David W. Ball

Metastable nanostructured metallized fluoropolymer composites for energetics

Fluoropolymers have long served as potent oxidizers for metal-based pyrolant designs for the preparation of energetic materials. Commercial perfluoropolyethers (PFPEs), specifically known as Fomblins®, are well-known to undergo accelerated thermal degradation in the presence of native metals and Lewis acids producing energetically favorable metal fluoride species. This study employs the use of PFPEs to coat nano-aluminum (n-Al) and under optimized stoichiometric formulations, harness optimized energy output. The PFPEs serve as ideal oxidizers of n-Al because they are non-volatile, viscous liquids that coat the particles thereby maximizing surface interactions. The n-Al/PFPE blended combination is required to interface with an epoxy-based matrix in order to engineer a moldable/machinable, structurally viable epoxy composite without compromising bulk thermal/mechanical properties. Computational modeling/simulation supported by thermal experimental studies showed that the n-Al/PFPE blended epoxy composites produced an energetic material that undergoes latent thermal metal-mediated oxidation. Details of the work include the operationally simple, scalable synthetic preparation, thermal properties from DSC/TGA, and SEM/TEM of these energetic metallized nanocomposite systems. Post-burn analysis using powder XRD of this pyrolant system confirms the presence of the predominating exothermic metal-mediated oxidized AlF3 species in addition to the production of Al2O3 and Al4C3 during the deflagration reaction. Details of this first epoxy-based energetic nanocomposite entrained with a thermally reactive formulation of PFPE coated n-Al particles are presented herein.

High-level ab initio calculations on hydrogen–nitrogen compounds. Thermochemistry of tetrazetidine, N4H4

Abstract As part of our series of investigations into the thermochemistry of hypothetical hydrogen/nitrogen binary compounds, we use several high-level ab initio techniques to investigate the heat of formation of cyclic N 4 H 4 , tetrazetidine. Comparisons to its straight-chain analog, N 4 H 6 , are offered.

Synthesis of 1,3-Diphenyl-6-alkyl/aryl-Substituted Fulvene Chromophores: Observation of π–π Interactions in a 6-Pyrene-Substituted 1,3-Diphenylfulvene

The synthesis, structural, and electronic properties of nine 1,3-diphenyl-6-alkyl/aryl substituted pentafulvenes were studied. Pyrene ring π-π interactions were revealed from analysis of the experimental crystal packing of 1,3-diphenyl-6-(1-pyrene)fulvene and supporting DFT calculations. Photophysical properties derived from UV-vis and fluorescence emission measurements demonstrated tunable and low HOMO-LUMO band gaps for the series. The presented results point to a model synthetic approach for incorporation of extended π systems and donor-π-acceptor groups for fulvene-based electronic materials.

Matrix isolation and theoretical studies of ONNO: Assignment of a new combination band and density functional calculations

Abstract An investigation of the nitric oxide dimer was conducted utilizing the matrix isolation technique coupled with Fourier transform infrared spectroscopy. A previously unreported absorption in matrices at 3609 cm−1 was observed and has been assigned to the NO dimer. This new absorption has been assigned as a combination band arising from the ν1 and ν5 stretches at 1866 cm−1 and 1776 cm−1, respectively. Density functional theoretical (DFT) calculations were also performed to determine the optimized structures and relative energies of the cis- and the trans-ONNO. The potential energy surface for isomerization via N-N bond torsion was also calculated predicting barriers to isomerization of 30.8 and 8.0 kJ/mol.

On the ΔHf values of tetrahedrane and cubane: density functional theory calculations

Abstract The optimized minimum-energy geometries of tetrahedrane (C 4 H 4 ) and cubane (C 8 H 8 ) were determined using several combinations of exchange and correlation functionals. Their heats of formation were calculated using homodesmic reactions and known heats of formations of other compounds in the reactions. With a single exception, all of the combined functionals did a poor job of predicting the ΔH f of both tetrahedrane and cubane relative to experiment (available for cubane only) and previously-published ab initio results.

Field guide to spectroscopy

This field guide covers a broad spectrum of topics in the field of spectroscopy, condensing the subjects to their essentials. As such, novices can use this guide to obtain an overview of the field, and experts can use it as a quick reference. Beginning with basic definitions and explanations, this guide then describes the instruments that are used in the field - from filters, lenses, mirrors, and modulators, to monochromators, interferometers, and detectors. A third section outlines theory and methods as they relate to spectroscopy: the Fourier transform, quantum mechanics, approximation methods, nuclear magnetic resonance, and more. Additional features include a glossary of variables and symbols, and an equation summary.

Formation and vibrational spectrum of trifluoromethyl sulfur pentafluoride, CF3SF5, a new greenhouse gas. Gaussian-2 and Gaussian-3 calculations

Abstract Trifluoromethyl sulfur pentafluoride was recently detected in the atmosphere, and measurements of its IR spectrum suggest that it is one of the most greenhouse-active gases detected to date. Though the anthropogenic source of CF 3 SF 5 is not known for certain, its presence in the atmosphere parallels that of SF 6 , another greenhouse gas. Given the new interest in this molecule, we performed G2 and G3 calculations to determine a structure, vibrational frequency, and energetics of formation for CF 3 SF 5 .

MATRIX ISOLATION AND DENSITY FUNCTIONAL STUDIES OF NOVEL TRANSITION METAL COMPLEXES. NO + FE, CO, NI, CU, AND ZN IN ARGON MATRICES

Abstract We have undertaken a study of the interaction and reaction of nitric oxide with the first row transition metal atoms. Such studies are applicable to catalytic processes (i.e. NOx reduction) as well as direct corrosion of metals. NO and transition metal vapors were trapped in cryogenic argon matrices and their interactions were probed using FTIR spectroscopy. A number of complexes of varying stoichiometry were detected; however, there was no detectable interaction between NO and Zn. Density functional studies using several functional combinations were performed to determine structures, vibrational frequencies, and binding energies of the MNO complexes. There is no obvious discernible trend in the binding properties across the row. DFT calculations do support the Zn NO results by predicting a negative binding energy for the ZnNO complex. A comparison with MCO complexes is offered.

Density functional calculations on the thermodynamic properties of a series of nitrosocubanes having the formula C8H8−x(NO)x (x = 1 − 8)

Recent studies have suggested that octanitrocubane and heptanitrocubane may be two of the most powerful non-nuclear high-energy materials currently known. Progressive substitution of the hydrogen atoms on cubane for nitroso groups is expected to also produce a new potential high-energy material, which should have thermodynamic properties similar to nitrocubane. In this study we predict optimized structures, vibrational frequencies, enthalpies of formation, and specific enthalpies of combustion for a series of nitrosocubanes ranging from mononitrosocubane to octanitrosocubane. Our results indicate, on the basis of the specific enthalpies of combustion alone, that mononitrosocubane should make the best new high-energy material; however, we speculate that the velocity of detonation of octa- and heptanitrosocubane will make them better high-energy materials.

B3LYP calculations on the thermodynamic properties of a series of nitroxycubanes having the formula C8H8−x(NO3)x (x = 1–8)

Recent studies have suggested that octanitrocubane and heptanitrocubane are two of the most powerful non-nuclear high-energy (HE) materials currently known. In this study, we suggest for consideration as new possible HE materials a series of nitroxycubanes, in which the hydrogen atoms on cubane have been progressively substituted for nitrate groups. We hypothesize that these molecules will be good HE materials due to their high nitrogen content and high density, the same reasons nitrocubanes are good high-energy materials. In this study, we predict optimized geometries, vibrational frequencies, enthalpies of formation, and specific enthalpies of combustion. Our results indicate that the enthalpies of formation decrease as the number of nitrate groups increases, which is in direct opposition to what calculations have shown occurs for both the nitroso and the nitrocubane series. Given the difficulty in synthesis of octanitrocubane, octanitroxycubane may still be a more viable candidate for use as a new potential high-energy material.