Laser-induced-breakdown-spectroscopy-based detection of metal particles released into the air during combustion of solid propellants

Synchronized measurement method of burning rate and combustion temperature of a solid propellant specimen

To characterize the combustion properties of solid propellants, the synchronized measurement method of burning rate and combustion temperature is proposed combined shadow imaging and radiation imaging. Using spectroscopic and filtering imaging, shadow and radiation images of a solid propellant specimen are obtained synchronously. Burning rate is calculated by burning surface movement velocity of shadow images, and combustion temperature is calculated by radiation image thermometry. Measurement accuracies of burning rate and combustion temperature of the solid propellant specimen are validated by other independent measurement methods. On this basis, the synchronized measurements of burning rate and combustion temperature of different formulations of solid propellant specimens under different working conditions are carried out. The results show that the influence on burning rate and combustion temperature of pressure and formulas is different. Therefore, the synchronized measurement of burning rate and combustion temperature can provide more direct data support for the evaluation of solid propellant combustion performance.

Flame Synthesis of Carbon and Metal-Oxide Nanoparticles: Flame Types, Effects of Combustion Parameters on Properties and Measurement Methods

Carbon and metal-oxide nanoparticles (NP) are currently synthesized worldwide for various applications in the solar-energy, optical, pharmaceutical, and biomedical industries, among many others. Gas phase methods comprise flame synthesis and flame spray pyrolysis (FSP), which provide high efficiency, low cost, and the possibility of large-scale applications. The variation of combustion operation parameters exerts significant effects on the properties of the NPs. An analysis of the latest research results relevant to NP flame synthesis can provide new insight into the optimization of these methods and the development of these techniques for a large scale. This review offers insight into the current status of flame synthesis for carbon and metal-oxide NPs-specifically containing analysis and comparison of the most common carbon and metal-oxide NP production techniques. The burner configurations used at the laboratory scale and large scale are also discussed, followed by the assessment of the influence of combustion parameters on the properties of NPs. Finally, the features of the measurement techniques applied for determining NP properties were described.

Review of Element Analysis of Industrial Materials by In-Line Laser—Induced Breakdown Spectroscopy (LIBS)

Laser-induced breakdown spectroscopy (LIBS) is a rapidly developing technique for chemical materials analysis. LIBS is applied for fundamental investigations, e.g., the laser plasma matter interaction, for element, molecule, and isotope analysis, and for various technical applications, e.g., minimal destructive materials inspection, the monitoring of production processes, and remote analysis of materials in hostile environment. In this review, we focus on the element analysis of industrial materials and the in-line chemical sensing in industrial production. After a brief introduction we discuss the optical emission of chemical elements in laser-induced plasma and the capability of LIBS for multi-element detection. An overview of the various classes of industrial materials analyzed by LIBS is given. This includes so-called Technology materials that are essential for the functionality of modern high-tech devices (smartphones, computers, cars, etc.). The LIBS technique enables unique applications for rapid element analysis under harsh conditions where other techniques are not available. We present several examples of LIBS-based sensors that are applied in-line and at-line of industrial production processes.

Interpol review of detection and characterization of explosives and explosives residues 2016-2019

This review paper covers the forensic-relevant literature for the analysis and detection of explosives and explosives residues from 2016-2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/Resources/Documents#Publications.

Evaluation of heavy metal element detection in municipal solid waste incineration fly ash based on LIBS sensor

Heavy metal elements are the main pollutants in municipal solid waste incineration (MSWI) fly ash, the online detection of heavy metals in MSWI fly ash could benefit its subsequent solidification treatment and land-filling. In this paper, laser induced breakdown spectroscopy (LIBS) was introduced to the rapid measurement of heavy metal elements in MSWI fly ash. Considering the serious matrix effect in MSWI fly ash, the multiple linear regression model combined with internal standard method was used to establish the calibration curves of heavy metals. Validated samples were used to evaluate the performance of quantitative analysis models. The results show that linear regression coefficients (R²) of the calibration curves for Cd, Cr, Cu, Pb, Zn are 0.981, 0.988, 0.968, 0.978 and 0.993, respectively. The average relative error of the prediction results are from 6.8 to 20.3%. The detection limits of the heavy metal content are Cd (11.13 μg/g), Cr (44.87 μg/g), Cu (36.18 μg/g), Pb (10.83 μg/g), Zn (12.27 μg/g), respectively, which are far below those required in the Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB16889-2008). All results indicate the great potential of LIBS sensor for online rapid detection of heavy metals in MSWI fly ash.

Imaging Aluminum Particles in Solid-Propellant Flames Using 5 kHz LIF of Al Atoms

Laser-induced fluorescence imaging of aluminum atoms (Al-PLIF) is used to analyze the spatio-temporal behavior of aluminized solid propellant combustion. Using alternating LIF and chemiluminescence emission images of the particles in the gaseous and liquid phase evolving close to and far above the dynamically varying propellant surface, sequences of images were recorded and analyzed. The good sensitivity achieved enabled us to track the dynamics of the flame in the vicinity of particles detected all along the flame extension and up to 1.5 MPa. Analysis of wide-field images enabled droplet velocity measurements due to the high LIF sampling rate (5 kHz). The observed typical plume structures were in good agreement with alumina-formation prediction and previous shadowgraphy visualization. High-resolution sequences of images showed gaseous distribution behavior around the molten particles. The Al vapor phase was thus found to extend between 3 and 6.5 radii around the particles. Particle detachment dynamics were captured just above the propellant surface.

Ultrashort-pulse laser-induced breakdown spectroscopy for detecting airborne metals during energetic reactions

Ultrashort-pulse laser-induced breakdown spectroscopy (LIBS), specifically using a femtosecond laser, has certain advantages over longer-pulse, nanosecond-duration lasers, in that they typically have kilohertz repetition rates and reduced background noise along with little-to-no laser-plasma interaction, all of which lead to a better chance of detecting LIBS signals from trace particles. In this work, femtosecond-LIBS is investigated for the detection of metallic particles in the hot flame zone of solid propellant strands burning in the atmosphere. The metallic particles doped into the solid propellants were aluminum (Al), copper, lead, lead stearate, and mercury chloride, which are all either typically found in energetic formulations as additives or impurities. Using an 80-fs-pulse-duration, amplified Ti:Sapphire laser operating at 1000 Hz, single-shot concentration measurement experiments were performed. The femtosecond-LIBS apparatus could detect all metallic additives, whereas a previous nanosecond-LIBS scheme with comparable conditions was able to detect only higher concentrations of Al. The single-shot concentration study, conducted with the Al-doped propellants, indicated that there is a linear relationship between the percentage of laser shots detecting a LIBS signal and the mass percentage of Al initially present in the strands. The present results illustrate the advantages of using a femtosecond laser over a nanosecond laser for LIBS detection during energetics material reactions.

Estimation of the Fe and Cu Contents of the Surface Water in the Ebinur Lake Basin Based on LIBS and a Machine Learning Algorithm

Traditional technology for detecting heavy metals in water is time consuming and difficult and thus is not suitable for quantitative detection of large samples. Laser-induced breakdown spectroscopy (LIBS) can identify multi-state (such as solid, liquid, and gas) substances simultaneously, rapidly and remotely. In this study, water samples were collected from the Ebinur Lake Basin. The water samples were subjected to LIBS to extract the characteristic peaks of iron (Fe) and copper (Cu). Most of the quantitative analysis of LIBS rarely models and estimates the heavy metal contents in natural environments and cannot quickly determine the heavy metals in field water samples. This study creatively uses the Fe and Cu contents in water samples and the characteristics of their spectral curves in LIBS for regression modelling analysis and estimates their contents in an unknown water body by using LIBS technology and a machine learning algorithm, thus improving the detection rate. The results are as follows: (1) The Cu content of the Ebinur Lake Basin is generally higher than the Fe content, the highest Fe and Cu contents found within the basin are in the Ebinur Lake watershed, and the lowest are in the Jing River. (2) A number of peaks from each sample were found of the LIBS curve. The characteristic analysis lines of Fe and Cu were finally determined according to the intensities of the Fe and Cu characteristic lines, transition probabilities and high signal-to-background ratio (S/B). Their wavelengths were 396.3 and 324.7 nm, respectively. (3) The relative percent deviation (RPD) of the Fe content back-propagation (BP) network estimation model is 0.23, and the prediction ability is poor, so it is impossible to accurately predict the Fe content of samples. In the estimation model of BP network of Cu, the coefficient of determination (R²) is 0.8, the root mean squared error (RMSE) is 0.1, and the RPD is 1.79. This result indicates that the BP estimation model of Cu content has good accuracy and strong predictive ability and can accurately predict the Cu content in a sample. In summary, estimation based on LIBS improved the accuracy and efficiency of Fe and Cu content detection in water and provided new ideas and methods for the accurate estimation of Fe and Cu contents in water.