本文選題：激光誘導擊穿光譜　切入點：定性分析　出處：《山西大學》2013年碩士論文　論文類型：學位論文

【摘要】：激光誘導擊穿光譜(Laser-Induced Breakdown Spectroscopy, LIBS)是一種新型光譜分析技術。利用激光誘導擊穿光譜的方法對未知樣品進行元素分析,具有可多元素同時分析,速度快,無輻射等優(yōu)勢,在電力、地礦、環(huán)保、冶金、考古等領域有廣闊的應用前景。 本文首先概述了LIBS技術的基本原理、理論以及應用現狀。然后針對目前該技術進行元素分析時,定性分析需采用人工方式尋峰,再確定譜線歸屬；而在定量分析過程中,由于脈沖激光能量起伏會導致測量的長期穩(wěn)定性差的缺點,從原理上和技術上解決了上述關鍵問題,開發(fā)煤質分析設備,可實現對煤樣灰分、發(fā)熱量等工業(yè)分析指標的測量,推動了該技術的實用化。 本文主要研究內容概括如下： 1.介紹了激光誘導擊穿光譜的電子密度、等離子體溫度等參數的計算方法,局部熱平衡態(tài)的判定。用LabVIEW編寫了等離子參數計算程序,根據高斯公式的面積與峰值關系建立了譜峰半高寬的算法,基于Boltzmann-Maxwell分布和Saha-Eggert公式計算電子密度、溫度。 2.利用二次微商法和閾值判定法對LIBS光譜數據進行降噪、尋峰,并通過參考NIST原子光譜數據庫,確定譜線歸屬�；贚abVIEW編寫了分析程序,確定了多種常見元素的特征波長,可以自動識別元素譜線,建立了定性分析算法。在此基礎上設計了便攜式元素分析設備,可通過手持式測量,實現對樣品所含元素種類的定性分析,快速確定未知樣品中所含元素種類。 3.建立閉環(huán)負反饋式激光能量鎖定裝置,通過將激光輸出能量與預設值進行比較并負反饋至激光電源,利用PID控制根據能量偏差值得到相應的控制量,自動調整氙燈供電電壓將脈沖激光能量鎖定在預設值附近。通過優(yōu)化PID參數,使激光能量起伏穩(wěn)定在士3.2%以內,實現長期穩(wěn)定測量,提高了LIBS技術在元素分析領域的可靠性和實用性。 4.利用二階多元非線性回歸建立了煤炭工業(yè)分析指標的定標模型,構建了新的數據分析方法,通過歸一化提高譜線相對強度計算精度,由LIBS分析得到的各元素譜線的相對強度擬合得到煤樣的灰分值和發(fā)熱量,測量的相對誤差分別為4.61%和7.32%。 5.基于上述研究,研制了適用于化驗室分析的光電一體化的全自動激光煤質分析設備,可在30-60s內完成對煤樣進行分析,得到其硫分、灰分、發(fā)熱量。該設備操作簡單,激光輸出功率穩(wěn)定,測量速度快,能實現長期穩(wěn)定測量。
[Abstract]:Laser-Induced Breakdown Spectroscopy (Libs) is a new spectral analysis technique. The method of laser-induced breakdown spectroscopy is used to analyze the elements of unknown samples. It has the advantages of simultaneous analysis of multiple elements, high speed, no radiation and so on. Geological and mineral resources, environmental protection, metallurgy, archaeology and other fields have broad application prospects. In this paper, the basic principle, theory and application status of LIBS technology are summarized firstly. Then, in the process of element analysis, the qualitative analysis needs to find the peak manually, and then determine the spectral line attribution, and in the process of quantitative analysis, Because the fluctuation of pulsed laser energy will lead to poor long-term stability of measurement, the above key problems are solved in principle and technology. The development of coal quality analysis equipment can realize the measurement of coal sample ash, calorific value and other industrial analysis indexes. It promotes the practicality of the technology. The main contents of this paper are summarized as follows:. 1. The calculation method of electron density, plasma temperature and the determination of local thermal equilibrium state of laser induced breakdown spectrum are introduced. The calculation program of plasma parameters is compiled by LabVIEW. Based on the relationship between the area and peak value of Gao Si formula, an algorithm for calculating the half-width of spectral peak is established. The electron density and temperature are calculated based on Boltzmann-Maxwell distribution and Saha-Eggert formula. 2. The LIBS spectral data are de-noised and peak-seeking by using the quadratic microquotient method and threshold determination method, and the spectral line attribution is determined by referring to the NIST atomic spectrum database. The analysis program based on LabVIEW is compiled and the characteristic wavelengths of various common elements are determined. On the basis of this, a portable element analysis device is designed, which can be used for qualitative analysis of elements in samples by hand-held measurement. Identify elements in unknown samples quickly. 3. The closed-loop negative feedback type laser energy locking device is established. By comparing the laser output energy with the preset value and negative feedback to the laser power supply, the corresponding control quantity is obtained by using PID control according to the energy deviation value. By automatically adjusting the power supply voltage of xenon lamp, the pulse laser energy is locked near the preset value. By optimizing the PID parameters, the laser energy fluctuation is stabilized within 3.2%, and the long-term stability measurement is realized. The reliability and practicability of LIBS in element analysis are improved. 4. The calibration model of coal industry analysis index is established by using second-order multivariate nonlinear regression, and a new data analysis method is constructed. The accuracy of relative intensity calculation of spectral line is improved by normalization. By fitting the relative strength of the spectral lines of each element from LIBS analysis, the ash score and calorific value of the coal samples were obtained. The relative errors of the measurements were 4.61% and 7.32, respectively. 5. Based on the above research, a fully automatic laser coal quality analysis equipment, which is suitable for laboratory analysis, has been developed. It can be used to analyze coal samples in 30-60 seconds and obtain its sulfur, ash and calorific value. The equipment is simple to operate. The laser output power is stable, the measuring speed is fast, and the long-term stable measurement can be realized.
【學位授予單位】：山西大學
【學位級別】：碩士
【學位授予年份】：2013
【分類號】：O433.4

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