Nanoenergetic Materials: Preparation, Properties, and Applications

Energetic materials (EMs) are considered to be pure components or mixtures of chemical substances, which consist of both fuel and oxidizer that could release a large amount of energy or gas upon ignition. EMs can broadly be classified into propellants, explosives, and pyrotechnics with a wide range of applications in ordnance, rockets, missiles, space technology, fireworks, gas generators, automobile airbags, deconstruction, welding, and mining, to cite a few [1]. Explosives generate supersonic detonation velocity but low energy density, whereas propellants and pyrotechnics provide high energy densities by subsonic deflagration process. Typically, EMs can be produced as either monomolecular materials or as composites. The first class, which contains reactants within the same molecule, exhibits a fast reaction process but presents low performance, whereas the second class, which displays better performance, suffers from the slow reaction process mainly due to the limited mass transport rate between species. Several additives such as catalysts, coolants, stabilizers, and plasticizers, in few percent ratios, could be added to the EM formulations to improve their peculiar features and tailor their performance [2]. The advancement in the synthesis approaches and the advent of material characterization tools at multiple length scales have pushed the energetic materials community to explore new opportunities. During the past two decades, several significant achievements in research on nanoenergetic materials (nEMs) have been realized, thanks to the technological novelties in the field of nanoscience and nanotechnology. The principle of nanoenergetics is the enhancement of the specific surface area and intimacy with chemical components to improve the reaction rate while reducing the ignition delay at an acceptable level of safety. Nanoenergetics started with the manufacturing of nano-sized metal particles, mainly aluminum, which was mainly used for rocket propulsion, since the second half of the 20th century. During the last two decades, the physical mixing of oxidizers and fuels is considered as the second stage of the development of nanoenergetics at the nanoscale for which the diffusion distances between the chemical species is improved and the surface-over-volume ratio is enhanced, currently reaching the advanced third stage, where modern technologies, which allowed producing novel types of reactive nanocomposites structures and morphology with tunable features, are applied [3,4]. nEMs, which are composed of nano-sized fuel and oxidizer with or without additives, have been found to be potential sources of extremely high heat release rates and tailored burning rates, reliability, and extraordinary combustion efficiency. Nowadays, they play a vital role in widespread applications such as miniaturized electro-explosive devices, the attitude control of micro/nano satellites, and actuation in lab-on-a-chip devices, to name a few. The improvement of properties and the discovery of new functionalities and methodologies are key goals that cannot be reached without a better understanding of the preparation, characterization, manufacturing, and properties that constitute