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Open AccessArticle

Surface Persistence of Trace Level Deposits of Highly Energetic Materials

R3-C Research and Education Component of ALERT DHS Center of Excellence for Explosives Research, Department of Chemistry, University of Puerto Rico, Mayaguez Campus, Mayaguez, PR 00681, USA
School of Basic and Biomedical Sciences, Universidad Simón Bolívar, Barranquilla, 080020 Atlantico, Colombia
Joseph Smith & Sons Inc., Capitol Heights, MD 20743, USA
Department of Chemistry and Biochemistry, George Mason University, Fairfax, VA 22030, USA
Department of Physics-Chemistry, University of Puerto Rico, Arecibo, PR 00614, USA
Authors to whom correspondence should be addressed.
Molecules 2019, 24(19), 3494;
Received: 23 August 2019 / Revised: 12 September 2019 / Accepted: 16 September 2019 / Published: 26 September 2019
(This article belongs to the Section Physical Chemistry)
In the fields of Security and Defense, explosive traces must be analyzed at the sites of the terrorist events. The persistence on surfaces of these traces depends on the sublimation processes and the interactions with the surfaces. This study presents evidence that the sublimation process of these traces on stainless steel (SS) surfaces is very different than in bulk quantities. The enthalpies of sublimation of traces of four highly energetic materials: triacetone triperoxide (TATP), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 1,3,5- trinitrohexahydro-s-triazine (RDX) deposited on SS substrates were determined by optical fiber coupled-grazing angle probe Fourier Transform Infrared (FTIR) Spectroscopy. These were compared with enthalpies of sublimation determined by thermal gravimetric analysis for bulk amounts and differences between them were found. The sublimation enthalpy of RDX was very different for traces than for bulk quantities, attributed to two main factors. First, the beta-RDX phase was present at trace levels, unlike the case of bulk amounts which consisted only of the alpha-RDX phase. Second, an interaction between the RDX and SS was found. This interaction energy was determined using grazing angle FTIR microscopy. In the case of DNT and TNT, bulk and traces enthalpies were statistically similar, but it is evidenced that at the level of traces a metastable phase was observed. Finally, for TATP the enthalpies were statistically identical, but a non-linear behavior and a change of heat capacity values different from zero was found for both trace and bulk phases. View Full-Text
Keywords: sublimation; explosive; FTIR; thermogravimetric analysis; grazing angle sublimation; explosive; FTIR; thermogravimetric analysis; grazing angle
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MDPI and ACS Style

Pacheco-Londoño, L.C.; Ruiz-Caballero, J.L.; Ramírez-Cedeño, M.L.; Infante-Castillo, R.; Gálan-Freyle, N.J.; Hernández-Rivera, S.P. Surface Persistence of Trace Level Deposits of Highly Energetic Materials. Molecules 2019, 24, 3494.

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