ProceedingsBookBerg

260) (invited) “Experiments Probing Fundamental Mechanisms of Energetic Material Initiation and Ignition”, Christopher M. Berg, Kathryn E. Brown, Rusty W. Conner, Yuanxi Fu, Hiroki Fujiwara, Alexei Lagutchev, William L. Shaw, Xianxu Zheng and Dana D. Dlott, MRS Online Proceedings Library vol. 1405.

ShockChemBrown2012_1

266) “Time-resolved emission of dye probes in a shock-compressed polymer”, Kathryn E. Brown, Yuanxi Fu, William L. Shaw and Dana D. Dlott, J. Appl. Phys. 112, 103508 (2012).

ShockChemBrown2012_2

266) “Time-resolved emission of dye probes in a shock-compressed polymer”, Kathryn E. Brown, Yuanxi Fu, William L. Shaw and Dana D. Dlott, J. Appl. Phys. 112, 103508 (2012).

ShockChemXianxu2013

269) “Shock initiation of nano-Al + Teflon: time-resolved emission studies”, Xianxu Zheng, Alexander D. Curtis, William L. Shaw and Dana D. Dlott, J. Phys. Chem. C 117, pp. 4866-4875 (2013).

ShockChemWillS2014_1

274) “Laser-driven flyer plates for shock compression spectroscopy”, William A. Shaw, Alexander D. Curtis, Alexandr A. Banishev and Dana D. Dlott, Journal of Physics: Conference Series 500, 142011 (2014).

ShockChemWillS2014_1

275) “Using laser-driven flyer plates to study the shock initiation of nanoenergetic materials”, William A. Shaw, Rayon A. Williams, Edward L Dreizin and Dana D Dlott, Journal of Physics: Conference Series 500, 182010 (2014).

ShockChemAlex2014_1

276) “Dynamics of shocks in laser-launched flyer plates probed by photon Doppler velocimetry, Alexander D. Curtis, William A. Shaw, Alexandr A. Banishev and Dana D. Dlott, Journal of Physics: Conference Series 500, 192002 (2014).

ShockChemWillS2014_3

282) “Ignition of nanocomposite thermites by electric spark and shock wave”, William L. Shaw, Dana D. Dlott, Rayon A. Williams, Edward L. Dreizin, Propell. Energet., Pyrotech. 39, pp. 444-453 (2014).

ShockChemAlex2014_2

284) “Laser-driven flyer plates for shock compression science: launch and target impact probed by photon Doppler velocimetry”, Alexander D. Curtis, Alexandr A. Banishev, William L. Shaw and Dana D. Dlott, Rev. Sci. Instum. 85, 043908 (2014).

Shock Induced Chemistry

The Dlott group is interested in studying materials that respond to shock waves by undergoing chemical transformations and understanding the underlying mechanisms that govern these reactions. Shock waves are nearly discontinuous changes in material speed, pressure, density and temperature that move through a substance. To comprehend the magnitude of a shock wave, keep in mind that the loudest sound waves in air increase the pressure by 0.005 atm where shock waves typically generate over 10,000 atm changes in pressure. We produce shock waves using the impact of laser-driven flyer-plates that move at speeds of upwards of 4.5 km/s (mach 13). Flyer motions and shock induced phenomenon are monitored using a home built photonic Doppler velocimeter and chemistry is probed using high speed spectroscopic methods.

Using shock waves allows us to examine materials in conditions where reactions can occur that are unobtainable in ambient conditions. Our focus is on examining both energetic materials and shock wave energy dissipating (SWED) compounds. Energetic materials such as explosives and thermites (solid state metal/metal oxide systems) have been studied extensively for their potential use in weapons systems, but the more intrinsic process that underlie their shock reactivity is poorly understood. This is because the size of large scale of typical experiments obscures intrinsic reaction rates. Our group studies samples of micron thicknesses which allow us to probe these fundamental processes and develop mechanisms for reaction. We are currently examining several systems including ball milled nano thermites, multi-layer nano thermties, and propellants prepared by collaborators.

 

Figure 1: Left: A typical flyer history tracked using our photonic Doppler velocimeter. Right: Our system can launch different thickness flyers, which produce shock durations from 5-20 ns, over a range of speeds.

 

Our second project is motivated by shock wave related injuries that account for 20% of the casualties sustained by USA troops in battle. This is a problem because our armors are capable of stopping a bullet or fragment of shrapnel, but not the shock that is generated by the impact. The Dlott group is exploring a new paradigm of SWED that uses molecular level volume collapse driven by chemical transformations in compounds in order to reduce the energy of a shock wave. This project will examine the material mechanisms that are most effective in SWED in order to create more effective materials that can be used to protect soldiers on the battlefield.

 

Figure 2: Time dependent emissions from thermite single particles for varying impact velocities

 

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