title: Varying the counter ion changes the kinetics, but not the final structure of colloidal gels.
abstract: We show that, while the gelation of colloidal silica proceeds much faster in the presence of added KCl than NaCl, the final gels are very similar in structure and properties. We have studied the gelation process by visual inspection and by small angle X-ray scattering for a range of salt and silica particle concentrations. The characteristic times of the early aggregation process and the formation of a stress-bearing structure with both salts are shown to collapse onto master curves with single multiplicative constants, linked to the stability ratio of the colloidal suspensions. The influence of the salt type and concentration is confirmed to be mainly kinetic, as the static structure factors and viscoelastic moduli of the gels are shown to be equivalent at normalized times. While there is strong variation in the kinetics, the structure and properties of the gel at long-times are shown to be mainly controlled by the concentration of particles, and hardly influenced by the type or the concentration of salt. This suggests that the differences between gels generated by different salts are only transient in time.
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France; Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710072, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France.
authors.forename: Alesya
authors.initials: A
authors.lastname: Mikhailovskaya
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France.
authors.forename: Doru
authors.initials: D
authors.lastname: Constantin
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Foffi
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France; School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
authors.forename: Joseph
authors.initials: J
authors.lastname: Tavacoli
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Schmitt
authors.affiliation: Laboratoire des Interfaces Complexes et de l'Organisation Nanométrique, ECE Paris Ecole d'Ingénieurs, 37 Quai de Grenelle, F-75015 Paris, France; Laboratoire Léon Brillouin, CEA Saclay, UMR CNRS 12, 91191 Gif sur Yvette, France.
authors.forename: François
authors.initials: F
authors.lastname: Muller
authors.affiliation: CERMAV, UPR 5301 CNRS, BP 53, 38041 Grenoble Cedex 9, France.
authors.forename: Cyrille
authors.initials: C
authors.lastname: Rochas
authors.affiliation: Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710072, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Langevin
authors.affiliation: Laboratoire de Physique des Solides, CNRS, Univ. Paris Sud, Université Paris Saclay, 91405 Orsay, France. Electronic address: anniina.salonen@u-psud.fr.
authors.forename: Anniina
authors.initials: A
authors.lastname: Salonen
mesh_terms: D003102:Colloids / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D011189:Potassium Chloride / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry
chemical_list: D003102:Colloids; D005782:Gels; D007477:Ions; D012965:Sodium Chloride; D011189:Potassium Chloride; D012822:Silicon Dioxide
keywords: Colloids; Gel; SAXS; Salt effect