Optical Emission Spectroscopy of Abnormal Glow Region in Nitrogen Plasma

Optical emission spectroscopy of the active species in N₂ plasma is carried out to investigate their concentration as a function of discharge parameters such as filling pressure (2.0–7.0 mbar), source power (100–200 W) and gas flow rate (50–300 mg/min). The primary motivation of this work is to obtain reliable information about the concentration of the active species of N₂ plasma, which play an important role in plasma surface nitriding processes. Emission intensity from the selected electronic excited states of molecular and atomic species is evaluated as a function of discharge parameters to investigate their concentration. The emission intensity ratio I(N₂⁺)/I(N₂) and I(N⁺)/I(N) of the electronic transitions is also evaluated as a function of discharge parameters to investigate the relative dependence of their concentrations. It is observed that the concentration of the active species of N₂ plasma is strongly affected by the filling pressure and source power whereas flow rate has no significant effect. An increased occurrence of N₂⁺ molecular ions in comparison with N₂ molecules, and N⁺ ions in comparison with N atoms is observed with source power whereas decreased occurrence of N₂⁺ molecular ions in comparison with N₂ molecules, and N⁺ ions in comparison with N atoms is observed with the rise in filling pressure.     

介质阻挡放电等离子体脱除氮氧化物的发射光谱研究

在大气压下, NO/N2体系中, 利用发射光谱技术对50 Hz和5 kHz交流介质阻挡放电等离子体在200～900 nm范围内进行了诊断. 在632、674.5、715.5和742 nm等处测得了N原子的谱线. 利用化学发光法NOx分析仪, 模块式红外吸收气体分析检测仪, 大气压下直连质谱多种检测手段对放电前后的稳定物种进行了分析, 观察到O2的生成. 初步讨论了无氧条件下介质阻挡放电等离子体中NO脱除的反应机制.     

强度调制光电流谱研究TiO2悬浮体系光催化机理

用强度调制光电流谱在光电化学电池中研究TiO2粒子悬浮液体系中的光催化反应机理,将强度按正弦变化的调制光照射TiO2粒子悬浮液,产生随频率变化的光电流响应,收集在Pt电极上,得到了光电流响应复数平面图,其上半圆和下半圆分别代表光生空穴和光生电子的阴极还原和阳极氧化反应过程.根据阴极和阳极光电流的幅度及上下半圆的特征频率分析讨论了光催化反应的机理及外加电压和H2O2添加物的影响.     

气相色谱—微波等离子体发射光谱法研究农药1605与人唾液的相互作用

用ＧＣ－ＡＥＤ联用技术研究了农药１６０５，得到１６０５所含六种元素的元素色谱图，并用该方法研究了人唾液与１６０５的相互作用。     

Time-resolved Optical Emission Spectroscopy in Water Electrical Discharges

The characteristics of the plasma initiated in ultrapure water between pairs of tungsten and tantalum electrodes were investigated by time-resolved optical emission spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depended on the electrode material, but had been independent on the polarity of the applied voltage pulses. All the reactive species presented the same evolution with time and have been identified with high concentration in the emission spectra between the pulses. The current–voltage characteristics showed the features of a spark discharge for the both types of electrodes used in the process. When tantalum electrodes were used to generate the discharge, a broad emission continuum (350–940 nm) dominated the spectrum due to a transition to arc discharge.     

Optical Emission Spectroscopy Measurements and Simulation of Radioelement Volatility During Radioactive Waste Treatment by Plasma

An optical emission spectroscopy (OES) method has been used to measure the concentration above the melt of some radioelements, ¹³⁷Cs, ⁶⁰Co and ¹⁰⁶Ru during the vitrification of radioactive wastes by thermal plasma. This method allows the study of non homogeneous optically thin plasmas exhibiting a symmetry plane without sophisticated tomographic systems. Local plasma temperatures above the melt have been evaluated using measured relative intensities of spectral lines of the plasma-forming gas. Radioelement concentrations in the plasma are deduced from the intensity ratio of the radioelement–gas spectral lines. A computer model is used to simulate the volatility of ¹³⁷Cs, ⁶⁰Co and ¹⁰⁶Ru, during the treatment of radioactive wastes by thermal plasma. This model is based on the calculation of system composition using the free enthalpy minimization method, coupled with the equation of mass transfer at the reactional interface. In this study, the OES measurements and the computer model allowed the determination of this radioelement volatility depending on the parameters like plasma current, and the nature of atmosphere furnace. The results of the model are compared to those obtained by OES measurements.     

Numerical Modeling in Radio Frequency Suspension Plasma Spray of Zirconia Powders

A comprehensive model was developed to investigate the suspension spraying for a radio frequency (RF) inductively coupled plasma torch. Firstly, the electromagnetic field is solved with the Maxwell equations and validated by the analytical solutions. Secondly, the plasma field with different power inputs is simulated by solving the governing equations of the fluid flow coupled with the RF heating. Then, the suspension droplets embedded with nano particles are modeled in a Lagrangian manner, considering feeding, collision, heating and evaporation of the suspension droplets, as well as tracking, acceleration, melting and evaporation of the nano or agglomerate particles. The non-continuum effects and the influence of the evaporation on the heat transfer are considered. This particle model predicts the trajectory, velocity, temperature and size of the in-flight nano- or agglomerate particles. The effects of operating conditions and intial inputs on the particle characteristics are investigated. The statistical distributions of multiple particles’ size, velocity, temperature are also discussed for the cases with and without consideration of suspension droplets collision.     

A Better Understanding of the Very Low-Pressure Plasma Polymerization of Aniline by Optical Emission Spectroscopy Analysis

In the wavelength range from 200 up to 1000 nm, optical emission from electronically excited fragments (CN, CH, NH, C₂, H₂, N₂, N₂⁺, and H-Balmer) is detected when aniline plasmas are generated in a multi-dipolar microwave reactor. The optical emission spectrum monitored in very low-pressure conditions (~?1 mTorr) shows important characteristics. The H_α, H_β and CN species are the most radiating systems and according to the NH/N₂ intensity ratio, two different operating regimes are observed suggesting a change in the reaction pathways. These two regimes are correlated to changes of the plasma characteristics (electron temperature and density) deduced from Langmuir probe measurements. The plasma thermodynamic state is quantified by implementing numerical simulation codes for synthetic spectra calculations. The rovibrational temperatures (T_r, T_v) are determined for some neutral species (CN, CH). The obtained values of T_r and T_v show the non-local thermodynamic equilibrium of the vibrational and rotational states (T_r?<?T_v). Moreover, the very low pressure aniline-based plasmas deviate substantially from the Boltzmann distribution. Correlation between the optical emission data and the solid phase analysis allows proving that the in situ characterization of the plasma phase is an important predictive tool of physico-chemical properties of the film. From these correlated data, we deduce preponderant chemical reaction pathways which help to better understand the plasma generation. Relative contributions of the dehydrogenation of C–H and N–H groups are established in order to deduce the leading initiation reaction for H-Balmer line formation.     

悬浮液进样电感藕合等离子体发射光谱中颗粒的输运和蒸发行为

以碳化硼为例,研究了悬浮液雾化进样中的粒子在传输和蒸发过程中的行为,并对分析结果出现负偏离的原因进行了详细探讨.对比悬浮液颗粒的原始粒径分布和经过传输过程后的粒径分布,获得到达等离子体的颗粒粒径上限小于10 Am.样品中存在的部分超大粒径的颗粒(d>>10 μm)会严重影响可传输区域颗粒(d<10 μm)的质量运输效率...     

Study by Optical Spectroscopy of Bismuth Emission in a Nanosecond-Pulsed Discharge Created in Liquid Nitrogen

Time-resolved optical emission spectroscopy of nanosecond-pulsed discharges ignited in liquid nitrogen between two bismuth electrodes is used to determine the main discharge parameters (electron temperature, electron density and optical thickness). Nineteen lines belonging to the Bi I system and seven to the Bi II system could be recorded by directly plunging the optical fibre into the liquid in close vicinity to the discharge. The lack of data for the Stark parameters to evaluate the broadening of the Bi I lines was solved by taking advantage of the time-resolved information supported by each line to determine them. The electron density was found to decrease exponentially from 6.5 ± 1.5 × 10¹⁶ cm⁻³ 200 ns after ignition to 1.0 ± 0.5 × 10¹⁶ cm⁻³ after 1050 ns. The electron temperature was found to be 0.35 eV, close to the value given by Saha’s equation.     

Microwave Digestion of Thermoluminescent Aluminium-Oxide Powders and Determination of Trace Impurities by Inductively Coupled Plasma Optical Emission Spectroscopy

 Five commercial and three laboratory prepared thermoluminescent aluminium-oxide powders as well as three reference samples were digested by a microwave digestion system and the impurities were determined by ICP-OES. The physico-chemical properties of the different samples were found to influence highly the decomposition efficiency. Optimized decompositi on parameters were determined for the samples with different physico-chemical properties (phase composition, grain size). The detection limits of the impurities of interest are presented, the analysis results for the aluminium- oxide dosimetric samples and the standards are given as well for Be, Ca, Ce, Cu, Fe, Cd, Mg, Mo, Na, Ni, Ti and Zn in the < 2–400 μg/g range. Received August 24, 1999. Revision December 1, 1999.     

四酸微波消解-电感耦合等离子体发射光谱(ICP-OES)法测定土壤和沉积物中全硼含量

土壤和沉积物的结构特点决定了全硼分析时存在消解不完全、易挥发损失等问题,为了提高全硼检测的效率和可靠性,利用微波消解仪对土壤和沉积物样品进行消解,选择分析谱线为208.957 nm,比较了不同酸体系消解的处理效果,并优化了赶酸温度,建立了一种四酸微波消解结合电感耦合等离子体发射光谱(ICP-OES)法测定土壤和沉积物中全硼含量的方法。在最优条件下,全硼含量在0.01~1.00 mg/L浓度范围内具有良好的线性关系,线性相关系数大于0.999,方法检出限为0.7 mg/kg,回收率为89.3%～96.5%,相对标准偏差为1.1~3.0%。方法可为土壤和沉积物中全硼的含量测定提供参考。     

Chemical Interactions by Low-Energy Electron-Induced X-Ray Emission Spectroscopy, LEXES

 The possibilities presented by low-energy electron-induced X-ray emission spectroscopy to study chemical interactions in solids are discussed. Examples of change observed for the emissions between core levels as a function of the chemical environment of the emitting atoms are given. By comparing the partial densities of the valence states associated to each type of atoms in the compound, it is shown that the strength of the metal-ligand interactions can be obtained. Information on the charge densities around each type of atoms can be deduced. Application to the study of the interactions at the atomic scale to solid–solid interfaces is presented.     

液下阴极放电等离子体的发射光谱诊断

基于尖端放电的原理,在2 g/L Na2SO4溶液中,以铂棒为阳极、针状铂电极为阴极,建立了 一种液下阴极放电等离子体诊断装置.利用直流电源的电流和电压示数绘制了电流-电压特性曲线,光纤光谱仪测量了 200～1 070 nm的发射光谱,普通相机拍摄了不同放电电压下的放电图斑.根据发射光谱数据,估算了电子温度、转动温度和...     

等离子体光谱光源技术的进展

光谱光源是光谱仪器和光谱技术的核心,等离子体光源是原子发射光谱技术的活跃领域之一,电感耦合等离子体(ICP)已成功地应用于原子发射光谱和无机质谱仪器。由于ICP光源采用氩气作为工作气体,耗量较大,降低氩气用量成为近些年来原子光谱技术研究和改进的重要目标。为此目的,已研究过各种低耗氩ICP光源,非氩气ICP光源,微波等离子体光源,射频电容耦合等离子体光源等。综述了近年这些等离子体发射光源的结构,分析性能及特点,以及它们所用工作气体情况。并归纳总结出,评价各种等离子体发射光谱光源应包括:等离子体温度(激发温度,气体温度),电子密度,工作气体种类及用量,元素检出限,光源的稳健性及经济方面等。     

Revisiting the Electrochemical Impedance Spectroscopy of Magnesium with Online Inductively Coupled Plasma Atomic Emission Spectroscopy

The electrochemical impedance of reactive metals such as magnesium is often complicated by an obvious inductive loop with decreasing frequency of the AC polarising signal. The characterisation and ensuing explanation of this phenomenon has been lacking in the literature to date, being either ignored or speculated. Herein, we couple electrochemical impedance spectroscopy (EIS) with online atomic emission spectroelectrochemistry (AESEC) to simultaneously measure Mg‐ion concentration and electrochemical impedance spectra during Mg corrosion, in real time. It is revealed that Mg dissolution occurs via Mg²⁺, and that corrosion is activated, as measured by AC frequencies less than approximately 1 Hz approaching DC conditions. The result of this is a higher rate of Mg²⁺ dissolution, as the voltage excitation becomes slow enough to enable all Mg²⁺‐enabling processes to adjust in real time. The manifestation of this in EIS data is an inductive loop. The rationalisation of such EIS behaviour, as it relates to Mg, is revealed for the first time by using concurrent AESEC.     

Analysis of Borosilicate Catalysts by Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

A method was developed for the analysis of borosilicate catalysts. Samples were prepared by fusion technique with potassium hydroxide and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The method was applied to a borosilicate NIST SRM 93 which was analyzed for major and minor elements (aluminum, sodium, silicon and boron). Despite the presence of relatively high concentration of the potassium, no matrix interferences were observed. This method provides precision and accuracy better than ±4% and ±6%, respectively.     

Optical Emission Spectroscopic Study of the Synthesis of Titanium Boride Nanoparticles in RF Thermal Plasma Reactor

Thermal plasma processes have been investigated by optical emission spectroscopy during the synthesis of TiB_x nanoparticles from TiO₂, B and C precursors using argon and helium both as plasma and sheath gases. Line-rich emission spectra were observed both in Ar–He–TiO₂–B and Ar–He–TiO₂–B–C cases. Emissions detected in the spectral region of 300–1000 nm were attributed to the electronic relaxation of excited Ti(I) and ionic fragments Ti(II), as well as the molecular species of TiO. The plasma temperature was calculated from the vibration–rotation temperature of the A–X electronic transition of TiO molecule by the least-squares fitting of experimental data to theoretical spectra. The temperatures at 100 mm downstream the torch outlet were found to be between 3800 and 2700 K for the Ar–He–TiO₂–B system, and between 5100 and 4300 K for the Ar–He–TiO₂–B–C system, respectively. The morphology of as-formed nanoparticles was characterized by transmission electron microscopy. Measurements of specific surface area, evaluated on the basis of Brunauer, Emmett and Teller equation, revealed that in all experimental setups titanium boride nanoparticles were formed with a mean particle size of 17–85 nm. On the basis of X-ray diffraction patterns, the solid reaction products were composed of TiB₂, boron doped titanium indicated as Ti(B), Ti₂O₃, H₃BO₃ and TiC. The actual composition of products depended on the synthesis conditions.     

电感耦合等离子体发射光谱(ICP-OES)法同时测定高纯钼中多种痕量元素

建立了电感耦合等离子体发射光谱(ICP-OES)法测定钼中Co、Cu、Fe、Mg、Mn、W、Zr元素含量的方法。确定了溶样方法和分析谱线,采用基体匹配消除干扰。对方法精密度和准确度进行实验,实验结果表明,各元素的相对标准偏差均小于3%,加标回收率在81.0%~110%。所建方法快速、准确,适用于钼中多元素同时测定。