激光诱导击穿光谱无标分析方法研究
发布时间：2019-01-15 07:00
【摘要】：激光诱导击穿光谱(Laser-Induced Breakdown Spectroscopy,LIBS)是通过会聚脉冲激光烧蚀并雾化微量样品产生等离子体,并分析发射光谱的波长和强度,获取样品定性和定量信息的元素分析方法。由于LIBS采用脉冲激光作为激发源,其具有许多优点,例如无需样品制备、近似无损、远程分析和多元素同时分析。近年来,LIBS已被广泛的应用于众多分析领域。由于有标LIBS分析有时难以找到基体匹配的标准样品或保证实验条件的恒定,极大的限制了 LIBS的应用。基于此,不需要使用标准样品建立定标曲线的无标激光诱导击穿光谱(Calibration-Free Laser-Induced Breakdown Spectroscopy,CF-LIBS)分析方法被提出,并被科研人员广泛研究。CF-LIBS是通过简单的数学模型来描述激光诱导等离子体的物理状态,所以其可以有效地克服基体效应的不利影响。然而,激光诱导等离子体又是十分复杂的无法用简单的物理公式准确进行描述,所以目前CF-LIBS的分析精度还没有达到有标LIBS或其它元素分析技术的水平。鉴于CF-LIBS的独特优势,理解并改进CF-LIBS算法具有重要的理论和应用价值。本论文主要从实验设置和基本理论假设两方面对影响CF-LIBS分析精度的因素进行分析,并从采集延迟和自吸收修正方面对算法进行相应的改进。主要研究内容如下:1、回顾了 LIBS的基本原理和特点;按照实验顺序,从激光与物质相互作用、光谱预处理、定性和定量分析四个方面介绍了 LIBS的发展历程;介绍了目前LIBS的应用、相关学术会议和已有的仪器设备;详细介绍了 CF-LIBS分析方法的国内外研究进展。2、搭建了用于CF-LIBS分析的实验系统,并综述了影响等离子体发射光谱展宽的主要机制。研究了激光脉冲数对光谱信号稳定性的影响;论述了光谱仪波长校准和相对效率修正的重要性;分析了造成谱线展宽的主要机制:自然展宽、Doppler展宽、Van derWaals展宽、共振展宽、Stark展宽、自吸收加宽和仪器加宽等。3、从光学厚且不均匀的一维等离子体理论出发,推导出CF-LIBS所要求的光学薄、均匀等离子体。详细介绍了 CF-LIBS的算法流程和基本理论假设。综述了影响CF-LIBS计算精确度的理论因素和近年来研究人员对其算法的改进。4、研究了时间分辨CF-LIBS分析。介绍了激光与物质相互作用和等离子体发射光谱随时间的演化过程;实验采集不同延迟时间下激光诱导炉渣等离子体发射光谱;提出了线状谱的寻峰、定峰和谱峰拟合算法;综述了等离子体温度的不同计算方法;研究了延迟时间对CF-LIBS精确度的影响;从自吸收和局域热力学平衡两方面对计算结果进行了解释。5、为了克服主量成分谱线的自吸收和微量成分谱线稀少的影响,基于局域热力学平衡假设,即所有存在于等离子体中的物种具有相同温度值,提出了标准参考线方法。基于主量成分谱线计算电子密度和等离子体温度,同时为每个元素的原子选择信噪比最好的一条谱线作为标准参考线,并计算其相应的标准参考浓度。比较了具有和没有自吸收标准参考线的定量分析结果。通过理论计算主量成分谱线的自吸收系数来优化标准参考线的选择。本论文的主要创新点在于:(1)开展了时间分辨CF-LIBS研究,获得了 CF-LIBS定量分析精度的最佳采集延迟。分别从自吸收和局域热力学平衡两个方面对计算结果进行了解释。(2)提出了标准参考线方法,克服了主量元素谱线的自吸收和微量元素谱线稀少的影响。(3)提出了理论计算线状谱的自吸收系数优化标准参考线的选择方法,避免了主观因素影响标准参考线的选择。
[Abstract]:Laser-induced breakdown spectroscopy (LIBS) is an element analysis method for obtaining the qualitative and quantitative information of the samples by the laser ablation of the convergent pulse and the atomization of the micro-sample to produce the plasma, and analyzing the wavelength and intensity of the emission spectrum. Since the LIBS uses pulsed laser as an excitation source, it has many advantages, for example without sample preparation, approximate non-destructive, remote analysis, and multi-element simultaneous analysis. In recent years, LIBS has been widely used in many fields of analysis. It is sometimes difficult to find a standard sample to match the matrix or to ensure the constant of the experimental conditions, which greatly limits the application of the LIBS. Based on this, there is no need to set up a calibration curve using a standard sample to establish a calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method, and is widely studied by researchers. The CF-LIBS is a simple mathematical model to describe the physical state of the laser-induced plasma, so it can effectively overcome the adverse effect of the base effect. However, the laser-induced plasma is very complex and cannot be accurately described with a simple physical formula, so the analysis accuracy of the CF-LIBS has not reached the level of the standard LIBS or other element analysis technology. In view of the unique advantages of CF-LIBS, it is important to understand and improve CF-LIBS algorithm. In this paper, the factors that influence the accuracy of CF-LIBS analysis are analyzed from the experimental setup and the basic theory hypothesis, and the algorithm is improved from the aspects of the acquisition delay and the self-absorption correction. The main contents of the research are as follows: 1. The basic principle and characteristics of LIBS are reviewed. According to the experimental order, the development course of LIBS is introduced from four aspects of laser and material interaction, spectrum pretreatment, qualitative and quantitative analysis, and the application of LIBS is introduced. In this paper, the research progress of CF-LIBS analysis is introduced in detail. The experimental system for CF-LIBS analysis is set up, and the main mechanism to influence the broadening of plasma emission spectrum is reviewed. The influence of the number of laser pulses on the stability of the spectral signal is studied. The importance of the correction of the wavelength calibration and relative efficiency of the spectrometer is discussed. The main mechanism of the broadening of the spectral line is analyzed: natural broadening, Doppler broadening, Van der Waals broadening, resonance broadening, Stark broadening, The optical thin and uniform plasma required by CF-LIBS is derived from the one-dimensional plasma theory of optical thick and non-uniform. In this paper, the algorithm flow and basic theory of CF-LIBS are introduced in detail. In this paper, the theoretical factors that influence the accuracy of CF-LIBS and the improvement of its algorithm in recent years are reviewed. The evolution of the interaction of the laser with the material and the time of the plasma emission spectrum is introduced. The emission spectrum of the laser-induced slag in the laser-induced slag under different delay time is collected. The peak-finding, the constant-peak and the spectral peak-fitting algorithm of the line spectrum are proposed. The effect of delay time on the accuracy of CF-LIBS is studied. The results are explained in terms of self-absorption and local thermodynamic equilibrium. A standard reference line method is proposed based on the local thermodynamic equilibrium assumption that all species present in the plasma have the same temperature value. the electron density and the plasma temperature are calculated based on the main-quantity component spectral line, and the best one of the signal-to-noise ratio is selected as a standard reference line for the atom of each element, and the corresponding standard reference concentration is calculated. The results of the quantitative analysis with and without the self-absorption standard reference line were compared. The self-absorption coefficient of the main component spectral line is theoretically calculated to optimize the selection of the standard reference line. The main innovation point of this thesis is: (1) The time-resolved CF-LIBS study is carried out, and the optimal acquisition delay of the quantitative analysis accuracy of CF-LIBS is obtained. The calculation results are explained from the two aspects of self-absorption and local thermodynamic equilibrium, respectively. (2) The standard reference line method is proposed to overcome the influence of the self-absorption and trace element spectral line of the main element spectral line. (3) The method of selecting the standard reference line of the self-absorption coefficient of the linear spectrum is put forward, and the selection of the reference line of the standard reference line is avoided.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN249
[Abstract]:Laser-induced breakdown spectroscopy (LIBS) is an element analysis method for obtaining the qualitative and quantitative information of the samples by the laser ablation of the convergent pulse and the atomization of the micro-sample to produce the plasma, and analyzing the wavelength and intensity of the emission spectrum. Since the LIBS uses pulsed laser as an excitation source, it has many advantages, for example without sample preparation, approximate non-destructive, remote analysis, and multi-element simultaneous analysis. In recent years, LIBS has been widely used in many fields of analysis. It is sometimes difficult to find a standard sample to match the matrix or to ensure the constant of the experimental conditions, which greatly limits the application of the LIBS. Based on this, there is no need to set up a calibration curve using a standard sample to establish a calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method, and is widely studied by researchers. The CF-LIBS is a simple mathematical model to describe the physical state of the laser-induced plasma, so it can effectively overcome the adverse effect of the base effect. However, the laser-induced plasma is very complex and cannot be accurately described with a simple physical formula, so the analysis accuracy of the CF-LIBS has not reached the level of the standard LIBS or other element analysis technology. In view of the unique advantages of CF-LIBS, it is important to understand and improve CF-LIBS algorithm. In this paper, the factors that influence the accuracy of CF-LIBS analysis are analyzed from the experimental setup and the basic theory hypothesis, and the algorithm is improved from the aspects of the acquisition delay and the self-absorption correction. The main contents of the research are as follows: 1. The basic principle and characteristics of LIBS are reviewed. According to the experimental order, the development course of LIBS is introduced from four aspects of laser and material interaction, spectrum pretreatment, qualitative and quantitative analysis, and the application of LIBS is introduced. In this paper, the research progress of CF-LIBS analysis is introduced in detail. The experimental system for CF-LIBS analysis is set up, and the main mechanism to influence the broadening of plasma emission spectrum is reviewed. The influence of the number of laser pulses on the stability of the spectral signal is studied. The importance of the correction of the wavelength calibration and relative efficiency of the spectrometer is discussed. The main mechanism of the broadening of the spectral line is analyzed: natural broadening, Doppler broadening, Van der Waals broadening, resonance broadening, Stark broadening, The optical thin and uniform plasma required by CF-LIBS is derived from the one-dimensional plasma theory of optical thick and non-uniform. In this paper, the algorithm flow and basic theory of CF-LIBS are introduced in detail. In this paper, the theoretical factors that influence the accuracy of CF-LIBS and the improvement of its algorithm in recent years are reviewed. The evolution of the interaction of the laser with the material and the time of the plasma emission spectrum is introduced. The emission spectrum of the laser-induced slag in the laser-induced slag under different delay time is collected. The peak-finding, the constant-peak and the spectral peak-fitting algorithm of the line spectrum are proposed. The effect of delay time on the accuracy of CF-LIBS is studied. The results are explained in terms of self-absorption and local thermodynamic equilibrium. A standard reference line method is proposed based on the local thermodynamic equilibrium assumption that all species present in the plasma have the same temperature value. the electron density and the plasma temperature are calculated based on the main-quantity component spectral line, and the best one of the signal-to-noise ratio is selected as a standard reference line for the atom of each element, and the corresponding standard reference concentration is calculated. The results of the quantitative analysis with and without the self-absorption standard reference line were compared. The self-absorption coefficient of the main component spectral line is theoretically calculated to optimize the selection of the standard reference line. The main innovation point of this thesis is: (1) The time-resolved CF-LIBS study is carried out, and the optimal acquisition delay of the quantitative analysis accuracy of CF-LIBS is obtained. The calculation results are explained from the two aspects of self-absorption and local thermodynamic equilibrium, respectively. (2) The standard reference line method is proposed to overcome the influence of the self-absorption and trace element spectral line of the main element spectral line. (3) The method of selecting the standard reference line of the self-absorption coefficient of the linear spectrum is put forward, and the selection of the reference line of the standard reference line is avoided.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN249
【相似文献】
相关期刊论文 前10条
1 张大成;;冬青叶子的激光诱导击穿光谱(英文)[J];IMP & HIRFL Annual Report;2008年00期
2 周南;周亢;丁圭吉;;关于激光诱导裂析谱专题的欧洲-地中海会议2007(Ⅰ)[J];分析试验室;2009年08期
3 周南;周亢;丁圭吉;;关于激光诱导裂析谱专题的欧洲-地中海会议2007(Ⅱ)[J];分析试验室;2009年09期
4 ;激光诱导脑电波[J];激光与光电子学进展;2009年06期
5 周政卓,邱明新,黄赛棠,毕琦秀,顾加O，
本文编号：2408953
本文链接：https://www.wllwen.com/kejilunwen/dianzigongchenglunwen/2408953.html
