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The Influence of Microgravity on Silica Sol-Gel FormationWe discuss space-flight experiments involving the growth of silica particles and gels. The effect of microgravity on the growth of silica particles via the sol-gel route is profound. In four different recipes spanning a large range of the parameter space that typically produces silica nanoparticles in unit-gravity, low-density gel structures were instead formed in microgravity. The particles that did form were generally smaller and more polydisperse than those grown on the ground. These observations suggest that microgravity reduces the particle growth rate, allowing unincorporated species to form aggregates and ultimately gel. Hence microgravity favors the formation of more rarefied structures, providing a bias towards diffusion-limited cluster-cluster aggregation. These results further suggest that in unit gravity, fluid flows and sedimentation can significantly perturb sol-gel substructures prior to gelation and these deleterious perturbations may be "frozen" into the resulting microstructure. Hence, sol-gel pores may be expected to be smaller, more uniform, and less rough when formed in microgravity.
Document ID
20010021264
Document Type
Preprint (Draft being sent to journal)
Authors
Sibille, L. (NASA Marshall Space Flight Center Huntsville, AL United States)
Smith, D. D. (NASA Marshall Space Flight Center Huntsville, AL United States)
Cronise, R. (NASA Marshall Space Flight Center Huntsville, AL United States)
Hunt, A. J. (NASA Marshall Space Flight Center Huntsville, AL United States)
Wolfe, D. B. (NASA Marshall Space Flight Center Huntsville, AL United States)
Snow, L. A. (NASA Marshall Space Flight Center Huntsville, AL United States)
Oldenberg, S. (NASA Marshall Space Flight Center Huntsville, AL United States)
Halas, N. (NASA Marshall Space Flight Center Huntsville, AL United States)
Rose, M. Franklin
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Subject Category
Space Processing
Meeting Information
Aerogels(Albuquerque, NM)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.