Real time and high-precision online determination of main components in iron ore using spectral refinement algorithm based LIBS.

The real-time online quantitative analysis instrument is highly desirable for many industrial fields. Herein, a new laser-induced breakdown spectroscopy (LIBS) setup with optimized optical route and high accuracy algorithm is designed and applied in a real industrial site. The components of total iron (TFe), silica (SiO2), aluminum oxide (Al2O3), and phosphorus (P) are quantitatively determined by the online LIBS system. The key optical part is a Maksutov-Cassegrain telescope, in which, two aspherical mirrors are specially designed and fabricated to reflect the broadband emission from ultraviolet 240 nm to infrared 890 nm with reflectivity over 90%, and pass the excited laser line of 1064 nm. The system could automatically adjust the focal length in the range of 780 mm to 940 mm. Based on the online LIBS system, the spectral pretreatment algorithm is also optimized including baseline removal and spectral normalization. The overlapped window slide (OWS) algorithm avoids the deformation of emission peaks in spectral baseline removal, in addition, two normalization steps by total back area and total spectral intensity within the sub-channel are applied to improve the spectral data stabilization. The calibration and validation are performed by utilizing the emissions that are insensitive to the detection distance. Compared with the traditional method, the prediction result shows that the root of mean square error of prediction (RMSEP) decreased from 5.091% to 1.2328%, and the mean absolute error (MAE) reduced from 4.801% to 0.9126% for TFe. Eventually, the online measurement shows good agreement with the official standard results. The high-precision online determination system based on LIBS will upgrade low frequency sampling of traditional detection to high-frequency real online determination in many industrial fields.

Determination of detonation characteristics by laser-induced plasma spectra and micro-explosion dynamics.

Determination of macroscale detonation parameters of energetic materials (EMs) in a safe and rapid way is highly desirable. However, traditional experimental methods suffer from tedious operation, safety hazards and high cost. Herein, we present a micro-scale approach for high-precision diagnosis of explosion parameters based on radiation spectra and dynamic analysis during the interaction between laser and EMs. The intrinsic natures of micro-explosion dynamics covering nanosecond to millisecond and chemical reactions in laser-induced plasma are revealed, which reveal a tight correlation between micro-detonation and macroscopic detonation based on laser-induced plasma spectra and dynamics combined with statistic ways. As hundreds to thousands of laser pulses ablate on seven typical tetrazole-based high-nitrogen compounds and ten single-compound explosives, macroscale detonation performance can be well estimated with a high-speed and high-accuracy way. Thereby, the detonation pressure and enthalpies of formation can be quantitatively determined by the laser ablation processes for the first time to our knowledge. These results enable us to diagnose the performance of EMs in macroscale domain from microscale domain with small-dose, low-cost and multiple parameters.

On-chip programmable optical switch based on CdS multibranched nanowire arrays.

Micro/nano optoelectronic devices are widely studied as basic building blocks for on-chip integrated microsystem and multichannel logic units with excellent optoelectronic properties that are especially important part for interconnection route construction. Here, based on anisotropic waveguides, an optical switch with an on/off ratio of 2.14 is built up in a 2D CdS branched nanowire array. Because the branches are obliquely distributed at the same side of the trunk in a highly ordered form, the guided photoluminescence (PL) intensity from the trunk into the branch tightly relates to its angle. Based on the different intensity of the guided PL emitted from the end of each branch, the position of the incident spot in the backbone area can be identified accurately, making a feasible construction of an on-chip position-sensitive detector to realize an all-optical information process.

Lithium ion detection in liquid with low detection limit by laser-induced breakdown spectroscopy.

Lithium (Li), as the lightest metal and the most important powerful material in battery fabrication, is widely used in many fields. The fast detection of Li is necessary for industrial application. The slow-speed detection methods, including atomic absorption spectroscopy and inductively coupled plasma mass spectroscopy with high accuracy and low limit of detection, are hard to utilize in in situ industrial control due to complex prepreparation of samples. Here, through the analysis of the typical spectrum line at Li I 670.79 nm, Li ions in water were detected quantitatively in 1 min, including sample preparation by laser-induced breakdown spectroscopy (LIBS) with filter paper as the adsorption substrate. The calibration curve by polynomial function fitting is used to predict the Li+ concentration. The limit of detection (LOD) as low as 18.4 ppb is obtained, which is much lower than the results ever reported by using filter paper. The related factor R2 reaches 99%, and the prediction error is lower than 2%, proving the fast and online monitor for Li+ by LIBS is feasible. Furthermore, by comparison with the results with filter paper enrichment, the Li+ detection from water directly shows higher LOD to 10.5 ppm. Moreover, the plasma images, by gate-controlled intensified charge-coupled device, illustrate a different morphology and evolution between that on water surface and filter paper surface through visual observation. This study provides experimental and theoretical experience in a fast way for the quantitative detection of the lightest metal ion (Li+) in liquid.