Formation of stable aggregates by fluid-assembled solid bridges
| Autor: | Ali Seiphoori, Paulo E. Arratia, Douglas J. Jerolmack, Xiaoguang Ma |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Length scale
Capillary pressure Materials science Static Electricity FOS: Physical sciences 02 engineering and technology Condensed Matter - Soft Condensed Matter 01 natural sciences evaporation Physics - Geophysics Soil Colloid solid bridges 0103 physical sciences Cohesion (geology) Colloids Particle Size aggregate stability Thermal equilibrium Multidisciplinary Capillary bridges 010304 chemical physics 021001 nanoscience & nanotechnology Grain size Geophysics (physics.geo-ph) Applied Physical Sciences cohesion Chemical physics Physical Sciences Hydrodynamics Soft Condensed Matter (cond-mat.soft) Particle 0210 nano-technology |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1913855117 |
| Popis: | Significance Fine particles are light and reactive, leading them to aggregate under a range of conditions. Here we directly observe the particle-scale assembly of aggregates formed by evaporation, determine their stability during rewetting, and measure their interparticle bonding strength. Particles segregate by size due to capillary forces to form remarkable fractal structures. We discover that particle size, and not material properties, controls the cohesive strength of these aggregates, and we use physical principles to explain why. Results provide a view on the granular origins of cohesion that may improve our understanding of the mechanics of particulate materials with applications ranging from landslides to pharmaceuticals. When a colloidal suspension is dried, capillary pressure may overwhelm repulsive electrostatic forces, assembling aggregates that are out of thermal equilibrium. This poorly understood process confers cohesive strength to many geological and industrial materials. Here we observe evaporation-driven aggregation of natural and synthesized particulates, probe their stability under rewetting, and measure bonding strength using an atomic force microscope. Cohesion arises at a common length scale (∼5 μm), where interparticle attractive forces exceed particle weight. In polydisperse mixtures, smaller particles condense within shrinking capillary bridges to build stabilizing “solid bridges” among larger grains. This dynamic repeats across scales, forming remarkably strong, hierarchical clusters, whose cohesion derives from grain size rather than mineralogy. These results may help toward understanding the strength and erodibility of natural soils, and other polydisperse particulates that experience transient hydrodynamic forces. |
| Databáze: | OpenAIRE |
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