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Domestic Cartridge Analysis By ICP-MS And SEM/EDX

Posted on:2022-08-16Degree:MasterType:Thesis
Country:ChinaCandidate:A A YangFull Text:PDF
GTID:2506306482465544Subject:Public Security Technology
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In shooting cases,cartridges are very important physical evidence.The elemental composition of cartridges can provide key information for inferring the source of bullets.In this study,major element composition of different components of the cartridge samples,including the lead core inside the bullet,bullet jacket,cartridge case and gunshot residue,were analyzed by SEM/EDX.The concentration of seven trace elements in the lead core of bullet was also determined by ICP-MS,in an effort to explore the variations and connections among samples from different manufacturers,models and batches,with respect to their elemental composition and individual differences.The results suggest:Within the 53 bullet samples,most of their lead cores consist of 100% Pb.Sb appears in some more recent production batches,mostly after the 21st century with the purpose of increasing the hardness of bullet;Except for the jackets of six 5.6 mm sporting rifle cartridges and the shells of four cartridge samples from factory 791,which display no obvious regularity,all analyzed jackets and shells are made of three types of Cu/Zn alloys,with Cu content ranging between 83%-84%,88%-90% and 67%-69%,respectively.The jacket and shell materials of bullet produced by the same manufacturer remain consistent over time.Over the past 60 years,samples from factory 121 all have their bullet jacket made of Cu/Zn alloy with 88-90% Cu,and their bullet shells made of Cu/Zn alloy with 67-69% Cu,which suggests that these two types of Cu/Zn alloy are common raw materials used by the factory.Four cartridge shell samples from factory 791 are made of Fe/Mn alloy with 0.7-0.9% Mn.This material hasn’t been found in other manufacturers and therefore,can be regarded as the signature raw material of factory 791.Except for the gunshot residue of six 5.6 mm sporting rifle bullet samples which have complex elemental composition,the rest analyzed residue samples all display a common pattern:K,Cl and Hg widely appear in samples before 1990s but disappear after then together with the appearance of Sn and Ba.The variation of these five elements reflects the changes in the composition of the primer used in domestic ammunition production in different ages: Before 1990s,the bullet primer mostly consisted of mercury fulminate and potassium chlorate,which were gradually replaced by lead stilbite and barium nitrate with the development of modern military technology.Sn is originated from the tin foil cover in modern primers.This study explored and optimized the detection of trace elements in bullet lead core through ICP-MS method.48 bullet samples were analyzed for content of seven trace elements.Using the sample concentration diagram to observe the variation pattern of elements and samples’ differences,the results show that Ni,As,Ag and Cd are relatively stable.Sn,Sb and Bi fluctuate significantly and therefore,can be considered as characteristic distinguishing elements.The results of cluster analysis and principal component analysis indicate that both methods can distinguish bullet samples effectively: Same model of cartridges from same manufacturer are classified into one category,while bullets from different manufacturers or models are significantly different,which proves the accuracy of this detection method.Then a example was given to briefly discuss the application of elemental composition data in the comparison of suspected bullets and the inference of unknown bullet sources in real cases.
Keywords/Search Tags:Cartridges, elemental analysis, ICP-MS, SEM/EDX
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