scholarly journals Gas Permeability of the Epiphragm of a Terrestrial Snail, Otala lactea

1983 ◽  
Vol 56 (3) ◽  
pp. 436-444 ◽  
Author(s):  
M. Christopher Barnhart
Keyword(s):  
Gas Permeability ◽  
Terrestrial Snail ◽  
Otala Lactea

Uric acid synthesis in the terrestrial snail, Otala lactea

1965 ◽  
Vol 15 (4) ◽  
pp. 457-468 ◽  
Author(s):  
Thomas W. Lee ◽  
James W. Campbell
Keyword(s):  
Uric Acid ◽  
Acid Synthesis ◽  
Terrestrial Snail ◽  
Otala Lactea

ANALYSIS OF GAS PERMEABILITY FOR LIQUID PHASE-SINTERED POROUS SiC COMPACT

2014 ◽  
Vol 17 (8) ◽  
pp. 705-713 ◽  
Author(s):  
Hikaru Maeda ◽  
Yoshihiro Hirata ◽  
Soichiro Sameshima ◽  
Taro Shimonosono
Keyword(s):  
Liquid Phase ◽  
Gas Permeability ◽  
Porous Sic

Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers

2020 ◽  
Author(s):  
Adlai Katzenberg ◽  
Debdyuti Mukherjee ◽  
Peter J. Dudenas ◽  
Yoshiyuki Okamoto ◽  
Ahmet Kusoglu ◽  
...  
Keyword(s):  
Rate Constant ◽  
Sulfonic Acid ◽  
Mass Fraction ◽  
Gas Permeability ◽  
Transport Processes ◽  
Segmental Mobility ◽  
The Matrix ◽  
Swelling Rate ◽  
Ion Conducting ◽  
Perfluorinated Sulfonic Acid

<p>Limitations in fuel cell electrode performance have motivated the development of ion-conducting binders (ionomers) with high gas permeability. Such ionomers have been achieved by copolymerization of perfluorinated sulfonic acid (PFSA) monomers with bulky and asymmetric monomers, leading to a glassy ionomer matrix with chemical and mechanical properties that differ substantially from common PFSA ionomers (e.g., Nafion™). In this study, we use perfluorodioxolane-based ionomers to provide fundamental insights into the role of the matrix chemical structure on the dynamics of structural and transport processes in ion-conducting polymers. Through <i>in-situ</i> water uptake measurements, we demonstrate that ionomer water sorption kinetics depend strongly on the properties and mass fraction of the matrix. As the PFSA mass fraction was increased from 0.26 to 0.57, the Fickian swelling rate constant decreased from 0.8 s<sup>-1</sup> to 0.2 s<sup>-1</sup>, while the relaxation rate constant increased from 3.1×10<sup>-3</sup> s<sup>-1</sup> to 4.0×10<sup>-3</sup>. The true swelling rate, in nm s<sup>-1</sup>, was determined by the chemical nature of the matrix; all dioxolane-containing materials exhibited swelling rates ~1.5 - 2 nm s<sup>-1</sup> compared to ~3 nm s<sup>-1</sup> for Nafion. Likewise, Nafion underwent relaxation at twice the rate of the fastest-relaxing dioxolane ionomer. Reduced swelling and relaxation kinetics are due to limited matrix segmental mobility of the dioxolane-containing ionomers. We demonstrate that changes in conductivity are strongly tied to the polymer relaxation, revealing the decoupled roles of initial swelling and relaxation on hydration, nanostructure, and ion transport in perfluorinated ionomers. </p>

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