Diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd membrane deposited on porous stainless-steel support

In this study, we present an intermetallic diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd-based composite membrane on porous stainless steel (PSS). A tubular PSS sample with 1/2 inch (12.7 mm) in diameter and 450 mm in length was used for the support. The support was welded with a stainless-steel cap and a 450-mm-long stainless-steel tube for each end. Before the diffusion barrier coating, the large-sized entrance pores were gradually blocked with sub-micron (similar to 500 nm) and nano (50 80 nm) yttria stabilized zirconia (YSZ). 8YSZ, i.e., 8wt.% YSZ, was used for the interdiffusion barrier material and dispersed on the surface of the pre-treated PSS using the blowing coating method. The blowing coating method has 4 steps: (i) spraying the 17 wt. % 8YSZ paste on the surface of the PSS tube,(ii) blowing the paste using compressed air,(iii) drying at room temperature, and (iv) heat treatment at 923 K for 2 h in air. Steps (i) and (ii) were repeated 3 times to have a similar to 240 nm thick 8YSZ layer. A thin palladium layer (similar to 3 mu m) was deposited on the pre-treated PSS using electroless plating, and the membrane stability was tested at 673-773 K for similar to 200 h. A hydrogen permeation flux of 9.86 x 10(-2) mol m(-2) s(-1) and an H-2/N-2 selectivity of 595 were obtained at 773 K and a transmembrane pressure difference of 20 kPa. The surface and cross-sectional SEM/EDX analysis confirmed that the 8YSZ layer sufficiently prevented the interdiffusion between Pd and PSS elements, such as Fe, Cr and Ni. (c) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.