Eun Mee Goh

Analysis of explosives using corona discharge ionization combined with ion mobility spectrometry-mass spectrometry.

Corona discharge ionization combined with ion mobility spectrometry-mass spectrometry (IMS-MS) was utilized to investigate five common explosives: cyclonite (RDX), trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotetramethylenetetranitramine (HMX), and 2,4-dinitrotoluene (DNT). The MS scan and the selected ion IMS analyses confirmed the identities of the existing ion species and their drift times. The ions observed were RDX·NO3(-), TNT(-), PETN·NO3(-), HMX·NO3(-), and DNT(-), with average drift times of 6.93 ms, 10.20 ms, 9.15 ms, 12.24 ms, 11.30 ms, and 8.89 ms, respectively. The reduced ion mobility values, determined from a standard curve calculated by linear regression of (normalized drift times)(-1) versus literature K0 values, were 2.09, 1.38, 1.55, 1.15, 1.25, and 1.60 cm(2) V(-1) s(-1), respectively. The detection limits were found to be 0.1 ng for RDX, 10 ng for TNT, 0.5 ng for PETN, 5.0 ng for HMX, and 10 ng for DNT. Simplified chromatograms were observed when nitrogen, as opposed to air, was used as the drift gas, but the detection limits were approximately 10 times worse (i.e., less sensitivity of detection).

Energetic salts based on nitroiminotetrazole-containing acetic acid

2-(5-Nitroiminotetrazol-1-yl)acetic acid (4) was synthesized from 100% nitric acid and ethyl 2-(5-aminotetrazol-1-yl)acetate (2), which was easily obtained by reaction of ethyl aminoacetate hydrochloride, sodium hydroxide, and cyanogen azide. Compound 4 was also formed with 100% nitric acid and 2-(5-aminotetrazol-1-yl)acetic acid which was prepared from sodium 5-aminotetrazolate and 2-chloroacetic acid. New energetic materials comprised of nitroiminotetrazolate salts with nitroiminotetrazolate and carboxylate anions have been characterized spectroscopically as well as with single crystal X-ray diffraction and elemental analyses. In addition, the heats of formation (ΔHf), and detonation pressures (P) and velocities (D) were calculated. All compounds were insensitive (>40 J) for impact with BAM Fallhammer.

Energetic salts based on 1-methoxy-5-nitroiminotetrazole

Eight new energetic salts based on 1-methoxy-5-nitroiminotetrazole, which was obtained by nitration of 1-methoxy-5-aminotetrazole, were synthesized. Guanidinium (5), aminoguanidinium (6), diaminoguanidinium (7), triaminoguanidinium (8), carbohydrazidinium (9), 3-amino-1,2,4-triazolium (10), 4-amino-1,2,4-triazolium (11), and 3,5-diamino-1,2,4-triazolium (12) salts were characterized by vibrational spectroscopy (IR, Raman), multinuclear spectroscopy (1H, 13C, 15N), elemental analysis, and single crystal X-ray diffraction analysis. Salts 5·1/3H2O and 7–9 crystallize in the triclinic space group P, whereas compounds 6 and 10 crystallize in the monoclinic space groups C2/c and P2(1)/n, respectively. Compound 11 is in orthorhombic group P2(1)2(1)2(1). In addition, the heats of formation (ΔHf), and detonation properties (pressure and velocity) were calculated using Gaussian 03 and EXPLO5 programs, respectively. Thermal stabilities were obtained by DSC measurements and the sensitivities toward impact and friction were determined by BAM methods.

Ti(N5)4 as a Potential Nitrogen-Rich Stable High-Energy Density Material

We have studied molecular structures and kinetic stabilities of M(N5)3 (M = Sc, Y) and M(N5)4 (M = Ti, Zr, Hf) complexes theoretically. All of these compounds are found to be stable with more than a 13 kcal/mol of kinetic barrier. In particular, Ti(N5)4 showed the largest dissociation energy of 173.0 kcal/mol and thermodynamic stability. This complex had a high nitrogen content (85% by weight), and a significantly high nitrogen to metal ratio (20:1) among the neutral M(N5)n species studied here and in the literature. Ti(N5)4 is thus forecasted to be a good candidate for a nitrogen-rich high-energy density material (HEDM). We reveal in further detail using ab initio molecular dynamics simulations that the dissociation pathways of M(N5)n involve the rearrangements of the bonding configurations before dissociation.