Coupling effects of oxygen surface exchange kinetics and membrane thickness on chemically induced stresses in perovskite-type membranes

Abstract The durability of the perovskite-type ceramic oxygen ion-conducted membranes strongly depends on the magnitude of the chemically induced stresses. This paper examines the influence of both membrane thickness and exchange of oxygen vacancies at the interface between the membrane surface and surrounding gas phase on the chemically induced stresses in the tubular perovskite-type membrane under the gradient of oxygen partial pressure created between air and an inert gas. A mathematical model relating the chemically induced strains and stresses in the tubular membrane to oxygen non-stoichiometry in perovskite-type oxide has been developed, and solved numerically by the ANSYS codes. Calculation results show that when the membrane thickness is significantly higher than the so-called characteristic membrane thickness, the largest first principal stress on the air feeding side of the membrane is practically identical to the one found under the assumption of the constant oxygen non-stoichiometry condition on the permeate side. An analogous comparison for the largest von Mises stress on the permeate side of the membrane gives rise to the difference by 50%. The influence of the oxygen surface exchange kinetics on the stresses strongly increases with decreasing thickness of the membrane. In case of the membrane of 0.1 mm thickness which is of the same order of magnitude as the characteristic membrane thickness, the largest first principal stress on the feeding side that was calculated without and with oxygen surface exchange effect is different by a factor of two, while the corresponding largest von Mises stresses on the permeate side are different by a factor of about four. In general, the presence of oxygen surface exchange resistance and reduced membrane thickness lower the chemically induced stresses.