%0 Journal Article
%K model
%K transportation
%K polymer electrolytes
%K electrolyte fuel-cells
%K in-situ
%K liquid water
%K microchannel plate detectors
%K nafion
%K schroeders-paradox
%K x-ray-scattering
%A Daniel S Hussey
%A Dusan Spernjak
%A Adam Z Weber
%A Rangachary Mukundan
%A Joseph Fairweather
%A Eric L Brosha
%A John Davey
%A Jacob S Spendelow
%A David L Jacobson
%A Rodney L Borup
%B Journal of Applied Physics
%D 2012
%N 10
%P 104906
%R 10.1063/1.4767118
%T Accurate measurement of the through-plane water content of proton-exchange membranes using neutron radiography
%V 112
%8 11/2012
%! J. Appl. Phys.
%X <p>The water sorption of proton-exchange membranes (PEMs) was measured <em>in situ</em> using high-resolution neutron imaging in small-scale fuel cell test sections. A detailed characterization of the measurement uncertainties and corrections associated with the technique is presented. An image-processing procedure resolved a previously reported discrepancy between the measured and predicted membrane water content. With high-resolution neutron-imaging detectors, the water distributions across N1140 and N117 Nafion membranes are resolved in vapor-sorption experiments and during fuel cell and hydrogen-pump operation. The measured <em>in situ</em> water content of a restricted membrane at 80 degrees C is shown to agree with <em>ex situ</em> gravimetric measurements of free-swelling membranes over a water activity range of 0.5 to 1.0 including at liquid equilibration. Schroeder's paradox was verified by <em>in situ</em> water-content measurements which go from a high value at supersaturated or liquid conditions to a lower one with fully saturated vapor. At open circuit and during fuel cell operation, the measured water content indicates that the membrane is operating between the vapor-and liquid-equilibrated states.</p>