral particle, the collision between ion and neutral particle. The charge reduces due to the collisions concluding electron-dust particle and ion-dust particle. In addition, the effect produced by ions’ collision is much more obviously compared with electrons’ collision.     

Prediction and Measurement of Electron Density and Collision Frequency in a Weakly Ionised Pine Fire

Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation, electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35 × 10¹⁶ m⁻³ and 3.43–5.97 × 10¹⁰ s⁻¹ respectively.