KCl添加剂对激光诱导土壤等离子体辐射强度的影响

为了提高激光诱导击穿光谱技术对低含量物质成分的检测能力,实验研究了KCl添加剂对土壤样品发射光谱的增强效应。利用高能量钕玻璃脉冲激光器烧蚀样品,由组合式多功能光栅光谱仪和CCD数据采集处理系统记录等离子体光谱,并通过测量光谱线的强度和Stark展宽分别计算了等离子体的电子温度和电子密度。实验结果证明,随着KCl加入量的增加,激光等离子体的光谱强度、信背比、电子温度和电子密度均呈现出先增大而后减小的规律。当KCl加入量为15%时,等离子体辐射最强,元素Mn,Fe,和Ti的谱线强度分别比无添加剂时提高了2.23,1.13和2.04倍,信背比分别提高了1.33,0.89和0.94倍;而等离子体的温度和电子密度比无添加剂时分别提高了14%和38%。     

样品添加剂对激光诱导等离子体辐射的增强效应

为了改善激光诱导等离子体的辐射特性,利用由高能量钕玻璃脉冲激光器、组合式多功能光栅光谱仪和CCD数据采集处理系统构成的光谱测量装置,以国家土壤标样为靶,研究了NaCl样品添加剂对激光等离子体辐射强度的影响,并由光谱线的强度和Stark展宽分别计算了等离子体的电子温度和电子密度。实验结果表明:随着NaCl加入量的增加,激光等离子体的光谱强度、信背比、电子温度和电子密度均呈现出先增大而后减小的趋势。当NaCl加入量为15%时,等离子体的辐射强度最大,元素Mn,K,Fe和Ti的谱线强度分别比无添加剂时提高了39.2%,42.5%,53.9%和33.8%,光谱信背比分别提高了64.4%,84.3%,44.5%和58.2%,而等离子体的电子温度和电子密度比无添加剂时分别提高了0.17倍和0.36倍。     

样品温度对纳秒激光诱导土壤等离子体辐射特性的影响（英文）

利用脉宽8 ns,波长为532 nm的Nd:YAG单脉冲纳秒激光器,在一个标准大气压下入射到土壤中(样品土壤来自蚌埠学院校园),改变样品温度,获得了不同样品温度下激光诱导击穿光谱.通过分析光谱,得到土壤中不同特征谱线的强度和信噪比.分别利用Boltzmann斜线法和Stark展宽法计算并分析了等离子体电子温度和电子密度随样品温度的演化规律;同时讨论了提高样品温度和激光诱导土壤等离子体辐射增强的原因.实验结果表明,随着样品温度的升高,等离子体的谱线强度、信噪比、电子温度和电子密度会逐渐增强,并且在温度为100℃时达到最大.     

激光诱导Ni等离子体特性的研究

以Nd·YAG激光器的二倍频输出作为激发源,获得了激光诱导Ni等离子体的发射光谱,基于发射光谱,对等离子体电子激发温度和电子密度进行了测量,其典型值分别为3 714 K,4.67×1016 cm-3。测量了等离子体电子激发温度和电子密度的空间分布,发现沿垂直于激光传播方向的径向,随到中心点距离的增加,等离子体辐射的强度减小,但线型和线宽不变,表明等离子体电子激发温度和电子密度沿径向均匀分布。沿激光传播方向,随到样品表面距离的增加,等离子体辐射强度、电子激发温度和电子密度先增加后降低,在距样品表面1.5 mm处,达到最大值。采用激光诱导击穿光谱技术进行相关探测时,收集距离样品表面1.5 mm处的发射谱,有利于提高探测灵敏度。     

样品温度对纳秒激光诱导土壤等离子体辐射特性的影响

利用脉宽8 ns,波长为532 nm的Nd:YAG单脉冲纳秒激光器,在一个标准大气压下入射到土壤中(样品土壤来自蚌埠学院校园),改变样品温度,获得了不同样品温度下激光诱导击穿光谱. 通过分析光谱,得到土壤中不同特征谱线的强度和信噪比. 分别利用Boltzmann斜线法和Stark展宽法计算并分析了等离子体电子温度和电子密度随样品温度的演化规律;同时讨论了提高样品温度和激光诱导土壤等离子体辐射增强的原因. 实验结果表明,随着样品温度的升高,等离子体的谱线强度、信噪比、电子温度和电子密度会逐渐增强,并且在温度为100 °C时达到最大.     

激光诱导煤粉等离子体的特性研究

本文研究了煤粉形态对于激光诱导煤粉等离子体特性的影响,以指导应用激光感生击穿光谱进行煤质测量时最佳样品形态的选择.建立了一套激光诱导击穿光谱的实验台架,对同一煤种的4个不同粒径范围的粉状样品进行激光激发与光谱分析,利用钙原子不同跃迁能级发射谱线的强度分布计算了0.3～0.5μs区间内的等离子体温度,并依据谱线Stark展宽与电子密度的关系得到了等离子体的电子密度.再对激发不同粒径煤粉样品产生的等离子体温度与电子密度进行了对比.实验证明,煤粉粒径越小,等离子体温度越高且电子密度越大,也即样品的等离子化程度越高,越有利于煤中元素的定量分析.     

不同样品温度下聚焦透镜到样品表面距离对激光诱导铜击穿光谱的影响

研究了不同温度下聚焦透镜到样品表面距离对激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)强度的影响,使用Nd:YAG脉冲激光激发样品并产生等离子体,探测的等离子体发射的光谱线为Cu(Ⅰ)510.55 nm,Cu(Ⅰ)515.32 nm和Cu(Ⅰ)521.82 nm.使用透镜的焦距为200 mm,测量的聚焦透镜到样品表面距离的范围为170—200 mm,样品温度从25℃升高到270℃,激光能量为26 mJ.总体上,升高样品温度能有效地提高LIBS光谱的辐射强度.在25℃和100℃时,光谱强度随着聚焦透镜到样品表面距离的增加而单调增加;在样品温度更高(150, 200, 250和270℃)时,光谱强度随着距离的增加出现先升高而后又降低的变化.同时,在样品接近焦点附近,随着样品温度的升高,LIBS光谱强度的变化不明显,还可能出现光谱强度随着样品温度升高而降低的情况,这在通过升高样品温度来提高LIBS光谱强度中特别值得我们注意.为了更进一步了解这两个条件对LIBS的影响,计算了等离子体温度和电子密度,发现等离子体温度和电子密度的变化与光谱强度的变化几乎一致,更高样品温度下产生的等离子体温度和电子密度更高.     

碳涂层对激光诱导金属等离子体辐射强度的影响

为了降低样品表面对激光束的反射率,提高激光诱导等离子体的辐射强度,文章报道了一种在钢样品表面涂抹碳层的方法.实验结果表明,当一束高能量激光(～25 D作用于覆盖有适当厚度碳涂层的钢样品时,激光等离子体发射的谱线强度提高了10%～28%.为解释谱线强度增强的机理,测量了等离子体的激发温度.此外,实验研究还发现,更强的原子发射光谱出现在激光等离子体径向的1 mm处,而不是在其中心位置.     

NaCl对激光诱导土壤等离子体辐射的增强效应

为了改善激光诱导击穿光谱质量,采用Nd:YAG激光器输出的纳秒脉冲激光激发土壤样品,由光栅光谱仪和光电检测系统记录等离子体发射光谱,研究了激光输出能量（100~500 mJ）和NaCl样品添加剂（质量分数0%~20%）对等离子体辐射强度的影响。实验结果表明,在激光能量为200 mJ的优化条件下,可以提高光谱强度和信噪比,而更高激光能量诱导的等离子体中光谱线自吸严重。当土壤样品中加入适量NaCl添加剂以后,能够进一步改善激光光谱质量。NaCl加入量为10%时,等离子体中元素Fe,Ba,Al和Ti的谱线强度比无添加剂时分别提高了37%,32%, 32% 和70%,光谱信噪比分别提高了33%,26%,16% 和38%。而样品烧蚀量、电子温度和电子密度比无添加剂时分别提高了14%,9.6%和26%。     

空气中YAG激光诱导Cu等离子体空间特性的研究

在空气中利用Nd:YAG脉冲激光诱导金属Cu靶,产生激光等离子体羽,并获得等离子体羽的空间谱;研究了空间谱线结构;分析了不同空间位置处电子温度和电子密度的空间演化规律;并对等离子体光谱的特性和产生机制进行了讨论.结果表明:谱线结构、谱线强度和等离子体的电子温度及电子密度都与空间位置变化密切相关,特征谱强度最大值出现在距靶面0.75～1.0mm的空间位置处,此处CuⅠ谱线相对强度最强,在1.25mm空间位置处的电子温度比周边的电子温度偏低,但此处电子密度反而升高,这种现象可以由级联效应得到解释.     

激光诱导等离子体光谱法(LIPS)测定不锈钢中微量元素

激光诱导等离子体光谱技术(LIPS)是一种非接触式实时检测技术,将其用于对钢铁成分检测,可满足大型钢铁企业高速化、连续化、自动化生产要求。以波长为1 064 nm的Nd∶YAG调Q固体激光器为激发光源,ICCD为探测器,标准不锈钢1Cr18Ni9Ti系列为样品在建立的LIPS实验装置上对样品中微量金属元素铝、锰、钴、钼和钛的含量进行了测量。实验中通过对ICCD工作的延迟时间和积分时间的合理设置得到高信噪比的谱线信号,在光谱数据处理时采用了基于基体效应的内标法。实验结果显示,测量元素的浓度与定标元素铁的浓度之比与它们的谱线强度之比均呈很好的线性关系,测试的五种微量元素探测极限不大于150 μg·g-1。     

大气压氩直流微放电光谱研究

微空心阴极放电或微放电是一种能够实现高气压下放电的有效方法。利用不锈钢空心针作阴极,不锈钢网作阳极,进行了大气压氩直流微放电实验研究。测量了大气压氩微放电光谱,发现氩气的发 射谱线主要集中在690～860 nm范围,且全部为氩原子4p—4s的跃迁。实验研究了不同放电电流、气体压强、气体流量与谱线强度之间的关系,发现谱线强度随放电电流、气体流量增加均增加,而谱线强 度随压强变化呈现不同特征：谱线强度随压强的增加先增加后降低,在13.3 kPa时强度最大。此外,选用跃迁波长为763.51和772.42 nm的两条光谱线,利用发射谱线强度比值法测量了氩气微放电等离子 体的电子激发温度。结果显示,其电子激发温度处于2 000～2 800 K之间,且随放电电流的增加而增加,随气体压强和气体流量的增加而降低。     

Biological response of stainless steel surface modified by N2O/O2 glow discharge plasma

Stainless steel wafers were treated with the glow discharge plasma of mixed N₂O and O₂ at different molar ratios at a certain discharge condition to create desirable biological characteristics to the surfaces. It was found that the molar ratio of N₂O to O₂ in the mixture at 1:1 used for plasma surface modification caused high apoptotic percentage. Contact angle measurement showed that the surface of stainless steel samples became very hydrophilic after the plasma modification with a value of 15°-30°. The control stainless steel chips without plasma treatment had a contact angle of 40 ± 2°. The data of Electron Spectroscopy for Chemical Analysis (ESCA) indicated that there was a certain amount of oxynitrites formed on the plasma treated surfaces, which was considered to play an important role to cell apoptosis and anti-clot formation in cell culture tests. The ESCA depth profile of up to 250 Å from the top surface showed the change of elemental compositions within 40-50 Å of the surface by the plasma treatment. The decreased platelet attachment, combined with increased apoptosis in fibroblasts is a distinct combination of biological responses arising from the mixed gas plasma treatment. These initial results suggest it may be of particular use relative to stainless steel stents where decreased platelet attachments are advantageous and induction of apoptosis could limit in-stent restenosis.     

飞秒激光烧蚀0Cr18Ni9不锈钢精度的影响因素

为了研究影响飞秒激光烧蚀0Cr18Ni9不锈钢精度的因素,采用飞秒激光对0Cr18Ni9不锈钢进行了切割和打孔实验。利用光学显微镜、光学金相显微镜等设备,对不锈钢烧蚀区形貌和切缝显微组织进行检测,基于烧蚀过程中CCD实时采集到的不锈钢表面的激光光斑图样,采用COMSOL Multiphysic数值模拟软件,模拟了烧蚀过程中激光束的发散传播行为,并计算了光束发散角。结果表明:当激光重复频率为5kHz时,厚度为160μm的0Cr18Ni9不锈钢切缝和孔边缘被明显烧黑,切缝处晶粒明显长大,存在热影响区;烧蚀过程中,由飞秒激光超高功率密度所致的金属-空气混合等离子体使光束沿传播方向上发生散射,发散角在6°～10°之间。热影响区的存在和混合等离子体的行为是影响飞秒激光烧蚀0Cr18Ni9不锈钢精度的主要因素。     

Aesthetic laser marking assessment using luminance ratios

In this paper, a luminous ratio was applied to evaluate four types of material surfaces; anodized aluminium, stainless steel, poly-butylene tetra-phthalate (PBT), and phenol formaldehyde, marked using a Nd:YAG laser. The luminous ratio was based on the spectral reflectance readings obtained from a spectrophotometer and computed for the case of scotopic (low illumination) and photopic (normal illumination) viewing. The method of using luminous ratios was able to produce quantitative results that determined visibility differences under photopic and scotopic viewing for stainless steel and phenol formaldehyde. The method revealed optimal marking speeds for all the materials studied; with the optimal speed found to be highest for PBT and lowest for stainless steel. By comparing the absolute luminous ratio differences at the respective optimal marking speeds, the method also revealed that markings on phenol formaldehyde and anodized aluminium had the highest and lowest visibility, respectively.     

Effect of cathode material on the opening performance ofmicrosecond-conduction-time plasma opening switch

Experiments were conducted to investigate the effect of cathode material on the opening performance of microsecond-conduction-time plasma opening switch with cathode made of aluminum, stainless steel, molybdenum and tungsten. Remarkably different opening characteristics have been shown for these materials, with tungsten or molybdenum corresponding to better opening performance than aluminum or stainless steel. Heuristic physical explanations are proposed for understanding the switch behavior     

低温下不锈钢导热系数的测量

在低温条件下利用稳态纵向热流法测量了制造低温阀门常用的316L不锈钢和17-4PH不锈钢的导热系数,通过实验表明两者的导热系数与316不锈钢的导热系数十分接近。     

Contribution to the application of the langmuir probe technique for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process

In the present paper the Langmuir probe technique was applied for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process. The experiments were performed in a stainless steel DC magnetron reactor with a planar magnetron cathode. Within the investigated range of the gas pressure, no time-stable condition of the discharge was found. The regular oscillations, of a frequency of approximately 32 kHz, were observed in the Ar and 20% n-hexane mixture at the total pressure of 10 Pa and the discharge current of 8 mA. The experimentally obtained probe characteristics were used to determine the density and the average energy of electrons. In the DC magnetron stainless steel reactor the electron average energy in the Ar and n-hexane mixture plasma was about one order of magnitude smaller than in the case in which the working gas inside the reactor was the pure Ar. The probe measurements in the magnetron reactor were supplemented by the experiment in the customary glass discharge tube with a hollow cathode. In the glass discharge tube and in the Ar and 10% n-hexane mixture plasma a region of plasma parameters was found, in which the plasma was stable and no instabilities were observed. At such conditions the experiments in the glass discharge tube were used for the study of the efficiency of the probe surface cleaning methods used. This report was financially supported by grant 202/97/1011, 202/98/0116 and 202/98/0666 of the Grant Agency of Czech Republic, by the grant 75/98 of the Grant Agency of Charles University and by project COST 516. This work has been done within the framework of Association for Education, Research and Application in Plasma Chemistry.     

Laser pulse transient method for measuring the normal spectral emissivity of samples with arbitrary surface quality

A laser pulse transient method for measuring normal spectral emissivity is described. In this method, a laser pulse (λ=1064 nm) irradiates the top surface of a flat specimen. A two-dimensional temperature response of the bottom surface is measured with a calibrated thermographic camera. By solving an axisymmetric boundary value heat conduction problem, the normal spectral emissivity at 1064 nm is determined by using an iterative nonlinear least-squares estimation procedure. The method can be applied to arbitrary sample surface quality. The method is tested on a nickel specimen and used to determine the normal spectral emissivity of AISI 304 stainless steel. The expanded combined uncertainty of the method has been estimated to be 18%.     

Surface enhancement of molecular ion H_2~+ yield in a 2.45-GHz electron–cyclotron resonance ion source

High current hydrogen molecular ion beam is obtained with a specially designed stainless steel liner permanent magnet2.45-GHz electron–cyclotron resonance(ECR) ion source(PMECR II) at Peking University(PKU). To further understand the physics of the hydrogen generation process inside a plasma chamber, theoretical and experimental investigations on the liner material of the plasma chamber in different running conditions are carried out. Several kinds of materials, stainless steel(SS), tantalum(Ta), quartz, and aluminum(Al) are selected in our study. Experimental results show that stainless steel and tantalum are much better than others in H~+_2 generation. During the experiment, an increasing trend in H~+_2 fraction is observed with stainless steel liner after O_2 discharge inside the ion source. Surface analyses show that the roughness change on the surface after O_2 discharge may be responsible for this phenomenon. After these studies, the pure current of H~+_2 ions can reach 42.3 mA with a fraction of 52.9%. More details are presented in this paper.