Crystallization kinetics of polydisperse colloidal hard spheres. II. Binary mixtures

Martin, S.; Bryant, Gary; Megen, W. van

doi:10.1103/physreve.71.021404

Cited by 42 publications

(39 citation statements)

References 21 publications

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“…Polydispersities above 6% destabilize the crystal phases 11,12 (10% in 2D 10 ), hence additional intraspecies fractionation is expected for strongly polydisperse systems 13,14 . Indications of polydispersity altered solidification dynamics have been observed in several HS experiments 15,16 including subtle influences of the skewness of the size distribution 17 1,2,7,18,19 and also the general sequence of phase diagram types was confirmed 20 , most parts of the phase diagram escape from a detailed experimental investigation; e.g., the exact locations of phase boundaries in compound forming systems have not yet been determined. Moreover, crystallization kinetics have not been obtained and, except for a recent 2D-study 21 , fractionation into coexisting Land S-crystals has not yet been observed.…”

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confidence: 99%

Polymer-enforced crystallization of a eutectic binary hard sphere mixture

et al. 2012

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We prepared a buoyancy matched binary mixture of polydisperse polystyrene microgel spheres of size ratio Γ = 0.785 at a volume fraction of Φ = 0.567 just below the kinetic glass transition. In line with theoretical expectations, a eutectic phase behaviour was observed, but only a minor fraction of the samples crystallized at all. By adding a short non-adsorbing polymer we enforce interspecies fractionation into coexisting pure component crystals, which in turn also shows signs of intra-species fractionation. We show that in formerly inaccessible regions of the phase diagram binary hard sphere physics are made observable using attractive hard spheres.Binary colloidal mixtures are valuable model systems for fundamental studies of crystallization [1][2][3] . Detailed predictions of their phase behaviour exist for hard sphere (HS) systems of different size ratio Γ = R S /R L (where R i are the radii of small (S) and large (L) spheres, respectively). These show a sequence of spindle to azeotropic to eutectic phase diagram types with decreasing Γ, vanishing miscibility in the crystal phase for Γ < 0.85 and a huge variety of crystal structures for compounds [4][5][6][7][8][9] . For zero miscibility eutectics the inter-species fractionation is expected to cause a pronounced slowing of nucleation 8 . Polydispersities above 6% destabilize the crystal phases 11,12 (10% in 2D 10 ), hence additional intraspecies fractionation is expected for strongly polydisperse systems 13,14 1,2,7,18,19 and also the general sequence of phase diagram types was confirmed 20 , most parts of the phase diagram escape from a detailed experimental investigation; e.g., the exact locations of phase boundaries in compound forming systems have not yet been determined. Moreover, crystallization kinetics have not been obtained and, except for a recent 2D-study 21 , fractionation into coexisting Land S-crystals has not yet been observed. One main reason for this is the interference of crystallization with the glass transition (GT) at large volume fractions 22 . Furthermore, gravity seemingly enhances the trend to dynamically arrest the systems 23 . In addition, it may lead to differential sedimentation and inhomogeneities in composition 24,25 .In the present paper we avoid sedimentation using a binary mixture of buoyancy matched microgel particles. We further exploit earlier observations on a variety of systems, in which both vitrification can be suppressed [26][27][28] and crystallization be accelerated 29 by adding a short chained, non adsorbing polymer. Doing so, one moves from HS to attractive HS (AHS), which in principle may significantly alter both phase behaviour and crystallization kinetics [30][31][32][33][34][35][36][37] . However, using a binary AHS mixture at a size ratio of Γ = 0.785 we here give the first demonstration of the simultaneous precipitation of S-and L-crystals over the full range of compositions. Thus, we recover the zero miscibility eutectic solidification process expected for pure HS. Moreover, we provide experimental support...

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Polymer-enforced crystallization of a eutectic binary hard sphere mixture

et al. 2012

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“…Two exemplary cases have been studied by light scattering in systems of monodisperse HS particles with an additional fraction (1-3%) of larger or smaller particles [90]; the size ratio of the small and large particles was α = r B /r A = 0.82. The crystallinity (fraction of the sample that gives rise to Bragg scattering), the position of the first Bragg peak and the average crystal size were determined.…”

Section: Polydispersitymentioning

confidence: 99%

Crystallization in three- and two-dimensional colloidal suspensions

Gasser

2009

J. Phys.: Condens. Matter

234

242

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Despite progress in the understanding of crystal nucleation and crystal growth since the first theories for nucleation were developed, an exact quantitative prediction of the nucleation rates in most systems has remained an unsolved problem. Colloidal suspensions show a phase behavior that is analogous to atomic or molecular systems and serve accordingly as ideal model systems for studying crystal nucleation with an accuracy and depth on a microscopic scale that is hard to reach for atomic or molecular systems. Due to the mesoscopic size of colloidal particles they can be studied in detail on the single-particle level and their dynamics is strongly slowed down in comparison with atomic or molecular systems, such that the formation of a crystal nucleus can be followed in detail. In this review, recent progress in the study of homogeneous and heterogeneous crystal nucleation in colloids and the controlled growth of crystalline colloidal structures is reviewed. All this work has resulted in unprecedented insights into the early stage of nucleation and it is also relevant for a deeper understanding of soft matter materials in general as well as for possible applications based on colloidal suspensions.

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“…51,52 The crystallization kinetics of polydisperse colloidal hard spheres were reported by van Megen et al 53,54 Here, we restrict ourselves to mention the details of the data evaluation applied within the present study, focused on bi-disperse charged silica spheres. Since the colloidal crystals formed are that of an substitutional alloy, with no observable superstructure formation present, the evaluation scheme used for single-component systems applies.…”

Section: Evaluation Of Key Parameters Of Nucleationmentioning

confidence: 90%

Nucleation and crystal growth in a suspension of charged colloidal silica spheres with bi-modal size distribution studied by time-resolved ultra-small-angle X-ray scattering

Hornfeck

Menke

Forthaus

et al. 2014

The Journal of Chemical Physics

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A suspension of charged colloidal silica spheres exhibiting a bi-modal size distribution of particles, thereby mimicking a binary mixture, was studied using time-resolved ultra-small-angle synchrotron X-ray scattering (USAXS). The sample, consisting of particles of diameters d(A) = (104.7 ± 9.0) nm and d(B) = (88.1 ± 7.8) nm (d(A)/d(B) ≈ 1.2), and with an estimated composition A(0.6(1))B(0.4(1)), was studied with respect to its phase behaviour in dependance of particle number density and interaction, of which the latter was modulated by varying amounts of added base (NaOH). Moreover, its short-range order in the fluid state and its eventual solidification into a long-range ordered colloidal crystal were observed in situ, allowing the measurement of the associated kinetics of nucleation and crystal growth. Key parameters of the nucleation kinetics such as crystallinity, crystallite number density, and nucleation rate density were extracted from the time-resolved scattering curves. By this means an estimate on the interfacial energy for the interface between the icosahedral short-range ordered fluid and a body-centered cubic colloidal crystal was obtained, comparable to previously determined values for single-component colloidal systems.

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Crystallization kinetics of polydisperse colloidal hard spheres. II. Binary mixtures

Cited by 42 publications

References 21 publications

Polymer-enforced crystallization of a eutectic binary hard sphere mixture

Polymer-enforced crystallization of a eutectic binary hard sphere mixture

Crystallization in three- and two-dimensional colloidal suspensions

Nucleation and crystal growth in a suspension of charged colloidal silica spheres with bi-modal size distribution studied by time-resolved ultra-small-angle X-ray scattering

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