Microfabricated Pd and Pd-25Ag alloy membranes

Defect-free Pd membrane with the thickness of 2.5 μm and Pd-25Ag alloy membranes with the thickness of 1.2 and 3 μm were successfully prepared on 50 μm thick Ni layer with channel structure by micro-electro-mechanical systems (MEMS) technology. Hydrogen permeation experiment was performed in a conventional gas permeation apparatus within the temperature range of 473-673 K using high purity hydrogen. Hydrogen permeance of the 2.5 μm thick Pd membrane increased by 2.9-4.1 times after the annealing at 673 K owing to the enhanced surface reaction. However, the 1.2 and 3 μm thick Pd-25Ag alloy membrane had lower hydrogen permeance than the 2.5 μm thick Pd membrane because the surface reaction was rate limiting. The surface morphology of the Pd and Pd-25Ag alloy membranes were examined by scanning electron microscope (SEM) before and after the hydrogen permeation.