Properties of Water in Prestretched Recast Nafion
Bibliographic record
Abstract
Uniaxially prestretched recast Nafion membranes exhibited an unusual combination of properties (a proton conductivity equal to that of commercial Nafion but with a lower methanol permeability) which make them ideal candidates for use in a direct liquid methanol fuel cell. To better understand the function and underlying morphology of the prestretched membranes, water uptake and mobility data were collected and analyzed for draw ratios ranging from 1 to 7. Macroscopic (gravimetric) water uptake and the water self-diffusion coefficient (measured by NMR) were found to be invariant with membrane elongation and essentially identical to those measured in a commercial Nafion 117 film (a similar behavior was observed for proton conductivity). The ratio of freezable/nonfreezable water in prestretched recast Nafion, the water electro-osmotic drag coefficient, and the spin−lattice relaxation time constant of deuterated water, however, decreased with increasing film elongation, up to a draw ratio of 4. The functional dependence of these properties on draw ratio was similar to that observed for methanol permeability. The combined water results indicated that there were a greater number of smaller ionic/hydrophilic domains in prestretched recast Nafion as compared to commercial Nafion. Transmission electron microscopy of membrane cross sections confirmed this conclusion.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".