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Hikal WM, Bhattacharia SK, Vaughn MW, Weeks BL. Sublimation and Diffusion Kinetics of 2,4,6-Trinitrotoluene (TNT) Single Crystals by Atomic Force Microscopy (AFM). Molecules 2022; 27:molecules27175482. [PMID: 36080250 PMCID: PMC9458093 DOI: 10.3390/molecules27175482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 11/30/2022] Open
Abstract
In this article, we report the in-situ nanoscale experimental measurement of sublimation rates, activation energy of sublimation, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals in air using atomic force microscopy (AFM). The crystals were prepared by slow evaporation at 5 °C using acetone-dissolved TNT. The mass loss was calculated by monitoring the shrinkage of the surface area of layered islands formed on the surface of the TNT crystals due to sublimation upon isothermal heating at temperatures below the melting point. The results suggest the sublimation process occurs via two-dimensional detachment of TNT molecules from the non-prominent facets on the crystal surface which imitates the nucleation and crystal growth process. Sublimation rates are one order of magnitude smaller than previously reported values. However, the calculated activation energy (112.15 ± 3.2 kJ/mol) and temperature-dependent sublimation rates agree well with the reported values for TNT thin films and microcrystals determined by UV-vis absorbance spectroscopy and quartz crystal microscopy (QCM) (90–141 kJ/mol). The average diffusion coefficient is (4.35 × 10–6 m2/s) which is within the range of the reported theoretical values with an average of 5.59 × 10–6 m2/s, and about 25% less than that determined using thermogravimetric analysis for powder TNT.
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Affiliation(s)
- Walid M. Hikal
- Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA
- Correspondence: (W.M.H.); (S.K.B.)
| | - Sanjoy K. Bhattacharia
- College of Engineering, West Texas A&M University, Canyon, TX 79016, USA
- Correspondence: (W.M.H.); (S.K.B.)
| | - Mark W. Vaughn
- Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA
| | - Brandon L. Weeks
- Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA
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Chang ZF, He B, Wang H, Zong Y, Zhang X, Huang L, Zhang S, Zhong Q. An organic-inorganic hybrid comprised of tetraphenylethene peripheries and octavinylsilsesquioxane core for aggregation-induced emission and photoelectric property. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.151125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Pacheco-Londoño LC, Ruiz-Caballero JL, Ramírez-Cedeño ML, Infante-Castillo R, Gálan-Freyle NJ, Hernández-Rivera SP. Surface Persistence of Trace Level Deposits of Highly Energetic Materials. Molecules 2019; 24:molecules24193494. [PMID: 31561514 PMCID: PMC6804148 DOI: 10.3390/molecules24193494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 09/12/2019] [Accepted: 09/16/2019] [Indexed: 12/05/2022] Open
Abstract
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.
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Affiliation(s)
- Leonardo C Pacheco-Londoño
- 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.
| | - José L Ruiz-Caballero
- 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.
- Joseph Smith & Sons Inc., Capitol Heights, MD 20743, USA.
- Department of Chemistry and Biochemistry, George Mason University, Fairfax, VA 22030, USA.
| | - Michael L Ramírez-Cedeño
- 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.
| | | | - Nataly J Gálan-Freyle
- 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.
| | - Samuel P Hernández-Rivera
- 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.
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