Shocked states from initially liquid oxygen–nitrogen systems

Abstract

Sets of pressures and their corresponding specific volumes and internal energies are derived from measurements on steadily propagating, planar shock waves propelled by explosively driven metal assemblies into a 1:1 atomic mixture of the elements nitrogen and oxygen in each of two liquid initial states. One of these is the equimolar solution of O2 and N2, at T≂85 K, v0≂1.06 cm3/g; the other is the pure explosive compound NO, at T≂122 K, v0≂0.79 cm3/g. Results for this system are calculated with effective spherical potentials and presented graphically for comparison with the measurements. Single- and reflected-shock states are reported, as are incidental new results on pure liquid N2 at 85 K. The method of measurement is described, with reference to its previous applications to liquid O2 and Ar. First-shock pressures from both initial forms lie between 10 and 30 GPa, and the Hugoniots intersect at a common state, near 21 GPa, where a single reflected-shock Hugoniot is centered. Concordant measured state variables at this intersection provide novel confirmation of the expectation, inherently incorporated into theory, that unique equilibrium states are reached. Accounting for densities of these states by theory indicates a significant amount of oxidized nitrogen, in reversible equilibrium with major, but not exclusive, N2 and O2 components. This is treated as residual NO only, although the uncertainty in the potentials for other oxides does not assure their absence.