RESUMO
Detonation nanodiamond (DND) is known to form aggregates that significantly reduce their unique nanoscale properties and require postprocessing to separate. How and when DND aggregates is an important question that has not been answered experimentally and could provide the foundation for approaches to limit aggregation. To answer this question, time-resolved small-angle X-ray scattering was performed during the detonation of high-explosives that are expected to condense particulates in the diamond, graphite, and liquid regions of the carbon phase diagram. DND aggregation into low fractal dimension structures could be observed as early as 0.1 µs, along with a separate scattering population also observed from an explosive that produces primarily graphitic products. A counterexample is the case of a high-explosive that produces nano-onions, where no hierarchical scattering was observed for at least 10 µs behind the detonation front. These results suggest that DND aggregation occurs on time scales comparable to particle formation.
RESUMO
Recent advances in Graded Density Impactor fabrication technique have increased the maximum achievable pressure in gas gun quasi-isentropic experiments to 5 Mbars. In this report, we outline the latest methodologies and applications of Graded Density Impactors in experiments at extreme conditions. These new Graded Density Impactors are essentially metallic discs made of nearly one hundred layers of precisely mixed Mg, Cu, and W. The density gradients in these impactors are specifically designed to generate the desired thermodynamic path required for each experiment. We carried out a number of experiments at various pressures using these Graded Density Impactors. These experimental results and their simulations will be presented here.
