Slow aggregation of colloidal silica

Journal Article · Thu Oct 01 04:00:00 EDT 1987 · Phys. Rev. A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.36.3415· OSTI ID:6039074

Martin, J E

We report the results of elastic and quasielastic light scattering measurements on dilute aggregates of colloidal silica. The elastic scattering measurements indicate a fractal dimension of 2.05 +- 0.06, in agreement with previous results, but the quasielastic measurements demonstrate several novel characteristics. First, it is found that the linewidth GAMMA scales as a fractional power, GAMMA--q/sup 2.7/, of the momentum transfer q. Second, the inverse average relaxation time, defined as the integral of the field autocorrelation function, does not scale with the same power of q as the linewidth, implying that the autocorrelation functions cannot be scaled by a single nondimensioned time. Third, ''stretched'' exponential behavior is found for the long-time behavior of the autocorrelation function. These observations are interpreted in terms of a power-law polydisperse ensemble of aggregate clusters, with a number distribution of the form N(m)--m/sup -//sup tau/, where tau = 1.9--2. Finally, the kinetics of growth are studied and the average radius is found to grow exponentially with time. These results are shown to be consistent, in part, with the predictions of the Smoluchowski equation and with simulations of aggregation.

• Research Organization: Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-5800
• OSTI ID: 6039074
• Journal Information: Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 36:7; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
AGGLOMERATION
CHALCOGENIDES
COLLOIDS
DIRECT REACTIONS
DISPERSIONS
GEOMETRY
KINETICS
LIGHT SCATTERING
MATHEMATICS
MINERALS
NUCLEAR REACTIONS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
QUASI-ELASTIC SCATTERING
QUASI-FREE REACTIONS
SCALE DIMENSION
SCATTERING
SILICA
SILICON COMPOUNDS
SILICON OXIDES