Seminar 2/23: Effects of Charged Nanoparticles on the Properties of Colloidal Dispersions

Department of Chemical Engineering
West Virginia University

Seminar

Effects of Charged Nanoparticles on the
Properties of Colloidal Dispersions

Dr. John Y. Walz
Professor and Head
Virginia Tech
Department of Chemical Engineering
133 Randolph Hall (M/C 0211)
Blacksburg, VA 24061

ABSTRACT

Controlling the stability of aqueous dispersions of colloidal particles is a critical issue in a variety of industrial processes, ranging from the production of paints and inks to the purification of drinking water. Over the past several years, we have been investigating the effects of macro-ions on the stability and behavior of a dispersion of larger, colloidal particles. Using the experimental tool of colloidal probe atomic force microscopy (CP-AFM), we have directly measured the effect of a variety of such macro-ions (e.g., charged nanoparticles, polyelectrolyte chains, ionic micelles) on the interaction force between colloidal particles. In addition to a short-range depletion attraction, the macro-ions can induce long-range structural forces between particles and surfaces that oscillate between attraction and repulsion and which can extend to several hundred nanometers. I will also present recent results on the effect of silica nanoparticles on the phase behavior of dispersions of disk-shaped, kaolinite particles. It has been found that the nanoparticles induce a transition to a gel phase in wh ich the clay particles are arranged in a ‘honeycomb-like' structure. The gels also show a unique ability to rejuvenate reproducibly after breakage by shear forces.

Friday, February 23, 2007 9:30am - 10:45am
Room 401, Engineering Sciences Building
Refreshments will be served at 9:15 am

Questions or Directions call: 304-293-2111, ext. 2418.

02/23/2007