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Abstract: Since the 1960s, hypervelocity impact experiments have been conducted to study the complex deformation mechanisms which occur in the subsurface of meteorite craters. Here, we present ultrasound tomography measurements of the damage zone underneath seven experimentally produced impact craters in sandstone cubes. Within the framework of the Multidisciplinary Experimental and Modeling Impact Research Network and the NEOShield Project, decimeter‐sized sandstone targets were impacted by aluminum and steel projectiles with radii of 2.5, 4, and 5 mm at velocities between ~3.0 and ~7.4 km s−1. The 2‐D ultrasound tomography clearly shows a correlation between impact energy and the damaged volume within the target blocks. When increasing impact energies from 805 to 2402 J, a corresponding increase in the damage radius from ~13.1 cm to ~17.6 cm was calculated. p‐Wave velocity reductions up to 18.3% (for the highest impact energy) were observed in the vicinity of the craters. The reduction in seismic velocity decreased uniformly and linearly with increasing distance from the impact point. The damage intensities correspond to peak damage parameters of 0.4–0.51 compared to undamaged target blocks. In addition to the damage zone below the crater, we could identify weakened zones at the sandstone walls which represent precursors of spalling. The volume of the damaged subsurface beneath experimentally produced craters determined through ultrasound tomography is larger than that obtained from previously reported p‐wave velocity reductions or to microscopic and microcomputed tomography observations of crack densities in experimentally produced craters. [ABSTRACT FROM AUTHOR]

Carbon as electrode material can be specifically tailored for fuel cell or supercapacitor applications. For both electrode systems, specific porosity is required. Vertically aligned multiwalled carbon nanotubes or films of mesoporous carbon are functionalized by incorporating nitrogen atoms into the CNTs or by infiltrating of transition metal precursors resulting in good catalytic behavior for oxygen reduction or increased specific capacitance. [ABSTRACT FROM AUTHOR]

Highly porous carbide-derived carbon (CDC) mesofoams (DUT-70) are prepared by nanocasting of mesocellular silica foams with a polycarbosilane precursor. Ceramic conversion followed by silica removal and high-temperature chlorine treatment yields CDCs with a hierarchical micro-mesopore arrangement. This new type of polymer-based CDC is characterized by specific surface areas as high as 2700 m2 g−1, coupled with ultrahigh micro- and mesopore volumes up to 2.6 cm3 g−1. The relationship between synthesis conditions and the properties of the resulting carbon materials is described in detail, allowing precise control of the properties of DUT-70. Since the hierarchical pore system ensures both efficient mass transfer and high capacities, the novel CDC shows outstanding performance as an electrode material in electrochemical double-layer capacitors (EDLCs) with specific capacities above 240 F g−1 when measured in a symmetrical two-electrode configuration. Remarkable capacities of 175 F g−1 can be retained even at high current densities of 20 A g−1 as a result of the enhanced ion-transport pathways provided by the cellular mesostructure. Moreover, DUT-70 can be infiltrated with sulfur and host the active material in lithium-sulfur battery cathodes. Reversible capacities of 790 mAh g−1 are achieved at a current rate of C/10 after 100 cycles, which renders DUT-70 an ideal support material for electrochemical energy-storage applications. [ABSTRACT FROM AUTHOR]