Jimmie C. Oxley

Ammonium nitrate: thermal stability and explosivity modifiers

Abstract Two basic approaches to diminish the explosivity of AN have been suggested: dilution of ammonium nitrate (AN) with a chemically inert material or incorporation of small amounts of material which increases the chemical reaction zone [Method of Desensitizing AN and the Product Obtained, United States Patent Office, No. 3,366,468 (1968); Fertilizer additives: can AN be defanged? C&E News (1995) 6]. While small-scale tests of these “deterred” AN formulations appeared promising, larger amounts (30 pounds under confinement) were found to be detonable, though with reduced performance [Institute of Makers of Explosives Report, 1995]. In this study thermal analysis was used to screen a large number of AN formulations in search of possible deterrents. The sodium, potassium, ammonium and calcium salts of sulfate, phosphate, or carbonate as well as certain high-nitrogen organics (urea, oxalate, formate, guanidinum salts) were chosen because they should enhance AN thermal stability and because they could be used with agricultural products. This study considers whether laboratory tests can be used as benchmarks in evaluating explosivity.

Decomposition of a Multi-Peroxidic Compound: Triacetone Triperoxide (TATP)

13 s 1 . Under all conditions the principle decomposition products were acetone (about 2 mole per mole TATP in the gas-phase and 2.5 ± 2.6 mole per mole in condensed-phase) and carbon dioxide. Minor products included some ascribed to reactions of methyl radical: ethane, methanol, 2-butanone, ethyl acetate; these increased at high temperature. Methyl acetate and acetic acid were also formed in the decomposition of neat TATP; the former was more evident in the gasphase decompositions (151C and 230C) and the latter in the condensed-phase decompositions (151C). The decomposition of TATP in condensed-phase or in hydrogen-donating solvents enhanced acetone production, suppressed CO2 production, and slightly increased the rate constant (a factor of 2 ± 3). All observations were interpreted in terms of decomposition pathways initiated by OO homolysis.

Raman and Infrared Fingerprint Spectroscopy of Peroxide-Based Explosives

A comparative study of the vibrational spectroscopy of peroxide-based explosives is presented. Triacetone triperoxide (TATP) and hexamethylenetriperoxide-diamine (HMTD), now commonly used by terrorists, are examined as well as other peroxide-ring structures: DADP (diacetone diperoxide); TPTP [3,3,6,6,9,9-Hexaethyl-1,2,4,5,7,8-hexaoxo-nonane (tripentanone triperoxide)]; DCypDp {6,7,13,14-Tetraoxadispiro [4.2.4.2]tetradecane (dicyclopentanone diperoxide)}; TCypDp {6,7,15,16,22,23-Hexaoxatrispiro[4.2.4.2.4.2] henicosane (tricyclopentanone triperoxide)}; DCyhDp {7,8,15,16-tetraoxadispiro [5.2.5.2] hexadecane (dicyclohexanone diperoxide)}; and TCyhTp {7,8,14,15,21,22-hexaoxatrispiro [5.2.5.2.5.2] tetracosane (tricyclohexanone triperoxide)}. Both Raman and infrared (IR) spectra were measured and compared to theoretical calculations. The calculated spectra were obtained by calculation of the harmonic frequencies of the studied compounds, at the density functional theory (DFT) B3LYP/cc-pVDZ level of theory, and by the use of scaling factors. It is found that the vibrational features related to the peroxide bonds are strongly mixed. As a result, the spectrum is congested and highly sensitive to minor changes in the molecule.

Thermal decomposition of ammonium nitrate-based composites

To evaluate the thermal stability of ammonium nitrate-water-in-oil emulsions, the thermal decomposition kinetics and resultant products were examined. As a baseline, the thermal stability of ammonium nitrate with individual components of the emulsion was determined. Only mineral oil had any effect on the decomposition. Generally, ammonium nitrate mixed with hydrocarbons has enhanced thermal stability. However, ammonium nitrate mixed, rather than emulsified, with mineral oil can decompose along a lower energy pathway than pure ammonium nitrate. The extent of decomposition along that pathway is not large before the decomposition process results in building-up of ammonia and, thus, in termination of that pathway. Mineral oil appears to be unique among the hydrocarbons in its ability to destabilize ammonium nitrate. The experiments utilized differential scanning calorimetry in combination with conventional isothermal techniques.

Detection of Explosives in Hair Using Ion Mobility Spectrometry

Abstract:  Conventional explosives 2,4,6‐trinitrotoluene (TNT), nitroglycerin (NG), and ethylene glycol dinitrate (EGDN) sorbed to hair can be directly detected by an ion mobility spectrometer (IMS) in E‐mode (for explosives). Terrorist explosive, triacetone triperoxide (TATP), difficult to detect by IMS in E‐mode, was detected in N‐mode (for narcotics). Three modes of sample introduction to IMS vapor desorption unit were used: (i) placement of hair directly into the unit, (ii) swabbing of hair and placement of swabs (i.e., paper GE‐IMS sample traps) into the unit, and (iii) acetonitrile extracts of hair positioned on sample traps and placed into the unit. TNT, NG, and EGDN were detected in E‐mode by all three sample introduction methods. TATP could only be detected by the acetonitrile extraction method after exposure of the hair to vapor for 16 days because of lower sensitivity. With standard solutions, TATP detection in E‐mode required about 10 times as much sample as EGDN (3.9 μg compared with 0.3 μg). IMS in N‐mode detected TATP from hair by all three modes of sample introduction.

The phase diagram of rdx (hexahydro-1,3,5-trinitro-s-triazine) under hydrostatic pressure

Abstract Raman spectroscopy has been used to determine the phase diagram and phase behavior of RDX (hexahydro-1,3,5-trinitro-s-triazhe) up to 16 GPa at temperatures ranging from 150 K to over 450 K. Two new stable solid polymorphs have been identified: a high pressure/low temperature form that converts reversibly to α-RDX (the form stable at ambient conditions) at 3.8 GPa, independent of temperature from 150 to 375 K. We also find a high pressure/high temperature form of RDX that is highly metastable, shows a very large hysteresis, and is probably the polymorph known as β-RDX.

Decompositions of Urea and Guanidine Nitrates

The decompositions of urea nitrate (UN) and guanidine nitrate (GN) are determined with isothermal heating followed by quantification of both remaining nitrate and remaining base. Activation energies determined for UN were 158 and 131 kJ/mol with the preexponential factors being 1.39 × 1012 s−1 and 2.66 × 109 s−1 for nitrate and urea, respectively. These pairs of Arrhenius constants predict decomposition rates less than a factor of two apart. For GN the activation energies were 199 and 191 kJ/mol with the preexponential factors being 1.94 × 1015 s−1 and 3.20 × 1014 s−1 for nitrate and guanidine, respectively. These pairs of Arrhenius constants predict identical decomposition rates. Literature values for ammonium nitrate decomposition indicate that it should decompose somewhat slower than UN and faster than GN. DSC also indicates this ordering but suggested that UN is substantially less stable than was observed in the isothermal experiments. Decomposition products, both gaseous and condensed, are reported for UN and GN, and decomposition routes are suggested. Experimental results indicate that is generated during the decomposition mechanism. This mechanism appears to differ from that of the analogous nitro derivatives.

Thermal decomposition of high-nitrogen energetic compounds—dihydrazido-S-tetrazine salts

Abstract The thermal stabilities of 3,6-dihydrazido-1,2,4,5-tetrazine (Hz 2 Tz) and its salts with diperchlorate [Hz 2 Tz(HClO 4 ) 2 ], dinitrate [Hz 2 Tz(HNO 3 ) 2 ], bisdintramidate [Hz 2 Tz(HDN) 2 ], and bisdinitroimidazolate [Hz 2 TzBim] have been examined and compared to other 3,6-disubstituted tetrazines. The neutral tetrazines exhibited two principal modes of decomposition: elimination of N 2 from the tetrazine ring followed by cleavage of the remaining NN bond, and loss of the substituent group, in some cases assisted by proton transfer. The salts Hz 2 TzX 2 undergo reversible equilibrium with the parent Hz 2 Tz and HX, thus, in several cases the decomposition rate of the parent tetrazine and the salt are essentially identical.

Thermal Decomposition Of Hydroxylamine Nitrate

used hydroxylamine nitrate decomposes within a few minutes in the temperature range 130-140°C. Added ammonium ion is converted to N2, while hydrazinium ion is converted to HN3. Nitrous acid is an intermediate and its formation is rate-determining. A hygride transfer process is postulated. The reaction pathways have been elucidated by use of N tracers.

Accumulation of Explosives in Hair

The sorption of explosives (TNT, RDX, PETN, TATP, EGDN) to hair during exposure to their vapors is examined. Three colors of hair were simultaneously exposed to explosive vapor. Following exposure of hair, the sorbed explosive was removed by extraction with acetonitrile and quantified. Results show that sorption of explosives, via vapor diffusion, to black hair is significantly greater than to blond, brown or bleached hair. Furthermore, the rate of sorption is directly related to the vapor density of the explosive: EGDN > TATP >>>TNT >> PETN > RDX. In some cases, the explosive-containing hair was subject to repeated washings with sodium dodecylsulfate or simply left out in an open area to determine the persistence of the explosive contamination. While explosive is removed from hair with time or washing, some persists. These results indicate that hair can be a useful indicator of explosive exposure/handling.