Spark-induced Breakdown Spectroscopy Research Articles

Deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy employed for rapid and accurate identification of bismuth brass

BackgroundOwing to its excellent machinability and less toxicity, bismuth brass has been widely used in manufacturing various industrial products. Thus, it is of significance to perform rapid and accurate identification of bismuth brass to reveal the alloying properties. However, the analytical lines of various elements in bismuth brass alloy products based on conventional laser-induced breakdown spectroscopy (LIBS) are usually weak. Moreover, the analytical lines of various elements are often overlaped, seriously interfering with the identification of bismuth brass alloys. To address these challenges, developing an advanced strategy enabling to achieve ultra-high accuracy identification of bismuth brass alloys is highly desirable. ResultsThis work proposed a novel method for rapidly and accurately identifying bismuth brass samples using deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS). With the help of fs-LA-SIBS, a spectral database containing high quality LIBS spectra on element components were constructed. Then, one-dimensional convolutional neural network (CNN) was introduced to distinguish five species of bismuth brass alloy. Amazingly, the optimal CNN model can provide an identification accuracy of 100 % for specie identification. To figure out the spectral features, we proposed a novel approach named “segmented fs-LA-SIBS wavelength”. The identification contribution from various wavelength intervals were extracted by optimal CNN model. It clearly showed that, the differences of spectra feature in the wavelength interval from 336.05 to 364.66 nm can produce the largest identification contribution for an identification accuracy of 100 %. More importantly, the feature differences in the four elements such as Ni, Cu, Sn, and Zn, were verified to mostly contribute to identification accuracy of 100 %. SignificanceTo the best of our knowledge, it is the first study on one-dimensional CNN configuration assisted with fs-LA-SIBS successfully employed for performing identification of bismuth brass. Compared with conventional machine learning methods, CNN has shown significant more superiority. To reveal the tiny spectra differences, the classification contribution from spectra features were accurately defined by our proposed “segmented fs-LA-SIBS wavelength” method. It can be expected that, CNN assisted with fs-LA-SIBS has great promising for identifying the differences from various element components in metallurgical field.

Rapid and accurate identification of steel alloys by femtosecond laser-ablation spark-induced breakdown spectroscopy and machine learning

This work investigates the application of femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) combined with machine learning algorithms for the rapid and accurate identification of steel alloys. Three algorithms, namely random forest (RF), support vector machine (SVM), and partial least squares identification analysis (PLS-DA), were compared and evaluated. The results indicate that, in 100 independent classifications, the RF model demonstrated an average accuracy of 0.9337, significantly surpassing the accuracies of the SVM model at 0.8281 and the PLS-DA model at 0.8646. In addition, in the evaluation of 5-fold cross-validation and the prediction set, the RF model achieved a near-perfect micro-average area under curve (AUC) of 0.9996, surpassing the AUCs of the SVM model at 0.9761 and the PLS-DA model at 0.9847. The PCA results provided valuable insights into the spectral features that most significantly contributed to the classification accuracy, further confirming the RF model's robustness and effectiveness. This integrated approach offers a powerful tool for the rapid classification and accurate identification of steel alloys in industrial applications.

Optical and thermodynamic investigation of jet-guided spark ignited hydrogen combustion

Hydrogen as an alternative fuel for engines is gaining interest to decarbonize the heavy-duty sector. Hydrogen combustion in engines conventionally relies on the Otto cycle and either port fuel or direct injection. This combustion concept usually results in poor power density and non-ideal efficiencies due to the lean premixed operation and low compression ratio required to avoid preignition and knocking. In this study, hydrogen is directly injected at high pressures into the combustion chamber and spark-ignited with two different ignition systems (inductive and nanosecond repetitively pulsed discharge) at the periphery of the jet, with fuel conversion taking place predominantly in jet-guided (diffusion) mode while injection remains active.A rapid compression expansion machine (RCEM) is used to investigate the jet-guided hydrogen combustion thermodynamically and optically by combining high-speed Schlieren and OH* chemiluminescence imaging, and spark-induced breakdown spectroscopy (SIBS).SIBS reveals low air to fuel ratios at ignition time and location, ranging from 2.8 up to pure air depending on the condition and significant variation among repetitions. Both OH* chemiluminescence and Schlieren images illustrate how air entrainment pushes the flame-plasma kernel from the ignition location at the periphery of the jet towards the fuel-richer core, resulting in fast combustion of the already premixed fuel. Subsequently, the combustion process becomes dominated by the mixing dynamics. Under conditions of low in-cylinder pressures, the Heat Release Rate (HRR) closely follows the injected mass flow rate multiplied by the lower heating value of hydrogen, i.e., the combustion is mixing controlled. However, as the cylinder pressure increases, the mixing and combustion rates fall below the injected mass flow until lower densities are reached again.The delay between the start of injection and ignition primarily impacts the premixed peak, but the in-cylinder pressure and ignition source also play significant roles. This distinctive combustion process shows essential similarities to compression ignition Diesel combustion. The process holds the potential to achieve high efficiency, as hydrogen can be burned using process parameters typical of Diesel combustion without facing the constraints of knock or preignition and a complete absence of soot.

Hydrogen concentration measurements using spark induced breakdown spectroscopy in a real engine

This study develops spark induced breakdown spectroscopy (SIBS) for measurements of direct injected hydrogen concentration in a multi-cylinder engine operated at real conditions. To this end, calibration is performed in the air excess ratio (λ) range of 2.1 ∼ 2.9 and simultaneously, high-speed schlieren imaging of laminar hydrogen flame propagation is performed in an optical high-pressure constant volume combustion chamber (CVCC). To achieve real engine applications, the SIBS is further developed using a modified conventional spark plug for sapphire window insertion onto the positive electrode and guided arc formation via a newly designed nipple type ground electrode. Specifically, the peak spectra intensity ratio of Hα (656 nm) to O (777 nm) is used for calibration, which shows a linear correlation with λ. For the first time, the calibrated SIBS is applied to a real engine operated at 46.2 ∼ 63.9 Nm load and 2000 rpm with 3.5 MPa hydrogen direct injection. The results show lower local λ than the global λ despite early injection timing of 165 crank angles before top dead centre, indicating a significant influence of in-cylinder flow motion on the spatial distribution of hydrogen-air mixtures.

Accurate prediction analysis of steel alloy elements by femtosecond laser-ablation spark-induced breakdown spectroscopy and out-of-bag random forest regression

Femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) and out-of-bag random forest regression (OOB-RFR) were developed for accurate quantitative analysis of the elements manganese (Mn), chromium (Cr), and nickel (Ni) in steel alloys.

Analysis of Cu and Zn contents in aluminum alloys by femtosecond laser-ablation spark-induced breakdown spectroscopy

Abstract To enhance the sensitivity of detecting Cu and Zn in aluminum alloys, we incorporated a spark discharge unit into the femtosecond laser-induced breakdown spectroscopy (fs-LIBS) system, forming a femtosecond laser ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) system. We utilized both fs-LA-SIBS and fs-LIBS techniques to detect Cu and Zn in various aluminum alloy samples with different contents. Our results reveal that the spark discharge extends the duration of laser-induced plasma atomic radiation and amplifies the peak intensity of atomic radiation, thereby significantly increasing the time-integrated signal intensity of laser-induced plasma. Under the present experimental conditions, the limits of detection (LoDs) of Cu and Zn in aluminum alloy by fs-LA-SIBS are 16 and 12 ppm, respectively. In contrast, the LoDs of Cu and Zn by fs-LIBS technique under the same laser pulse energy are 96 and 84 ppm, respectively. Hence, for Cu, the LoDs by the fs-LA-SIBS technique are 1/6 of those by the fs-LIBS technique, and for Zn, the LoDs by the fs-LA-SIBS technique are 1/7 of those by the fs-LIBS technique. Our findings demonstrate that the fs-LA-SIBS technique is more sensitive than the fs-LIBS technique in the quantitative analysis of elements and may be a practical approach for elemental analysis in alloys.

One-Point and Multiline Calibration Fiber-Optic Laser-Ablation Spark-Induced Breakdown Spectroscopy for Quantitative Analysis of Elements in Aluminum Alloys

Rapid and accurate analysis of element concentrations in aluminum alloys is crucial due to their widespread use in modern industry. This paper proposes a one-point and multiline calibration fiber-optic laser-ablation spark-induced breakdown spectroscopy (OP-MLC FO-LA-SIBS) for the quantitative analysis of elements in aluminum alloys. The experimental system utilizes a compact fiber laser as the laser-ablation source and spark discharge to enhance the atomic emission. A portable multichannel fiber spectrometer is used to quickly collect spectra in the nongated mode. The concentrations of four elements (Mg, Cr, Cu, and Mn) in four aluminum alloy samples were calculated using the simple and efficient OP-MLC method, which involves taking another sample with a similar matrix as the standard sample. The average relative errors (AREs) for Mg, Cr, Cu, and Mn were 6.38%, 28.09%, 21.92%, and 18.97%, respectively. When the certified concentrations are greater than 0.02 wt.%, the ARE is only 13.04%. The OP-MLC FO-LA-SIBS system is compact, features simple spectra processing, and offers effective measurement, providing a convenient method for rapid and efficient quantitative analysis of elements in aluminum alloys in industrial production.

Quantitative elemental analysis of bismuth brass by microchip laser-ablation spark-induced breakdown spectroscopy

A compact microchip laser-based LIBS coupled with spark discharge was developed to realize sensitive and high spatial resolution elemental analysis.

Quantitative analysis of elemental concentrations of aluminum alloys using calibration-free femtosecond laser-ablation spark-induced breakdown spectroscopy

In this work, the calibration-free (CF) methodology combined with femtosecond laser-ablation spark-induced breakdown spectroscopy (fs LA-SIBS) was applied for the quantitative analysis of elements in aluminum alloy. A femtosecond laser (800 nm) operated at a repetition rate of 1 kHz with a pulse width of 35 fs was used as the laser-ablation source, and the plasma emission was enhanced by the spark discharge. Spectra were acquired using a compact fiber spectrometer coupled to a charge-coupled device and recorded at 200–500 nm. The aluminum alloy sample was mounted on a two-dimensional motion platform, and the effect of the sample moving speed on the spectral intensity was investigated. To evaluate the analysis performance of this technique, five standard aluminum alloy samples with certified elemental concentrations were tested. The average estimated electron density from these five transitions was (1.5 ± 0.3) × 1017 cm−3, which was determined by fitting the ion spectrum of Al II (281.62 nm) with Lorentz fitting. The plasma temperature was calculated to be 6300 ± 300 K using Saha–Boltzmann plots under the local thermodynamic equilibrium state. Trace elements with the content of <0.1% were detected by the proposed technique, and the analysis error of Al was <0.3%. This study shows that the CF fs LA-SIBS technique can be employed for quantitative analysis of major, minor, and trace elements in multi-composition alloys.

Application of quantitative analysis for aluminum alloy in femtosecond laser-ablation spark-induced breakdown spectroscopy using one-point and multi-line calibration

To achieve the quantitative elemental analysis of aluminum alloy samples, the one-point and multi-line calibration (OP-MLC) method and femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) were combined in this study. An ultrafast Ti: sapphire laser with high single-pulse energy and high repetition–rate operation was used as the laser source to ablate the sample at a 1k Hz pulse repetition rate and achieve re-excitation using spark discharge. Subsequently, an enhanced spectral peak intensity was achieved, which increased the sensitivity and analytical capabilities of laser-induced breakdown spectroscopy (LIBS) technique. Considering only one confirmed sample, the OP-MLC method was used to calculate the concentration ratios of trace elements Mg, Cr, Cu, Mn and Zn in four aluminum alloy samples to the calibration samples by the integral intensity ratio of the elemental characteristic lines between the two samples. The average relative errors with the identified concentrations were 3.99%, 15.13%, 8.76%, 9.30% and 9.64%, respectively. The results showed that the combination of OP-MLC method and fs-LA-SIBS has good accuracy in the quantitative analysis of elements, and has the advantages of simplicity, rapidity and high sensitivity.

Elemental Analysis of V, Mo, Cr, Mn, Al, Ni, and Cu in Steel Alloy with Femtosecond Laser Ablation Spark-Induced Breakdown Spectroscopy

Femtosecond laser ablation spark-induced breakdown spectroscopy (fs LA-SIBS) was developed to quantitatively analyze vanadium, molybdenum, chromium, manganese, aluminum, nickel, and copper in a steel alloy. In the experiment, a femtosecond laser operating at a repetition rate of 1 kHz was used as the laser ablation source, and spark discharge was utilized to re-excite the plasma and enhance the atomic intensity. A compact fiber spectrometer was used to record and analyze the plasma emission spectra in a nongated signal-recording mode. The calibration curves of V, Mo, Cr, Mn, Al, Ni, and Cu elements in steel alloy samples were established, and the detection limits of these elements were determined to be 10.9, 12.6, 4.0, 5.7, 8.7, 7.9, and 3.1 ppm with fs LA-SIBS, respectively, which were 4–12-fold better than those achieved with femtosecond laser-induced breakdown spectroscopy (fs LIBS). Compared with conventional LIBS, the fs LA-SIBS technique provided a rapid and high spatial resolution approach to quantitative elemental analysis, with better analytical sensitivity.

Atmospheric air plasma sustainment by semiconductor microwave for hydroxyl radical production and powder metal element analysis

A semiconductor microwave device that generates a series of burst microwaves at a sub-microsecond duration has been successfully used in a breakdown plasma spectrometer in atmospheric conditions. Microwave delivery has been changed to couple the microwave with laser sparks and electric sparks which are typical plasma ignition sources in laser-induced breakdown spectroscopy (LIBS) and spark-induced breakdown spectroscopy (SIBS). A helical antenna was used for the laser spark, while a coaxial antenna was considered more appropriate for the electric spark. The weak and transient sparks in LIBS and SIBS are enlarged by the microwaves which are stably sustained in the air. The microwave's output power and pulse duration are easily controllable, resulting in tunable plasma intensity and sustained production of hydroxyl radicals (OH radicals). Even in continuous-wave operation by microwave, the low-energy system prevented the formation of high-temperature thermal plasma (>10,000 K) without any mechanical cooling system. The microwave-enhanced LIBS (MW-LIBS) and microwave-enhanced SIBS (MW-SIBS) could be applied to optical emission spectroscopy analyses. In analytical applications, MW-SIBS produces no shockwave in contrast with MW-LIBS which is a great advantage in powdered samples. The MW-SIBS successfully analyzed the direct introduction of copper metal powders.

Spark-Induced Breakdown Spectroscopy In A Direct-Injected Natural Gas Spark-Ignition Engine

The purpose of this study is to investigate the fuel concentration around the spark plug obtained using spark-induced breakdown spectroscopy (SIBS) method with the spark plug with an optical fiber in the direct-injected natural gas SI engine. Effect of exposure duration on measurement accuracy of fuel concentration was discussed. Equivalence ratio around the spark plug in the direct-injected natural gas SI engine were measured under different natural gas injection timing. When the exposure duration is shortened, the emission of potassium elements near the emission wavelength of oxygen elements can be suppressed, and the measurement accuracy in the calculation of the emission intensity ratio can be improved. The relationship between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio of homogeneous mixture of natural gas and air was investigated and it was found that there was a positive correlation between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio. As a result of measuring the equivalence ratio around the spark plug of direct-injected natural gas SI engine using the SIBS method, an equivalence ratio of 0.67 was measured for a set value of 0.8 using the luminescence intensity ratio of hydrogen and oxygen.

Improving quantitative analysis of spark-induced breakdown spectroscopy: Multivariate calibration of metal particles using machine learning

We have recently developed a low-cost spark-induced breakdown spectroscopy (SIBS) instrument for in-situ analysis of toxic metal aerosol particles that we call TARTA (toxic-metal aerosol real time analyzer). In this work, we applied machine learning methods to improve the quantitative analysis of elemental mass concentrations measured by this instrument. Specifically, we applied least absolute shrinkage and selection operator (LASSO), partial least squares (PLS) regression, principal component regression (PCR), and support vector regression (SVR) to develop multivariate calibration models for 13 metals (e.g., Cr, Cu, Mn, Fe, Zn, Co, Al, K, Be, Hg, Cd, Pb, and Ni), some of which are included on the US EPA hazardous air pollutants (HAPS) list. The calibration performance, adjusted coefficient of determination (R2) and normalized root mean square error (RMSE), and limit of detection (LOD) of the proposed models were compared to those of univariate calibration models for each analyte. Our results suggest that machine learning models tend to have better prediction accuracy and lower LODs than conventional univariate calibration, of which the LASSO approach performs the best with R2 > 0.8 and LODs of 40–170 ng m−3 at a sampling time of 30 min and a flow rate of 15 l min−1. We then assessed the applicability of the LASSO model for quantifying elemental concentrations in mixtures of these metals, serving as independent validation datasets. Ultimately, the LASSO model developed in this work is a very promising machine learning approach for quantifying mass concentration of metals in aerosol particles using TARTA.

The performance of an inexpensive spark-induced breakdown spectroscopy instrument for near real-time analysis of toxic metal particles

To meet the demand for identifying and controlling toxic air contaminants in environmental justice communities, we have recently developed a cost-effective spark-induced breakdown spectroscopy (SIBS) instrument for detecting and quantifying toxic metal air pollutants. We characterized the detection limit and linearity of this SIBS instrument by analyzing nebulized elemental standard solutions. The experimental parameters affecting SIBS performance were optimized, including the time delay to observation, the distance between electrodes, and the ablation voltage. The instrument successfully detected Cr, Cu, Mn, Fe, Zn, Co, and Ni, with limits of detection ranged from 0.05 μg m−3 to 0.81 μg m−3 at a flow rate of 15 l min−1 and a 30 min sampling duration. Similar to other investigations using ion breakdown spectroscopy, we did not observe strong emissions lines for As, Sb, Se, Hg, Pb, and Cd, which were likely due to spectral overlap, matrix effects, and the limited detection range of the optical components. Overall, SIBS is a promising technique for field measurements of toxic metals for environmental justice, industrial and urban applications.

Accurate elemental analysis of alloy samples with high repetition rate laser-ablation spark-induced breakdown spectroscopy coupled with particle swarm optimization-extreme learning machine

High repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) coupled with particle swarm optimization-extreme learning machine (PSO-ELM) was developed to realize quantitative elemental analysis of aluminum alloy accurately. A compact Nd: YAG laser operated at 1 kHz was used as the ablation laser and a spark discharge was utilized to enhance the plasma emission. The characteristic lines of the elements were selected as input variables and the parameters of ELM were optimized by the PSO algorithm. The PSO-ELM calibration models were established. The correlation coefficient of prediction set reached to 0.9996, 0.9972 and 0.9999, the root mean square error of prediction set decreased to 0.0138%, 0.0045% and 0.0095% for Mg, Cr, and Cu analysis, respectively. Better predictive performance has been demonstrated in comparison with the univariate and SVM methods. HRR LA-SIBS coupled with PSO-ELM can give convenient, rapid and accurate elemental analysis of alloy samples. Moreover, it will extend the potential applications of HRR LA-SIBS in intelligent manufacturing and on-line monitoring in the future.

Quantitative elemental analysis of aluminum alloys with one-point calibration high repetition rate laser-ablation spark-induced breakdown spectroscopy

A one-point calibration method has been successfully used to improve the analytical accuracy of the calibration free HRR LA-SIBS technique.

Quantitative analysis of trace elements in bismuth brass with high repetition rate laser-ablation spark-induced breakdown spectrum

Bismuth brass has very good mechanical properties and is friendly to environment. Therefore, it can be widely used in different fields. In order to realize the convenient, rapid and sensitive elemental analysis of trace elements in bismuth brass, fiber laser based high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) is developed. In the experiments, a compact fiber laser operated at 5 kHz pulse repetition rate is used to ablate the sample and produce plasma, and the spark discharge is used to further break down the ablated sample and enhance the plasma emission for sensitive elemental analysis. A compact fiber-optic spectrometer coupled with non-intensified charge-coupled device (CCD) is used to record the spectra. Bismuth, lead and tin in several bismuth brass standard samples are quantitatively analyzed. The plasma temperature is determined to be about 7962 ± 300 K by using the Boltzmann plots of copper, zinc and tin elements; the electron density is determined to be about 1.049 × 10&lt;sup&gt;–17&lt;/sup&gt; cm&lt;sup&gt;–3&lt;/sup&gt; based on the Stark broadening of Cu (I) 510.47 nm analytical line. The plasma is determined to be in local thermodynamic equilibrium (LTE) state according to McWhirter criterion as well as appended criteria for transient plasma. Under the present experimental condition, the calibration curves of bismuth, lead and tin in bismuth brass are built with fitting goodness of higher than 95%. The detection limits of bismuth, lead and tin are determined to be 25.5 ppm, 64.2 ppm and 316.5 ppm, respectively. The weak transition probability of tin atoms leads to worse detection limit of tin than the scenarios of bismuth and lead. The ways to further improve the analytical sensitivity and minimize system dimensions are discussed in this article. It is demonstrated that high repetition rate laser-ablation spark-induced breakdown spectrometer based on compact fiber laser as well as compact fiber-optic spectrometer can be used to realize the convenient, rapid and sensitive elemental analysis of trace elements in bismuth brass. This study is also helpful in analyzing the trace harmful elements, including bismuth, lead and tin in high temperature alloys with HRR LA-SIBS. In comparison with laser-induced breakdown spectroscopy (LIBS), the HRR LA-SIBS technique has several intrinsic advantages, such as fast spectral data collection speed, cost-effective system and low continuum background and so on. This technique is very useful in implementing the elemental analysis of different alloy samples and can be potentially used in metallurgical industry in the future.

스파크 유도 플라즈마 분광 시스템을 이용한 우주탐사용 암석 분석연구

스파크 유도 플라즈마 분광법 (SIBS)은 전기 스파크를 사용하여 강력한 플라즈마를 유도한 후 원자 방출 스펙트럼 신호를 수집하는 방법이다. 이 연구는 우주 탐사에 활용되는 기존의 레이저 유도 분해 분광법 (LIBS) 대신 SIBS를 사용할 수 있는지의 잠재력을 보기 위해 진행되었다. 과거에는 SIBS를 사용하여 부피가 큰 고체 샘플을 대상으로 실험하는 것이 성공적이지 않았기 때문에, 본 연구에서는 전극 위치 및 전극 재료의 SIBS의 최적화 연구가 수행되었다. LIBS를 사용할 때에 비해 SIBS의 검출 한계 (LOD)가 78에서 20ppm으로 최대 4배 향상되어 있음을 볼 수 있었다. 생성된 플라즈마의 더 높은 에너지로 인해, SIBS에 의한 신호 세기는 동일한 분광계 설정에서 LIBS보다 3배 정도 높았다.

Laser ablation assisted spark induced breakdown spectroscopy and its application

Recently, laser ablation assisted spark induced breakdown spectroscopy (LA-SIBS) has been growing rapidly and continue to be extended to a broad range of materials analysis. Characterized by employing a specifically designed high voltage and pulse discharge circuit to generate a spark and used to enhance plasma emission produced by laser ablation, allows direct analysis of materials without prior sample preparation. This paper reviews recent development and application of laser ablation assisted spark induced breakdown spectroscopy for material analysis. Following a summary of fundamentals and instrumentation of the LA-SIBS analytical technique, the development and applications of laser ablation assisted spark induced breakdown spectroscopy for the analysis of conducting materials and insulating materials is described.