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Weapons and Materials Research Directorate Research Areas

Energetic Materials

Vibrational Spectroscopy of Energetic Materials

Advisor: KL McNesby

Key words: vibration, Fourier-transformation spectra, Raman spectra, energetic materials, supercritical fluids

This research opportunity focuses on utilizing Fourier-transform infrared absorption spectroscopy and Fourier-transform Raman spectroscopy to study energetic materials. We use these spectral techniques to characterize new energetic materials, predict impact sensitivity, detect energetic materials as environmental contaminants, and decompose energetic materials in high-pressure environments.

Supercritical fluids are used as a medium in which energetic materials are spectrally monitored at high pressures and temperatures. Fourier-transform Raman spectroscopy is used to probe the dynamics of solvent-solute interactions, and to investigate changes in basic spectral parameters (e.g., rotational and rovibrational linewidths) as a system goes supercritical. Reaction kinetics of the decomposition of energetic materials are also examined as a function of temperature and pressure.

Mechanical Response of Energetic Materials

Advisor: RJ Lieb

Key words: energetic materials, interior ballistics, propellant combustion, fracture mechanics

Experimental and theoretical research opportunities are available to study the deformation and mechanical response of energetic materials, and the effects of this deformation on decomposition and combustion. Research includes uniaxial and multiaxial response characterization at strain rates ranging from static to 5000/s over the temperature range of ballistic interest, -52oC to 60oC, using a variety of devices. We study the effects of deformation using morphological analysis with optical and scanning electron microscopy instruments. Recent studies include viscoelastic characterization of gun propellant, rocket propellants, and High Energy explosives  through stress relaxation measurements, characterization of the onset and nature of fracture using scattered techniques, development of a thermoviscoelastic constitutive model to predict response and damage within material, and characterization of the fracture generated surface area of specimens damaged under controlled uniaxial compression.

Laser-Based Sensitive Detection of Energetic Materials

Advisor:  RC Sausa                            

Key words: energetic material sensitive detection, laser photofragmentation, laser-induced fluorescence, fragment detection

Laser-based spectroscopic techniques are important for chemical analysis because they offer the combination of high sensitivity and selectivity with real-time monitoring capabilities. This research opportunity centers on laser-photofragmentation/fragment detection (PF/FD) methods for detecting trace quantities of energetic materials in real time and in situ. PF/FD methods are often utilized when the analyte molecule does not lend itself to direct spectroscopic detection because it is either a poor fluorophor or because it predissociates with the absorption of laser radiation. In PF/FD methods, a single laser both photofragments the target energetic molecule and facilitates the detection of the characteristic photofragments, especially nitric oxide (NO). NO possesses a favorable combination of strong optical transitions and exhibits sharp, well-resolved spectral features. Thus, it can be detected readily by resonance-enhanced multiphoton ionization with miniature electrodes or by laser-induced fluorescence with a photodetector. The NO fragment is characteristic of the NO2 functional group, which is present in the energetic molecules and contributes to the selectivity of the analytical method. Experiments are conducted with both ultraviolet and visible laser radiation and the analytical merit of the methods is demonstrated on various energetic materials such as TNT, PETN, and RDX.

Reference
Cabalo J, Sausa R: Applied Spectroscopy 57(9): 1196, 2003