Micron-scale restructuring of gelling silica subjected to shear

Liliana de Campo, Christopher J. Garvey*, Chris D. Muzny, Christine Rehm, Howard J.M. Hanley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Hypothesis/objective: We examine the time dependent viscometric behavior of a well-defined system of gelling colloidal silica and how this behavior may be understood from a simple theoretical model which incorporates the microstructure of the gel. The ultra-small angle neutron scattering (USANS) technique is used to interrogate structure during the gelation process. Experiments: The investigations focused on a system where both particles and interactions are well-defined: 7 nm silica particle acid-treated aqueous solution subjected to a constant applied shear in Couette geometry. Ultra-small angle neutron scattering (USANS) time-dependent scattering intensities were measured at wave vectors, q, in the range, 1.0 × 10−3 ≤ q/nm ≤ 7.3 × 10−2 coupled with viscosity data recorded simultaneously. The interpretation of the USANS scattering data is reliant on an isotropic sample. This assumption has been investigated, over a limited range of scattering vectors, using more suitable small angle neutron scattering (SANS) instrumentation with a restricted q-range. Findings: The first recorded direct kinetic measurements of the micron-scale structure in a gelling system. A critical micro-structural feature of the intensity-viscosity time behavior of a gelling colloid subjected to a shear is the cluster size. A viscosity/intensity coupling observed at the time of a viscosity maximum that corresponds to a time-dependent critical stress and speculated to be independent of the wave vector over a wide q-range.

Original languageEnglish
Pages (from-to)136-143
Number of pages8
JournalJournal of Colloid and Interface Science
Volume533
DOIs
StatePublished - 1 Jan 2019

Keywords

  • Anisotropy
  • Colloidal silica
  • Gelation
  • Kinetics
  • Micron length scale
  • Shear
  • USANS
  • Viscosity

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