In a recent manuscript prepared for publication, Viewing Internal Bubbling and Microexplosions in Molten Metal Particles: a Next Step Towards Controlling Combustion, authors Elliot Wainwright, Shashank Lakshman, Andrew Leong, Alex Kinsey, John Gibbins, Shane Arlington, Tao Sun, Kamel Fezzaa, Todd Hufnagel, and Timothy Weihs present visual evidence of the bubbling that drives the microexplosions of metal particles.
Through the use of synchrotron x-ray phase contrast imaging at Advanced Photon Source, the group was able to view the complete combustion lifecycle that went from “ignition, heating into molten spheres, interior bubble formation, and microexplosions”. The group then delved further into the combustion behavior by observing that various bubble growth rates, cause different combustion products. This series of experiments involved adjusting the chemistry and size of the metal fuel powders.
In the videos below, aluminum-zirconium composite particles were attached to a wire under tension. The wire was heated to begin the combustion process of the particles. Once the wire snapped, the particles can be observed as they move through the air. The first video shows the reactions in high speed. The second video gives a close-up of the particles breaking from the wire and shows an in-depth view of the rapid bubbling happening inside the particles.
Wainwright and his fellow researchers theorize that by controlling the bubbling and subsequent microexplosions of metal particles through alloying, researchers will be able to tune the combustion performance in a manner of different ways. This ability will speed the insertion of these powders into applications relevant to defense agencies attempting to counteract or neutralize, bio and chemical agents.
*This research is funded by the Defense Threat Reduction Agency.