Search

Thin dense palladium (Pd) membranes (approximately 5 μm) were fabricated on rotating porous stainless steel supports using electroless plating. During electroless Pd plating, the rate of Pd deposition increased as the support rotation rate increased. Compared with conventional electroless plating methods, the proposed modified electroless plating using a support rotation technique yielded Pd membranes that had considerably more uniform and smooth surface morphology, which substantially enhanced the membrane stability. The membranes exhibited a hydrogen permeance as high as 78 m 3 /m 2 h bar 0.5 (3.0×10 −3 mol/m 2 s Pa 0.5 ) and an ideal permselectivity exceeding 400 when the pressure difference was 4 bar and the temperature was 400 °C. Moreover, the membranes were stable during long-term temperature cycling performed between room temperature and 400 °C over a period of 350 h. These results indicated that the electroless plating combined with support rotation process was a simple, effective method for preparing thin dense Pd membranes featuring high hydrogen permeation flux and high thermal durability. [ABSTRACT FROM AUTHOR]

Abstract: A layered double hydroxide (LDH) layer was grown directly on a porous stainless steel (PSS) surface to reduce the pore opening of the PSS and to be a middle layer retarding Pd/Fe interdiffusion. A thin Pd film (∼7.85 μm) was plated on the modified PSS tube by an electroless plating method. A helium leak test proved that the thin Pd on the LDH-modified PSS substrate was free of defects. The membrane had a H2 flux of 28–36 m3/(m2 h) and H2/He selectivity larger than 2000 at a pressure difference of 1 bar. Thermal cycling between room temperature and 673 K was performed and showed that the membrane exhibited good permeance and selectivity. Long-term evaluation (1500 h) of the membrane at 673 K showed static results of H2 flux (∼30 m3/(m2 h)) and H2/He selectivity (∼2000) over the 1500 h test period. [Copyright &y& Elsevier]

Abstract: Thin Pd membranes for hydrogen filtration were deposited on modified porous stainless steel (PSS) tubes using an electroless plating technique. Alumina oxide (Al2O3) particles of two different sizes were subsequently used to modify the non-uniform pore distribution and the surface roughness of the PSS tubes. The principle of the modification was to use large Al2O3 particles (∼10 μm) to fill larger pores on the surface, and leave the smaller pores intact. Small Al2O3 particles (∼1 μm) were then used to further decrease the surface roughness. The detailed manufacturing steps of the Al2O3 modification were investigated and optimized to achieve a continuous dense Pd membrane with a minimum thickness of 4.4 μm on the modified PSS tubes. The highest hydrogen permeance of the membrane was 2.94 × 10−3 mol/m2-s-kPa0.5 at 773 K, with a selectivity coefficient (H2/He) of 1124 under a pressure difference of 800 kPa. In comparison, the thickness and hydrogen permeance of a dense Pd membrane on unmodified PSS tubes were 31.5 μm and 5.97 × 10−4 mol/m2-s-kPa0.5, respectively, at 773 K under an 800 kPa pressure difference. The stability of the membranes at high temperatures was also investigated. The hydrogen permeation flux at 773 K was stable during a test period of 500 h. These results demonstrate that the two-step method modifies the surface of PSS tubes in a relatively simple way and results in thin, dense Pd membranes with high hydrogen permeance and good thermal stability. [Copyright &y& Elsevier]