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The high pressure equation of state response of hot pressed bismuth trioxide (Bi2O3) powder compacts is determined through a series of parallel plate impact gas-gun experiments. Loose powders of Bi2O3 are hot-pressed to an average density of 9.202 g/cm3, corresponding to 96% theoretical maximum density. Shock compaction of the compacts to pressures between 4-17 GPa reveal full consolidation occurring at pressures above ∼ 8 GPa. Using the experimentally determined Hugoniot of the 96% dense compact, calculations are performed to obtain the equation of state parameters for solid density Bi2O3.

Dynamic evolution of microstructure during laser shock loading and spall failure of single crystal Al at the atomic scales

The low- and high-strain-rate compaction response of three distinct morphology CeO2 powders was measured experimentally. At low-strain-rates, the compression path was found to vary with initial particle morphology as a result of differences in initial packing structure and particle rearrangement at low stresses. However, similar compression responses were observed at higher stresses under low-strain-rate loading. Dynamic experiments were performed at impact velocities between 0.15 and 0.78 km/s, and resulted in compaction stresses of 0.51-4.59 GPa in the powders. In contrast to the behavior observed at low stresses and low-strain-rates, dynamic loading resulted in a similar compaction response for all morphology powders. The dynamic results were treated with a Hayes equation of state augmented with a P-α compaction model, and good agreement between experimental and theoretical results was achieved. From the observed similarities in compressibility for the three morphology powders at elevated stresses at both low- and high-strain-rates, a relationship is proposed linking the measured strength properties at low-strain-rates to those controlling the compaction response under dynamic loading.

An experimental technique and analysis methodology for obtaining high-fidelity Hugoniot measurements with defined uncertainty bounds on powder compacts using optical velocimetry is presented. Impedance matching is used to calculate the shocked state in the powder from the measured initial compact density, ρ(00), impact velocity, V(Imp), and shock velocity, U(S). Detailed characterization of the powder thicknesses at precise locations results in improvements in characterization of the initial density state and accurate measurements of the powder thickness at locations corresponding to shock velocity measurements. These measurements result in high accuracies in the equilibrium Hugoniot state and reduced uncertainties in the measured and calculated Hugoniot parameters. Assumptions in this analysis include a constant and homogeneous initial porous density, and steady state wave propagation. The approach is applied to a system of CeO(2) powder pressed to 4.0 g/cm(3) (55% theoretical maximum density), and results indicate a complex dynamic response.