Yield stress measurements and microstructure of colloidal kaolin powders clusterized and dispersed in different liquids--颗粒学报PARTICUOLOGY

Beruto, D. T., Lagazzo, A., Botter, R., & Grillo, R. (2009). Yield stress measurements and microstructure of colloidal kaolin powders clusterized and dispersed in different liquids. Particuology, 7(6), 438–444. https://doi.org/10.1016/j.partic.2009.06.011

Yield stress measurements and microstructure of colloidal kaolin powders clusterized and dispersed in different liquids

Dario T. Beruto ^a *, Alberto Lagazzo ^a, Rodolfo Botter ^a, Roberto Grillo ^b

a Department of Civil, Environmental and Architectural Engineering (DICAT), University of Genoa, P.le Kennedy (Fiera del Mare), Pad. D, 16129 - Genoa, Italy
b Artigo S.p.A., loc. Carpeneto, 17014 - Cairo Montenotte (SV), Italy

10.1016/j.partic.2009.06.011

Volume 7, Issue 6, December 2009, Pages 438-444

Received 16 March 2009, Revised 9 June 2009, Accepted 14 June 2009, Available online 15 October 2009.

E-mail: dabe@unige.it

Highlights

Abstract

Rheological measurements of four colloidal kaolin powders dispersed in water, paraffinic oil and liquid rubber have been done at solid concentration θ (V_S/V_L) in the range 8–33%. In quasi-static conditions the yield stress τ° values were derived. An S-shaped relationship between τ° and θ exists, that allows to evaluate the percolation threshold θ_c values. In water θ_c ranges between 29% and 33%, while it is between 17% and 21% in oil and in liquid rubber. In water the microstructure units, i.e. the primary clusters among kaolin crystallites, are denser and bigger than the ones in the two other liquids. Furthermore, in quasi-static condition, the aqueous microstructure units have less tendency to cling together to form a network that can span all over the liquid phase. The different kaolin dispersions at θ equal to 22% are characterized by yield stress ranging between 7.5 Pa and 59 Pa in water, 66–250 Pa in oil and 230–770 Pa in liquid rubber. It has been found that for any kaolin types the ∂logτ°/∂θ evaluated near to the percolation threshold is a conservative parameter of the three different liquids. These results are useful to design colloidal dispersions with selected microstructure.

Graphical abstract

Keywords

Yield stress; Colloid; Dispersions; Microstructure units; Cluster; Kaolin; Rheology

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