The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a...The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a 1064 nm Nd：YAG laser, a vacuum pump, a spectrometer and a vacuum chamber. The vacuum varies from 10 Pa to 1 atm. Atomic lines as well as singly and doubly charged ions are confirmed under the vacuums. A temporal evolution analysis of intensity is performed for the atomic lines of C I 193.09 nm and C I 247.86 nm under different vacuum conditions. Both time-integrated and time-resolved intensity evolutions under vacuums are achieved. The lifetimes of the two atomic lines have similar trends, which supports the point of view of a ＇soft spot＇. Variations of plasma temperature and electron density under different vacuums are measured. This study is helpful for research on carbon detection using LIBS under vacuum conditions.展开更多
Our recent work has determined the carbon content in a melting ferroalloy by laser- induced breakdown spectroscopy （LIBS）. The emission spectrum of carbon that we obtained in the laboratory is suitable for carbon co...Our recent work has determined the carbon content in a melting ferroalloy by laser- induced breakdown spectroscopy （LIBS）. The emission spectrum of carbon that we obtained in the laboratory is suitable for carbon content determination in a melting ferroalloy but we cannot get the expected results when this method is applied in industrial conditions： there is always an unacceptable error of around 4% between the actual value and the measured value. By comparing the measurement condition in the industrial condition with that in the laboratory, the results show that the temperature of the molten ferroalloy samples to be measured is constant under laboratory conditions while it decreases gradually under industrial conditions. However, temperature has a considerable impact on the measurement of carbon content, and this is the reason why there is always an error between the actual value and the measured value. In this paper we compare the errors of carbon content determination at different temperatures to find the optimum reference temperature range which can fit the requirements better in industrial conditions and, hence, make the measurement more accurate. The results of the comparative analyses show that the measured value of the carbon content in molten state （1620 K） is consistent with the nominal value of the solid standard sample （error within 0.7%）. In fact, it is the most accurate measurement in the solid state. Based on this, we can effectively improve the accuracy of measurements in laboratory and can provide a reference standard of temperature for the measurement in industrial conditions.展开更多
Our recent progress on developments of laser-induced breakdown spectroscopy （L[BS） based equipments for on-line monitoring of pulverized coal and unburned carbon （UC） level of fly ash are reviewed. A fully softwar...Our recent progress on developments of laser-induced breakdown spectroscopy （L[BS） based equipments for on-line monitoring of pulverized coal and unburned carbon （UC） level of fly ash are reviewed. A fully software-controlled LIBS equipment comprising a self-cleaning device for on-line coal quality monitoring in power plants is developed. The system features an automated sampling device, which is capable of elemental （C, Ca, Mg, Ti, Si, H, Al, Fe, S, and organic oxygen） and proximate analysis （Qad and Aad） through optimal data processing methods. An automated prototype LIBS apparatus has been developed for possible application to power plants for on-line analysis of UC level in fly ash. New data processing methods are proposed to correct spectral interference and matrix effects, with the accuracy for UC level analysis estimated to be 0.26%.展开更多
Carbon is hard to be sensitively detected in laser-induced breakdown spectroscopy(LIBS).The optical emission can be significantly enhanced by resonantly exciting CN radicals in the plasma center using LIBS assisted wi...Carbon is hard to be sensitively detected in laser-induced breakdown spectroscopy(LIBS).The optical emission can be significantly enhanced by resonantly exciting CN radicals in the plasma center using LIBS assisted with laser-induced fluorescence(LIBS-LIF).However,the nitrogen source for CN formation is provided by ambient gas.Therefore,we propose a new approach of periphery excitation in plasma to improve CN fluorescence.The optical and spatial characteristics of CN radicals in plasma were discussed.A fluorescence map was established by combining focal point location and fluorescent intensity,demonstrating that plasma periphery had 4.2 times stronger fluorescence than the center.展开更多
利用激光诱导击穿光谱(LIBS)技术进行飞灰含碳量分析时常用的C I 247.86 nm谱线附近存在强烈的谱线干扰。位于深紫外区无干扰的C I 193.09 nm常用作分析谱线以避免谱线干扰,但该谱线在空气中会被氧气吸收而影响定量分析的准确性。为了...利用激光诱导击穿光谱(LIBS)技术进行飞灰含碳量分析时常用的C I 247.86 nm谱线附近存在强烈的谱线干扰。位于深紫外区无干扰的C I 193.09 nm常用作分析谱线以避免谱线干扰,但该谱线在空气中会被氧气吸收而影响定量分析的准确性。为了进一步提高利用该谱线定量分析飞灰含碳量效果,在光谱仪中充入氩气并在等离子体区域用氩气吹扫,对比分析了两种气氛下采用C I 193.09 nm谱线定量分析飞灰含碳量的效果。研究结果表明,在氩气气氛下获得的谱线强度及其信噪比、重复测量精度和含碳量的检测限均有显著改善,两个检验样品的含碳量预测绝对误差分别降至0.02%和0.42%(质量分数),含碳量的检测限也降至0.37%(质量分数)。展开更多
基金supported by the National Special Fund for the Development of Major Research Equipment and Instruments of China(No.2014YQ120351)
文摘The influence of a vacuum on the laser-induced breakdown spectroscopy （LIBS） of carbon in the ultraviolet wavelength range is studied. Experiments are performed with graphite using a LIBS system, which consists of a 1064 nm Nd：YAG laser, a vacuum pump, a spectrometer and a vacuum chamber. The vacuum varies from 10 Pa to 1 atm. Atomic lines as well as singly and doubly charged ions are confirmed under the vacuums. A temporal evolution analysis of intensity is performed for the atomic lines of C I 193.09 nm and C I 247.86 nm under different vacuum conditions. Both time-integrated and time-resolved intensity evolutions under vacuums are achieved. The lifetimes of the two atomic lines have similar trends, which supports the point of view of a ＇soft spot＇. Variations of plasma temperature and electron density under different vacuums are measured. This study is helpful for research on carbon detection using LIBS under vacuum conditions.
基金supported by National Natural Science Foundation of China(No.51374040)supported by Laser-Induced Plasma Spectroscopy Equipment Development and Application,China(No.2014YQ120351)
文摘Our recent work has determined the carbon content in a melting ferroalloy by laser- induced breakdown spectroscopy （LIBS）. The emission spectrum of carbon that we obtained in the laboratory is suitable for carbon content determination in a melting ferroalloy but we cannot get the expected results when this method is applied in industrial conditions： there is always an unacceptable error of around 4% between the actual value and the measured value. By comparing the measurement condition in the industrial condition with that in the laboratory, the results show that the temperature of the molten ferroalloy samples to be measured is constant under laboratory conditions while it decreases gradually under industrial conditions. However, temperature has a considerable impact on the measurement of carbon content, and this is the reason why there is always an error between the actual value and the measured value. In this paper we compare the errors of carbon content determination at different temperatures to find the optimum reference temperature range which can fit the requirements better in industrial conditions and, hence, make the measurement more accurate. The results of the comparative analyses show that the measured value of the carbon content in molten state （1620 K） is consistent with the nominal value of the solid standard sample （error within 0.7%）. In fact, it is the most accurate measurement in the solid state. Based on this, we can effectively improve the accuracy of measurements in laboratory and can provide a reference standard of temperature for the measurement in industrial conditions.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 61127017, 61205216, 61275213, 61178009, 61108030, and 60978018）, the National Basic Research Program （973 Program） （Grant No. 2012CB921603）, International Science ＆ Technology Cooperation Program of China （Grant No. 2001DFA12490）, Major Program of the National Natural Science Foundation of China （Grant No. 10934004）, NSFC Project for Excellent Research Team （Grant No. 61121064）, Environmental Project of Shanxi Province （Grant No. 2011256）.
文摘Our recent progress on developments of laser-induced breakdown spectroscopy （L[BS） based equipments for on-line monitoring of pulverized coal and unburned carbon （UC） level of fly ash are reviewed. A fully software-controlled LIBS equipment comprising a self-cleaning device for on-line coal quality monitoring in power plants is developed. The system features an automated sampling device, which is capable of elemental （C, Ca, Mg, Ti, Si, H, Al, Fe, S, and organic oxygen） and proximate analysis （Qad and Aad） through optimal data processing methods. An automated prototype LIBS apparatus has been developed for possible application to power plants for on-line analysis of UC level in fly ash. New data processing methods are proposed to correct spectral interference and matrix effects, with the accuracy for UC level analysis estimated to be 0.26%.
基金supported by the National Key Research and Development Program of China(No.2017YFB-1104500)Key-Area Research and Development Program of Guangdong Province(No.2020B090922006)+4 种基金Guangdong Basic and Applied Basic Research Foundation(No.2019A1515111120)Science and Technology Program of Guangzhou(No.202002030165)Featured Innovation Project of Guangdong Education Department(No.2019KTSCX034)Young Innovative Talents Project in Universities of Guangdong Province(No.2018KQNCX057)Young Scholar Foundation of South China Normal University(No.19KJ13)。
文摘Carbon is hard to be sensitively detected in laser-induced breakdown spectroscopy(LIBS).The optical emission can be significantly enhanced by resonantly exciting CN radicals in the plasma center using LIBS assisted with laser-induced fluorescence(LIBS-LIF).However,the nitrogen source for CN formation is provided by ambient gas.Therefore,we propose a new approach of periphery excitation in plasma to improve CN fluorescence.The optical and spatial characteristics of CN radicals in plasma were discussed.A fluorescence map was established by combining focal point location and fluorescent intensity,demonstrating that plasma periphery had 4.2 times stronger fluorescence than the center.
文摘利用激光诱导击穿光谱(LIBS)技术进行飞灰含碳量分析时常用的C I 247.86 nm谱线附近存在强烈的谱线干扰。位于深紫外区无干扰的C I 193.09 nm常用作分析谱线以避免谱线干扰,但该谱线在空气中会被氧气吸收而影响定量分析的准确性。为了进一步提高利用该谱线定量分析飞灰含碳量效果,在光谱仪中充入氩气并在等离子体区域用氩气吹扫,对比分析了两种气氛下采用C I 193.09 nm谱线定量分析飞灰含碳量的效果。研究结果表明,在氩气气氛下获得的谱线强度及其信噪比、重复测量精度和含碳量的检测限均有显著改善,两个检验样品的含碳量预测绝对误差分别降至0.02%和0.42%(质量分数),含碳量的检测限也降至0.37%(质量分数)。
