Electrical Phenomena accompanying the Phase Change of Dilute KCl Solutions into Single Crystals of Ice

The Workman-Reynolds effect was investigated during the phase change of dilute (about 2 × 10-4 N) KCl solutions into single crystals of ice. The ice crystals were oriented with the c-axes either parallel or perpendicular to the growth direction. The solute distribution in the liquid phase. near the interface (within 10 mm), was obtained with a wire-type conductivity cell. For a crystal growth rate 8.8 μm/s the freezing potentials were + 10.0 V and + 6.0 V and the specific charge séparations were 1.3 ± 0 1 × 10-6 C/g of ice and 1 4 ± 0.1 × 10-6 C/g of ice for growth parallel and perpendicular. Respectively, to the c-axes of the ice crystals . The equilibrium solute distribution coefficient was found to be 4 × 10-3 for KCl solutions for both crystal orientations. An “apparent” (because of convection in the liquid phase) distribution coefficient ranged from 0.031- 0.074. The “apparent” diffusion coefficients ranged from 1.3–4.9 × 10-3 mm2/s and varied linearly with growth rate. The ionic distribution coefficients. K+ and K-, were approximately K+ - K- = - 2 × 10-5 and K+ + K - = 8 × 10-3 for the KCl solutions.

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Freezing Potentials and Currents in Potassium Fluoride Solutions at Constant Growth Rates

Journal of Glaciology ◽

10.1017/s0022143000031890 ◽

1973 ◽

Vol 12 (66) ◽

pp. 483-499 ◽

Cited By ~ 1

Author(s):

T. O’D. Hanley ◽

A. H. Weber

Keyword(s):

Growth Rate ◽

Charge Transfer ◽

Growth Rates ◽

Potassium Fluoride ◽

Distribution Coefficients ◽

Interface Resistance ◽

Apparent Diffusion Coefficients ◽

Apparent Diffusion ◽

Interface Capacitance ◽

Constant Growth

The Workman–Reynolds effect was studied in the growth of ice on a monocrystalline seed, at constant growth rates and under steady-state conditions, from KF solutions at concentrations from 2 × 10−5 to 10 × 10−5 Normal. Freezing potentials increased with growth rate to a maximum of 12 V at 11.2 μm/s. Discharge currents through a 105 Ω shunt generally increased with freezing rate until a maximum of 1.5 μA at 11.2 μm/s. The charge transfer decreased with growth rate to 200 μC at 10.3 μm/s and then reached a maximum of 850 μC at 11.2 μm/s. Apparent diffusion coefficients of about 2 × 10−3 mm2/s increased slowly with growth rate until a rapid increase began, apparently associated with interface breakdown. Distribution coefficients of the order of 10−3, calculated from a criterion for constitutional supercooling, increased with concentration. Parameters for LeFebre’s model of the interface showed an interface thickness of about 6 mm, an interface capacitance near one-half pF/mm2, and an interface resistance of about 6 × 104 Ω/mm2. Several empirical relations between these quantities were disclosed. Comparison with values obtained for KC1 solutions with the same freezing cell shows that the KF solutions yielded higher values of freezing potential, charge transfer, and distribution coefficient, and lower values of diffusion coefficient, interface capacitance, and interface resistance.

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Freezing Potentials and Currents in Potassium Fluoride Solutions at Constant Growth Rates

Journal of Glaciology ◽

10.3189/s0022143000031890 ◽

1973 ◽

Vol 12 (66) ◽

pp. 483-499

Author(s):

T. O’D. Hanley ◽

A. H. Weber

Keyword(s):

Growth Rate ◽

Charge Transfer ◽

Growth Rates ◽

Potassium Fluoride ◽

Distribution Coefficients ◽

Interface Resistance ◽

Apparent Diffusion Coefficients ◽

Apparent Diffusion ◽

Interface Capacitance ◽

Constant Growth

The Workman–Reynolds effect was studied in the growth of ice on a monocrystalline seed, at constant growth rates and under steady-state conditions, from KF solutions at concentrations from 2 × 10−5 to 10 × 10−5 Normal. Freezing potentials increased with growth rate to a maximum of 12 V at 11.2 μm/s. Discharge currents through a 105 Ω shunt generally increased with freezing rate until a maximum of 1.5 μA at 11.2 μm/s. The charge transfer decreased with growth rate to 200 μC at 10.3 μm/s and then reached a maximum of 850 μC at 11.2 μm/s. Apparent diffusion coefficients of about 2 × 10−3 mm2/s increased slowly with growth rate until a rapid increase began, apparently associated with interface breakdown. Distribution coefficients of the order of 10−3, calculated from a criterion for constitutional supercooling, increased with concentration. Parameters for LeFebre’s model of the interface showed an interface thickness of about 6 mm, an interface capacitance near one-half pF/mm2, and an interface resistance of about 6 × 104 Ω/mm2. Several empirical relations between these quantities were disclosed. Comparison with values obtained for KC1 solutions with the same freezing cell shows that the KF solutions yielded higher values of freezing potential, charge transfer, and distribution coefficient, and lower values of diffusion coefficient, interface capacitance, and interface resistance.

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Freezing Controlled by Natural Convection

Journal of Heat Transfer ◽

10.1115/1.3451040 ◽

1979 ◽

Vol 101 (4) ◽

pp. 578-584 ◽

Cited By ~ 54

Author(s):

E. M. Sparrow ◽

J. W. Ramsey ◽

R. G. Kemink

Keyword(s):

Growth Rate ◽

Natural Convection ◽

Liquid Phase ◽

Phase Change ◽

Vertical Tube ◽

Freezing Process ◽

Freezing Time ◽

Fusion Temperature ◽

Invariant Temperature ◽

Time Invariant

Experiments were performed for freezing under conditions where the liquid phase is either above or at the fusion temperature (i.e., superheated or nonsuperheated liquid). The liquid was housed in a cylindrical containment vessel whose surface was maintained at a uniform, time-invariant temperature during a data run, and the freezing occurred on a cooled vertical tube positioned along the axis of the vessel. The phase change medium was n-eicosane, a paraffin which freezes at about 36°C (97°F). In the presence of liquid superheating, the freezing process is drastically slowed and ultimately terminated by the natural convection in the liquid. The terminal size of the frozen layer and the time at which freezing terminates can be controlled by setting the temperature parameters which govern the intensity of the natural convection. The stronger the natural convection, the thinner the frozen layer and the shorter the freezing time. In the absence of liquid superheating, a cylindrical frozen layer grows continuously as predicted by theory, but the growth rate is higher than the predictions because of the presence of whisker-like dendrites on the freezing surface.

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Distribution Coefficient of Arsenic Durng Liquid-Phase Epitaxy Layer Growth of Phosphide-Arsenide of Gallium

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1036.140 ◽

2014 ◽

Vol 1036 ◽

pp. 140-145

Author(s):

Iurie Ciofu ◽

Andrei Ciofu

Keyword(s):

Liquid Phase ◽

Distribution Coefficient ◽

Chemical Elements ◽

Construction Materials ◽

Distribution Coefficients ◽

Zone Melting ◽

Layer Growth ◽

Epitaxial Layers ◽

Thermal Methods ◽

High Purification

It is crucial to know the distribution coefficients of chemical elements in melts. This is essential for obtaining a given composition and properties of epitaxial layers grown from the liquid phase, for determining the regimes of high purification of materials obtained by zone melting, for producing the desired gradient of distribution of alloying elements throughout the layers of construction materials treated by chemical-thermal methods, etc. This paper presents the results of computing the distribution coefficient of arsenic during the growth of layers of phosphide-arsenide of gallium from the liquid phase (molten gallium), saturated with phosphorus. We also obtain the dependencies between the distribution coefficient of arsenic, the temperature and the concentration of arsenic inside the gallium melt during the growth of epitaxial layers. As well a practical application of the results with a given gradient of concentration for the gallium arsenide layer is demonstrated.

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Zur Verteilung von Mn und Co in K(Zn,Mn,Co) F3-Einkristallen / The Distribution of Mn and Co in K(Zn, Mn, Co) F3-Single Crystals

Zeitschrift für Naturforschung A ◽

10.1515/zna-1977-1113 ◽

1977 ◽

Vol 32 (11) ◽

pp. 1281-1286 ◽

Cited By ~ 1

Author(s):

G. Dickten ◽

K. Recker ◽

C. Triché

Keyword(s):

Crystal Growth ◽

Distribution Coefficient ◽

Single Crystals ◽

Electron Microprobe ◽

Growth Parameters ◽

Distribution Coefficients ◽

Bridgman Method ◽

Crystal Region

AbstractFor the investigation of perfection, homogenity, absorption and luminescence a large number of K(Zn, Mn, Co) F3-single crystals with variable Mn and Co contents were grown by the Stockbarger-Bridgman method under vacuum and argon protection gas. From these crystals the Mn-and Co-contents were determined quantitatively as a function of the crystal region by means of the electron-microprobe- and absorption-techniques. The distribution curves [cS/c0 = f(x)] are discussed as a function of the crystal growth parameters. The distribution-coefficients have been determined with the help of Pfann's formula and a proposed formula which permits the computation of the distribution-coefficient for every crystal region. Both methods lead to the same results: for Mn in KZnF3 : ke = 1.73, for Co in KZnF3 : ke = 1.64 (at growth-begin).

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Microstructure and microanalysis of sintered Fe-Nd-B permanent magnets

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178082 ◽

1990 ◽

Vol 48 (4) ◽

pp. 990-991

Author(s):

Mahesh Chandramouli

Keyword(s):

Electron Microscope ◽

Liquid Phase ◽

Permanent Magnets ◽

Phase Distribution ◽

Energy Dispersive Spectrometer ◽

Nucleation And Growth ◽

Liquid Phase Sintering ◽

Domain Wall Energy ◽

Oxide Phases ◽

Scanning Electron

Magnetization reversal in sintered Fe-Nd-B, a complex, multiphase material, occurs by nucleation and growth of reverse domains making the isolation of the ferromagnetic Fe14Nd2B grains by other nonmagnetic phases crucial. The magnets used in this study were slightly rich in Nd (in comparison to Fe14Nd2B) to promote the formation of Nd-oxides at multigrain junctions and incorporated Dy80Al20 as a liquid phase sintering addition. Dy has been shown to increase the domain wall energy thus making nucleation more difficult while Al is thought to improve the wettability of the Nd-oxide phases.Bulk polished samples were examined in a JEOL 35CF scanning electron microscope (SEM) operated at 30keV equipped with a Be window energy dispersive spectrometer (EDS) detector in order to determine the phase distribution.

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