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Dynamics of Disorder-Order Transitions in Hard Sphere Colloidal Dispersions in micro-gWe performed a series of experiments on 0.518 millimeter PMMA spheres suspended in an index matching mixture of decalin and tetralin the microgravity environment provided by the Shuttle Columbia on mission STS-73. The samples ranged in concentration from 0.49 to 0.62. volume fraction (phi) of spheres, which covers the range in which liquid, coexistence, solid and glass phases are expected from Earth bound experiments. Light scattering was used to probe the static structure, and the particle dynamics. Digital and 35 mm photos provided information on the morphology of the crystals. In general, the crystallites grew considerably larger (roughly an order of magnitude larger) than the same samples with identical treatment in 1 g. The dynamic light scattering shows the typical short time diffusion and long time caging effects found in 1 g. The surprises that were encountered in microgravity include the preponderance of random hexagonal close packed (RHCP) structures and the complete absence of the expected face centered cubic (FCC) structure, existence of large dendritic crystals floating in the coexistence samples (where liquid and solid phases coexist) and the rapid crystallization of samples which exist only in glass phase under the influence of one g. These results suggest that colloidal crystal growth is profoundly effected by gravity in yet unrecognized ways. We suspect that the RCHP structure is related to the nonequilibrium growth that is evident from the presence of dendrites. An analysis of the dendritic growth instabilities is presented within the framework of the Ackerson-Schatzel equation.
Document ID
19970000422
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Zhu, J. X.
(Princeton Univ. NJ United States)
Li, M.
(Princeton Univ. NJ United States)
Phan, S. E.
(Princeton Univ. NJ United States)
Russel, W. B.
(Princeton Univ. NJ United States)
Chaikin, Paul M.
(Princeton Univ. NJ United States)
Rogers, Rick
(NASA Lewis Research Center Cleveland,OH United States)
Meyers, W.
(NASA Lewis Research Center Cleveland,OH United States)
Date Acquired
August 17, 2013
Publication Date
September 1, 1996
Publication Information
Publication: Third Microgravity Fluid Physics Conference
Subject Category
Materials Processing
Accession Number
97N10389
Funding Number(s)
CONTRACT_GRANT: NAG3-1762
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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