Palladium:
Palladium, Uranium, and alloys of zirconium, vanadium, lanthanum, and titanium are presently used or are proposed for pumping and controlled delivery of tritium gas. Several of these alloys are in use in the commercial sector for hydrogen pumping, storage, and release applications. A Gaseous overpressure above a hydride (tritide) phase varies markedly with temperature; control of temperature is therefore the only needed for swings among pumping and compressing the gas.
In follow, pumping speeds or gaseous delivery rates (the kinetic approach to equilibrium) are functions of temperature (diffusion inside the material), hydride particle size, and surface areas and conditions. A Poisoning of a uranium or zirconium surface occurs while oxygen or nitrogen is admitted and chemically combines to form surface barriers to hydrogen permeation. With practice, these impurities might be diffused into the metal bulk at elevated temperature, by reopening active sites and recovering much of the lost kinetics. Another metals and alloys (for instance, LaNi3) are less subject to poisoning, while alloy decomposition could occur.