Hydrogen Permeability through Composite Asymmetric Nb Membranes with Metal Barrier Layers
Alexander Panichkin, Bagdaulet Kenzhaliyev, Aidar Kenzhegulow, Akerke Imbarova, Zhanar Karboz
The article discusses the possibility of using various metals to create barrier layers between the niobium membrane and palladium catalytic layers. Such layers are necessary to reduce the degradation of the palladium catalyst layers during membrane operation. For this, the maximum hydrogen permeability of asymmetric niobium foil membranes was determined, on the one hand covered with a W, Re, Mo, Cu, Co, Ni, Ag film, and the maximum hydrogen permeability of the Nb/Me/Pd membranes was determined, where Me is W, Re, Mo, Cu, Co, Ni, Ag. The change in the structure and composition of the palladium catalytic layer on the surface of composite membranes made of niobium after isothermal holding in vacuum at 420 and 520 ° C for 100 h was studied. It has been found that membranes coated only with a Ni or Co layer are comparable in terms of hydrogen permeability to membranes coated with a Pd layer. Membranes coated with layers of W, Re, Mo, Cu, Ag have low hydrogen permeability, which increases with decreasing thickness of these layers. The hydrogen permeability of such membranes after the deposition of a palladium layer increased by an amount in the case of a barrier layer: from W 170 - 760 times; from Mo by 0.5-10 times; from Re by 23-500 times; from Cu 1.6 - 14 times; from Co by 2.7 times; from Ag by 1.1-10 times. When palladium was applied to the surface of the Ni layer, the hydrogen permeability did not increase. When the thickness of the barrier layers of Cu, Mo, Re, W, Ni, Co is from 13 to 400 nm, the hydrogen permeability of the Nb/Me/Pd composite membranes corresponds to the values â€‹â€‹3.9-7.0*10-5 mol/s*m2*Pa0.5. Minimal changes in the structure and composition of the Pd layer were observed upon prolonged heating of Nb/W/Pd membranes.