To improve the quantitative analysis accuracy of an aqueous solution using surface-enhanced laser-induced breakdown spectroscopy (SENLIBS), the filter paper was used as a transmission medium by ...placing it onto the surface of a metallic substrate to make the microdroplet spreading more uniform in a fixed region of the substrate surface. The trace elements (Cu, Pb, Cd, and Cr) in an aqueous solution were detected successfully using this method. The results showed that the sample preparation repeatability of SENLIBS was noticeably improved with the aid of filter paper. Moreover, the limit of detection (LoD) values was similar to those without filter paper. Furthermore, the R
values were improved from 0.6192~0.9321 to 0.9481~0.9766, the RMSECV values were decreased from 0.53~1.95 μg/mL to 0.33~1.06 μg/mL, and the average relative error (ARE) values were decreased from 8.96~22.31% to 4.28~14.37% with the aid of filter paper. This demonstrated that the use of filter paper could improve the quantitative analysis accuracy of SENLIBS by increasing the sample preparation repeatability.
Hollow spheres can be prepared by pulsed laser irradiation of colloidal nanoparticles in solution, but the detailed mechanism of this formation process was still not revealed. In this work, the ...formation mechanism of hollow spheres was explored by investigating the influence of liquid medium, stirring method, laser fluence, and irradiation time on the formation of hollow spheres. It was found that the melting caused by the laser was dominant for the sphere formation, and air inside the agglomerates is a significant factor for the void formation. Moreover, the movement of the inside air results in the decentered void formation.
In this study, slow strain rate tensile tests under in situ hydrogen electrochemical charge are performed to investigate the hydrogen embrittlement (HE) behavior of selective laser-melted (SLM) and ...post-heat-treated Inconel 718 alloys in tandem with microstructure evolution and cracking feature characterization. The results indicate that the high density of dislocations and local strain along the cellular structure walls in the as-SLM sample increase local hydrogen concentration, leading to a crack along the cell walls of the cellular structure. The tensile strength and the HE susceptibility are significantly enhanced by the precipitation of the γ′, γ″, and δ phases generated by solution aging. Solution-aged samples suffer from the severe HE susceptibility caused by the δ phase formation along the grain boundaries and the cell walls, which lead to the δ/γ interface cracking.
Spatial confinement is a simple and cost-effective method for enhancing signal intensity and improving the detection sensitivity of laser-induced breakdown spectroscopy (LIBS). However, the spatial ...confinement effects of LIBS under different pressures remains a question to be studied, because the pressure of the ambient gas has a significant influence on the temporal and spatial evolution of plasma. In this study, spatial confinement effects of LIBS under a series of reduced air pressures were investigated experimentally, and the plasma characteristics under different air pressures were studied. The results show that the reduced air pressure can lead to both earlier onset and weakening of the enhancement effect of the spatial confinement on the LIBS line intensity. When the air pressure drops to 0.1 kPa, the enhancement effect of the emission intensity no longer comes from the compression of the reflected shock wave on the plasma, but from the cavity’s restriction of the plasma expansion space. In conclusion, the enhancement effect of spatial confinement technology on the LIBS is still effective when the pressure is reduced, which further expands the research and application field of spatial confinement technology.
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In this work, laser-induced breakdown spectroscopy (LIBS), near-infrared spectroscopy (NIR), and LIBS joint NIR (LIBS–NIR) were investigated for the identification of citrus huanglongbing (HLB). The ...content of minerals like calcium (Ca), zinc (Zn), and potassium (K) was obtained by atomic absorption spectroscopy (AAS). The spectra of LIBS, NIR, and LIBS–NIR were operated by discriminating analysis (DA) and multi-layer perception (MLP). The results of AAS and Kolmogorov–Smirnov Test (K–S test) showed that the Ca and Zn decreased significantly in HLB infected leaves, but K is not significantly influence by HLB. The LIBS–NIR combining with MLP-PCA had highest diagnostic accuracy of 89.5% and 95.7% in training and test set, respectively. These results proved that joint spectrum of LIBS–NIR is a feasible method to identify citrus HLB.
•A simple and effective method to mitigate macrosegregation of laser-arc hybrid welds by using beam oscillation is proposed.•The macrosegregation of the weld cross-section with beam oscillation is ...300% lower than that of the non-oscillation weld.•The macrosegregation of the weld longitudinal section with beam oscillation is 220% lower than that of the non-oscillation weld.•Mechanism for improving solute transfer and reducing macrosegregation attributes to stirring and vortex suction effect produced by high-frequency oscillating beam.
Macrosegregation is rather serious during laser-arc hybrid welding (LAHW) due to poor arc penetration ability. Here we presented a simple and effective method to improve solute transfer and mitigate macrosegregation by using beam oscillation. When oscillating amplitude A ≥0.8 mm and frequency f ≥ 300 Hz, the macrosegregation of the overall weld cross-section was 300% lower than that of the non-oscillation weld, and the longitudinal section reduced by 220%. The reduction of macrosegregation was attributed to the stirring and vortex suction effect produced by high-frequency oscillating beam, which improved turbulent flow and the convection of molten pool to homogenize the alloying elements of hybrid weld.
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•Toxic elements of cadmium and lead in rice were determined quantitatively using LIBS.•A simple and low cost sample pretreatment method named SLST was proposed.•Toxic elements in rice were prepared ...through ultrasound assisted extraction with hydrochloric acid solution.
Stability and sensitivity of toxic elements determination is still unsatisfactory in agricultural product using laser-induced breakdown spectroscopy (LIBS). A simple and low cost sample pretreatment method named solid–liquid-solid transformation method was proposed in this work. The target analytes of cadmium (Cd) and lead (Pb) from rice samples were prepared through ultrasound assisted extraction in hydrochloric acid solution. The solution was dropped on the glass slide after centrifuging process and was further dried on a heater. Finally, the glass slide contained the analytes was carried out for LIBS determination. Compare with conventional pellet method, the spectral intensity of Cd and Pb element were enhanced significantly using LIBS. The limits of detection were 2.8 and 43.7 μg/kg, respectively. The limits of quantification were 9.3 and 145.7 μg/kg, respectively. The results demonstrated that LIBS coupled with ultrasound assisted extraction should be a promising tool to detect toxic elements in rice.
The self-absorption effect seriously affects the accuracy of determination in laser-induced breakdown spectroscopy (LIBS). In this work, we proposed to reduce multielemental self-absorption within a ...wide spectral range (200-900 nm) by using microwave-assisted excitation in LIBS (MAE-LIBS). Self-absorption reduction of sodium (Na), potassium (K), aluminum (Al), silicon (Si), and calcium (Ca) in potassium feldspar using MAE-LIBS was investigated. The mechanisms of self-absorption reduction in MAE-LIBS were also investigated. The results show that the serious self-absorption of spectral lines (Na and K) was reduced. The full widths at half maximum (FWHMs) of Na I 589.0 nm, Na I 589.6 nm, K I 766.5 nm, and K I 769.9 nm in potassium feldspar were reduced by 43%, 43%, 53%, and 47%, respectively. MAE-LIBS also has a little FWHM reduction for spectral lines with weak self-absorption. The results demonstrate that MAE-LIBS can simultaneously reduce multielemental self-absorption.
Accurate determination of major elements using limited standard samples is always a big challenge in laser-induced breakdown spectroscopy (LIBS). Based on a simple calculation process, we propose a ...new one-point calibration method called single-sample calibration LIBS (SSC-LIBS) to build the calibration and improve the accuracy of determination of major elements. In this work, several major elements (Fe, Cu, Zn, Ni, Cr, Nb, and Mo) in three sets of matrix-matched certified samples were determined without sample preparation. The results showed that compared with multipoint calibration LIBS (MPC-LIBS), the R2, RMSECV, and ARE of Cu elements were improved from 0.40 to 0.97, 3.55 wt% to 0.76 wt%, and 5.19% to 1.05%, respectively, while the ARSD decreased from 16.22% to 1.15%. Furthermore, the AREs in the concentration ranges of 1–10, 10–20, 30–40, 50–60, 60–70, and 80–100 wt% were 5.16%, 2.55%, 1.75%, 1.69%, 1.05%, and 0.44%, respectively, with almost all less than 5%, as calculated by SSC-LIBS. These results demonstrated that SSC-LIBS can improve the accuracy and stability of detecting major elements using only one standard sample, which can greatly promote the application of LIBS.
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•Accurate determination of major elements is always a big challenge in LIBS.•Single-sample calibration LIBS (SSC-LIBS) was proposed to achieve the accurate determination of major elements.•The method uses only one standard sample for quantitative analysis.•The analytical performance of SSC-LIBS was compared with multi-point calibration LIBS.
Laser-induced breakdown spectroscopy (LIBS) is well known for its feature of remote detection. In this review, the development of remote detection based on LIBS is presented. Three kinds of remote ...LIBS configurations and their characteristics have been illustrated. Owing to an inferior efficiency and intensity of spectral signals collected in a remote distance, different methods have been studied to enhance signals. This review briefly summarized the advanced enhancement approaches for remote LIBS, which further improves the capabilities of LIBS for real-time and in situ measurement. Furthermore, the recent development and application of remote LIBS in a variety of fields have been presented. The potential of LIBS in remote detection and its existing problems have also been discussed.
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