Accurate measurement of the through-plane water content of proton-exchange membranes using neutron radiography
Date Published |
11/2012
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Publication Type | Journal Article
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Authors | |
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DOI |
10.1063/1.4767118
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Abstract |
The water sorption of proton-exchange membranes (PEMs) was measured in situ 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 in situ water content of a restricted membrane at 80 degrees C is shown to agree with ex situ 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 in situ 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. |
Journal |
Journal of Applied Physics
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Volume |
112
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Year of Publication |
2012
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Issue |
10
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Pagination |
104906
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ISSN Number |
00218979
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Short Title |
J. Appl. Phys.
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