The Effects of Added Nanoparticles on Aqueous Kaolinite Suspensions: I. Structural Effects

Abstract

The results of an experimental study focused on the effect of added silica nanospheres on the structure of an aqueous suspension of disc-shaped kaolinite particles are presented. In the absence of any additives, kaolinite particles rapidly aggregate and settle. When only nanoparticles were added to a 14% vol. kaolinite suspension, some stabilization was observed, although a thick, fluid-like sediment still formed. Adding both nanoparticles and salt (NaCl or KCl), however, caused the entire suspension to transition into a solid material that was strong enough to actually be sliced. A phase diagram was constructed showing the concentration of salt and nanoparticles needed to produce this transition. With smaller nanoparticles, the transition occurred at much lower nanoparticle volume fractions. Scanning electron micrographs of both the sediment and solid-like material, obtained by cryogenic drying, showed that the latter consisted of a porous, 'sponge-like' structure. The characteristic size of the pores decreased as the number density of the added nanoparticles increased. Although the nanoparticles were not visible in the SEM images, it is believed that they had separated into the pores of the solid-like material. While a similar type of transition could be produced in suspensions containing only the silica nanospheres, the structure and flow behavior of this material were markedly different from that obtained with the added clay. © 2005 Elsevier Inc. All rights reserved.

Department(s)

Mining Engineering

Keywords and Phrases

Clay Gels; Clay Suspensions; Liquid-Solid Phase Transition; Nanoparticle/Colloid Mixtures

International Standard Serial Number (ISSN)

0021-9797

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 Elsevier, All rights reserved.

Publication Date

01 Jan 2006

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