Application of laser-induced plasma spectroscopy to the measurement of Stark broadening parameters

In this work, we have studied the main conditions that a laser-induced plasma must fulfill in order to be considered as adequate for the measurement of Stark broadening parameters. We investigated the effect of the temporal window, the self-absorption, the crater size, and the effect of the spatial inhomogeneity on the emission profiles coming from a laser-induced plasma. Starting from the spatially resolved values of the plasma parameters, obtained by emission spectroscopy, the error in the determination of the Stark electron width due to the spatial inhomogeneity has been estimated and, for the present experimental conditions, was found to be lower than 7%. As a test of the method, the Stark electron broadening constant of Fe I 381.58 nm has been measured using the Fe I 538.34 nm emission line as the reference to determine the electron density. The plasma was produced under a controlled atmosphere of argon at atmospheric pressure, on an iron–nickel alloy sample. The emission was collected by a system with high spectral resolution, for different temporal windows after the laser pulse. For time delays between 2.75 and 21 μs, the electron density showed an evolution in the range 2.0–0.13 × 10¹⁷ cm^− 3, while the temperature varied from 11 100 to 7100 K. The representation of the Stark electron width of Fe I 381.58 nm, measured for each temporal window, versus the Stark electron width of the reference line showed a linear behavior with a high correlation coefficient. From the slope of this linear fit and the Stark electron broadening constant of the reference line, the Stark width of Fe I 381.58 nm was obtained to be 1.10 ± 0.07 × 10^− 2 nm for an electron density of 10¹⁷ cm^− 3.     

Characterization of a laser-induced plasma by spatially resolved spectroscopy of neutral atom and ion emissions.: Comparison of local and spatially integrated measurements

The local values of the parameters that characterize a laser-induced plasma (temperature, electron density, relative number densities of neutral atoms and ions) have been obtained by spatially resolved emission spectroscopy, including the deconvolution of the measured intensity spectra. The plasma has been generated using a Nd:YAG laser with a Fe–Ni alloy in air at atmospheric pressure, and the emission in the time window 3.0–3.5 μs has been detected. The temperature values obtained from neutral atom and ion emissions have been compared in the cases of local and spatially-integrated measurements. Local Boltzmann and Saha–Boltzmann plots with high correlation to linear fittings have been obtained using two broad sets of optically thin neutral atom and ion lines (21 Fe I lines and 15 Fe II lines), resulting in local values of the electronic temperature that coincide within the error. These results of local measurements contrast with those of spatially integrated measurements, for which two different temperatures are obtained from the Boltzmann plots of neutral atoms (9100±150 K) and ions (13 700±300 K). This difference is explained according to the measured distributions of the electronic temperature and the neutral atom and ion number densities, that result in separated emissivity (or population) distributions of neutral atom and ion lines, leading to different neutral atom and ion apparent temperatures (population-averages of the local electronic temperature). Local values of the plasma parameters have been obtained at all the positions with significant emission, including the determination of the electronic temperature from Saha–Boltzmann or Boltzmann plots. The ionization degree is high- and low-varying at the inner part of the plasma, decaying only near the plasma front. The maximum of the ion density does not coincide with the temperature maximum; on the contrary, the axial variation of both the neutral atom and ion densities (that decrease towards the sample surface) is opposite to that of the temperature, a behaviour that is interpreted to result from the plasma expansion process.     

低功率微波等离子体炬（MPT）光源基本性质的初步研究

对低功率微波等离子体炬(MPT)光源基本性质进行了初步研究,采用“双线法”测定了有、无样品引入时光源中激发温度随观测高度的变化;测定了Zn、Cd、Mg的原子线和离子线发射强度随观测高度的变化;还研究了一些实验参数对等离子体激发温度的影响。     

盐酸煮沸提取和ICP-AES测定植株中矿质元素

本文研究了用4N盐酸煮沸提取植株中的K、Na、Ca、Mg、P、Cu、Zn、Fe、Mn、Sr、Ba和B的实验条件。浸提液用ICP-AES测定,获得了满意的结果。方法简单、操作简便、安全。与硝酸-高氯酸湿消化法进行了对照,结果非常一致,除硼外十一种元素都不存在显著差异。并测定了国家级标准甘兰物质GBW 08504,其结果与标准值相符。     

Measurement of neutron emission from a Ti−D2 system

Neutron emission from the d-d nuclear fusion reaction, D/d,n/³He, in and on titanium metals /titanium sponge and the mixture of titanium powder/ trapped deuterium at about 1 atm has been ascertained by using a high resolution liquid scintillation detector. The neutron emissions from 11 samples which were provided under wide varieties of conditions were measured by temperature change in the range of liquid nitrogen temperature to 350 °C. As a result, it was proved that the neutron emission observed can be divided into two types, such as cooling and heating, by the evolved conditions. Moreover, by estimating the neutron emission efficiencies of samples, it was suggested that the neutron emission reactions are closely related to the deuterium trapped in the surface of titanium metal.     

Simultaneous determination of bismuth and tellurium in steels by high power nitrogen microwave induced plasma atomic emission spectrometry coupled with the hydride generation technique

An annular-shaped, high power nitrogen microwave induced plasma (N₂-MIP) produced at atmospheric pressure by an Okamoto cavity, as a new excitation source for atomic emission spectrometry (AES), has been used for the simultaneous determination of bismuth and tellurium in steels with the hydride generation method. Under the optimized experimental conditions, the best attainable detection limits at the Bi I 195.389 nm and Te I 200.200 nm lines were 110 and 86 ng/ml for bismuth and tellurium, respectively. The linear dynamic ranges for bismuth and tellurium were 300 to 30,000 ng/ml. The presence of several diverse elements was found to cause a more or less depressing interference with the proposed technique. When bismuth and tellurium in steels were determined, a large amount of Fe(III) in the solution caused a severe depressing interference, while the presence of Fe(II) showed little or no significant interference. Of the several interference-releasing agents examined, l-ascorbic acid was found to be the most preferable to reduce Fe(III) to Fe(II) prior to hydride generation. The concentrations of bismuth and tellurium in steels were determined by the proposed technique. The results obtained by this method were in good agreement with their certified values.     

盐酸浸提-电感耦合等离子体发射光谱法测定烟草中的多元素

研究了用5mol/L盐酸煮沸提取烟叶中的部分金属元素，用ICP－AES测定浸提液，K、Ca、Mg、Cu、B、Ba、Zn获得了较满意的结果，P、Fe、Mn的测定结果稍微偏低。此方法操作简便、快速安全，特别适合大批量烟草样的快速检测。与硝酸－高氯酸湿消化法进行对照，结果吻合得较好。并测定了国家烟草标准样品GBW08514和GBW08515，其结果与标准值相符。     

In-situ monitoring of degradation of C/C composites and coatings in an inductively coupled plasma by a spectroCCD camera

Spatially and spectrally resolved profiles of atomic emission around the surface of C/C composites with double layer coatings in an inductively coupled plasma (ICP) have been measured by means of a spectroCCD camera. The plasma temperature around the sample disk was measured with the two-line method using atomic lines of iron, and found to be higher under oxidizing conditions because of combustion heat. This is a good measure of reflecting that the degradation is more significant under the oxidizing condition. The degradation procedure of the C/C composites with the double layer coatings has also been measured by a multi-channel spectrometer. The degradation of the sealant and the following attack of the plasma on a SiC layer were observed by the temporal change in emission intensity.     

微波等离子体炬原子发射光谱法测定米粉中微量元素——一个大学化学仪器分析实验的设计与实践

设计了一个科研参与型的大学化学仪器分析实验。本实验应用MPT原子发射光谱仪对米粉中的金属元素(Ca,Cu,Fe,Mn)进行了检测分析。对影响金属元素检测性能的实验条件,如微波等离子体炬的微波功率和维持气流量进行了系统的考查及优化。最后,通过对样品进行测定,证实与标准含量相符,结果比较满意。学生在实验过程中,可以学习和掌握样品的前处理方法、原子发射光谱的机理和仪器测试条件的优化。     

电感耦合等离子体原子发射光谱法(ICP-AES)测定N18锆合金中Nb,Sn,Fe,Cr元素含量

建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定N18锆合金中Nb,Sn,Fe和Cr含量的分析方法。对溶样方法、基体影响、谱线选择等进行了讨论,结果表明,锆基体对测定结果有一定的影响,在实验中采用基体匹配法消除基体干扰,并对实验条件进行了优化。在优化的实验条件下,该方法用于样品中Nb、Sn、Fe、Cr的测定,测定结果与化学法测定结果基本一致,加标回收率为96.7%~101.0%,相对标准偏差(RSD,n=11)均小于3%。     

高压微波消解-电感耦合等离子体原子发射光谱同时测定进口奶粉中Fe、Zn、Ca、Mg、Cu含量

通过优化试验确定仪器的最佳工作参数,硝酸-过氧化氢微波消解样品,采用电感耦合等离子体原子发射光谱同时测定进口奶粉中的Fe、Zn、Ca、Mg、Cu多种金属元素含量．试验过程方便快捷,多种元素同时测定节约测定时间．方法的准确度、精密度均符合日常检验的需要．     

Temperaturmessungen am Argon-Niederstrombogen zur Bestimmung der Übergangswahrscheinlichkeiten von Si I-, Se I- und S I-Linien im nahen Vakuum-UV

The temperatures of scon-cooled argon-d.c.-arc under variousexperimental conditions have been measured. It is shown that the Ornstein-method can be applied in the vacuum-ultraviolet region because the optimum temperatures of the spectral lines in this region are very high. The temperature of the arc has been determined in respect to the electric current and the electrode distance. The temperature of the arc rises with increasing current, whereas by varying the distance of the electrodes a temperature maximum is observed which can be explained by the amount of power absorbed by the electrodes. The relative transition probabilities of several lines of Si I, Se I and S I in the vacuum-u.v. have been measured. Some of the values which had already been determined theoretically and experimentally by other authors agree very well with our results.     

镁铁双羟基复合金属氧化物的可控合成及晶面生长特征研究

采用成核/晶化隔离法合成镁铁双羟基复合金属氧化物MgFe-LDH,考察了Mg ∶ Fe摩尔比对MgFe-LDH晶形的影响,探讨了晶化温度及晶化时间对晶面生长选择性及晶粒尺寸的影响规律.结果表明,随Mg ∶ Fe摩尔比增大,层板阳离子排列更为规整.晶化温度对晶粒尺寸的影响显著大于晶化时间的影响.晶化温度相同,随晶化时间延长, MgFe-LDH的晶体结构趋于完整,晶粒尺寸变化不大;晶化时间相同,随晶化温度升高,晶体结构趋于完整,晶粒尺寸明显增大.所得到的MgFe-LDH沿a轴方向的晶粒尺寸对晶化温度变化的敏感程度远大于对晶化时间变化的敏感程度,但总是沿a轴方向的晶粒尺寸大于沿c轴方向的尺寸,即[110]晶面的生长速率比[002]晶面的生长速率快.     

Quantitative Analysis of Fe Content in Iron Ore via External Calibration in Conjunction with Internal Standardization Method Coupled with LIBS

The external calibration in conjunction with internal standardization(ECIS) coupled with laser-induced breakdown spectroscopic(LIBS) technique was proposed to perform the quantitative analysis of Fe content in iron ore. The plasma temperature and the electron number density were calculated to prove that the plasma was under local thermodynamic equilibrium(LTE) conditions and to ensure that the integral intensities of Fe I lines were reasonable. In addition, the result of the quantitative analysis shows a content of (20.26±0.59)% by mass of Fe in the iron ore. It was determined by four calibration curves, drawn for four emission lines of Fe I(373.48, 373.71, 404.58 and 438.35 nm) normalized by Mn I line, base on the ECIS method which can eliminate the influence of matrix effect and improve the accuracy of quantitative analysis, compared with the standard addition method. Both the results of these two analytical methods were compared with that listed in the Standard Substance Certificate. The percentage content of Fe in the same sample of iron ore by the ECIS method was (20.17±0.08)% by mass, which shows a good performance to analyze the Fe content of iron ore in combination with LIBS.     

Comparison of detection limits, for two metallic matrices, of laser-induced breakdown spectroscopy in the single and double-pulse configurations

Limits of detection have been studied for several elements in aluminium and steel alloys, at atmospheric pressure in air, by use of the single and collinear double-pulse configurations of laser-induced breakdown spectroscopy. For this purpose, calibration plots were constructed for Mg, Al, Si, Ti, Cr, Mn, Fe, Ni, and Cu using a set of certified aluminium alloy samples and a set of certified steel samples. The investigation included optimization of the experimental conditions to furnish the best signal-to-noise ratio. Inter-pulse delay, gate width, and acquisition delay were studied. The detection limits for the elements of interest were calculated under the optimum conditions for the double-pulse configuration and compared with those obtained under the optimum conditions for single-pulse configuration. Significantly improved detection limits were achieved, for all the elements investigated, and in both aluminium and steel, by use of the double-pulse configuration. The experimental findings are discussed in terms of the measured plasma conditions (particle and electron density, and temperature).     

Laser-assisted synthesis of superparamagnetic Fe@Au core-shell nanoparticles

A novel method combining wet chemistry for synthesis of an Fe core, 532 nm laser irradiation of Fe nanoparticles and Au powder in liquid medium for deposition of an Au shell, and sequential magnetic extraction/acid washing for purification has been developed to fabricate oxidation-resistant Fe@Au magnetic core-shell nanoparticles. The nanoparticles have been extensively characterized at various stages during and up to several months after completion of the synthesis by a suite of electron microscopy techniques (HRTEM, HAADF STEM, EDX), X-ray diffraction (XRD), UV-vis spectroscopy, inductively coupled plasma atomic emission spectroscopy, and magnetometry. The surface plasmon resonance of the Fe@Au nanoparticles is red shifted and much broadened as compared with that of pure colloidal nano-gold, which is explained to be predominantly a shell-thickness effect. The Au shell consists of partially fused approximately 3-nm-diameter fcc Au nanoparticles (lattice interplanar distance, d = 2.36 A). The 18-nm-diameter magnetic core is bcc Fe single domain (d = 2.03 A). The nanoparticles are superparamagnetic at room temperature (300 K) with a blocking temperature, T(b), of approximately 170 K. After 4 months of shelf storage in normal laboratory conditions, their mass magnetization per Fe content was measured to be 210 emu/g, approximately 96% of the Fe bulk value.     

Spatial distributions of the number densities of neutral atoms and ions for the different elements in a laser induced plasma generated with a Ni-Fe-Al alloy

Spatially-resolved emission spectroscopy, including spatial devonvolution of the spectra, has been used to determine the three-dimensional distributions of the relative number densities of neutral atoms and ions of the elements present in a laser-induced plasma generated with a Ni-Fe-Al alloy. The method is based on the precise measurement of the local electronic temperature from Saha–Boltzmann plots constructed with Fe I and Fe II lines. The plasma was generated in air at atmospheric pressure using a 1064-nm Nd:YAG laser, and the emission was detected in the time window 3.0–3.5 μs. The ionization fraction was very high (above 0.9) for the three elements in the sample, only decreasing behind the expanding plasma front. The relative number densities were obtained from the emissivities of selected elemental lines as well as the temperature. The error in this procedure was estimated, and it was found that it is largely due to the uncertainties in the transition probability values used. The spatial distributions of the total relative number densities of the three elements were shown to coincide within the error, a result which is relevant to the development of models of plasma emission used in analytical applications. The ratios of the total number densities of the elements in the plasma were compared to their concentration ratios in the sample; however, the relatively high errors in the relative number densities did not permit any definitive conclusions to be drawn about the stoichiometry of the laser ablation process.     

Preconcentration neutron activation analysis of lanthanides by cloud point extraction using PAN

Summary Methods for the simultaneous preconcentration of lanthanides by cloud point extraction and their determination using neutron activation analysis have been developed. The preconcentration method involves the use of a nonionic surfactant and a chelating agent. A fairly small volume of surfactant-rich phase was obtained under optimized experimental conditions, leading to detection limits between 0.3 and 3.0 ng ^. g^-1. Critical parameters that influence extraction efficiency were solution pH and concentration of chelating agent, and to a lesser extent, ionic strength and temperature. Most of the chelates were quantitatively extracted (>90%) at high pH values. Selective separation can be achieved by varying some of the experimental conditions.     

Load-displacement behavior for double-edge cracked plate of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) has been employed in many engineering applications, mainly due to its special properties such as high electrical resistivity, high melting temperature, chemical inertness, corrosion resistance and very low friction. Although there are many works on PTFE, very few attempts have been made to understand the fracture behavior of this material. For this reason, the load-displacement behavior of double-edge cracked specimens of PTFE was examined and modeled and is reported in this paper. Specimens were tested under monotonic tensile load in quasi-static conditions at constant temperature. Images of the region around the crack were captured with a high-resolution camera and then processed by digital image correlation to obtain the displacement fields. Using these data, values of crack tip opening displacement and crack extension were estimated. To model the behavior of PTFE, a constitutive phenomenological model based on saturation and power law expressions combined with a damage evolution equation is proposed. The predictions are in good agreement with the experimental data.     

Carbon film growth on iron substrates by a CVD method

Carbon film coatings have been produced by a hot‐wall chemical vapor deposition (CVD) method under moderate conditions from pyrolysis of a mixture of propane and argon on an Fe(110) substrate at temperatures of 800–900 °C for different deposition times. The effects of temperature and reaction time on the growth of the carbon films were studied. Field‐emission scanning electron microscopy (FESEM), Raman microscopy, Auger electron spectroscopy (AES) and x‐ray diffraction methods have been performed to study the surface morphologies, growth features and microstructures of the carbon film coatings. The FESEM analyses indicated that carbon films on an Fe substrate consisted of flat‐layer and filamentous morphologies. Raman and AES analyses showed that the carbon initially was crystalline but the degree of disorder in the top layer of the carbon film increased with increasing deposition temperature. High‐resolution transmission electron microscopy studies are also in agreement with Raman results. The same trend was observed when the deposition time was increased from 5 to 30 min. Copyright © 2005 John Wiley & Sons, Ltd.