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Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.

Soft-recovery plate impact experiments have been conducted to study the evolution of damage in polycrystalline Al2O3 samples. Examination of the recovered samples by means of scanning electron microscopy and transmission electron microscopy has revealed that microcracking occurs along grain boundaries; the cracks appear to emanate from grain-boundary triple points. Velocity-time profiles measured at the rear surface of the momentum trap indicate that the compressive pulse is not fully elastic even when the maximum amplitude of the pulse is significantly less than the Hugoniot elastic limit. Attempts to explain this seemingly anomalous behavior are summarized. Primary attention is given to the role of the intergranular glassy phase which arises from sintering aids and which is ultimately forced into the interfaces and voids between the ceramic grains. Experiments are reported on the effects of grain size and glass content on the resistance of the sample to damage during the initial compressive pulse. To further understand the role of the glass, plate impact experiments were conducted on glass with chemical composition comparable to that which is present in the ceramic. These experiments were designed to gain further insight into the possibility of ‘‘failure waves’’ in glasses under compressive loading.

The dynamic behavior of a tungsten carbide filled epoxy composite is studied under planar loading conditions. Planar impact experiments were conducted to determine the shock and wave propagation characteristics of the material. Its stress-strain response is very close to a similar alumina filled epoxy studied previously, suggesting that the response of the composite is dominated by the compliant matrix material. Wave propagation characteristics are also similar for the two materials. Magnetically driven ramp loading experiments were conducted to obtain a continuous loading response which is similar to that obtained under shock loading. Spatially resolved interferometry was fielded on one experiment to provide a quantitative measure of the variability inherent in the response of this heterogeneous material. Complementing the experiments, a two-dimensional mesoscale model in which the individual constituents of the composite are resolved was used to simulate its behavior. Agreement of the predicted shock and release wave velocities with experiments is excellent, and the model is qualitatively correct on most other aspects of behavior.

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