Energetic materials, as distinct from fuels, include explosives, propellants and ignitable liquids. One typically associates the study of energetic materials with forensics, in the detection and prevention of terrorism or crime. Indeed, this is the primary focus of the Group's activity in the area of energetic materials, although many technological spinoffs have resulted from these aspects. Our goal here is to provide the characterization of vapors of energetic materials that form the basis of detection, in the laboratory and in the field.
The detection of energetic materials (primarily explosives and propellants) in the field depends on a sound knowledge base that allows for the certification of instruments. Thus, it is critical for the detection of, for example, a plastic explosive formulation that one understands what components might form in the vapor space (or headspace) above the solid material, and at what concentration. We have developed a highly sensitive sampling method that makes the measurement possible. A number of interesting and useful technical spin offs (in forensics and food safety) have resulted from our work on explosive vapors. Related to the characterization of the vapor space is the measurement of the fundamental quantity of vapor pressure. In any theoretical description of fluid behavior, the first fundamental property that must be measured is the vapor pressure. Unfortunately, the vapor pressure of low volatility materials such as explosives and propellants is extremely difficult to measure. The task is rendered even more challenging by the presence of multiple components and impurities. We have developed a technique to measure this important parameter with very low uncertainty. Our method is an extension of classical gas saturation or (vapor transpiration) metrology. Another in-the-field problem that has become prominent is the remote or standoff detection of the fluid contents of plastic bottles. Especially in a transportation setting, it is critical to know if the bottle being carried by a passenger contains water or something that can be used to generate an explosion or fire. To help address this issue, we measure the permeation of various liquids across polymer barriers. Finally, we have applied our fuel characterization metrology to the study of ignitable liquids that have been used in arson fires.