Utilization of prompt‐γ neutron activation analysis in the evaluation of Nafion membranes

Abstract

Researchers have performed evaluations on Nafion membranes for many years. An important aspect of the membranes is their chemical composition and uniformity. One technique that could provide accurate and fast quantitative measurements of the chemical composition and water within the membranes is prompt‐γ neutron activation analysis (PGAA). In this work, PGAA was applied to the chemical characterization of Nafion membranes in various forms. The evaluation confirmed the necessity of pretreatment of the membranes for the elimination of contamination. A series of counterion‐exchanged membranes were examined so that we could determine the degree of conversion achieved under different conditions and residual water levels. The results indicated that the type of counterion was an important factor determining conversion levels, that partial conversion could be achieved, and that counterion displacement could be forced to occur in certain environments. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1485–1492, 2003

Small‐angle neutron scattering investigation of structural changes in nafion membranes induced by swelling with various solvents

“…All membranes were preconditioned and converted into the sulfonic acid form in an initialization procedure reported previously by Mauritz et al18 Membranes were exchanged to the acid form through refluxing in 50/50 (v/v) HCl/HNO 3 solutions, the leaching of excess acid in deionized water reflux (3×), and vacuum drying at 125 °C. All membranes were changed into this standard initial state before counterion exchange and were evaluated with prompt γ‐activation analysis to ensure maximum sample reproducibility 19…”

New Insights into Perfluorinated Sulfonic-Acid Ionomers

“…Historically, these studies are related to (i) transport of alkali ions in PFSA (Li + , K + , and Na + ), (ii) alkaline-earth metals (Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ ), with more of a focus on their impact on thermal stability, and (iii) transition metals (Fe 3+ , Mn 2+ , Ni 2+ , Cu 2+ , and Zn 2+ ), including their binary compositions in the membrane. ,,, Reversible ion-exchange up to 95 to 100% has been shown to occur through immersion of the ionomer into a saturated solution at ambient conditions, with divalent and trivalent cations having a higher exchange level with respect to initial form (99%) vs monovalent ones (∼94%), resulting from their stronger interactions as discussed above. There exists a fair amount of studies focusing on the impact of cations on a PFSA membrane’s water uptake and structure-sorption relationship, ,,,,,,,,,,,,, thermal decomposition and stability, ,,,,,,− gas permeability, ,,, density, ,, mechanical properties, ,,,,, thermal transitions, ,,,,,,,,,,,,,, conductivity, transference numbers, and mobility, ,,,,,,,,,,,, ionic self-diffusion, ,, free volume, water permeability, ,,…”

Measurement Of Hydrogen In Advanced Materials By Cold Neutron Prompt Gamma-ray Activation Analysis

“…Measurement of the H/S ratios in these materials has yielded vital information needed to improve the synthesis of these materials. 16 …”