Palladium membranes supported on porous ceramics prepared by chemical vapor deposition

Palladium films on porous alumina supports were prepared by the chemical vapor deposition (CVD) technique of reducing PdCl2 with hydrogen. The phase composition and morphology of Pd composite membranes were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM). A well-crystallized palladium layer was deposited on porous alpha-alumina supports. The thickness and grain size of the palladium layer were estimated to be about 4 mu m, The palladium grains consisted of columnar crystallites of 20-40 nm in length and 5-8 nm in width. The penetration depth of pallldium into the alpha-alumina support was as large as 20 mu m. An opposite-diffusion CVD technique is suggested for preparing a denser thin palladium membrane with high hydrogen permeability and good mechanical stability. (C) 1997 Elsevier Science S.A.