TRANSIENT ANALYSIS OF HYDROGEN PERMEATION THROUGH NICKEL MEMBRANES

The permeation of hydrogen through polycrystalline nickel membranes has been studied as a function of temperature, pressure, and membrane thickness. The steady state flux from gas phase charging experiments have been observed to obey an Arrhenius behaviour for temperature between 270 and 600 K. A value for the lattice diffusivitv of 3.57 x 10(-7) exp(-37.8 kJ . mol-1/RT) m2/s has been calculated using a time lag technique for hydrogen pressures and temperatures of 1-100 kPa and 370-600 K. The permeation transients have been found to be pressure dependent in the temperature range of 270-340 K. This pressure dependence has been associated with the trapping of hydrogen at internal defects sites in nickel. Using the time lag technique, a trap density of 2.2 x 10(23) sites/m3 and a binding energy of 34 kJ/mol have been measured.