Mechanical-strain-induced influences on hydrogen diffusion within Pd77Ag23 alloy membranes

Numerical simulation of diffusivity of hydrogen in thin tubular metallic membranes affected by self-stresses

“…Firstly, we concentrate on the chemopotential-step situation for experiments of gas/membrane/gas [17][18][19][20][21][22] under pressure-step in gas phase absorption or electrolyte/membrane/gas under potentiostatic charging in electrochemical absorption. Secondly, the ux-step for electrolyte/membrane/gas with galvanostatic charging is discussed [1,2,[13][14][15][16].…”

“…where E is the Young's modulus, E =100-200 GPa; is the Poisson's ratio, = 0:3-0.4; C0 is the concentration of H in M corresponding to nH = 1, C0 = 0:1-0:15 mol H cm −3 for materials used experimentally [1,2,[13][14][15][16][17][18][19][20][21][22][23][24][25][26]; L is the membrane thickness; z is the coordinate along the thickness direction, the upstream side is z = 0 (outer surface) and the downstream side is z = L (inner surface). The hydrogen ux has the form…”

“…In experiments, the applicability of time characteristics is determined by the techniques employed. For gas/membrane/gas and electrolyte/membrane/gas situations, L is easily acquired by the measurement of pressure change; therefore, the time-lag method has been used widely [1,2,[13][14][15][16][17][18][19][20][21][22][23][24]. If an electrolyte is introduced in the tube [16], L can be estimated from the potential change and 1=2 can be evaluated from the anodic current, which re ects the di used ux.…”

“…For the gas/membrane/gas situation, i.e. only the gas and solid phases are involved [17][18][19][20][21][22], the boundary condition at the outer surface is …”

“…The UHD phenomena, the time courses of pressure change in a tube during hydrogen absorption and interruption of steady di usion [1,2,[13][14][15][16][17][18][19][20][21][22][23][24] were demonstrated and interpreted by these theories. Besides these phenomena, it has been found that self-stresses lead to changes of apparent di usion coe cient (ADC) if traditional relations are applied in experiments [1,2,[13][14][15][16][17][18][19][20][21][22][23][24][25][26]. This is one of the reasons that ADCs of H in metal (alloy) hydrides di er from one work to another.…”