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Lithium Distribution in Structured Graphite Anodes Investigated by Laser-Induced Breakdown Spectroscopy
摘要： For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.
关键词： laser-induced breakdown spectroscopy,3D battery,lithium-ion battery,ultrafast laser ablation,graphite anode
更新于2025-09-12 10:27:22
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Femtosecond laser-induced breakdown spectroscopy of a preheated Cu target
摘要： We present a study detailing femtosecond laser-induced breakdown spectroscopy (LIBS) of Cu with the sample preheated to di?erent temperatures (22–120 °C). The detected spectral intensity of the plasma emission increased with the target temperature. Additionally, laser-induced plasma temperature was calculated by Boltzmann plot method. The plasma temperature rose along with the target temperature, indicating an enhanced interaction between the laser and the target in the case of a higher target temperature. We also simulated the thermal behavior of Cu irradiated by the femtosecond laser via a two-temperature model. As the sample temperature increased from 22 °C to 120 °C, the increase in the lattice temperature under femtosecond laser irradiation was approximately 200–300 K, and the ablated depth increased. The simulated results suggested that increasing the sample temperature led to an increase in the ablated mass. Based on this work, it can be seen that the method of preheating the ablation target can help enhance the spectral intensity and the detection sensitivity of femtosecond LIBS.
关键词： LIBS,Sample temperature,Femtosecond laser,Laser-induced breakdown spectroscopy
更新于2025-09-12 10:27:22
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Simultaneous measurements of fuel concentration and temperature in gas jets by laser induced breakdown spectroscopy
摘要： Laser induced breakdown spectroscopy (LIBS) enables quantitative measurements of the equivalence ratio in flames, spray and gas jets. Although there are always considerable temperature differences between the calibrations and the LIBS measurements in flames and fuel jets, the temperature effects on LIBS were rarely mentioned and not corrected in the previous LIBS measurements. In this study, a novel method to simultaneously measure the equivalence ratio and the gas temperature by LIBS in a single laser shot is proposed. This method can correct the temperature effects based on the linear correlation between the peak intensity ratio (PIR) of atomic lines and the gas temperature. The PIR of H656/N746 and the full width at half maximum (FWHM) of H656 are employed to establish calibration curves with the equivalence ratio and the gas temperature, respectively, and both of calibrations show high coefficients of determination (R2). Then, the measurement accuracy and precision of the proposed method are discussed in detail. The total uncertainties in measurements of equivalence ratio and gas temperature are estimated by 5.6% and 5.8%, respectively. Finally, the simultaneous measurements of equivalence ratios and gas temperatures in methane jets at different positions and at different injection pressures are conducted. The comparison of equivalence ratios before and after correction of the temperature effects indicates that the accuracy of the fuel concentration measurements by LIBS would be remarkably degraded if the temperature variations were neglected.
关键词： Measurement uncertainties,Laser-induced breakdown spectroscopy (LIBS),Equivalence ratio,Gas temperature,Full width at the half maximum (FWHM)
更新于2025-09-12 10:27:22
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Investigation of compositional variations in chromitite ore with imaging Laser Induced Breakdown Spectroscopy and Spectral Angle Mapper classification algorithm
摘要： This paper focusses on the applicability of the Spectral Angle Mapper (SAM) algorithm for supervised classification of imaging Laser Induced Breakdown Spectroscopy (LIBS) data. Our main objective is to investigate variations in the chemical/mineralogical composition of complex ore from the sub-millimetre to the metre scale, which may offer novel and barely investigated interpretation opportunities for exploration purposes. This research is based on coarse chromitite ore from Merensky Reef, represented by a drill core and a small section through the upper chromitite layer. Detailed LIBS-based imaging measurements were accompanied by space-resolved reference measurements based on SEM/MLA and EDXRF, as well as bulk chemical analyses for multiple core slices. The SAM algorithm was applied for classification of LIBS hyperspectral images with respect to differences in mineral chemistry. Our investigations focused on the pre-processing of LIBS spectra prior to SAM classification, on spectral library development, as well as on the validation of the classified data. The SAM classification algorithm, which is solely based on ratios between spectral intensities, was found insensitive to normal shot-to-shot plasma variations and to chemically induced matrix effects. However, the algorithm may become inaccurate at low signal to noise ratios, at the border between different mineral grains (mixed spectra), or when classifying chemically similar phases such as pyrite and pyrrhotite. The extent of mixed spectra depends both on the size of the mineral grains as well as on the spot size of the LIBS laser. The SAM algorithm was successfully applied for classification of several base metal sulphides, rock-forming minerals, accessory minerals, as well as several mixed phases representing the main borders between different mineral grains. The resulting classified LIBS image shows the spatial distribution of the different phases, which is in very good agreement with the space-resolved reference measurements based on EDXRF and SEM/MLA. The results also highlight the extremely heterogeneous distribution of e.g. the sulphide phases in the investigated core piece. The applicability of the LIBS-SAM classification image for estimating metal concentrations based on point counting has been explored for Cu, Ni, S, and Cr. We conclude that this approach, when applied on sufficiently large surfaces, enables semi-quantitative data analysis, as well as the possible detection of trace elements (e.g. Pt, Pd) that occur in very small nuggets.
关键词： Chromitite Ore,Core Scanner,Spectral Angle Mapper,Geochemical Exploration,Laser Induced Breakdown Spectroscopy (LIBS),Mineral Classification
更新于2025-09-12 10:27:22
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Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture
摘要： The lack of soil data, which are relevant, reliable, a?ordable, immediately available, and su?ciently detailed, is still a signi?cant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within ?elds, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, di?erent calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural ?elds in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The ?rst method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both ?elds. The second univariate model derived the calibration from the reference analytics of all samples from one ?eld. The prediction is validated by LIBS data of the second ?eld. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the ?rst ?eld are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the ?rst ?eld and independently on the second ?eld data. The second univariate method yielded better calibration and prediction results compared to the ?rst method, since matrix e?ects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method.
关键词： laser-induced breakdown spectroscopy,soil nutrients,elemental composition,proximal soil sensing,LIBS
更新于2025-09-12 10:27:22
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Influence of distance between target surface and focal point on CN emission of nanosecond laser-induced PMMA plasma in air
摘要： Laser-induced breakdown spectroscopy (LIBS) is a technique for spectral composition analysis of materials containing atomic and ionic emission lines, as well as a few molecular emission bands. Here we focused our study on molecular emission from CN (B2∑+→X2∑+) based on LIBS method. Polymethyl methacrylate (PMMA) was ablated by employing a Nd:YAG laser system in air under atmospheric pressure. In the ultraviolet range, the molecular emission intensities of CN violet bands were observed with a spectrometer equipped with an intensified CCD detector. The effect of distance between sample surface and focal point (DTSFP) on the intensities of molecular emission was studied in detail. The results showed that the molecular emission intensities of CN violet bands exhibited a strong dependence on the DTSFP. As the surface of the PMMA sample approached the focal point gradually, the emission intensity of CN increased at first and then dropped down. In addition, vibrational temperature of CN molecule was also calculated. The vibrational temperature showed the similar change in the emission intensity, while the position at the maximum vibrational temperature was inconsistent with the position at the CN intensity.
关键词： CN,distance between sample surface and focal point,laser-induced breakdown spectroscopy,PMMA
更新于2025-09-12 10:27:22
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Enhancement of Analytical Signal of Laser Induced Breakdown Spectroscopy by Deposition of Gold Nanoparticles on Analyzed Sample
摘要： Efficiency of LIBS signal enhancement by deposition of gold nanoparticles prepared by laser ablation in acetone on the surface of the analyzed sample has been studied. Characteristics of laser plasma generated on steel surface before and after deposition of the nanoparticles are compared. It is found that deposition of nanoparticles increases plasma volume and lifetime, but does not affect erosion of the material. Deposition of nanoparticles results in the enhancement of spectral lines intensities depending on the zone of the plasma plume selected for analysis: signal enhancement grows with distance from the sample.
关键词： nanoparticles,laser-induced breakdown spectroscopy,spectral line intensity
更新于2025-09-12 10:27:22
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Quantitative analysis of cadmium and zinc in algae using laser-induced breakdown spectroscopy
摘要： In the demand for renewable energy sources, algae are considered to have a good potential for biodiesel production. Fast detection of heavy metals in energetic algae is of vital importance for algal biomass and biodiesel production environment monitoring. This study aims to determine cadmium (Cd) and zinc (Zn) contents in algal pellets with laser-induced breakdown spectroscopy (LIBS) technology. Partial least squares (PLS) regression and extreme learning machine (ELM) were constructed after spectral preprocessing by standard normal variate transformation (SNV), multiplicative scatter correction (MSC) and Savitzky–Golay smoothing (SG). For univariate analysis, ELM models based on Cd II 226.45 nm and Zn II 206.19 nm of SNV preprocessed spectra achieved the best results for Cd and Zn content prediction respectively, with Rp, RMSEP and RPD values of 0.9866, 50.71 mg kg?1 and 6.95 for the former, and 0.9873, 30.08 mg kg?1 and 6.44 for the latter. Multivariate analysis of Cd based on the PLS model with global spectra achieved the best performance with Rc and Rp values of 0.9965 and 0.9972, RMSECV and RMSEP values of 25.57 mg kg?1 and 23.63 mg kg?1, and an RPD value as high as 13.27, showing the excellent robustness and effectiveness of the model for Cd detection. For Zn analysis, the best performance was achieved by the ELM model based on feature variables selected by regression coefficients, with Rc and Rp values of 0.9836 and 0.9920, RMSEC and RMSEP values of 34.25 mg kg?1 and 24.64 mg kg?1, and an RPD value of 7.87. The results indicated that the LIBS technique combined with appropriate preprocessing algorithms and multivariate chemometric methods could be a rapid and accurate way for quantitative analysis of Cd and Zn contents in algae and the aquatic environment.
关键词： laser-induced breakdown spectroscopy,quantitative analysis,chemometric methods,zinc,algae,cadmium
更新于2025-09-12 10:27:22
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Hyperspectral images: a qualitative approach to evaluate the chemical profile distribution of Ca, K, Mg, Na and P in edible seeds employing laser-induced breakdown spectroscopy
摘要： In the present study, laser-induced breakdown spectroscopy (LIBS) combined with chemometric tools was used to investigate the metal composition in nine seed samples. The samples were directly analyzed, and a matrix with 9 rows and 9 columns (81 points) and 10 consecutive pulses were analyzed in each point. A total of 810 emission spectra were collected from 186 to 1042 nm from the surface and bulk of the sample. The dataset was normalized by Euclidian norm and principal component analysis (PCA) was used for the initial exploratory investigation. Calcium, Mg, Na, K and P were mainly identified in all samples; the distribution of metals in these samples is not completely homogeneous, however, i.e., composition of the elements change from one layer to another. This fact can be probably related to the absorption capability of nutrients resulting from different factors such as soil characteristics, physiology of the plant, water source composition and fertilizers which can influence the distribution of the elements in different seeds. To confirm the elements observed by LIBS, the samples were digested using microwave-assisted digestion, and Ca, K, Mg, Na and P were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). In addition, some minor nutrients such as S and Zn were also investigated and the relationships between elements were observed through the Pearson correlation graph, and some of them, such as Mg and Na, P and Na, S and P, S and Zn, are extremely correlated; it means that, for example, when the concentration of Mg increases, that of Na also increases.
关键词： Chemometric tools,Laser-induced breakdown spectroscopy,Edible seeds,Chemical profile distribution,Hyperspectral images
更新于2025-09-12 10:27:22
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Micro-invasive depth profile analysis by laser-induced breakdown spectroscopy (LIBS): the case of mercury layers on Sasanian coins
摘要： Laser-Induced Breakdown Spectroscopy (LIBS) was used for depth-profile analysis of one Sasanian coin of the emperor Khusro II (591–628) from the Coin Collection of the Kunsthistorisches Museum of Vienna. The peculiarity of this coin, also found in analogous samples of the same and other collections, was the presence of an external Hg layer. The thickness and homogeneity of the Hg layer were characterized with the calibration-free inverse method, a variant of the classical calibration-free LIBS approaches in which one sample of known concentration is used to determine the plasma temperature. We demonstrated the feasibility of the inverse method also in cases of unknown samples with matrices different from that of the employed standard. In this work, the standard was a Cu-based alloy and the sample was an Ag-based alloy, also containing Hg and other minor components. The LIBS results were in good agreement with two previous independent micro-XRF measurements performed with a destructive approach, i.e. using a cross section of the same sample. This confirmed the applicability of the inverse method to unconventional matrices, for which the use of matrix-matched standards may be unfeasible. The conclusions of this work strongly support the use of laser ablation techniques for calibration-free and micro-invasive analysis of layered samples, in particular when the integrity of samples has to be preserved.
关键词： micro-invasive analysis,Laser-Induced Breakdown Spectroscopy,Hg layer,depth-profile analysis,calibration-free inverse method,Sasanian coin,LIBS
更新于2025-09-12 10:27:22