Journal of Membrane Science, Vol.502, 57-64, 2016
Characteristics of dense palladium alloy membranes formed by nano-scale nucleation and lateral growth
In this study, fine, uniform nano-scale layers of Pd were deposited by an advanced sputtering system with high vacuum, high temperature, and high power to overcome the limitations of existing sputtering systems. Thin Pd films formed by continuous sputtering exhibited vertical growth, combined with the lateral growth of Pd clusters due to the improved reactivity of Pd nano-particles, the diffusion of activated Pd atoms at high temperature, and the self-catalyst effect of the porous nickel support (PNS). Additionally, uniformly dense Pd structures were formed by the successive deposition of Pd particles, and Pd clusters formed with a uniform density. A fine Pd-Au alloy membrane manufactured by this advanced sputtering system not only improved hydrogen selectivity due to the pinhole-free membrane surface but also increased hydrogen permeability because the thin film had a thickness less than 6 mu m and a uniformly fine grained structure. Additionally, the Pd alloy membrane exhibited enhanced durability because the inter-diffusion of the support component to the membrane surface was prevented by the low temperature of the heat treatment for crystallization and the low alloying temperature. (C) 2015 Elsevier B.V. All rights reserved.