We describe a simplified system of laser-driven flyer plates for shock compression science and shock spectroscopy. We used commercially available one-box Nd:YAG lasers and beam homogenization solutions to create two launch systems, one based on a smaller (400 mJ) YAG laser and an inexpensive diffusive optic, and one based on a larger (2500 mJ) laser and a diffractive beam homogenizer. The flyer launch, flight, and impact processes were characterized by an 8 GHz fiberoptic photon Doppler velocimeter. We investigated effects of different substrates, adhesives, absorbers, ablative layers, and punching out disks from continuous foils versus fabricating individual foil disks, and found that a simple metal foil epoxied to a glass window was satisfactory in almost all cases. Our simplified system launched flyer plates with velocities up to 4.5 km s(-1) and kinetic energies up to 250 mJ that can drive sustained steady shocks for up to 25 ns. The factor that limits these velocities and energies is the laser fluence that can be transmitted through the glass substrate to the flyer surface without optical damage. Methods to increase this transmission are discussed. Reproducible flyer launches were demonstrated with velocity variations of 0.06% and impact time variations of 1 ns. The usefulness of this flyer plate system is demonstrated by Hugoniot equation of state measurements of a polymer film, emission spectroscopy of a dye embedded in the polymer, and impact initiation and emission spectroscopy of a reactive material consisting of nanoscopic fuel and oxidizer particles.

We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s(-1) impacts with transparent target materials. Laser-launching Al flyers 25-100 μm thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.

Metal-organic frameworks (MOFs) have potential applications as energy absorbing materials for shock wave energy mitigation due to their nanoporosity. Here we have examined km/s laser-driven flyer plate impacts on a prototypical MOF, ZIF-8. We observed particle fragmentation and morphological changes in microcrystals of ZIF-8 at lower shock pressures (≈2.5 GPa), and amorphization and structural collapse at higher pressures (≈8 GPa). High-speed emission spectroscopy revealed that 50 ns after flyer plate impacts, an emission pulse was generated by ZIF-8 resulting from chemical bonds that were broken and subsequently reformed. MOFs may prove useful in the dissipation of shock wave energy through large structural changes (free volume collapse and endothermic bond breakage).

Recent investigations into the mechanical properties and mechanochemical reactions of metal−organic frameworks (MOFs) have suggested the potential for energy dissipation by multiple mechanisms. Although the possibility of efficient multifunctional shock dissipation by MOFs was suggested by static high pressure studies, there is little known about MOFs under shock compression. Here, we measure the attenuation of shock wave by the MOF denoted zeolitic-imidazolate framework (ZIF-8) in its desolvated, porous state. We find that shock wave dissipation by ZIF-8 occurred by multiple processes: powder compaction, nanopore-collapse, and chemical bond-breakage. The shock energy absorbance in ZIF-8 is proportional to ZIF-8 thickness, allowing the prediction of the thickness of MOF layer needed to attenuate shock waves to a desired lower energy. Compared with PMMA, often used as a standard, ZIF-8 attenuates 7 times more shock energy per unit mass for impacts at a lower velocity of 0.75 km/s and 2.5 times more at a higher velocity of 1.6 km/s. This research illustrates how to improve the ability to attenuate shock waves for personnel and equipment protection by engineering multifunctionality into the shock wave absorbing armor material.

Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by high-resolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures.