光纤光栅传感器的工作原理及发展前景

给出了光纤光栅传感器的工作原理,光纤光栅的特点,并针对光纤光栅传感器实际应用中存在的问题及解决途径进行了讨论.     

土壤中Pb、Cr元素激光诱导击穿光谱技术定量分析

采用激光诱导击穿光谱技术(Laser-induced b reakdown spectroscopy,LIBS)对土 壤样品中的Pb和Cr元素进行了分析,以PbI280.17 nm和CrI425.43 nm作为分析线,优化了透 镜到样品的距离(Lens to sample distance,LTSD)、延迟时间对光谱信号强度及信噪比 SNR 的影响。在最佳实验条件下,对两种元素的谱峰强度和元素浓度进行分析,针对外标法 和内标法分别建立了谱线峰值强度、谱线峰值积分面积与对应元素浓度的定标曲线。采用谱 线峰值积分面积法对土壤中重金属Pb和Cr元素的检测,相比于外标法,内标法将Pb和Cr元素 最大相对误差分别从13.56%和12.68%降低到了 6.7%;Pb和Cr元素定标曲线的拟合相关 系数R²分别从0.978和0.975提高到了0.996和0.991。实 验结果表明:采用LIBS技术对土 壤中Pb、Cr元素检测具有可行性,采用谱线峰值积分面积的内标法,可以降低最大相对误差 并提高测量精度。     

Study on energy threshold and spectral characteristics with spot radius based on LIBS technology

The aim of this study is to investigate the relationship between the laser-induced optical breakdown energy threshold and the spectral signal changes with the spot radius. First of all, using the avalanche breakdown threshold theory calculates the threshold avalanche ionization rate ηc. Combining with the theory of light intensity distribution and the relationship between pulse energy and peak power, numerical calculations have obtained the law of change of spot radius and threshold laser energy. Secondly, the variation of the spectral signal-to-noise ratio (SNR) with the laser energy is measured according the experimental measurement, and the threshold laser energy required for optical breakdown at different spot radius is obtained. The theoretical threshold model of the relationship between the threshold laser energy and the quadratic function of the spot radius obtained by numerical calculation is verified, and it is revised, the results show that the relative error between the revised theoretical threshold model and the experimental threshold model is less than 5.3%. At last, the influence of the spot radius on the spectral signal and electron density is also analyzed, it is found that both the spectral intensity and the electron density have a maximum at the spot radius of 11 μm. The results show that it is necessary to find the best spot radius during the laser induced breakdown spectroscopy (LIBS) experiment. This provides a reliable theoretical basis and experimental reference for further study of the influence of spot radius on LIBS technology measurement.     

基于磁场约束下激光诱导击穿光谱技术的重金属检测研究

为提高激光诱导击穿光谱(laser induced breakdown spectroscopy, LIBS)技术定量分析的精度,开展了磁场约束下LIBS技术对土壤中重金属元素检测的研究,并采用多谱线强度归一化内标法进行数据处理。通过比较磁场强度分别为0 T、0.3 T、0.8 T、1.25 T时的光谱特性,得到光谱强度和信噪比(signal-to-noise ratio,SNR)随磁场强度增大而增大,在1.25 T磁场强度时,样品元素Cd和Cu的光谱强度和SNR要比无磁场作用分别增强了34.77%、56.33%和40.83%、74.12%,构建了磁场强度为1.25 T时的Cd和Cu元素定量分析模型。结果显示,相对于传统内标法,采用多谱线强度归一化内标法的元素检测限分别从52.78 mg/kg和49.18 mg/kg降低到23.87 mg/kg和18.06 mg/kg;相关系数分别从0.961 3和0.942 7提高到0.996 9和0.999 3。本实验研究改善了LIBS的光谱特性,提高了定量分析的精度,采用多谱线强度归一化内标法降低了重金属的检出限和测量误差。     

基于背景扣除法消除土壤基底中Al元素干扰的LIBS实验研究

土壤中重金属的污染严重影响了农业和食品安全，因此，对重金属污染的高效、准确的检测是目前亟需解决的问题。采用激光诱导击穿光谱技术（Laser induced breakdown spectroscopy，LIBS）对土壤中Ni元素进行定量分析时发现，土壤中波长为373.68 nm的Ni元素的特征峰会受到Al元素在373.39 nm处谱线的影响，因此，将纯铝基底土壤光谱与压片土壤光谱进行了对比测量。提出了以纯Al作为基底，采用纯Al基底谱线扣除土壤背景中Al元素谱线的方法，来消除土壤背景中Al元素对Ni元素干扰，该方法被称为背景扣除法。实验确定了两种土壤样品的最佳延迟时间均为1.0 μs，透镜到样品的距离（Lens to sample distance，LTSD）分别为97 mm和96 mm。采用内标法对两种土壤样品中的Ni进行了定量分析，得到纯Al基底土壤样品中Ni元素的定标曲线拟合效果较好，相关系数R2为0.997，最大标准偏差（Relative standard deviation，RSD）为4.34%，采用基底背景扣除法后的纯铝基底土壤样品中Ni元素检测的相对误差降低到4%。实验结果表明:采用LIBS技术对土壤中重金属元素含量测量时，在元素特征谱线有限的情况下，为避免谱线干扰，提高检测精度，采用背景扣除的方法能够有效消除元素间的谱线的干扰。     

基于偏最小二乘法的CO2加权组合测量研究

为了解决光谱之间相互干扰、建模速度慢等缺点,采用多波段加权组合模型与偏最小二乘(partial least squares,PLS)法结合进行定量分析提高测量精度。本文搭建了基于超连续谱激光吸收光谱(spectrum laser absorption spectrum,SCLAS)技术的气体检测系统,基于PLS对近红外不同波段二氧化碳(CO₂)进行加权组合测量研究。在常温常压下对1 425—1 443 nm、1 565—1 587 nm、 1 595—1 616 nm波段内不同浓度CO₂的吸收光谱进行了测量,基于PLS建立了单一波段回归模型,得出的决定系数(coefficient of determination,R²)分别为0.989 7、0.948 6、0.949 7。通过R²和均方根误差(root mean square error,RMSE)分别确定单一波段模型的权重,采用多波段加权组合模型算法建立了新的PLS组合模型,得出的R²分别为0.985 2、0.991 2。实验结果表明,基于PLS的加权组合模型能够提高CO₂浓度的预测精度与稳定性,有效避免建模速度慢和干扰问题。     

基于可调谐激光的CO监测仪的不确定度评定

采用可调谐二极管激光吸收光谱技术(TDLAS)对CO气体的浓度进行测量,应用整体二次谐波最小二乘法对测量信号的实验数据进行反演处理。基于可调谐二极管激光吸收光谱技术, 对CO在线监测仪测量结果的不确定度来源进行了分析, 采用直接评定法对各种因素引起的不确定度分量、标准不确定度和合成不确定度进行了评定。实验结果表明, 仪器示值引入的不确定度、标准气体浓度定值的不确定度以及环境温度变化和电源电压波动引入的不确定度是影响测量不确定度的主要因素。     

Plasma characteristics and quantitative analysis of Pb and Ni in soil based on LIBS technology

When measured by laser induced breakdown spectroscopy, the characteristic parameters of the plasma fluctuate significantly with the experimental parameters, which would have a greater impact on the quantitative measurement. The effects of two experimental parameters, lens to sample distance(LTSD) and delay time, on plasma temperature and electron density were analyzed. Thereafter the optimal LTSD and delay time for quantitative analysis of Pb and Ni in soil were identified. Two element calibration curves were calculated by the internal standard method under the optimal LTSD and delay time. About the two elements, correlation coefficient of the calibration curves is above 0.993. The maximum relative standard deviation(RSD) were 4.47% and 4.76%, respectively, and the maximum relative errors were 12% and 4.8%, respectively. The experimental results showed that laser induced breakdown spectroscopy method in combination with plasma characteristic parameter analysis shows the advantage on quantitative analysis of heavy metals in soil.     

氮掺杂多孔碳负载铁单原子对电极的膜厚对染料敏化太阳能电池性能的影响

利用分子笼封装前驱体而后热解的策略,制备了具有高催化活性的氮掺杂多孔碳(NPC)负载孤立的单个Fe原子(Fe-ISAs/NPC)电催化剂,并作为对电极用于染料敏化太阳能电池(dye-sensitized solar cells,DSSCs).通过电化学测试研究了Fe-ISAs/NPC对电极的膜厚对DSSCs光电性能的影...