Porosity: The Key to Initiating Metallic Composite Particles under Shock Compression*

Thermitic composites of metal and metal oxides can produce twice as much energy as conventional explosives but the diffusion-controlled reaction is too slow (microseconds) to produce detonations. If we can design metal-based composites that can react in tens of nanoseconds in strong shock waves, they can be used to boost the energy of conventional explosives or possibly be used as high explosives. One way to increase the reaction rate is to design composites with void structures that can produce hot spots. Recent work has shown that arrested reactive ball milling in fluid emulsions can produce micrometer-sized composites with a variety of void configurations. We can characterize the void structures by cross-sectioning the composite particles. We can then determine the efficiency of these void structures in producing fast energetic chemistries using a tabletop high-throughput system that uses km/s laser launched flyer plates to input detonation-strength shocks into the particles, whose shock reactivity can be characterized with nanosecond video and optical pyrometry