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Rheological characterization of yield stress gels formed via electrostatic heteroaggregation of metal oxide nanoparticles

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Abstract

Mixtures of fumed fractal metal oxide nanoparticles (np's) dispersed in water, at a solution pH where one species is positively charged and the other is negatively charged, form yield stress gels at volume fractions as low as 1.5%, due to electrostatic heteroaggregation into networks as confirmed by small-angle neutron scattering. These gels exhibit a measurable yield stress and an apparent viscosity that follows a power law relationship with shear rate. Rotational and oscillatory shear rheology is presented for binary mixtures of fumed silica, fumed alumina, and fumed titania in aqueous dispersions. Gels were characterized at various particle concentrations, solution pHs, mixture ratios, and salt concentrations. The strength of the gel network, as evaluated by the storage modulus and yield stress, is maximized when the mixture contains a mixture of particles with an approximately equal, but opposite, number of charged groups.

Graphical abstract: Rheological characterization of yield stress gels formed via electrostatic heteroaggregation of metal oxide nanoparticles

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Publication details

The article was received on 24 May 2017, accepted on 10 Aug 2017 and first published on 18 Aug 2017


Article type: Paper
DOI: 10.1039/C7SM01035D
Citation: Soft Matter, 2017, Advance Article
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    Rheological characterization of yield stress gels formed via electrostatic heteroaggregation of metal oxide nanoparticles

    J. S. Weston, J. H. Harwell and B. P. Grady, Soft Matter, 2017, Advance Article , DOI: 10.1039/C7SM01035D

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