A new method for measuring the adsorption induced stresses of zeolite films using magnetoelastic sensors

A new method is presented for measuring the stresses imposed on a substrate from a zeolite membrane either due to the synthesis of the zeolite film or due to adsorption induced strains. The resonance and anti-resonance frequencies of a zeolite/Metglas ribbon were measured and were related to the stress imposed on Metglas using the phenomenological theory of magnetoelasticity. The adsorption of water in FAU and LTA films were selected as representative systems to be studied. For both zeolite membranes, the stress had a non monotonic dependence (passed through a minimum) on water loading. The measured stresses are in qualitative agreement with the literature data about changes of the zeolite unit cell size as a function of humidity. The developed methodology is general and it can be used for measuring strains due to adsorption in any microporous film as long as it can be deposited as uniform layer on a magnetoelastic ribbon