Papers by Keyword: LIBS

Abstract: The second harmonic of a pulsed Nd: YAG laser (532 nm) has been used for the ablation of aluminum alloy in air at atmospheric pressure and the laser-induced plasma characteristics are examined in detail. The electron density of 6.7 × 10¹⁷ cm^-3 is inferred from the Stark broadening of the profile of Si (I) 288.16 nm, while the plasma temperature (5982 K) is obtained using the Boltzmann plot method of four neutral aluminum lines. The calibration curve for silicon is established using a set of six samples of standard aluminum alloy, and its limit of detection is 0.0681 wt%. The plasma is verified to be in local thermodynamic equilibrium (LTE) based on the experimental results.

Abstract: This paper introduces a homemade high-resolution miniature fiber optic spectrometer for LIBS detection. The circuit part of the system is mainly controlled by a cortex-M3 chip, transmits data to the personal computer (PC) through the Universal Serial BUS (USB2.0), and a set of spectrometer test software is finished. The optical system is based on Czerny-Turner imaging system, using 1800grv/mm plane diffraction grating, 16μm slit and 2048 pixels linear array CCD as detector, high-resolution spectral output in the range of 335-455nm is required. By precisely calibration and testing, the precision of the system is 0.05nm, and the resolution of the wavelength at the blaze wavelength can up to 0.1nm which can fulfill the general LIBS detection.

Abstract: LIBS of aluminum under the ambient pressure from 1 atm to 10 Pa were implemented. Results showed that the temperature of plasma increased with the decreased pressure and leaded to the raise of density of Al II, decrease of density of Al I. Furthermore, in order to understand the influence of air flow to quantification of LIBS an alloy of aluminum and silicon was measured by LIBS under different level wind. Results showed the ratio of Si I/Al I which is important in quantitative analysis changed with wind despite the pressure change a little. Therefore, the ambient atmosphere must be steady enough in order to improve the accuracy in quantitative analysis of LIBS.

Abstract: The purpose of this research is to detect the atomic spectrum of cesium using laser-induced breakdown spectroscopy (LIBS). In this study, pollucite ((Cs,Na)(AlSi₂)O₆.nH₂O) was used as a test sample for the LIBS measurement. LIBS is a useful tool for the determination of the elemental composition of various materials and it does not require any preprocessing step. The Nd:YAG laser was operated at 1064 nm to generate a 50-mJ Q-switched pulse with a width of 8 ns (full width at half maximum, FWHM). The breakdown emissions were dispersed by a grating with a groove density of 1200 lines/mm and the resulting electrical signal was recorded using a streak camera. The plasma intensity was optimized with respect to the background. Spectral measurements were carried out after an appropriate delay time to allow for the decay of the continuum radiation. In the experiments, 100 laser shots were used to record data for each spectrum in ambient air. The results of the experiments showed that the atomic signals corresponding to pollucite were obtained easily by LIBS measurements. Thus, spectrum peaks due to cesium, sodium, aluminum, and silicon are observed. In particular, the characteristics of the cesium spectrum play an important role in establishing the LIBS system for environmental monitoring, which may be used to detect radioactive elements emitted from nuclear plants.

Abstract: Using LIBS (laser-induced-breakdown-spectroscopy)technology, element percent in ferroalloy can be measured. High energy laser beam focus on high temperature plasma of ferroalloy surface, using fiber spectrometer detected plasma emission spectral lines in the cooling process to determine the type and content in the ferroalloy elements. In the application of quantitative analysis internal standard method in ferroalloy C content, according to the measuring principle built experimental platform, according to Fe for internal standard elements, setting up the calibration curve of C content, and using the curves to ferroalloy samples in a quantitative analysis on the C element. The results show, LIBS internal standard method to determine the relative error of the ferroalloy C content for no more than 10%, verifying the internal standard method used in the determination of the elements in ferroalloy feasibility.

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been employed for the fast and reliable chemical characterization of silicon used for the photovoltaic industry. Silicon for photovoltaic panels is subject to certain constraints on its purity, and notably must contain low concentration of boron. The use of LIBS could be advantageous because it allows rapid and simultaneous multi-elemental chemical analysis of silicon without any sample preparation. LIBS was applied to boron analysis and a detection limit of 0.23 ppmw was found for optimized gas and pressure conditions.

Abstract: This paper mostly summarizes experimental device of laser-induced plasma and taking pictures of plasma plume. The progress in the experimental study on laser-induced plasma was discussed. The experimental apparatus include the laser、delay device; The system of the plasma radiation gathered and radiation received were reviewed. In addition, photos of plasma plume were discussed; at last, dynamic process of laser-induced plasma plume explosion was discussed.

Abstract: We calculate the temperature of excited plasma, found that will be enhanced with pulse energy increased. The delay time and the pulse energy were very important to the LIBS signal and define the -0.5μs was very suitable to this experiment, determined the intensity of emission spectra was linear to the pulse energy when the delay time was fixed. By change the delay time, got the emission of bivalence ionization of Zn was just less than 500ns.At last, we had researched the effect of element concentration and the thickness of film on signal intensity. When the concentration of Al being increased from 2.5% to 5%, the intensity of signal enhanced double. At the same time the content of Zn being decreased from 78% to 76%, the intensity of signal had just no change.

Abstract: In this paper, laser-induced breakdown spectroscopy (LIBS) using micro-droplet NaCl solution and set-up for control of micro-droplets are described. Micro-droplets controlling technique is important for solution quantitative analysis. In this study, micro-droplet ejection system for sampling is designed and presented. This micro-droplet ejection system enable a constant volume of the sample liquid to be obtained and it takes advantage of the liquid physical state; the density of the solution can be controlled accurately. The method presented here generates small droplets (diameter 30 μm) by confining the entire volume of the sample material in the laser beam spot area (minimum beam spot diameter: 53.2 μm) and separating it from its surroundings. Using this liquid micronizing method, improved sensitivities are obtained. The Advantage of LIBS is a useful method for determining the elemental composition of various materials regardless of their physical state (solid, liquid, or gas) and without any preprocessing; it is a type of atomic emission spectroscopy (AES). Despite the advantage of qualitative analysis, quantitative analysis is difficult because of sample and plasma fluctuations. Generating constant volume of micro-size sample and proper sample control technique contribute to LIBS quantitative analysis.

Abstract: The impurity diffusion coefficients of Cu in Fe have been determined in the temperature range of 1073 - 1163 K by means of Laser Induced Breakdown Spectrometry (LIBS). The volume diffusion coefficients for Cu impurity diffusion in a-iron found in this work are in good agreement with the previously published result. The grain boundary diffusion coefficient gb D s d was also calculated using the volume diffusivity and processing the tails of the measured profiles. The values of the activation energy for volume and grain boundary diffusion were approximately 280 and 161 kJmol-1, respectively. This indicates the possibility of a monovacancy diffusion mechanism in case of volume diffusion. The results for the diffusion coefficients are Dv= 2.2 ×10-2exp(-280 kJmol-1/RT) m2s-1 and gb D s d = 2.6 ×10-11exp(-161 kJmol-1/RT) m3s-1.