Interface pinning causes the hysteresis of the hydride transformation in binary metal hydrides

Hydriding and dehydriding transitions in bulk nanocrystalline binary metal hydrides were studied using the Pd-H model system by measuring pressure-composition isotherms with situ x-ray diffractometry. Nanocrystalline Pd showed a smaller pressure hysteresis, solvus hysteresis lattice parameter, compared to Pd. The time-dependence of equilibration was measured after dosing aliquots hydrogen, giving times that much faster single-phase regions than two-phase plateaus. In broad plateaus, relaxations exponential functions time. An explanation is developed based on dissipative potential barrier impedes motion interface due interactions between defects interface. are consistent for this mechanism. For simple pinning potential, maximum an order magnitude less typical grain boundary energies. These effects substantially different Pd, suggesting differences hydriding