Gel formation and aging in weakly attractive nanocolloid suspensions at intermediate concentrations
Bibliographic record
Abstract
We report x-ray photon correlation spectroscopy (XPCS) and rheometry experiments to study the temporal evolution of gel formation and aging in suspensions of silica nanocolloids possessing a tunable short-range attraction. The colloid volume fractions, φ = 0.20 and 0.43, are below the glass regime at high concentration and above the fractal regime at low concentration. Following a sudden initiation of the interparticle attraction, the suspensions display a protracted latency period in which they remain fluid before acquiring a measurable elastic shear modulus. The duration of the latency period and the subsequent rate of increase of the modulus vary strongly with the strength of the attraction. The XPCS results indicate dynamic heterogeneity among the colloids during this gel formation in which a growing fraction of the particles become localized. The temporal evolution of this localization correlates with that of the rheology. In particular, the time scale over which the fraction of localized particles increases tracks the duration of the latency period. Also, at φ = 0.20 the localization length characterizing the motion of the localized fraction scales onto the shear modulus with no free parameters as predicted by a self-consistent theory based on mode coupling [K. S. Schweizer and G. Yatsenko, J. Chem. Phys. 127, 164505 (2007)], while deviations from the predicted scaling at φ = 0.43 are observed near the gel point. The XPCS results also reveal slow, hyperdiffusive motion of the colloids in the newly formed gels that is attributed to strain from the relaxation of internal stress. While some features of this motion correlate with the evolving rheology, others appear decoupled from the macroscopic mechanical behavior.
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How this classification was reachedexpand
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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 | 0.000 |
| 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".