Effective interaction of charged platelets in aqueous solution: Investigations of colloid laponite suspensions by static light scattering and small-angle x-ray scattering
- Physikalische Chemie I, University of Bayreuth, 95440 Bayreuth (Germany)
- Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart (Germany) and Institut fuer Theoretische und Angewandte Physik, Universitaet Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart (Germany)
We study dilute aqueous solutions of charged disklike mineral particles (laponite) by a combination of static light scattering (SLS) and small-angle x-ray scattering (SAXS). Laponite solutions are known to form gels above a certain critical concentration that must be described as nonequilibrium states. Here we focus on the investigation by SLS and SAXS at concentrations below gelation (c<0.016 g/L) and at low concentrations of added salt (0.001M and 0.005M). Thus, we have obtained the scattering function of single Laponite platelets as well as the structure factor describing their interaction at finite concentration. A detailed analysis of the combined sets of data proves that the solutions are in a well-defined equilibrium state. Moreover, this analysis demonstrates the internal consistency and accuracy of the scattering functions obtained at finite concentrations. We find that laponite particles interact through an effective pair potential that is attractive on short range but repulsive on longer range. This finding demonstrates that Laponite solutions exhibit only a limited stability at the concentration of added salt used herein. Raising the ionic strength to 0.005M already leads to slow flocculation as is evidenced from the enhanced scattering intensity at smallest scattering angles. All data strongly suggest that the gelation occurring at higher concentration is related to aggregation.
- OSTI ID:
- 20709832
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 72, Issue 5; Other Information: DOI: 10.1103/PhysRevE.72.051504; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-651X
- Country of Publication:
- United States
- Language:
- English
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