scholarly journals Orientation and Velocity Dependence of the Nonequilibrium Partition Coefficient

1995 ◽  
Vol 398 ◽  
Author(s):  
K.M. Beatty ◽  
K.A. Jackson
Keyword(s):  
Monte Carlo ◽  
Diffusion Coefficient ◽  
Partition Coefficient ◽  
Interface Velocity ◽  
Velocity Dependence ◽  
Step Velocity ◽  
Equilibrium Partition ◽  
Equilibrium Partition Coefficient ◽  
Solid Liquid Interface ◽  
Solid Liquid

ABSTRACTMonte Carlo simulations based on a Spin-1 Ising Model for binary alloys have been used to investigate the non-equilibrium partition coefficient (kneq ) as a function of solid-liquid interface velocity and orientation. In simulations of Si with a second component kneq is greater in the [111] direction than the [100] direction in agreement with experimental results reported by Aziz et al. The simulated partition coefficient scales with the square of the step velocity divided by the diffusion coefficient of the secondary component in the liquid.

Transient Conductance Measurements During Pulsed Laser Annealing

1981 ◽  
Vol 4 ◽  
Author(s):  
M. O. Thompson ◽  
G. J. Galvin ◽  
J. W. Mayer ◽  
R. B. Hammond ◽  
N. Paulter ◽  
...  
Keyword(s):  
Single Crystal ◽  
Laser Annealing ◽  
Pulsed Laser ◽  
Interface Velocity ◽  
Laser Pulses ◽  
Molten Layer ◽  
Pulsed Laser Annealing ◽  
Complete Melting ◽  
Solid Liquid Interface ◽  
Solid Liquid

ABSTRACTMeasurements were made of the conductance of single crystal Au-doped Si and silicon-on-sapphire (SOS) during irradiation with 30 nsec ruby laser pulses. After the decay of the photoconductive response, the sample conductance is determined primarily by the thickness and conductivity of the molten layer. For the single crystal Au-doped Si, the solid-liquid interface velocity during recrystallization was determined from the current transient to be 2.5 m/sec for energy densities between 1.9 and 2.6 J/cm2, in close agreement with numerical simulations based on a thermal model of heat flow. SOS samples showed a strongly reduced photoconductive response, allowing the melt front to be observed also. For complete melting of a 0.4 μm Si layer, the regrowth velocity was 2.4 m/sec.

Solute Trapping in Metals

1992 ◽  
Vol 279 ◽  
Author(s):  
Patrick M. Smith ◽  
Riccardo Reitanot ◽  
Michael J. Aziz
Keyword(s):  
Partition Coefficient ◽  
Growth Model ◽  
Solidification Velocity ◽  
Continuous Growth ◽  
Solute Trapping ◽  
Solute Partitioning ◽  
Equilibrium Partition ◽  
Conductance Technique ◽  
Equilibrium Partition Coefficient ◽  
Alloy Properties

ABSTRACTMany of the advances in rapid solidification processing of metallic alloys exploit the trapping of solute which occurs at high solidification velocities. The difficulty of performing experiments which measure such high solidification velocities in metals has until now prevented accurate measurements of solute trapping in these systems. We have observed the transition from near-equilibrium solute partitioning to solute trapping during solidification at m/s velocities in aluminum alloys, and have compared the predictions of various solute trapping models. Aluminum thin films deposited on insulators were ion-implanted with Sn, Cu, Ge, and In, and were pulsed-laser melted; plane-front solidification was achieved, and regrowth velocities of 0.6 m/s to 5 m/s were measured with the transient conductance technique. Of the existing solute trapping models, the Continuous Growth Model of Aziz was found to fit the observed dependence of the partition coefficient on solidification velocity more closely than any other single-parameter model. The diffusive speed, which locates the transition from solute partitioning to solute trapping, was found to vary from 6 m/s to 38 m/s for various solutes in aluminum. We have examined correlations between the diffusive speed in the Continuous Growth Model and known alloy properties in order to allow better estimates of the diffusive speed to be made for alloy systems in which it has not been measured; the relation between the diffusive speed and the equilibrium partition coefficient will be discussed.

Crystallization of liquids in the vicinity of a solid

1981 ◽  
Vol 34 (1) ◽  
pp. 1
Author(s):  
JE Lane ◽  
TH Spurling
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Solid Phase ◽  
Adsorbed Layer ◽  
Liquid Interface ◽  
Spherically Symmetric ◽  
Present Evidence ◽  
Ensemble Monte Carlo ◽  
Solid Liquid Interface ◽  
Solid Liquid

We present evidence, gained from grand ensemble Monte Carlo simulations of the solid/liquid interface, that an adsorbed layer of spherically symmetric liquid particles can have a crystal-like structure even if the solid phase is structureless.

Solid–liquid interface velocity and diffusivity in laser-melt amorphous silicon

2000 ◽  
Vol 77 (15) ◽  
pp. 2337-2339 ◽  
Author(s):  
Luigi Brambilla ◽  
Luciano Colombo ◽  
Vittorio Rosato ◽  
Fabrizio Cleri
Keyword(s):  
Amorphous Silicon ◽  
Interface Velocity ◽  
Liquid Interface ◽  
Solid Liquid Interface ◽  
Solid Liquid

Simulation of porosity reduction in random structures

1990 ◽  
Vol 5 (10) ◽  
pp. 2184-2196 ◽  
Author(s):  
P. B. Visscher ◽  
Joseph E. Cates
Keyword(s):  
Interface Velocity ◽  
Periodic Boundary Conditions ◽  
Pressure Solution ◽  
Forward Motion ◽  
Porosity Reduction ◽  
Random Structures ◽  
The Difference ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Rate Limiting

We describe an algorithm for computing the motion of a solid-liquid interface in 2D, which is applicable to geological pressure solution or to pressure sintering. The backward motion (toward the solid) of the interface is due to dissolution of the solid, and the forward motion (away from the solid) is due to the inverse process of reprecipitation. The interface velocity is assumed proportional to the difference between the solubility of the solid and the concentration of the solution. The former is dependent upon stress (the phenomenon of “pressure solution”), so our algorithm must also keep track of the stress. We use a Lagrangian grid, with constant-stress periodic boundary conditions. The method has been applied to porosity reduction in sandstone. It is applicable to other interface-following problems, such as freezing, if the motion is slow enough that heat transport is not rate-limiting.

scholarly journals Adsorption of amyloglucosidase from Aspergillus niger NRRL 3122 using ion exchange resin

2008 ◽  
Vol 51 (5) ◽  
pp. 1015-1024 ◽  
Author(s):  
Ana Paula Manera ◽  
Eliana Setsuko Kamimura ◽  
Luciana Machado Brites ◽  
Susana Juliano Kalil
Keyword(s):  
Aspergillus Niger ◽  
Partition Coefficient ◽  
Partition Coefficients ◽  
Deae Cellulose ◽  
Ion Exchange Resin ◽  
Least Square ◽  
Optimum Conditions ◽  
Equilibrium Partition ◽  
Equilibrium Partition Coefficient ◽  
Least Square Procedure

Amyloglucosidase enzyme was produced by Aspergillus niger NRRL 3122 from solid-state fermentation, using deffated rice bran as substrate. The effects of process parameters (pH, temperature) in the equilibrium partition coefficient for the system amyloglucosidase - resin DEAE-cellulose were investigated, aiming at obtaining the optimum conditions for a subsequent purification process. The highest partition coefficients were obtained using 0.025M Tris-HCl buffer, pH 8.0 and 25ºC. The conditions that supplied the highest partition coefficient were specified, the isotherm that better described the amyloglucosidase process of adsorption obtained. It was observed that the adsorption could be well described by Langmuir equation and the values of Qm and Kd estimated at 133.0 U mL-1 and 15.4 U mL-1, respectively. From the adjustment of the kinetic curves using the fourth-order Runge-Kutta algorithm, the adsorption (k1) and desorption (k2) constants were obtained through optimization by the least square procedure, and the values calculated were 2.4x10-3 mL U-1 min-1 for k1 and 0.037 min-1 for k2 .

Effect of High Rotating Magnetic Field on the Solidified Structure of Al–7wt.%Si–1wt.%Fe Alloy

2013 ◽  
Vol 752 ◽  
pp. 57-65 ◽  
Author(s):  
András Roósz ◽  
Jenő Kovács ◽  
Arnold Rónaföldi ◽  
Árpád Kovács
Keyword(s):  
Magnetic Field ◽  
Interface Velocity ◽  
Longitudinal Section ◽  
Rotating Magnetic Field ◽  
Christmas Tree ◽  
Binary Eutectic ◽  
Si Content ◽  
The One ◽  
Solid Liquid Interface ◽  
Solid Liquid

Al–7wt.-% Si–1wt.-% Fe alloy was solidified unidirectionally in the Crystallizer with High Rotating Magnetic Field (CHRMF). The diameter of sample was 8 mm and its length was 120 mm. The parameters of solidification were as follows: solid/liquid interface velocity ~0.082 mm/s, temperature gradient 7+/-1 K/mm, magnetic induction 0 and 150 mT, frequency of magnetic field 0 and 50 Hz. The structure solidified without rotating magnetic field (RMF) showed a homogeneous, columnar dendritic one. The structure solidified by using magnetic stirring showed a dual periodicity. On the one hand, the branches of the “Christmas tree”-like structure known from the earlier experiments contained Al+Si binary eutectic. On the other hand, bands with higher Fe- and Si-content formed in the sample, which were at a larger distance from each other than the branches of the “Christmas tree” structure. The developed microstructure was analyzed by SEM with EDS. The average Si- and Fe-concentrations were measured on the longitudinal section at given places along the length of sample. Furthermore the Si- and the Fe-concentrations close to the bands and among the bands as well as the composition of the compound phases were determined.

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