In situ elemental analysis and failures detection during additive manufacturing process utilizing laser induced breakdown spectroscopy.

A feasibility of real-time quantitative multielemental analysis during parts growth by additive manufacturing technology has been demonstrating for the first time using laser induced breakdown spectroscopy (LIBS). A low weight and compact LIBS probe was developed to equip the laser cladding head installed at six axis industrial robot. LIBS quantitative analysis of key components (carbon and tungsten) has been demonstrated in real-time conditions during synthesis of high wear resistant coatings of nickel alloy reinforced with tungsten carbide particles. Hot solidified clad as well as a melt pool surface was sampled by LIBS probe but better analytical results were achieved for the latter case due to low partial sinking of heavy tungsten carbide particles in nickel matrix. LIBS system was calibrated for quantitative measurements by offline analysis with energy dispersive X-ray spectrometry (EDX). We didn’t observe any impact of laser ablation (LIBS sampling) on clad dimensions even when LIBS probe ablated melt pool. LIBS system was capable to quantify concentrations for both light (carbon, silicon) and heavy (nickel, tungsten, chromium, etc.) elements at frequency of 10 Hz. A good correspondence was achieved between online LIBS measurements and offline analysis opens wide perspectives for LIBS technique as a powerful tool for controlling process of parts growth by additive manufacturing

The assets of laser-induced breakdown spectroscopy (LIBS) for the future of heritage science

Determination of inorganic nutrients in wheat flour by laser-induced breakdown spectroscopy and energy dispersive X-ray fluorescence spectrometry

Complementarity of XRFS and LIBS for corrosion studies

The continuously increasing needs for fast, reliable and easy to use analytical techniques operating remotely and in situ, under laboratory and/or field conditions have boosted considerable research efforts towards the development of novel analytical techniques satisfying these requirements. In that view, Laser-Induced Breakdown Spectroscopy (LIBS) has been proposed as an efficient tool for elemental analysis of various types of samples exhibiting several attractive advantages. LIBS is a laser based spectroscopic technique which permits the simultaneous atomization and excitation of the sample in one step, without requiring any sample preparation. In addition, LIBS operates successfully with all kinds of samples while the results are obtained within few seconds. Because of these advantages and its attractive simplicity, LIBS has become rapidly the most popular laser based analytical technique. In this work, LIBS is used in two different fields: the study of combustible hydrocarbon-air mixtures and the study of the created plasma in polymeric samples. In hydrocarbon –air flames, LIBS was applied for the determination of the local equivalence ratio in different hydrocarbon (gaseous and liquid) -air mixtures. In particular, it is shown that the ratio of the intensities of atomic spectral lines of H, C and O, emitted from a laser induced spark in the gaseous mixture, can be used for the rapid and accurate determination of the local equivalence ratio. There are also obtained spatially resolved equivalence ratio profiles in laminar premixed flames of different geometries (Bunsen type and impinging flames), which are used in order to reveal and quantify important flame structure features. Additionally, it is shown that LIBS can be used for the detection of humidity in air and in hydrocarbon-air flames. The results obtained showed that humidity causes significant changes in flame characteristics, and through the atomic spectral lines of H, N and O, humidity can be qualitatively be determined. In polymeric samples, LIBS technique is used for the identification of polymers and plastics for recycling purposes. Due to the importance of this application, the properties of the plasma created are extensively studied. It is shown that plasma generation and expansion is effected by the laser properties (laser energy, laser pulse) and by the environmental conditions (pressure).

Laser-induced breakdown spectroscopy (LIBS) has played a critical role in Mars exploration missions, substantially contributing to the geochemical analysis of Martian surface substances. However, the complex nonlinearity of LIBS processes can considerably limit the quantification accuracy of conventional LIBS chemometric methods. Hence chemometrics based on artificial neural network (ANN) algorithms have become increasingly popular in LIBS analysis due to their extraordinary ability in nonlinear feature modeling. The hidden layer activation functions are key to ANN model performance, yet common activation functions usually suffer from problems such as gradient vanishing (e.g., Sigmoid and Tanh) and dying neurons (e.g., ReLU). In this study, we propose a novel LIBS quantification method, named the Bayesian optimization-based tunable Softplus backpropagation neural network (BOTS-BPNN). Based on a dataset comprising 1800 LIBS spectra collected by a laboratory duplicate of the MarSCoDe instrument onboard the Zhurong Mars rover, we have revealed that a BPNN model adopting a tunable Softplus activation function can achieve higher prediction accuracy than BPNN models adopting other common activation functions if the tunable Softplus parameter β is properly selected. Moreover, the way to find the proper β value has also been investigated. We demonstrate that the Bayesian optimization method surpasses the traditional grid search method regarding both performance and efficiency. The BOTS-BPNN model also shows superior performance over other common machine learning models like random forest (RF). This work indicates the potential of BOTS-BPNN as an effective chemometric method for analyzing Mars in situ LIBS data and sheds light on the use of chemometrics for data analysis in future planetary explorations.

Quantitative elemental detection of size-segregated particles using laser-induced breakdown spectroscopy

Laser-Induced Breakdown Spectroscopy (LIBS) characterization of granular soils: Implications for ChemCam analyses at Gale crater, Mars

Application of elastic net in quantitative analysis of major elements using Martian laser-induced breakdown spectroscopy datasets

Summary Laser‐optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on‐line and in situ analysis. We have investigated laser‐induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q‐switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm −2 . The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non‐linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations < 2 μg kg −1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water‐saturated BaCl 2 mixed soil samples, and no significant difference in the detection limit for barium was obtained.

Due to its superior advantageous over the conventional analytical tools, laser-induced breakdown spectroscopy (LIBS) technique nowadays is becoming an emerging analytical tools and it is expected to be new future super star of analytical tool. This technique is based on the use of optical emission from the laser-induced plasma for analyzing spectrochemically the constituent and content of the sampled object. The capability of this technique is examined on analysis of trace elements in coal sample. Coal is one difficult sample to analyze due to its complex chemical composition and physical properties. It is inherent that coal contains trace element including heavy metal, thus mining, beneficiation and utilization poses hazard to environment and to human beings. The LIBS apparatus used was composed by a laser system (Nd-YAG: Quanta Ray; LAB SERIES; 1,064 nm; 500 mJ; 8 ns) and optical detector (McPherson model 2061; 1,000 mm focal length; f/8.6 Czerny-Turner) equipped with Andor I*Star intensified CCD 1024×256 pixels. The emitted laser was focused onto coal sample with a focusing lens of +250 mm. The plasma emission was collected by a fiber optics and sent to the the spectrograph. The coal samples were taken from Province of Aceh. As the results, several trace elements including heavy metal (As, Mn, Pb) can surely be observed, implying the eventuality of LIBS technique to analysis the presence of trace element in coal.

Heavy metal concentrations in soils as determined by laser-induced breakdown spectroscopy (LIBS), with special emphasis on chromium

The present paper deals with the detection and quantification of toxic heavy metals like Cd, Co, Pb, Zn, Cr, etc. in environmental samples by using the technique of laser-induced breakdown spectroscopy (LIBS) and calibration-free LIBS (CF-LIBS). A MATLABTM program has been developed based on the CF-LIBS algorithm given by earlier workers and concentrations of pollutants present in industrial area soil have been determined. LIBS spectra of a number of certified reference soil samples with varying concentrations of toxic elements (Cd, Zn) have been recorded to obtain calibration curves. The concentrations of Cd and Zn in soil samples from the Jajmau area, Kanpur (India) have been determined by using these calibration curves and also by the CF-LIBS approach. Our results clearly demonstrate that the combination of LIBS and CF-LIBS is very useful for the study of pollutants in the environment. Some of the results have also been found to be in good agreement with those of ICP-OES.

Recent advances and future trends in LIBS applications to agricultural materials and their food derivatives: An overview of developments in the last decade (2010–2019). Part I. Soils and fertilizers

Chapter 16 - LIBS study of geological samples coupled with chemometric methods