激光誘導(dǎo)擊穿光譜無標(biāo)分析方法研究
發(fā)布時間：2019-01-15 07:00
【摘要】：激光誘導(dǎo)擊穿光譜(Laser-Induced Breakdown Spectroscopy,LIBS)是通過會聚脈沖激光燒蝕并霧化微量樣品產(chǎn)生等離子體,并分析發(fā)射光譜的波長和強(qiáng)度,獲取樣品定性和定量信息的元素分析方法。由于LIBS采用脈沖激光作為激發(fā)源,其具有許多優(yōu)點(diǎn),例如無需樣品制備、近似無損、遠(yuǎn)程分析和多元素同時分析。近年來,LIBS已被廣泛的應(yīng)用于眾多分析領(lǐng)域。由于有標(biāo)LIBS分析有時難以找到基體匹配的標(biāo)準(zhǔn)樣品或保證實(shí)驗(yàn)條件的恒定,極大的限制了 LIBS的應(yīng)用。基于此,不需要使用標(biāo)準(zhǔn)樣品建立定標(biāo)曲線的無標(biāo)激光誘導(dǎo)擊穿光譜(Calibration-Free Laser-Induced Breakdown Spectroscopy,CF-LIBS)分析方法被提出,并被科研人員廣泛研究。CF-LIBS是通過簡單的數(shù)學(xué)模型來描述激光誘導(dǎo)等離子體的物理狀態(tài),所以其可以有效地克服基體效應(yīng)的不利影響。然而,激光誘導(dǎo)等離子體又是十分復(fù)雜的無法用簡單的物理公式準(zhǔn)確進(jìn)行描述,所以目前CF-LIBS的分析精度還沒有達(dá)到有標(biāo)LIBS或其它元素分析技術(shù)的水平。鑒于CF-LIBS的獨(dú)特優(yōu)勢,理解并改進(jìn)CF-LIBS算法具有重要的理論和應(yīng)用價值。本論文主要從實(shí)驗(yàn)設(shè)置和基本理論假設(shè)兩方面對影響CF-LIBS分析精度的因素進(jìn)行分析,并從采集延遲和自吸收修正方面對算法進(jìn)行相應(yīng)的改進(jìn)。主要研究內(nèi)容如下:1、回顧了 LIBS的基本原理和特點(diǎn);按照實(shí)驗(yàn)順序,從激光與物質(zhì)相互作用、光譜預(yù)處理、定性和定量分析四個方面介紹了 LIBS的發(fā)展歷程;介紹了目前LIBS的應(yīng)用、相關(guān)學(xué)術(shù)會議和已有的儀器設(shè)備;詳細(xì)介紹了 CF-LIBS分析方法的國內(nèi)外研究進(jìn)展。2、搭建了用于CF-LIBS分析的實(shí)驗(yàn)系統(tǒng),并綜述了影響等離子體發(fā)射光譜展寬的主要機(jī)制。研究了激光脈沖數(shù)對光譜信號穩(wěn)定性的影響;論述了光譜儀波長校準(zhǔn)和相對效率修正的重要性;分析了造成譜線展寬的主要機(jī)制:自然展寬、Doppler展寬、Van derWaals展寬、共振展寬、Stark展寬、自吸收加寬和儀器加寬等。3、從光學(xué)厚且不均勻的一維等離子體理論出發(fā),推導(dǎo)出CF-LIBS所要求的光學(xué)薄、均勻等離子體。詳細(xì)介紹了 CF-LIBS的算法流程和基本理論假設(shè)。綜述了影響CF-LIBS計算精確度的理論因素和近年來研究人員對其算法的改進(jìn)。4、研究了時間分辨CF-LIBS分析。介紹了激光與物質(zhì)相互作用和等離子體發(fā)射光譜隨時間的演化過程;實(shí)驗(yàn)采集不同延遲時間下激光誘導(dǎo)爐渣等離子體發(fā)射光譜;提出了線狀譜的尋峰、定峰和譜峰擬合算法;綜述了等離子體溫度的不同計算方法;研究了延遲時間對CF-LIBS精確度的影響;從自吸收和局域熱力學(xué)平衡兩方面對計算結(jié)果進(jìn)行了解釋。5、為了克服主量成分譜線的自吸收和微量成分譜線稀少的影響,基于局域熱力學(xué)平衡假設(shè),即所有存在于等離子體中的物種具有相同溫度值,提出了標(biāo)準(zhǔn)參考線方法�；谥髁砍煞肿V線計算電子密度和等離子體溫度,同時為每個元素的原子選擇信噪比最好的一條譜線作為標(biāo)準(zhǔn)參考線,并計算其相應(yīng)的標(biāo)準(zhǔn)參考濃度。比較了具有和沒有自吸收標(biāo)準(zhǔn)參考線的定量分析結(jié)果。通過理論計算主量成分譜線的自吸收系數(shù)來優(yōu)化標(biāo)準(zhǔn)參考線的選擇。本論文的主要創(chuàng)新點(diǎn)在于:(1)開展了時間分辨CF-LIBS研究,獲得了 CF-LIBS定量分析精度的最佳采集延遲。分別從自吸收和局域熱力學(xué)平衡兩個方面對計算結(jié)果進(jìn)行了解釋。(2)提出了標(biāo)準(zhǔn)參考線方法,克服了主量元素譜線的自吸收和微量元素譜線稀少的影響。(3)提出了理論計算線狀譜的自吸收系數(shù)優(yōu)化標(biāo)準(zhǔn)參考線的選擇方法,避免了主觀因素影響標(biāo)準(zhǔn)參考線的選擇。
[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.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：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.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TN249
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