Structure and Yielding of Colloidal Silica Gels Varying the Range of Interparticle Interactions

Research output: Contribution to journalArticle

Abstract

The relationship between interaction range, structure, fluid-gel transition, and viscoelastic properties of silica dispersions at intermediate volume fraction, φv ≈ 0.1 and in alkaline conditions, pH = 9 was investigated. For this purpose, rheological, physicochemical, and structural (synchrotron-SAXS) analyses were combined. The range of interaction and the aggregation state of the dispersions were tuned by adding either divalent counterions (Ca2+) or polycounterions (PDDA). With increasing calcium chloride concentration, a progressive aggregation was observed which precludes a fluid-gel transition at above 75 mM of calcium chloride. In this case, the aggregation mechanism is driven by short-range ion-ion correlations. Upon addition of PDDA, a fluid-gel transition, at a much lower concentration, followed by a reentrant gel-fluid transition was observed. The gel formation with PDDA was induced by charge neutralization and longer range polymer bridging interactions. The refluidification at high PDDA concentrations was explained by the overcompensation of the charge of the silica particles and by the steric repulsions induced by the polycation chains. Rheological measurements on the so-obtained gels reveal broad yielding transition with two steps when the size of the silica particle clusters exceeds ≈0.5 μm.

Details

Authors
  • Fabrice Brunel
  • Isabelle Pochard
  • Sandrine Gauffinet
  • Martin Turesson
  • Christophe Labbez
Organisations
External organisations
  • University of Burgundy - Franche-Comté
  • The French National Centre for Scientific Research (CNRS)
  • University of Burgundy
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Chemistry
Original languageEnglish
Pages (from-to)5777-5785
Number of pages9
JournalJournal of Physical Chemistry B
Volume120
Issue number25
Publication statusPublished - 2016 Jun 30
Publication categoryResearch
Peer-reviewedYes