Micron-scale restructuring of gelling silica subjected to shear.
J Colloid Interface Sci
; 533: 136-143, 2019 Jan 01.
Article
em En
| MEDLINE
| ID: mdl-30165295
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 7â¯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, 1.0â¯×â¯10-3â¯≤â¯q/nmâ¯≤â¯7.3â¯×â¯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.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article