Heterogeneous and homogeneous crystal nucleation in colloidal hard-sphere like microgels at low metastabilities

Franke, Markus; Lederer, Achim; Schöpe, Hans Joachim

doi:10.1039/c1sm06081c

Cited by 30 publications

(29 citation statements)

References 85 publications

(101 reference statements)

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“…To discriminate heterogeneous and homogeneous nucleation at the container wall in scattering experiments, evaluation has to exploit the 2D scattering pattern or individually address different peaks [210,211]. To discriminate between these two scenarios in the bulk of a system, Turnbull devised a dispersion method isolating small volumes of melt to obtain a large number of independently monitored crystallization events [212].…”

Section: Data Acquisition and Evaluationmentioning

confidence: 99%

Crystallization kinetics of colloidal model suspensions: recent achievements and new perspectives

Palberg

2014

J. Phys.: Condens. Matter

125

132

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Colloidal model systems allow studying crystallization kinetics under fairly ideal conditions, with rather well-characterized pair interactions and minimized external influences. In complementary approaches experiment, analytic theory and simulation have been employed to study colloidal solidification in great detail. These studies were based on advanced optical methods, careful system characterization and sophisticated numerical methods. Over the last decade, both the effects of the type, strength and range of the pair-interaction between the colloidal particles and those of the colloid-specific polydispersity have been addressed in a quantitative way. Key parameters of crystallization have been derived and compared to those of metal systems. These systematic investigations significantly contributed to an enhanced understanding of the crystallization processes in general. Further, new fundamental questions have arisen and (partially) been solved over the last decade: including, for example, a two-step nucleation mechanism in homogeneous nucleation, choice of the crystallization pathway, or the subtle interplay of boundary conditions in heterogeneous nucleation. On the other hand, via the application of both gradients and external fields the competition between different nucleation and growth modes can be controlled and the resulting microstructure be influenced. The present review attempts to cover the interesting developments that have occurred since the turn of the millennium and to identify important novel trends, with particular focus on experimental aspects.

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Section: Data Acquisition and Evaluationmentioning

confidence: 99%

Crystallization kinetics of colloidal model suspensions: recent achievements and new perspectives

Palberg

2014

J. Phys.: Condens. Matter

125

132

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“…These highly correlated systems become widely recognized as model systems for condensed matter physics. Since the nineties of the last century, colloidal suspensions have been viewed as potential models for fundamental investigations on the structure and dynamics of condensed matter [21], and the 'colloids as atoms' paradigm has led to many interesting studies on their phase behavior and phase transition kinetics [30,33,34,35,36,37,38,39]. They are guided by valuable instrumental and theoretical developments and complemented by a multitude of computer studies [40].…”

Section: Ducting Materials If the Eriences A Timementioning

confidence: 99%

Overview: Experimental studies of crystal nucleation: Metals and colloids

Herlach

Palberg

Klassen

et al. 2016

The Journal of Chemical Physics

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Crystallization is one of the most important phase transformations of first order. In the case of metals and alloys, the liquid phase is the parent phase of materials production. The conditions of the crystallization process control the as-solidified material in its chemical and physical properties. Nucleation initiates the crystallization of a liquid. It selects the crystallographic phase, stable or meta-stable. Its detailed knowledge is therefore mandatory for the design of materials. We present techniques of containerless processing for nucleation studies of metals and alloys. Experimental results demonstrate the power of these methods not only for crystal nucleation of stable solids but in particular also for investigations of crystal nucleation of metastable solids at extreme undercooling. This concerns the physical nature of heterogeneous versus homogeneous nucleation and nucleation of phases nucleated under non-equilibrium conditions. The results are analyzed within classical nucleation theory that defines the activation energy of homogeneous nucleation in terms of the interfacial energy and the difference of Gibbs free energies of solid and liquid. The interfacial energy acts as barrier for the nucleation process. Its experimental determination is difficult in the case of metals. In the second part of this work we therefore explore the potential of colloidal suspensions as model systems for the crystallization process. The nucleation process of colloids is observed in situ by optical observation and ultra-small angle X-ray diffraction using high intensity synchrotron radiation. It allows an unambiguous discrimination of homogeneous and heterogeneous nucleation as well as the determination of the interfacial free energy of the solid-liquid interface. Our results are used to construct Turnbull plots of colloids, which are discussed in relation to Turnbull plots of metals and support the hypothesis that colloids are useful model systems to investigate crystal nucleation.

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“…colloidal hard spheres [9][10][11][12][13], discrepancies between the observed and predicted nucleation rates can be as big as ten orders of magnitude [14]. While numerical simulations have found a rapid increase of the nucleation rate with increasing colloid volume fraction φ, growing by more than 15 orders of magnitude from φ = 0.52 to φ = 0.56 [14][15][16][17][18][19][20][21][22][23][24], experiments on both polymethyl methacrylate and polystyrene microgel systems, instead report nucleation rates that are much less sensitive to volume fraction [25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

105

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Nucleation is an activated process in which the system has to overcome a free energy barrier in order for a first-order phase transition between the metastable and the stable phases to take place. In the liquid-to-solid transition the process occurs between phases of different symmetry, and it is thus inherently a multi-dimensional process, in which all symmetries are broken at the transition. In this Focus Article, we consider some recent studies which highlight the multi-dimensional nature of the nucleation process. Even for a single-component system, the formation of solid crystals from the metastable melt involves fluctuations of two (or more) order parameters, often associated with the decoupling of positional and orientational symmetry breaking. In other words, we need at least two order parameters to describe the free-energy of a system including its liquid and crystalline states. This decoupling occurs naturally for asymmetric particles or directional interactions, focusing here on the case of water, but we will show that it also affects spherically symmetric interacting particles, such as the hard-sphere system. We will show how the treatment of nucleation as a multi-dimensional process has shed new light on the process of polymorph selection, on the effect of external fields on the nucleation process, and on glass-forming ability.

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Heterogeneous and homogeneous crystal nucleation in colloidal hard-sphere like microgels at low metastabilities

Cited by 30 publications

References 85 publications

Crystallization kinetics of colloidal model suspensions: recent achievements and new perspectives

Crystallization kinetics of colloidal model suspensions: recent achievements and new perspectives

Overview: Experimental studies of crystal nucleation: Metals and colloids

Crystal nucleation as the ordering of multiple order parameters

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