Reactive Structural Materials: Preparation and Characterization

Abstract

Reactive structural materials, which can serve both as structural elements as well as a source of chemical energy released upon initiation have emerged as an important class of metal-based composites for use in various energetic systems. Such materials rely on a variety of exothermic reactions, from oxidation to formation of metal-metalloid and intermetallic phases. The rates of these reactions are as important as the energy that may be released, in order for them to occur at the time scales compatible with the requirements of applications. Therefore, chemical composition, scale at which reactive components are mixed, and the structure and morphology of materials are important and can be controlled by the method of preparation and compaction of the composite materials. Methods of preparation of the composite structures are briefly reviewed as well as methods of characterization of their mechanical and energetic properties. In addition to common thermo-analytical and static mechanical property measurements, dynamic tests of mechanical properties as well as ignition and combustion experiments are necessary to understand the fragmentation, initiation, and heat release expected for these materials when they are stimulated by an impact, shock, or rapid heating. Reaction mechanisms are studied presently for the thin layers and small samples of reactive materials initiated in carefully designed experiments. In other experiments, impact and explosive initiation are characterized for larger material compacts in the conditions imitating practical scenarios. Examples of results describing thermal, impact, and explosive initiation of some of the reactive materials are presented.

Mechanical Alloying: A Novel Technique to Synthesize Advanced Materials

“…This area has received a great impetus in recent years since the combustion rates of nanostructured metal particles are much higher than those of coarse metal particles. The particle size cannot be exceedingly small because the surface may be coated with a thin oxide layer and make the particles passive [61–63]. MA is very well suited to prepare such materials because the reactions are easily initiated by impact or friction, and at the same time, milling is a simple, scalable, and controllable technology capable of mixing reactive components on the nanoscale.…”

Progress in Additive Manufacturing of Energetic Materials: Creating the Reactive Microstructures with High Potential of Applications

“…Generally, these systems have no need for nanosized components, and the manufacturing techniques are different from those for RMS production. Detailed information on reactive structural materials can be found in recent reviews [2,3].…”

“…These systems with increased intimacy of components -nanocomposites -are highly promising due to enhanced reaction kinetics. These compositions are also known as "reactive materials" [2,3], "metastable intermolecular composites" [4], or "pyrolants" [5,6]. The key feature of these systems is the high heat release during metal oxidation, e. g., 31 kJ (g of metal) À 1 for aluminum, which is much higher than the enthalpy of detonation for powerful explosives (6.2 kJ g À 1 for HMX [7]) and the typical capacity of lithium batteries (near 1 kJ g À 1 [8]).…”

The Influence of Initial Defects on Impact Ignition of Aluminum/Polytetrafluoroethylene Reactive Material

“…The reactive material is a new class of energetic materials that provides a means to increase the lethality of direct hit or fragmentation warheads, which usually consists of two or more nonexplosive solid materials. Unlike traditional steel/tungsten alloys, reactive fragments made from reactive materials can induce multiple mechanism damage, including both kinetic energy damage and additional explosion/deflagration damage under impact . As an important representative of the reactive materials, the aluminum/polytetrafluoroethylene(Al/PTFE) component has received widespread attention due to its high‐energy level and inertness, its unique properties of energy release, and its considerable mechanical properties.…”