Forensic methodology for the thermochemical characterization of ANNM and ANFO homemade explosives

Nazarian, Ashot; Presser, Cary

doi:10.1016/j.tca.2015.04.006

Cited by 11 publications

(25 citation statements)

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“…The LDTR experimental facility and theory of analysis are detailed in Nazarian and Presser [10, 20, 25]. The pertinent information regarding the experimental apparatus is summarized for clarity, along with a description of the current facility modifications for these experiments.…”

Section: Methodsmentioning

confidence: 99%

“…As mentioned above, the details of the theoretical analysis [10, 20, 25], as well as results for AN, NM, ANNM, and ANDF, provide examples of the quantitative information that can be obtained with the LDTR technique (noting again that this investigation focused on the signature features). The following summarizes briefly how one can determine sample endothermic/exothermic behavior, specific heat release rate, and total specific heat release from the thermograms.…”

Section: Methodsmentioning

confidence: 99%

“…For this approach, the sample and reactor temperatures (i.e., for the baseline without sample) are recorded for two runs at two different laser fluences, see Refs. [20, 25]. The temperature-dependent relaxation time τ (also referred to as the heat transfer parameter) is given by:

τ true(T true) = \frac{T_{2} - T_{1}}{{(\frac{d T}{italicdt})}_{1} - {(\frac{d T}{italicdt})}_{2}}

where T 1 and T 2 are the baseline temperatures (i.e., with only the copper substrate and without the sample) for the two different laser fluences at time t 1 and t 2 , respectively, which correspond to the same reactor temperature.…”

Section: Methodsmentioning

confidence: 99%

“…A developing laser-heating technique, referred to as the laser-driven thermal reactor (LDTR), was used because it can address several of the issues associated with the commercially available calorimetry techniques [20]. Some of the advantages include: 1) an order of magnitude higher heating rate and larger sample mass capability to capture the thermal behavior of volatile constituents, thus allowing application to nonhomogeneous, multicomponent, multiphase samples, 2) direct laser heating that enables measurement of the total energy loss due to both thermal and chemical heat release; there is no single conventional technique available that provides both thermochemical properties, and chemical kinetic rates and reactions [25], 3) laser heating of the reactor sphere eliminates convective heating of the surrounding gases under reduced pressures (heating is essentially by radiation and conduction), 4) analyses can be carried out in different surrounding environments (e.g., inert, pyrolytic, oxidative), and 5) sampling of decomposition/reaction gaseous byproducts enables species analysis by gas chromatography/mass spectrometry (not carried out in this investigation). Table 1 lists the ANF mixtures and precursors studied in this investigation.…”

Section: Introductionmentioning

confidence: 99%

“…Ammonium nitrate/nitromethane (ANNM) mixture and its individual constituents, as well as ammonium nitrate/No. 2 diesel fuel oil (ANDF) were also investigated under a variety of operating conditions (i.e., fuel aging) and preparation protocols [20, 25]. This investigation further expands the analysis of ANF to identifying thermal behavior and signature subtleties associated with mixture composition for an additional ten mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Thermal signature measurements for ammonium nitrate/fuel mixtures by laser heating

Nazarian

Presser

2016

Thermochimica Acta

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Measurements were carried out to obtain thermal signatures of several ammonium nitrate/fuel (ANF) mixtures, using a laser-heating technique referred to as the laser-driven thermal reactor (LDTR). The mixtures were ammonium nitrate (AN)/kerosene, AN/ethylene glycol, AN/paraffin wax, AN/petroleum jelly, AN/confectioner’s sugar, AN/cellulose (tissue paper), nitromethane/cellulose, nitrobenzene/cellulose, AN/cellulose/nitromethane, AN/cellulose/nitrobenzene. These mixtures were also compared with AN/nitromethane and AN/diesel fuel oil, obtained from an earlier investigation. Thermograms for the mixtures, as well as individual constituents, were compared to better understand how the sample thermal signature changes with mixture composition. This is the first step in development of a thermal-signature database, to be used along with other signature databases, to improve identification of energetic substances of unknown composition. The results indicated that each individual thermal signature was associated unambiguously with a particular mixture composition. The signature features of a particular mixture were shaped by the individual constituent signatures. It was also uncovered that the baseline signature was modified after an experiment due to coating of unreacted residue on the substrate surface and a change in the reactor sphere oxide layer. Thus, care was required to pre-oxidize the sphere prior to an experiment. A minimum sample mass (which was dependent on composition) was required to detect the signature characteristics. Increased laser power served to magnify signal strength while preserving the signature features. For the mixtures examined, the thermal response of each ANF mixture was found to be different, which was based on the mixture composition and the thermal behavior of each mixture constituent.

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Section: Methodsmentioning

confidence: 99%