Characteristic Line Intensities Research Articles

New Approach for Direct Determination of Manganese Valence State in Ferromanganese Nodules by X-ray Fluorescence Spectrometry

A new X-ray fluorescence technique is proposed as an alternative to the labor-consuming volumetric method for the estimation of manganese valence state in ferromanganese nodules. The approach is based on the measurement of the relative intensities of some X-ray fluorescence spectrum characteristic spectral lines and satellites (MnKβ5 and MnKβ′) preconditioned by electron transfer from the valence shell. Calibration curves were created using manganese oxide samples (MnO, Mn2O3, MnO2) and 12 certified reference materials of ferromanganese nodules, cobalt-bearing ferromanganese crusts, and manganese ores with certified (or determined by approved methods) total and tetravalent manganese content. The presence of high iron content was taken into account. A set of oceanic ferromanganese nodules samples collected in the Magellan Seamounts (Pacific Ocean) were analyzed. Differences between the results of the X-ray fluorescence method and volumetric techniques for tetravalent manganese content were 4.9 rel.%, which is comparable with the accuracy of the volumetric technique (3.6 rel.%).

Optical properties of N2/Ar plasma generated by electron beams with silicon nitride transmission window at high pressures

In this paper, we report the generation of nitrogen/argon electron beam plasmas with a 0.4 μm-thick silicon nitride transmission window. The measured transmittance of the electron beam is about 92% when the incident energy of electron beam is 40 keV. The optical properties of the electron beam plasma are investigated at high pressures. The luminescence intensity distribution of nitrogen and argon electron beam plasmas shows a good similarity with changing the gas pressure, suggesting that electron beam ionization is independent of background gas. At the same gas pressure, the nitrogen plasma with conical structure has a longer length along the incident direction of the electron beam and a smaller divergence cone angle compared with the argon plasma. In the nitrogen discharge, it is found that the intensities I380.4, I399.7, and I391.4 corresponding to characteristic lines at 380.4, 399.7, and 391.4 nm decrease along the incident direction of the electron beam, which is correlated with the reduction of the electron density along the incident direction of the electron beam. There is no change in the ratio of I399.7 to I380.4, indicating the spatial uniformity of the electron temperature. When the pressure increases, the ionization process induced by primary electron is enhanced, generating more plasma electrons, which is responding to the increase in the characteristic line intensity. At the same time, the neutral particle collision processes are enhanced and the electron temperature decreases with the increase in the pressure, which is believed to contribute to the observed reduction of the I399.7/I380.4 ratio.

Measurement and Calculation of X-Ray Production Efficiencies for Copper, Zirconium, and Tungsten.

Electron probe microanalysis (EPMA) is based on physical relations between measured X-ray intensities of characteristic lines and their X-ray production efficiency, which depends on the specimen composition. The quality of the analysis results relies on how realistically the physical relations describe the generation and emission of X-rays. Special experiments are necessary to measure X-ray production efficiencies. A challenge in these experiments is the determination of the detection efficiency of the spectrometer as a function of the photon energy. An energy-dispersive spectrometer was used in this work, for which the efficiency was determined at metrological synchrotron beamlines with an accuracy of ±2%. X-ray production efficiencies for the L series and the Kα series of copper and zirconium and for the M and L series of tungsten were determined at energies up to 30 keV in a scanning electron microscope. These experimental values were compared with calculated X-ray production efficiencies using physical relations and material constants applied in EPMA. The objective of the comparison is the further improvement of EPMA algorithms as well as extending the available database for X-ray production efficiencies. Experimental data for the X-ray production efficiency are also useful for the assessment of spectrum simulation software.

Detection of calcium homogeneity distribution in magnesia-aluminum spinel using laser-induced breakdown spectroscopy

To further improve the yield of producing magnesium aluminum spinel and detect the distribution of sintering aid in raw materials, the Mg–Al spinel samples were prepared using MgO and Al2O3 as raw materials and CaO as sintering aids. Information on the distribution of the sintering aid Ca element in mixed samples was rapidly obtained by laser-induced breakdown spectroscopy (LIBS) mapping using a picosecond laser and a closed chamber filled with Ar gas. The optimal mixing time and environmental parameters of the raw materials were determined through optimization experiments, and the calibration models of Ca/Al and Ca/Mg were established with the intensities of Al and Mg characteristic lines as the internal standard. The correlation coefficient R2, Root Mean Square Error of Calibration (RMSEC) and Mean Relative Error (MRE) of different calibration curves were evaluated. The feasibility of LIBS technique to detect the uniform distribution of sintering aids in Mg–Al spinel is verified by comparing with the images scanned by X-ray energy dispersive spectroscopy (EDS). Finally, we performed LIBS scans in the depth direction and obtained the spatial distribution of the Ca element. This work opens up a new research route for realizing the application of LIBS analysis in magnesia-aluminum spinel.

Electron probe microanalysis of light elements: Improvements in the measurement and signal extraction methods

AbstractQuantitative electron probe microanalysis (EPMA) by wavelength dispersive spectrometry of light elements is a significant challenge due to difficulties of signal extraction for low intensities. Therefore, a good choice of measurement parameters and a suitable signal treatment, accurate background description and interference correction are crucial. For light elements, peak to background ratios (P/B) can easily approach unity and special care needs to be paid to the setting of the pulse height analyser (PHA) to avoid noise contribution to the emission peak. Furthermore, the background may have a high curvature and the classical approach of a linear background fit is no longer valid. This work investigates the EPMA of light elements from Be to F with the aim to determine the best experimentation parameters (dispersive element, accelerating voltage, PHA). It also provides detailed information about peak shifts, peak broadening and the influence of different background fits on quantification. In total, 25 samples containing light elements were analysed and Monte Carlo simulations were carried out. These simulations show that the X‐ray intensity of the light element's characteristic line can be increased by working with low accelerating voltages around 5 kV. PHA should be used in automatic differential or integral mode. Our work also shows that a third degree linear polynomial describes the background better than an exponential or linear function. Consequently overestimation of P/B values leading to large quantification errors can be avoided. This paper provides a large database containing peak position and peak shifts, peak full width at half maximum, as well as P/B ratios and information about peak enlargement for different materials of various compositions.

Online detection of laser paint removal based on laser-induced breakdown spectroscopy and the K-nearest neighbor method

Laser paint removal is a new highly efficient and environmentally friendly cleaning technology. Compared with traditional paint removal methods, laser paint removal is less labor intensive and can reduce environmental pollution. During laser paint removal, real-time monitoring is necessary to ensure efficient cleaning and process automation. Current methods for real-time monitoring of laser paint removal only determine whether the sample surface has been cleaned but provide no information on the status of any residual paint. In this article, spectral data of the sample surface have been obtained using laser-induced breakdown spectroscopy. It is shown that Zn and Fe spectral lines can be used in real time to characterize the effectiveness of paint removal and that the intensities of characteristic spectral lines are positively correlated with the single-pulse energy of the excitation light. The K-nearest neighbor algorithm was used to evaluate and automatically classify the extent of cleaning of sample surfaces in real time. When K = 3, the classification accuracy of distinguishing different levels of cleaning was 100%. The results of this study provide technical support for automatic and intelligent laser paint removal.

Classification of steel using laser-induced breakdown spectroscopy combined with deep belief network.

The identification of steels is a crucial step in the process of recycling and reusing steel waste. Laser-induced breakdown spectroscopy (LIBS) coupled with machine learning is a convenient method to classify the types of materials. LIBS can generate characteristic spectra of various samples as input variable for steel classification in real time. However, the performance of classification model is limited to the complex input due to similar chemical composition in samples and nonlinearity problems between spectral intensities and elemental concentrations. In this study, we developed a method of LIBS coupled with deep belief network (DBN), which is suitable to deal with a nonlinear problem, to classify 13 brands of special steels. The performance of the training and validation sets were used as the standard to optimize the structure of DBN. For different input, such as the intensities of full-spectra signals and characteristic spectra lines, the accuracies of the optimized DBN model in the training, validation, and test set are all over 98%. Moreover, compared with the self-organizing maps, linear discriminant analysis (LDA), k-nearest neighbor (KNN) and back-propagation artificial neural networks (BPANN), the result of the test set showed that the optimized DBN model performed second best (98.46%) in all methods using characteristic spectra lines as input. The test accuracy of the DBN model could reach 100% and the maximum accuracy of other methods ranged from 62.31% to 96.16% using full-spectra signals as input. This study demonstrates that DBN can extract representative feature information from high-dimensional input, and that LIBS coupled with DBN has great potential for steel classification.

A study on the relationship between spectral characterization and composition of plasma in laser additive manufacturing of gradient materials

PurposeThe purpose of this paper is to predict and control the composition during laser additive manufacturing, since composition control is important for parts manufactured by laser additive manufacturing. Aluminum and steel functionally graded material (FGM) were manufactured by laser metal deposition, and the composition was analyzed by means of spectral analysis simultaneously.Design/methodology/approachThe laser metal deposition process was carried out on a 5 mm thick 316L plate. Spectral line intensity ratio and plasma temperature were chosen as two main spectroscopic diagnosis parameters to predict the compositional variation. Single-trace single-layer experiments and single-trace multi-layer experiments were done, respectively, to test the feasibility of the spectral diagnosis method.FindingsExperiment results showed that with the composition of metal powder changing from steel to aluminum, the spectral intensity ratio of the characteristic spectral line is proportional to the elemental content in the plasma. When the composition of deposition layers changed, the characteristic spectrum line intensity ratio changed obviously. And the linear chemical composition analysis results confirmed the gradient composition variation of the additive manufacturing parts. The results verified the feasibility of composition analysis based on spectral information in the laser additive manufacturing process.Originality/valueThe composition content of aluminum and steel FGM was diagnosed by spectral information during laser metal deposition, and the relationship between spectral intensity and composition was established.

New data on brown coal occurrences in the Yamutarida and Dyuntaturku-yamu river basin in the northern part of the Yenisei-khatanga trough

Background. New information was obtained on brown coal occurrences in the northern part of the Yenisei-Khatanga trough (Lake Taimyr area). This region continues to attract the attention of geologists and oil producers due to its established oil and gas potential.Aim. To study the lithological features of rocks and material-petrographic composition of coals from a new promising area of the Yenisei-Khatanga trough in northern Russia.Materials and methods. A set of geological, lithological, and petrographic research methods was used to study a series of samples of coals and host rocks. Measurements were carried out on a QDI-302 Craic Spectrophotometer microscope with a 50× objective lens according to the standard methodology ISO 7404-5 in reflected polarised light using a Spinel standard (Ro = 0.426%) in oil immersion. X-ray fluorescence analysis was performed using a Respect device with an energy dispersive spectrometer without vacuum, having an X-ray tube with a silver anode (registration of elements only from K to U). Anode voltage — 30 kV. Current — 0.3 mA. Exposure time (τ) — 300 s. Y axis — intensity of characteristic lines, rel. unitsResults. The lithological features of the studied samples were elucidated, and the material-petrographic composition of the coals was studied. In the spore-pollen assemblage from the studied deposits, the dominant associations were determined by the predominance of two-bag pollen of Disaccites (Pinaceae) conifers. On this basis, the age of the Begichevskaya Formation rocks was established as belonging to the Albian and Cenomanian stages of the Lower-Middle Cretaceous.Conclusion. The degree of variability of coals was estimated; their grades (technological groups) and the trace element composition of ash were determined. The reflection values of vitrinites were measured in order to clarify the stage of changes in brown coals and obtain the quantitative characteristics of their quality. The reflection values of vitrinites (Ro) are from 0.32 to 0.52%, which corresponds to the stages of brown coal changes, technological groups 1B—3B.

A Simple Approach for Thickness Measurements Using Electron Probe Microanalysis.

A simple and fast method for thickness measurements using electron probe microanalysis (EPMA) is described. The method is applicable on samples with a thickness smaller than the electron depth range and does not require any knowledge of instrumental parameters. The thickness is determined by means of the distance that electrons travel inside the sample before crossing through it. Samples are first deposited on a substrate that, when reached by the transmitted electrons, produces an X-ray signal. The measured characteristic X-ray line intensity of the substrate is later used to determine the energy of transmitted electrons, which is proportional to the distance that electrons travel inside the sample. The study was performed on spherical K411 glass particles and cylindrical particles of U–Ce oxide with a size ranging from 0.2 to 4 μm. The measured thicknesses of all the studied particles showed good agreements with the real values. Although the method is only validated on particles with usual shapes, it can be applied to determine a local thickness of thin samples with irregular morphologies. This can help solving multiple issues in analysis with EPMA of non-bulk samples exhibiting complex geometries. Three dimensional microscopic imaging could also find a good utility in the described method.

Impact Energy and Angular Dependence of L X-ray Emission from a Thick Polycrystalline Tungsten Element Induced by 15–25 keV Electrons

The impact energy and angular dependence of L X-rays of a thick polycrystalline tungsten (W; atomic number, Z = 74) target induced by 15–25 keV electrons has been measured at different angles varying from 15° to 75° at intervals of 5° using a Si PIN photodiode detector. The variation of measured relative intensity of Ll, Lα, Lβ and Lγ characteristic lines as a function of incidence angle is found to be anisotropic and the measured variation compares well with the PENELOPE simulation results. The angular variation of intensity ratio of Ll/Lα and Lβ/Lα shows anisotropic distribution, whereas the angular variation of the Lγ/Lα ratio exhibits almost isotropic distribution within the uncertainty of measurements. These measured ratios are found to be in good agreement with Monte Carlo (MC) calculations. The measured intensity ratios of Lβ/Lα and Lγ/Lα at a given incidence angle show a linear dependence with impact energy and exhibit good agreement with simulation results; however, the measured intensity ratio of Ll/Lα shows a non-linear variation with the impact energy and yields poor agreement with theoretical calculations.

Mathematical Modeling of Mutually Influencing Elements by the Fundamental Parameter Method for X-Ray Fluorescence Analysis of High-Entropy AlCrFeCoNiCu Alloy

A mathematical model and a software program (FLUOR81) were developed to implement the fundamental parameter method for X-ray fluorescence analysis of new alloy types. The model takes into account the X-ray tube excitation by polychromatic radiation and the secondary excitation of some elements by others. The program was tested using state standard samples of steels and alloys with nickel and cobalt matrices to show that the intensity of characteristic lines could be calibrated using pure elements in the absence of standard samples. In this case, the relative measurement error was no more than 3–4%. This approach was employed for mathematical modeling of the mutual influence of elements in the AlCrFeCoNiCu high-entropy alloy (HEA). The stoichiometric coefficients in the AlCrxFeCoxNixCu alloy were varied (x = 0.5, 1, 2) to find that the relative deviations of initial concentrations of components (ignoring their mutual influence) from the stoichiometric values were within ±50% and slightly changed with concentration. These patterns can be used for semiquantitative estimates of the HEA compositions for which no standard samples are available. To obtain results with a relative error of 3–4%, calculations with the software developed are needed.

Study on the plasma spatial distribution characteristics of laser-induced breakdown on the oil-water interface

The technology of oil-water separation is very important for the improvement of water resources and environment. The detection of oil-water interface characteristics is one of the key requirements of the technology. In this paper, the laser plasma spectroscopy is used to detect the oil-water interface, and the theoretical research and verification are carried out. The spatial distribution characteristics of plasma electron temperature and electron density are experimentally studied. The semi-ellipsoid model of laser plasma spatial distribution is proposed, combined with the laser focusing characteristic. The position of oil-water interface was determined by the laser-induced plasma spectroscopy based on the difference of element luminescent characteristics. According to the relationship between the intensity of spectral lines and the concentration of elements, the relationship between the intensity of characteristic spectral lines and the number of elements is obtained based on the semi-ellipsoid model. Furthermore, the relationship between the intensity ratio of characteristic elements and the thickness of the oil film is studied, and the spectral measurement of oil layers with different thickness is realized. In this paper, the law of the self-absorption effect of C and H elements with the thickness of the oil film is analyzed, and the rationality of the direct judgment of oil film thickness by the relative strength ratio of the characteristic elements of the detection spectrum signal is verified. According to the intensity ratio of spectral lines, the scatter distribution of oil thickness, and the simulation curve, the variation rule of experimental error with oil thickness are obtained. The relative error is less than 20%, which also verifies the reliability of the method.

A novel strategy for quantitative analysis of soil pH via laser-induced breakdown spectroscopy coupled with random forest

pH is one of the significant properties of soil, and is closely related to the decomposition of soil organic matter, anion-cation balance, growth of plants and many other soil processes. In the present work, laser-induced breakdown spectroscopy (LIBS) technique coupled with random forest (RF) was proposed to quantify the pH of soil. First, LIBS spectra of soil was collected, and some common elements in soil were identified based on the National Institute of Science and Technology database. Then, in order to obtain a better predictive result, the influence of different input variables (full spectrum, different spectral ranges, the intensity of characteristic bands and characteristic lines) on the predictive performance of RF calibration model was explored with the evaluation indicators of root mean square error (RMSE) and coefficient of determination (R2), the characteristic bands of four elements (Al, Ca, Mg and Si) were determined as the optimal input variables. Finally, the predictive performance of RF calibration model was compared with partial least squares calibration model with the optimal input variables and model parameters, and RF calibration model showed a better predictive performance, and the four evaluation indicators of RMSEP, mean absolute error and mean relative error were 0.9687, 0.1285, 0.1114 and 0.0136, respectively. It indicates that LIBS technique coupled with RF algorithm is an effective method for pH determination of soil.

Investigation of a Contamination Film Formed by the Electron Beam Irradiation

In the study of materials on electron probe devices in the field of action of the electron beam, a contaminating hydrocarbon film is formed, which affects the experimental results. In this paper, we have studied the influence of a contamination film on carbon-film-coated dielectrics on the intensity of cathodoluminescence and characteristic X-ray lines. The absorption coefficient of the contamination film in the visible and UV ranges has been determined. Filming mechanisms at different parameters of the electron beam have been discussed.

Univariate and Multivariate Analysis of Phosphorus Element in Fertilizers Using Laser-Induced Breakdown Spectroscopy.

Rapid detection of phosphorus (P) element is beneficial to the control of compound fertilizer production process and is of great significance in the fertilizer industry. The aim of this work was to compare the univariate and multivariate analysis of phosphorus element in compound fertilizers and obtain a reliable and accurate method for rapid detection of phosphorus element. A total of 47 fertilizer samples were collected from the production line; 36 samples were used as a calibration set, and 11 samples were used as a prediction set. The univariate calibration curve was constructed by the intensity of characteristic line and the concentration of P. The linear correlation coefficient was 0.854 as the existence of the matrix effect. In order to eliminate the matrix effect, the internal standardization as the appropriate methodology was used to increase the accuracy. Using silicon (Si) element as an internal element, a linear correlation coefficient of 0.932 was obtained. Furthermore, the chemometrics model of partial least-squares regression (PLSR) was used to analysis the concentration of P in fertilizer. The correlation coefficient was 0.977 and 0.976 for the calibration set and prediction set, respectively. The results indicated that the LIBS technique coupled with PLSR could be a reliable and accurate method in the quantitative determination of P element in complex matrices like compound fertilizers.

Исследование контаминационной пленки, формирующейся под действием электронного пучка

During the study of materials on electron probe devices in the field of the electron beam, a contamination hydrocarbon film is formed, which influences the results of experiments. In this paper, we studied the effect of a contamination film formed on carbon-coated dielectric samples on the intensity of cathodoluminescence and X-ray characteristic emission lines. The absorption coefficient of the film for the visible and UV ranges was determined. The mechanism of film formation for various parameters of the electron beam is discussed.

Spectroscopic Investigation of the Evolution of Fractal Nanoobjects in Film-Forming Sols of Orthosilicic Acid

The evolution of fractal nanoparticles of medium size and concentration, which are formed and dynamically change during hydrolytic polycondensation, has been investigated using IR spectroscopy. It is shown that the application of the Smoluchowski rapid coagulation model combined with analysis of the characteristic absorption line intensity in the IR spectra provides a satisfactory estimate of evolution processes occurring in sols of orthosilisic acid. The obtained spectroscopic dependences are compared qualitatively with atomic force microscopy data.

Engineering bright fluorescent nitrogen-vacancy (NV) nano-diamonds: Role of low-energy ion-irradiation parameters

Bright emission from fluorescent nanodiamonds (FNDs) is highly desirable for optical bio-imaging applications. Here we report about optimized ion-irradiation and heat treatment conditions for efficient creation of Nitrogen-vacancy (NV) centers in high pressure high temperature (HPHT) grown type Ib Nanodiamond samples irradiated in energy range (20-50 KeV) and at varying fluence (1012-1016 ions/cm2). Different low energy ion irradiations are not detrimental for the crystallinity of nanodiamonds as confirmed by X-ray diffraction and HRTEM. The concentration of defects near the outer surface (non-diamond carbon) has been increased for highest ion dose (50 KeV, 1016 ions/cm2) as compared to lower ion dose (50 KeV, 1013 ions/cm2). The relative emission intensity of characteristic Zero-phonon lines of NV°, NV- centers as compared to broad emission in the range 550-750 nm was monitored with varying NV creation conditions. Sample irradiated at 50 KeV and with fluence of 1013 ions/cm2 show maximum emission in the phonon side band (550-750 nm) with maxima at 680 nm. These optimized ion irradiation conditions leads to the fabrication of 12.5±0.8 ppm concentration of NV- centers in nanodiamonds. This is desirable for their use as biomarker. This work provides a recipe for creating bright nanodiamonds for optical imaging applications.

Quantitative Analysis of Magnesium in Soil by Laser-Induced Breakdown Spectroscopy Coupled with Nonlinear Multivariate Calibration

Laser-induced breakdown spectroscopy (LIBS) coupled with the nonlinear multivariate regression method was applied to analyze magnesium (Mg) contents in soil. The plasma was generated using a 100 mJ Nd:YAG pulsed laser, and the spectra were acquired using a multi-channel spectrometer integrated with a CCD detector. The line at 383.8 nm was selected as the analysis line for Mg. The calibration model between the intensity of characteristic line and the concentration of Mg was constructed. The traditional calibration curve showed that the concentration of Mg was not only related to the line intensity of itself, but also to other elements in soil. The intensity of characteristic lines for Mg (Mg I 383.8 nm), manganese (Mn) (Mn I 403.1 nm), and iron (Fe) (Fe I 407.2 nm) were used as input data for nonlinear multivariate calculation. According to the results of nonlinear regression, the ternary nonlinear regression was the most appropriate of the studied models. A good agreement was observed between the actual concentration provided by inductively coupled plasma mass spectrometry (ICP-MS) and the predicted value obtained using the nonlinear multivariate regression model. The correlation coefficient between predicted concentration and the measured value was 0.987, while the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were reduced to 0.017% and 0.014%, respectively. The ratio of the standard deviation of the validation to the RMSEP increased to 8.79, and the relative error was below 1.21% for nine validation samples. This indicated that the multivariate model can obtain better predicted accuracy than the calibration curve. These results also suggest that the LIBS technique is a powerful tool for analyzing the micro-nutrient elements in soil by selecting calibration and validation samples with similar matrix composition.