利用激光诱导击穿光谱技术,分析由快速灰化法制得的粉煤灰样品中的未燃碳。实验中发现,常用的C元素分析谱线C 247.86 nm附近存在明显的Fe 247.95nm谱线干扰,严重影响未燃碳的激光诱导击穿光谱分析。选用处于深紫外区不存在其他光谱干扰的C193.03 nm谱线作为分析线,建立未燃碳的定量分析曲线。研究结果表明,在大气常压环境下,通过对光谱探测系统进行深紫外增强镀膜处理,选用短焦距准直透镜和抗紫外光纤,可以探测到明显的C 193.03 m谱线,由此分析未燃碳可以得到良好的定标曲线,拟合度为0.99,检测限为0.74%（质量分数）。

研究了水分对激光诱导击穿煤粉等离子体特性的影响,以分析水分对激光诱导击穿煤粉定量测量的影响。实验选取了空干基C和Si元素含量相近但水分差别较大的神华煤和平朔煤,分别采用其收到基和干燥基共4个样品进行实验。采用Ca的原子谱线计算了各样品在延迟时间分别为83 ns,500 ns,917 ns和1292 ns时的激光诱导击穿等离子体温度,并分别用C247.856nm和Si390.5523 nm特征谱线估算了电子密度。实验表明,各样品的激光等离子体温度随着延迟时间的增大而降低,含水分的煤样其激光诱导击穿等离子体的温度较低,而电子密度受水分的影响不大,含水分的煤样其激光诱导击穿的特征谱线强度较弱。

等离子体温度是激光诱导击穿光谱测量中一个重要的因素.采用Nd:YAG脉冲激光器作为光源击穿样品形成等离子体,其发射光谱由中阶梯光栅光谱仪和ICCD进行分光和光电转换.通过实验得出了300～450 nm波段的光谱图,定性分析出了Ca Ⅱ 315.9, 317.9, 393.4, 396.9 nm和Ca Ⅰ 422.7 nm等发射谱线.根据激光诱导击穿光谱定量公式,等离子体温度的变化对谱线强度有影响.先假设实验中等离子体处于局部热平衡状态,选用Ca的4条一价离子谱线,根据Boltzmann斜线法计算出了等离子体温度,并得到了等离子体温度与Ca质量分数的关系.随着Ca质量分数的增加,等离子体温度也相应增加.但当Ca质量分数小于0.50%时等离子体温度增加的幅度较小,而质量分数大于0.50%时等离子体温度的上升幅度相对较大.最后经过验证,实验中等离子体处于局部热平衡状态的假设成立.

The purpose of this work is to improve the precision of the elemental analysis of coal using laser-induced breakdown spectroscopy (LIBS). The LIBS technique has the ability to allow simultaneous elemental analysis and on-line determination, so it could be used in the elemental analysis of coal. Organic components such as C, H, O, N and inorganic components such as Ca, Mg, Fe, Al, Si, Ti, Na, and K of coal have been identified. The precision of the LIBS technique depends strongly on the experimental conditions, and the choice of experimental parameters should be aimed at optimizing the repeatability of the measurements. The dependences of the relative standard deviation (RSD) of the LIBS measurements on the experimental parameters including the sample preparation parameters, lens-to-sample distance, sample operation mode, and ambient gas have been investigated. The results indicate that the precision of LIBS measurements for the coal sample can be improved by using the optimum experimental parameters.

采用激光诱导击穿光谱分析技术测量煤中的主要灰成分元素.实验用Nd: YAG固体激光器的1064 am激光脉冲激发烧蚀部分煤块样品,形成样品的等离子体形态;通过光谱仪与光电探测器采集等离子体的发射光谱,以定量分析激发样品中包含的元素种类以及对应浓度.本实验定量分析了燃煤中Si、Mg、Al、Ca、Fe、Ti、Na与K元素,与传统的实验室原子吸收光谱的元素分析结果相对比,该方法的定量分析的相对误差在1%～8%之间,各元素可达到的质量浓度探测限均低于元素在煤中的一般含量,验证了基于激光诱导击穿光谱法在线快速实现煤质分析的可行性.

激光诱导击穿样品产生的等离子体寿命通常在微秒量级,对其时间演化过程进行了解有利于优化信号采集.定标曲线是定量分析的基础,并且与测量灵敏度和准确度密切相关.采用聚焦的脉冲激光束击穿样品形成等离子体,其发射光谱由中阶梯光栅光谱仪分光,并由增强型电荷耦合器件(ICCD)进行光电探测采集.为了实现对金属元素的激光诱导击穿光谱(LIBS)测量,在石墨中分别加入Ca,Al,Na,K等元素制作成片状实验样品,利用实验装置进行了系统的激光击穿光谱探测研究.应用ICCD100 ns光学门宽的时间分辨率,通过实验得到了等离子体的时间演化特性曲线,分析了激光击穿固体样品后各待测元素的演化过程.根据含有不同浓度的同种元素样品的LIBS实验结果,归纳出各元素浓度与谱线强度的定标曲线,且大多数定标曲线的线性拟合相关度较高.同一元素不同波长的谱线,其定标曲线的斜率不同,对其差异进行了分析.

综述了激光诱导击穿光谱分析技术(LIBS)在不同对象领域应用中的谱图分析方法.随着激光诱导击穿光谱应用对象的不断扩展与分析要求的变化,其定量分析方法已不局限于传统标样定标曲线分析模型,发展出了自由定标模型、各类内标法模型、自相关定量模型、神经网络分析模型等新的激光诱导击穿光谱分析方法.对每种方法的定量分析原理、分析能力水平与适用对象范围进行了详细的分析比较.

Laser-induced breakdown spectroscopy was used to analyze unburned carbon in fly ash. The samples were gotten using fast ashing method and excited by pulse laser and plasma was formed at atmospheric pressure. The emitted signal which contains the information of unburned carbon in fly ash was detected. The calibration curve constructed base on six samples of one kind of coal ash, and two samples of other two kinds of coal ash were analyzed. The experimental results show that calibration curve constructed with the data from same kind of coal ash can be used to analyze the different kinds of fly ash using proper data processing method. The relative standard deviation of repetition of measured values are less than 8.08%, the relative errors are less than 2.27%. It is indicated that laser-induced breakdown spectroscopy is suitable for rapidly detect unburned carbon in fly ash with receptible applicability.

选用不同产地的3种代表性煤样为对象,采用粉状煤样和不同压力下制备成的片状煤样进行实验,以分析煤样致密度的影响.得出了粉状煤样和片状煤样在200~850 nm波段内的光谱图,定性分析了C,H,O,N,Al,Fe,Ca,Mg,Si,Ti,Na和K等元素.对强度大、干扰小的C,Al,Ca,Mg,Si和Ti元素的谱线进行分析,通过谱线强度及其相对标准偏差、谱线强度比及其相对标准偏差来比较煤样致密度对定标曲线法和内标法测量的影响.实验结果表明:致密度对定标曲线法定量分析的影响较大,而对内标法定量分析的影响较小.

对用激光诱导击穿光谱方法分析玻璃样品成分进行了实验研究,采用自南定标计箅方法定量分析了玻璃样品的成分.通过实验的对比表明,在多元素同步分析时,光谱采样的延迟时间与门宽均设置为1.0us时光谱分析效果较好.激光脉冲的聚焦点位于样品表面之上3mm时,发射光谱的稳定性与强度综合性能最优.实验结果表明,在实验设置的观测时间段内等离子体平均温度为12774K,定量分析的相对误差在3.6%～11.2%之间.相对标准偏差在1.6%～7.7%之间,重复试验的稳定性很好.

Laser-induced breakdown spectroscopy(LIBS) was applied to measure the elements in pulverized coal.An intense laser radiation was focused on the surface of sample to generate a plasma plume which vaporized a small amount of pulverized coal.The emission spectrum emitted as the plasma cooling off,which contained the information of elemental species and concentration in coal,was collected and analyzed by fiber spectrometer,and internal standard method based on carbon element quantitative technique was introduced.An experiment apparatus was set up according to the principle of analysis technique.Experimental studies were carried out separately,with the standard samples which were made of chemical C6H7NO3S,C and SiO2.According to the internal standard method,and with silicon element as internal standard element,calibration curve of carbon element were constructed for quantitative determination.Afterwards,carbon element in pulverized coal sample was analyzed with the calibration curve.From the experiment results for quantitative analysis of carbon content of pulverized coal,the analysis accuracy with relative error is 1.46%,which proved that the internal standard method using in the pulverized coal quantitative analysis by laser-induced breakdown spectro-scopy is applicable.

将激光诱导击穿光谱技术应用于煤质检测,分析了燃煤形态对激光烧蚀特性的影响.利用532 nm激光在大气常压环境下烧蚀样品.同时使用多通道光纤光谱仪和CCD探测器对激光烧蚀形成的等离子体发射信号进行分光和探测.对比分析两种不同形态煤样的等离子体温度、电子密度以及元素特征谱线强度随脉冲能量变化的规律.实验研究表明,样品形态对燃煤的激光烧蚀特性有显著影响.不问形态燃煤的等离子体温度、电子密度以及元素特征谱线强度随脉冲能量的变化规律有所不同.相同实验条件下,粉状煤样形成的等离子体温度和电子密度均比块状煤样的高,但块状煤样的元素特征谱线强度则更大.

A laser induced breakdown spectroscopy-based apparatus for the analysis of element, employing a 532 nm laser and a multi-channel optical spectrometer with a non-intensified CCD array, has been built and tested. It was applied to analyze the carbon content of coal fly ash. Seven groups of pulse laser in the range of 35 to 98 mJ were used to ablate the fly ash samples. The electron densities and plasma temperatures with different laser energy were determined, and the influence of laser energy on the intensity of analysis carbon lines was also analyzed. The results show that carbon line intensity increases slowly with the increase in laser energy in the range of 35 to 46 mJ, and increases fast in the range of 46 to 78 mJ, then trends to saturation and has a little drop. At the same time, air breakdown has increased significantly, and has an obvious effect on sample plasma. Furthermore, the electron density and plasma temperature increase with the laser energy until 78 mJ and then begin to decrease. It indicates that a proper laser energy can enhance the plasma emission signal, and avoid the negative impact of air breakdown that prevent the pulse laser from reaching the surface of sample and ablating it. In this experiment situation, the measurement accuracy of the carbon line can be improved.

The laser-induced breakdown spectroscopy is used to analyze the lead content in soils.The analyzed spectral line profile is fitted by Lorentzian function for determining the background and the full-width at half-maximum (FWHM) intensity of spectral line.A self-absorption correction model based on the information of spectral broadening is introduced to calculate the true value of spectral line intensity, which refers to the elemental concentration.The results show that the background intensity obtained by spectral profile fitting is very effective and important due to removing the interference of spectral broadening, and a better precision of calibration analysis is acquired by correcting the self-absorption effect.

Samples were excited by pulse laser and plasma was formed at atmospheric pressure.The technique of laser induced breakdown spectroscopy(LIBS) was applied to analyzing the carbon content in the samples.The matrix element Si was selected as internal standard,calibration curves were drawn respectively using the peak intensity of carbon line and the intensity ratio of carbon line and silica line.The fitting degree of two different calibration curves,signal reproducibility and the accuracy of calibrated values were analyzed.The results of the analysis show that the intensity ratio method seems more adequate than the peak intensity method for establishing the calibration cures.

激光诱导发射光谱分析技术是目前正被广泛发展的一种元素定量检测手段,其分析结果的准确性与精度和分析基体的物理化学特性紧密相关.本文采用波长为1064nm的激光烧蚀煤样,以中阶梯光谱仪和ICCD分析诱导产生的等离子体发射光谱.通过试验基体的不同形态特性对各种元素定量分析特征光谱的强度、稳定性以及元素分析探测限的影响,研究激光诱导煤粉发射光谱的基体效应规律,并从激光等离子体形成的理论机制上进行实验分析.研究表明,适中的煤粉颗粒尺寸与样品密度更有利于激光诱导煤粉发射光谱的定量分析.

Fast quantitative analysis of lead in the simulated soil made of chemical reagents(PbCl2,SiO2,CaCO3 and KBr)was carried out with the laser-induced breakdown spectroscopy.The result shows that the signal-to-noise ratio increases and then decreases with the time delay.The calibration curves of Pb content were constructed with the spectrogram acquired in experiments.It is found by the investigation that the average relative error of the method for the fast quantitative analysis of lead in soil is 8.33% and the minimum detection limit is 89 μg/g.The experimental result proves LIBS is capable of being used in the detection of lead in soil.

Laser-induced breakdown spectroscopy is a new technology of elementary analysis, and it will be used in coal analysis. The delay time of signal is an important parameter of spectral analysis. A LIBS system was set up and three kinds of coal (Jiangxipingxiang coal, Shanxixishan coal and Guizhoupingzhai coal) were chosen for this investigation. The spectra in the range of 240 to 250 nm and 275 to 290 nm of the each three coal samples are shown and they record several spectral lines of components such as C, Mg and Si according to the NIST database. The temporal evolution of SNR of spectral line was obtained, and the value of SNR increased with the time delay, then decayed. The temporal evolution of SNR was different as the coal, element and spectral line differs. Finally, optimum delay time of each spectral lines of elements in the coal samples was calculated according to the biggest value of signal-to-noise ratio, and the relation between the characteristic of coal, element, spectral line and the op timum delay time was analyzed.

An intense laser radiation was focused on the surface of the sample to generate a plasma plume which vaporized a small amount of alloy material. The emission spectrum emitted as the plasma cooling off, which contained the information of elemental species and concentration in alloy, was collected and analyzed by high-resolution echelle grating spectrometer coupled to intensified charge coupled device (ICCD) camera. A series of standard aluminum alloy reference samples were analyzed for their alloying elements, including Fe, Si, and Cu. Results for Fe, Si, and Cu indicated limits of detection that ranged from 6 × 10-5 - 10 × 10-5 and almost all measurement relative errors less than 5% when mass concentration are over 0.01%. The absolute measurement errors for element with mass concentration under 0.01% were less than 0.001%.

A method of real-time evaluation of slagging propensities of coals based on element quantitative technique by laser-induced breakdown spectroscopy was introduced.An experiment apparatus was set up according to the principle of analysis technique,and in which six typical coals samples were analyzed.Four ones were used to construct calibration curves of the analyzed elements as a reference diagram determining the relation between element concentration and spectral intensity,afterwards,analyzed silicon element and aluminum element in other samples were surveyed with the reference diagram.Ratios of silicon dioxide to aluminum trioxide were computed subsequently according to chemical calculation to evaluate the slagging propensities of coals.Comparing the evaluation with the computed result based on ash composition analyzed with conventional measure,the two match well.After all,some improvement programs to optimize the measurement mecha-nism were discussed.