Aerogels and Sol–Gel Composites as Nanostructured Energetic Materials

In the last 20 years, there have been a significant number of investigations of the application of aerogels and sol–gel-derived materials and methods to the field of energetic materials (e.g., explosives, propellants, thermites, and pyrotechnics) specifically through the synthesis and characterization of nanostructured energetic composites. Aerogels have unique density, composition, porosity, and particle sizes as well as low temperature and benign chemical synthetic methods all of which make them attractive for energetic nanomaterials candidates. The application of these materials and methods to this technology area has resulted in three general types of sol–gel energetic materials: (1) sol–gel inorganic oxidizer/metal fuel thermite-like composites; (2) sol–gel-derived porous pyrophoric metal powders, films, and monoliths; and (3) sol–gel metal or organic fuel/inorganic oxidizer nanocomposites (propellant, explosive, thermite, and pyrotechnic composites). This chapter summarizes results from synthesis and characterization research in all three areas. General trends are detailed, analyzed, and discussed. In general, all sol–gel nanostructured energetic material behaviors are highly dependent on several factors including the nanomorphology of the network, its surface area, the degree of mixing and contact area between phases, the type of mixing (sol–gel, physical mixing, interpenetration), solids loading, and the presence of impurities. Sol–gel methods are attractive to the area of nanostructured energetics because they offer a great deal of many processing options such as monoliths, powders, and films and have broad compositional versatility. These attributes coupled with strong synthetic control of the microstructural properties of the sol–gel matrix enable the preparation of energetic nanocomposites with tunable performance characteristics. Various aspects of the present literature work are reviewed and future challenges for this technological area are presented and discussed.