Abstract
Permeation of hydrogen in transition metals is an important catalytic reaction. The preparation and properties of hydrogen permeable membranes have been studied in energy technologies for many years. The palladium-silver alloy membrane has been extensively studied in recent years due to the absence of α→βphase transition and embrittlement associated with hydrogen permeation. In addition to the application for ultra high purity hydrogen separation, it is also widely utilized in recovery or purification of hydrogen in petroleum industry, hydrogen reactor in fuel cells, and methane stream reforming. In the present work, microcrystalline silver powder was used as the substrate material. Porous silver substrate was obtained after sintering at 350oC in air for 1hr. Prior to deposition, the surface was filled with nanocrystalline Pd70Ag30 particles to reduce the pore size, followed by deposition with a Pd70Ag30 alloy film. The palladium-silver alloy film was sputter deposited on the substrate as a separation membrane. The surface and cross-section morphologies of the sintered silver substrates were examined by scanning electron microscopy. Besides, the permeation rate of hydrogen at 250oC was measured by a gas permeation apparatus. A new rotation design was also built for sputter coating on tube substrates. It was observed that a dense and continuous film of a thickness 10μm could be achieved on the modified substrate. The hydrogen permeation flux through the membrane increases monotonically with the pressure but deviates from the Sievert’s law. A rotation design was made and a copper tube was tested. The uniformity of thickness was fairly good.