Effect of Processing Variables on the Structural Evolution of Silica Gels

E Drabarek; John R Bartlett; H J M Hanley; J L Woolfrey; C D Muzny

doi:10.1023/A:1013905110885

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Effect of Processing Variables on the Structural Evolution of Silica Gels

Journal article

Peer reviewed

Effect of Processing Variables on the Structural Evolution of Silica Gels

E Drabarek, John R Bartlett, H J M Hanley, J L Woolfrey and C D Muzny

International Journal of Thermophysics, Vol.23(1), pp.145-160

2002

DOI: https://doi.org/10.1023/A:1013905110885

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Abstract

Classical Physics

Physical Chemistry (incl. Structural)

Rheology

gelation mechanism

gel point

gel structure

restructuring

silica

viscosity

viscoelasticity

Constant shear rate and dynamic rheological measurements have been used to investigate the effect of shear on the processes controlling the structural evolution (size and volume fraction of clusters and the extent of cluster-cluster cross-linking) during the gelation of colloidal silica sols. In the absence of shear, the storage and loss moduli (Gâ€² and Gâ€³, respectively) initially increase slowly prior to gelation, indicating that cluster growth and network formation are initially proceeding slowly, but then the system evolves rapidly, with cluster growth occurring at a slightly faster rate than network formation. In contrast, sols presheared for 4 h prior to gelation exhibit rapid increases in both Gâ€² and Gâ€² immediately after cessation of the applied shear, reflecting significant differences in the evolution of the gel structure. On aging, the viscoelastic properties of the unsheared and presheared samples are similar, indicating that their structures are comparable on the length scales (several microns) being probed by the frequency range used here. However, their chemical and microstructural properties differ significantly, due to differences in the intercluster bonds. The effect of shear rate, initial pH, colloid particle size, and volume fraction on the structure of the resulting sols and gels is discussed.

Details

Title: Effect of Processing Variables on the Structural Evolution of Silica Gels
Authors: E Drabarek (Author) - Australian Nuclear Science and Technology Organisation Materials Department
John R Bartlett (Author) - Australian Nuclear Science and Technology Organisation Materials Department
H J M Hanley (Author) - National Institute of Standards and Technology, United States
J L Woolfrey (Author) - Australian Nuclear Science and Technology Organisation Materials Department
C D Muzny (Author) - National Institute of Standards and Technology, United States
Publication details: International Journal of Thermophysics, Vol.23(1), pp.145-160
Publisher: Springer New York LLC
Date published: 2002
DOI: 10.1023/A:1013905110885
ISSN: 0195-928X
Organisation Unit: School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland
Language: English
Record Identifier: 99447767302621
Output Type: Journal article

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Collaboration types: Domestic collaboration; International collaboration
Web Of Science research areas: Chemistry, Physical; Mechanics; Physics, Applied; Thermodynamics