Preparation of energetic metastable nano-composite materials by arrested reactive milling

Highly metastable, nano-scale energetic materials were prepared by Arrested Reactive Milling (ARM). When reactive milling is carried out with materials systems suitable for Self-Propagating High Temperature Synthesis (SHS), reaction between the components occurs spontaneously and violently after a certain period of milling. In this research, metastable nanocomposites with high energy density, were prepared by arresting the milling process prior to the spontaneous reaction. Products thus obtained are powders with particle sizes in the 10-50 μm range. Individual particles are intimate mixtures of reactive components, comparable to Metastable Intermolecular Composites (MIC), with near theoretical maximum density. The time of arrest determines the degree of grain refinement and therefore the sensitivity to mechanical, electrical, or thermal initiation. Particle sizes of the product powders can be adjusted by appropriate choice of milling parameters. This paper describes the application of ARM to the material systems Al-Fe₂O₃ and Al-MoO₃. After empirical determination of optimum milling parameters, the reactive composites are structurally characterized by electron microscopy and x-ray diffraction. First results of combustion tests are presented.