Preliminary analysis of the organic gunshot residues

• Main Authors: Chia-Hsiang Yen, 顏家祥
• Other Authors: Li-Ling Cho
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/c8tnbn

碩士 === 中央警察大學 === 鑑識科學研究所 === 104 === The mainstream of the traditional indentification method of gunshot residue is using SEM / EDS to examine the inorganic gunshot residue particles, however, recently, confined to the widespread use of lead-free and non-toxic ammunition, making the indentification of inorganic gunshot residues being challenged nowadays. For lead-free and non-toxic ammunition having been stipulated to the ASTM criterion, however in the case of an established fairly complete indentification of SEM / EDS of inorganic gunshot residues, beening a part of the systematic indentifation, this thesis is to analysis the smokeless propellent and gunshot residues particles by the appearance characteristic and Raman microspectroscopy. Firstly, in this thesis, not only the composition of propellents and gunshot residues and characteristics by literature review, but how the Raman spectroscopy is applied to identify the gunshot residue in recent years, including the acheviment, the limits and how to overcome limitations and other parts are discussed, as to beening the reference to a follow-up experiment. In this thesis, propellent samples collected from 27 kinds of bullets, propellent samples on the shape, size and color are classified, and the results are displayed that in different powder samples were characterized by the appearance of a considerable difference. Followed by 780nm laser as an excitation source, the Raman spectrums of the propellent sample are measured, the results shows that some samples can be obtained directly Raman signal, and the remaining powder samples are subject to interference of the fluorescence and can not measure Raman signals, so one focus of this thesis is to evaluate the pre-treatment process to eliminate the fluorescence. In the pre-treatment process to eliminate the fluorescence assessed by reference the results of the selection using the mixed methanol / ethanol solvent and 2-butanone solvent as the pretreatment of propellent, the results show using the mixed methanol / ethanol solvent after one-time-washing the fluorescence interference can not be eliminated, and 2-butanone solvent after washing can reduce the fluorescence interference. Therefore, subsequent experiments using 2-butanone solvent washing method as the pretreatment of propellent samples and gunshot residues samples. In this thesis, the choice of 27 kinds of propellent standard bullets washed by 2-butanone solvent measuring by laser excitation wavelength of 780nm microscope Raman spectral, and according to the peak position and comparing with nitrocellulose smokeless powder additives standards, 27 kinds of propellent standards were analysised. The results showed that the Raman spectra of the propellent sample contain nitrocellulose main component peak, and can be successfully distinguished the additives such as nitroglycerin, 2-nitro-diphenylamine, methyl or ethylcentrilate, and dinitrotoluenes and other smokeless powder additives. Follow-up the propellent sample by Raman spectra peak position between the additive and spectral peaks at different locations are classified, the results show that 27 kinds of propellent samples can be divided into 20 subcategories, the discriminating power is 0.980. 6 kinds of propellent samples were put into shooting and collected the gunshot residues indentified by the laser excitation wavelength of 780nm microscopic Raman spectral. The results showed that some samples may detect direct Raman signal the rest still interfered by the fluorescence, after washed by 2-butanone solvent samples can detect remnants main component nitrocellulose, and may correspond to the source propellent. Another shooting test is to use different fabric surface, analysis showed that different materials will not affect the Raman spectrums of the gunshot residues.