Engineering topics

Liu, Chunyi

Publications and source records attributed to Liu, Chunyi.

4 records

DOE OSTI2023

Laser induced breakdown spectroscopy of liquid

Chemical composition of liquid phase samples is determined based on laser induced ablation spectroscopy of droplets. An aerosol jet comprising a carrier gas and liquid phase sample droplets, less than about 10 microns in diameter, is formed. An emissive plasma plume is generated from the sample droplets using a pulsed laser to deposit energy at a focal point in the aerosol jet. Light from the plasma plume is gathered with a concave mirror and focused into one end of a fiber optic lightguide. The lightguide can transmit spectral emissions from the plume to a spectrometer/detector which can send wavelength and intensity values to a computer. The computer is operable to determine a liquid sample composition based on the wavelength and intensity values.

Bol'shakov, Alexander A.↗

DOE OSTI2023

Evolution of LIBS technology to mobile instrumentation for expediting firearm-related investigations at the laboratory and the crime scene

Gunshot residue (GSR) is one of the few forensic disciplines that lack accurate screening techniques. This study proposes using a mobile LIBS instrument to detect inorganic GSR and compares performance to a previously validated laboratory instrument. The mobile LIBS is designed with advanced configurations specifically for on-site GSR analysis, including a CMOS detector and a sampling chamber that holds up to six typical GSR collection devices with separate gas flow ports to prevent cross-contamination. A significant novelty of the portable instrument is its image magnification, which allows quick searching and visualization of GSR particle morphology. The single-particle imaging and elemental composition capability is one of a kind and offers superior confirmatory features for GSR. The mobile LIBS performance was evaluated for residues collected from the hands of shooters (100 samples) and non-shooters (200 background samples), analyzed sequentially by the mobile instrument and then the laboratory instrument. Accuracies better than 98.8% were obtained by both instruments, demonstrating their suitability for trace IGSR detection from skin specimens. Implementation of this methodology is anticipated to drastically speed up response times (i.e., from several hours per sample by standard SEM-EDS practice to a few minutes by LIBS). The screening methods can be easily incorporated into workflows to improve decision-making processes at the crime scene and laboratory settings, reduce backlogs, and improve case management.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

Methods for multiphase laser ablation analysis

Methods of liquid and solid materials analysis by laser induced ablation spectroscopy are disclosed. The liquid and solid materials are analyzed in an instrument having one pulsed laser to produce emissive plasma plumes and ablate solid material. Liquid phase samples are aerosolized before streaming to an analysis zone where they are dissociated into a plasma plume. A large number of sites within solid phase sample structures and be analyzed using a movable x-y-z stage and displayed in a chemical map.

Bol'shakov, Alexander A.↗

DOE OSTI2021

Analysis of liquid petroleum using a laser-induced breakdown spectroscopy instrument

Here, a prototype analyzer for the direct LIBS analysis of nebulized liquid samples was developed and tested, particularly for the analysis of petroleum, organic solvents and aqueous solutions. The LIBS analyzer requires about 750 µl of liquid sample, 1 liter of N 2 gas, and 10 s of the analysis time to record 100 spectra. The limits of detection in oil and solvent are as low as 0.01–0.04 ppm for Li, Mg, and Cu. They increase for the difficult elements, such as Pb and Hg (7-10 ppm), Cl (250 ppm), and S (~0.7%). The relative standard deviation of measuring 100 ppm vanadium in oil and solvent was 1.5%. The LIBS detection limits and repeatability are better than required by the standard method ASTM D5185 for the analysis of lubricating oils in ICP-OES. Several petroleum samples were analyzed by LIBS and the quantitative results for V, Ni, and Fe compared to the ICP-OES data. Light crude oils can be nebulized and analyzed directly. Medium crude oils require minimal dilution at least 1:1, otherwise errors of determination become large. Presumably, utilization of the internal standard and chemometrics can be useful to correct for the matrix effects. In addition to the trace element analysis, the LIBS prototype demonstrated ability to measure the hydrogen-to-carbon ratio in organic liquid samples. Several unidentified features were observed in the carbon spectrum. Their possible origin is discussed.

02 PETROLEUM↗