Preface

Herlach, D.M.; Galenko, Peter; Holland‐Moritz, D.

doi:10.1016/s1470-1804(07)80023-x

Cited by 103 publications

(174 citation statements)

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“…In this case the energetics controls the growth [65]. In glass-forming systems, however, the mobility of the atomic movement rapidly decreases if ∆T is approaching ∆T g = T L − T g .…”

Section: Dendrite Growth In Undercooled Glass-forming Cu 50 Zr 50 Alloymentioning

confidence: 99%

Non-Equilibrium Solidification of Undercooled Metallic Melts

Herlach

2014

Metals

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Abstract:If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.

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Section: Dendrite Growth In Undercooled Glass-forming Cu 50 Zr 50 Alloymentioning

confidence: 99%

Non-Equilibrium Solidification of Undercooled Metallic Melts

Herlach

2014

Metals

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“…(27) Both speeds (26) and (27) become complex with the inequality α(k) < −1/(4τ ), which holds in the region k > k uc , i.e., behind the ultraviolet cutoff given by the wave-number k = k uc (25). Also, the group speed (27) diverges at α(k) = −1/(4τ ) and k = k uc .…”

Section: Propagative Speedsmentioning

confidence: 99%

“…Fast front dynamics proceeds when the driving force for the phase transition is large. This occurs when the free energy difference between the (meta)stable periodic solid and initially unstable phase is very large which in general occurs when a system is quenched far below a transition point, or in this case far below the equilibrium temperature of phase transition 26 . These conditions lead to a fast phase transition when the velocity of the front is comparable to the speed of atomic diffusion or the speed of local structural relaxation.…”

Section: Introductionmentioning

confidence: 99%

Marginal stability analysis of the phase field crystal model in one spatial dimension

Galenko

Elder

2011

Phys. Rev. B

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The problem of wave-length k f and velocity V selection for a solid front invading an unstable homogeneous phase is considered. A marginal stability analysis is used to predict k f and V for the parabolic and hyperbolic (or modified) phase-field crystal models in one-dimension. It is shown that the marginally selected wave-number of the periodic crystal monotonically increases with increasing undercooling and relaxation times. At high undercooling and relaxation times it is found that the system can select a k f that is unstable to an Eckhaus instability in the bulk phase. This may imply a transition to highly defected or glassy states in higher dimensions.

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“…Nucleation of crystals from fluid phases is an important problem [1][2][3][4][5] with important applications, such as formation of ice crystals in the atmosphere, solidification of molten silicates in processes deep underneath the earth crust, and last but not least crystallization processes of various materials are ubiquitous in many technical processes. However, nevertheless crystal nucleation is rather poorly understood on a quantitative level: one mostly relies on the concept of classical nucleation theory [2,[6][7][8][9][10], but since almost always the "critical nucleus" that triggers the phase transition contains only a few tens to at most a few thousand particles, considerations based on macroscopic concepts (balancing bulk and surface free energies, using the interfacial tension of macroscopic flat interfaces, etc.…”

Section: Introduction and Overviewmentioning

confidence: 99%

“…However, nevertheless crystal nucleation is rather poorly understood on a quantitative level: one mostly relies on the concept of classical nucleation theory [2,[6][7][8][9][10], but since almost always the "critical nucleus" that triggers the phase transition contains only a few tens to at most a few thousand particles, considerations based on macroscopic concepts (balancing bulk and surface free energies, using the interfacial tension of macroscopic flat interfaces, etc. [1][2][3][4][5]) are doubtful. Moreover, in most cases of interest nucleation is not homogeneous (i.e., triggered by spontaneous thermal fluctuations) but rather heterogeneous [9,[11][12][13][14][15] (i.e., triggered by defects, e.g.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Simulation of fluid-solid coexistence in finite volumes: A method to study the properties of wall-attached crystalline nuclei

Deb

Winkler

Virnau

et al. 2012

The Journal of Chemical Physics

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The Asakura-Oosawa model for colloid-polymer mixtures is studied by Monte Carlo simulations at densities inside the two-phase coexistence region of fluid and solid. Choosing a geometry where the system is confined between two flat walls, and a wall-colloid potential that leads to incomplete wetting of the crystal at the wall, conditions can be created where a single nanoscopic wall-attached crystalline cluster coexists with fluid in the remainder of the simulation box. Following related ideas that have been useful to study heterogeneous nucleation of liquid droplets at the vapor-liquid coexistence, we estimate the contact angles from observations of the crystalline clusters in thermal equilibrium. We find fair agreement with a prediction based on Young's equation, using estimates of interface and wall tension from the study of flat surfaces. It is shown that the pressure versus density curve of the finite system exhibits a loop, but the pressure maximum signifies the "droplet evaporation-condensation" transition and thus has nothing in common with a van der Waals-like loop. Preparing systems where the packing fraction is deep inside the two-phase coexistence region, the system spontaneously forms a "slab state", with two wall-attached crystalline domains separated by (flat) interfaces from liquid in full equilibrium with the crystal in between; analysis of such states allows a precise estimation of the bulk equilibrium properties at phase coexistence.

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Preface

Cited by 103 publications

References 0 publications

Non-Equilibrium Solidification of Undercooled Metallic Melts

Non-Equilibrium Solidification of Undercooled Metallic Melts

Marginal stability analysis of the phase field crystal model in one spatial dimension

Simulation of fluid-solid coexistence in finite volumes: A method to study the properties of wall-attached crystalline nuclei

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