Search results for "crystal growth"
showing 10 items of 130 documents
Rotating magnetic fields as a means to control the hydrodynamics and heat/mass transfer in the processes of bulk single crystal growth
1999
The report discusses the possibility of using different types of rotating magnetic fields (RMF) and combinations of these to control the hydrodynamics and heat/mass transfer in the processes of bulk semiconductor single crystal growth. Some factors contributing to the efficiency of RMF influence in different technologies are analysed. Their specific practical application is illustrated by some examples.
CdTe crystal growth process by the Bridgman method: numerical simulation
2001
Abstract Numerical simulation of the CdTe crystal growth process by the Bridgman method is made by using the commercial computational code FLUENT for the mathematical solution of the governing equations. To reduce computational effort, we have made use of a two level strategy. In the first level we have considered the whole system formed by the ampoule with the liquid–solid charge, the furnace, and the air between them. The heat transfer is assumed to occur by conduction, convection and radiation between the furnace and the ampoule, and only by conduction through the ampoule wall and the solid and liquid CdTe. In the second level we focus on the ampoule and its content, using the values of …
Influence of growth parameters and melt convection on the solid-liquid interface during RF-floating zone crystal growth of intermetallic compounds
2001
Abstract The influence of growth parameters and melt convection on the solid–liquid interface of the intermetallic compound Ni3Si grown by the RF-floating zone technique was investigated experimentally as well as numerically. Numerical simulations showed that the heat transfer is strongly influenced by the electromagnetically driven and Marangoni convections whereas both the buoyancy and feed rotation have a negligible effect. It was found experimentally that the inductor design, the rod diameter and the length of the molten zone influence the solid–liquid interface shape significantly. The electromagnetically driven convection increases dramatically with increasing zone length due to the r…
Convective phenomena in large melts including magnetic fields
2007
The set of characteristic parameters which describe modern large industrial CZ silicon single crystal growth systems is introduced. The main melt flow driving mechanisms are considered, and the characteristic density values of various in the melt acting forces are estimated. The analysis is illustrated with examples of numerical simulation and comparisons with experiments.
Classical growth of hard-sphere colloidal crystals.
1995
The classical theory of nucleation and growth of crystals is examined for concentrated suspensions of hard-sphere colloidal particles. The work of Russel is modified, extended, and evaluated, explicitly. Specifically, the Wilson-Frenkel growth law is modified to include the Gibbs-Thomson effect and is evaluated numerically. The results demonstrate that there is a critical nucleus radius below which crystal nuclei will not grow. A kinetic coefficient determines the maximum growth velocity possible. For large values of this coefficient, quenches to densities above the melting density show interface limited growth with the crystal radius increasing linearly with time. For quenches into the coe…
Computational stability of an initially radial solution of a growth/dissolution problem in a nonradial implementation
1991
We consider a free boundary problem modelling the growth/dissolution of a crystal. The aim is to investigate the following question: Does the solution to the crystal growth problem posed in two dimensions with radially symmetric initial and boundary condition evolve as a radially symmetric solution?
Heterogeneous and homogeneous crystal nucleation in a colloidal model system of charged spheres at low metastabilities
2011
We have studied the nucleation kinetics in the bulk as well as at the container walls of a charged sphere colloidal model system under salt-free conditions close to the fluid–crystal phase boundary. We determined time resolved nucleation rate densities for heterogeneous nucleation on the wall, the corresponding nucleation rate densities for homogeneous nucleation and compare the resulting nucleation barrier heights. The homogeneous barrier height decreases exponentially with increasing metastability, while the heterogeneous barrier displays a sharp transition from a constant value close to the phase boundary to zero at higher metastability. As a consequence the microstructure evolution is d…
Observation of instability of faceted crystals in lipid monolayers
1998
Abstract The morphological instabilities of two-dimensional hexagonal crystals in lipid monolayers are studied. Fluorescence microscopy indicates that beyond a critical size the faceted crystal develops into dendrites with unusual tip growth behavior, which is not consistent with the current theory of dendritic growth. The morphological transitions in relation to the driving force for two-dimensional crystal growth are also studied.
Anisotropic lattice distortions in biogenic calcite induced by intra-crystalline organic molecules.
2006
9 pages; International audience; We have performed precise structural measurements on five different calcitic seashells by high-resolution X-ray powder diffraction on a synchrotron beam line and by laboratory single crystal X-ray diffraction. The unit cell parameters a and c of biogenic calcite were found to be systematically larger than those measured in the non-biogenic calcite. The maximum lattice distortion (about 2.10(-3)) was detected along the c-axis. Under heat treatment above 200 degrees C, a pronounced lattice relaxation was observed, which allowed us to conclude that anisotropic lattice swelling in biogenic calcite is induced by organic macromolecules incorporated within the sing…
Crystal Growth of HgSe by the Cold Travelling Heater Method
2002
We report on the low-temperature synthesis and growth of HgSe crystals making use of the cold travelling heater method. Ingots so obtained are analyzed by means of scanning microscopy, including EDAX and backscattered electron modes, and X-ray diffraction techniques.