基于正交双波长双脉冲LA-LIBS技术分析银饰品中的微量元素

发布时间：2018-06-04 20:44

本文选题：激光剥离-激光诱导击穿光谱 + 剥离阈值　；参考：《华南理工大学》2015年硕士论文

【摘要】：为了填补对贵重样品原子分布进行原位、少损耗、快速且准确检测技术的空缺,同时为了解决单脉冲激光诱导击穿光谱技术(LIBS)在空间分辨率和灵敏度之间的矛盾,本文提出使用正交双波长双脉冲激光剥离-激光诱导击穿光谱技术(LA-LIBS),解决现有技术中存在的相关问题,并基于该技术对不同银饰品中的微量元素进行分析。首先,为了追求更好的剥离效果,准确把握样品的剥离阈值和聚焦激光的焦点光斑尺寸的关系,本文提出一种简便方法,基于聚焦激光束在焦平面上的分布为高斯分布的假设,理论推导激光能量与激光在样品表面所烧蚀的坑洞半径的关系,利用LA-LIBS实验平台测量出不同能量的脉冲激光在样品表面烧蚀的坑洞半径,并通过数值拟合来实现对聚焦激光束的焦点光斑尺寸和样品剥离阈值的同时测量,测量误差约为±10%。本文基于单台Nd:YAG激光器,先后建立532+1064 nm和266+1064 nm波长组合LA-LIBS系统,对银样品进行微区分析,并比较两种系统各自的空间分辨本领和分析灵敏度。532+1064 nm波长组合下样品表面烧蚀坑洞直径为17μm,铜的检出限为44 ppm;266+1064 nm波长组合下样品表面烧蚀坑洞直径为6.5μm时,铜的检出限为37.4 ppm。另外,在相同激光脉冲能量,相同激光脉冲数下532 nm与266 nm波长烧蚀坑洞直径大小对比,分别为25μm和17μm。通过对比得出,266 nm激光比532 nm激光拥有更好的剥离效果,266+1064 nm波长组合比532+1064 nm波长组合能获得更高的空间分辨率和分析灵敏度。本文还通过研究铜324.75 nm谱线强度与银328.07 nm谱线强度在1064 nm激光的焦点中心与样品表面之间的不同距离的条件下的相关性,以及相同1064 nm激光脉冲能量、不同266 nm或532 nm激光脉冲能量下的相关性,发现两个参数具有较高的线性性,因此可以采用内标法,用银328.07 nm的谱线作为内标线,建立铜的校正曲线,从而降低或消除由于实验参数变化而对信号强度及样品定量分析结果产生的影响。正交双波长双脉冲LA-LIBS技术能够在原位测量的情况下保证高空间分辨率和高分析灵敏度,适用于贵重样品微区分析,同时还能应用在如工业生产检测、环境实时检测等不同的领域。
[Abstract]:In order to fill the gap of in situ, less loss, fast and accurate detection of atomic distribution in precious samples, and to solve the contradiction between spatial resolution and sensitivity of monopulse laser induced breakdown spectroscopy (LIBS), In this paper, the orthogonal dual-wavelength double-pulse laser stripping and laser-induced breakdown spectroscopy technique is proposed to solve the related problems in the existing technology. Based on this technique, trace elements in different silver ornaments are analyzed. First of all, in order to obtain a better peeling effect and to accurately grasp the relationship between the peeling threshold of the sample and the focus spot size of the focused laser, this paper presents a simple method, which is based on the assumption that the focus laser beam is distributed as Gao Si distribution on the focal plane. The relationship between laser energy and the radius of the hole ablated by laser on the surface of the sample was derived theoretically. The radius of the hole ablated on the surface of the sample by pulsed laser with different energy was measured by using the LA-LIBS experimental platform. The focus spot size and the sample stripping threshold of the focused laser beam are measured simultaneously by numerical fitting. The measurement error is about 卤10. 0. Based on a single Nd:YAG laser, a combined wavelength LA-LIBS system of 532 1064 nm and 266 1064 nm was established to analyze the microregion of silver samples. The spatial resolution and analytical sensitivity of the two systems were compared when the sample surface ablation hole diameter was 17 渭 m under the wavelength combination of 1064 nm, and the detection limit of copper was 44 ppm, 266 1064 nm, when the sample surface ablation hole diameter was 6.5 渭 m. The detection limit of copper is 37.4 ppm. In addition, the diameter of ablated holes at 532 nm and 266 nm is 25 渭 m and 17 渭 m, respectively, at the same laser pulse energy and number of laser pulses. The results show that 266nm laser has better peeling effect than 532nm laser, and the combination of 266 1064 nm wavelength can obtain higher spatial resolution and higher analytical sensitivity than 532 1064 nm wavelength combination. The correlation between copper 324.75 nm line intensity and silver 328.07 nm line intensity at different distances between the focal center of the 1064 nm laser and the surface of the sample is also studied, and the same 1064 nm laser pulse energy is also studied. It is found that the two parameters have high linearity under different laser pulse energy at 266nm or 532nm. Therefore, the calibration curve of copper can be established by using the internal standard method and the silver 328.07 nm spectral line as the internal standard line. Thus, the influence of the change of experimental parameters on the signal intensity and the quantitative analysis results of the sample is reduced or eliminated. The orthogonal dual-wavelength dual-pulse LA-LIBS technique can guarantee high spatial resolution and high analytical sensitivity in the case of in-situ measurement. It is suitable for microanalysis of precious samples and can also be used in industrial production detection. Environment real-time detection and other different fields.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O433;TN249

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