Article

# Phase diagram of mixtures of hard colloidal spheres and discs: a free-volume scaled-particle approach.

Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584CH Utrecht, The Netherlands.

The Journal of Chemical Physics (Impact Factor: 3.12). 03/2004; 120(5):2470-4. DOI: 10.1063/1.1637573 Source: PubMed

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**ABSTRACT:**Using a geometry-based fundamental measure density functional theory, we calculate bulk fluid phase diagrams of colloidal mixtures of vanishingly thin hard circular platelets and hard spheres. We find isotropic-nematic phase separation, with strong broadening of the biphasic region, upon increasing the pressure. In mixtures with large size ratio of platelet and sphere diameters, there is also demixing between two nematic phases with differing platelet concentrations. We formulate a fundamental measure density functional for mixtures of colloidal platelets and freely overlapping spheres, which represent ideal polymers, and use it to obtain phase diagrams. We find that, for low platelet-polymer size ratio, in addition to isotropic-nematic and nematic-nematic phase coexistence, platelet-polymer mixtures also display isotropic-isotropic demixing. By contrast, we do not find isotropic-isotropic demixing in hard-core platelet-sphere mixtures for the size ratios considered.Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 04/2013; 371(1988):20120259. · 2.86 Impact Factor -
##### Article: Capillary nematization of hard colloidal platelets confined between two parallel hard walls

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**ABSTRACT:**We use density functional theory to study the capillary phase behaviour of a discotic system of colloidal platelets that are confined in a planar slit pore. The model plates have circular shape, continuous orientations and vanishing thickness; they interact via hard-core repulsion with each other and with the walls which induces homeotropic wall anchoring of the nematic director. We find that the isotropic–nematic capillary binodal is shifted to lower values of the chemical potential as compared to bulk isotropic–nematic coexistence. Capillary isotropic–nematic coexistence vanishes below a critical wall separation distance which is significantly larger than it is in a reference system of thin hard (Onsager) rods confined between two parallel hard walls that act on the particle centres.Journal of Physics Condensed Matter 07/2007; 19(32):326103. · 2.22 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Based upon Green–Kubo linear response theory, we use the exact expression for the heat flux vector of the base fluid plus nanoparticle system to estimate the contribution of nanoparticle Brownian motion to thermal conductivity. We find that its contribution is too small to account for abnormally high reported values. The possibility of convection caused by Brownian particles is also found to be unlikely. We have estimated the mean free path and the transition speed of phonons in nanofluid through density functional theory. We found a layer structure can form around the nanoparticles and the structure does not further induce fluid–fluid phase transition in the bulk fluid. By analyzing the compressibility of the fluid, we have also investigated the sound speed in the nanofluid. For the models of an asymmetric hard sphere mixture representing the single spherical nanoparticles and a mixture of rods and hard spheres representing aggregates, both suspended in the fluid, we found that for the very low volume fraction cases, the compressibility changes little. This shows that the speed of phonon transition does not change due to the addition of nanoparticles of either type. Our results indicate that, besides the enhancement due to the high thermal conductivity of nanoparticles themselves, fluid molecules make no evident contribution to the enhancement of thermal conductivity attributable to the presence of the nanoparticles at volume fractions less than 5%.International Journal of Heat and Mass Transfer 03/2008; 51(s 5–6):1342–1348. · 2.52 Impact Factor

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