scholarly journals Bridgman Crystal Growth of an Alloy With Thermosolutal Convection Under Microgravity Conditions

2001 ◽  
Vol 123 (5) ◽  
pp. 990-998 ◽  
Author(s):  
James E. Simpson ◽  
Suresh V. Garimella ◽  
Henry C. de Groh ◽  
Reza Abbaschian
Keyword(s):  
Crystal Growth ◽  
Growth Conditions ◽  
Convective Cell ◽  
Two Dimensions ◽  
Experimental Results ◽  
Thermosolutal Convection ◽  
Microgravity Environment ◽  
Uniform Grid ◽  
Microgravity Conditions ◽  
Bridgman Crystal Growth

The solidification of a dilute alloy (bismuth-tin) under Bridgman crystal growth conditions is investigated. Computations are performed in two dimensions with a uniform grid. The simulation includes the species concentration, temperature and flow fields, as well as conduction in the ampoule. Fully transient simulations have been performed, with no simplifying steady state approximations. Results are obtained under microgravity conditions for pure bismuth, and for Bi-0.1 at.% Sn and Bi-1.0 at.% Sn alloys, and compared with experimental results obtained from crystals grown in the microgravity environment of space. For the Bi-1.0 at.% Sn case the results indicate that a secondary convective cell, driven by solutal gradients, forms near the interface. The magnitude of the velocities in this cell increases with time, causing increasing solute segregation at the solid/liquid interface. Finally, a comparison between model predictions and results obtained from a space experiment is reported. The concentration-dependence of the alloy melting temperature is incorporated in the model for this case. Satisfactory correspondence is obtained between the predicted and experimental results in terms of solute concentrations in the solidified crystal.

scholarly journals The Study of the Mechanism of Protein Crystallization in Space by Using Microchannel to Simulate Microgravity Environment

Crystals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 400 ◽  
Author(s):  
Yong Yu ◽  
Kai Li ◽  
Hai Lin ◽  
Ji-Cheng Li
Keyword(s):  
Growth Rates ◽  
Simulated Microgravity ◽  
Crystal Surface ◽  
Protein Crystallization ◽  
Experimental Results ◽  
Protein Crystals ◽  
Microgravity Environment ◽  
Microgravity Conditions ◽  
Lysozyme Crystals ◽  
Lysozyme Crystal

Space is expected to be a convection-free, quiescent environment for the production of large-size and high-quality protein crystals. However, the mechanisms by which the diffusion environment in space improves the quality of the protein crystals are not fully understood. The interior of a microfluidic device can be used to simulate a microgravity environment to investigate the protein crystallization mechanism that occurs in space. In the present study, lysozyme crystals were grown in a prototype microchannel device with a height of 50 μm in a glass-polydimethylsiloxane (PDMS)-glass sandwich structure. Comparative experiments were also conducted in a sample pool with a height of 2 mm under the same growth conditions. We compared the crystal morphologies and growth rates of the grown crystals in the two sample pools. The experimental results showed that at very low initial supersaturation, the morphology and growth rates of lysozyme crystals under the simulated microgravity conditions is similar to that on Earth. With increasing initial supersaturation, a convection-free, quiescent environment is better for lysozyme crystal growth. When the initial supersaturation exceeded a threshold, the growth of the lysozyme crystal surface under the simulated microgravity conditions never completely transform from isotropic to anisotropic. The experimental results showed that the convection may have a dual effect on the crystal morphology. Convection can increase the roughness of the crystal surface and promote the transformation of the crystal form from circular to tetragonal during the crystallization process.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

Néel temperature of zinc-blende, MBE-grown MnTe layers: modification by the crystal growth conditions

2004 ◽  
Vol 1 (4) ◽  
pp. 953-956 ◽  
Author(s):  
W. Szuszkiewicz ◽  
E. Dynowska ◽  
J. Z. Domagala ◽  
E. Janik ◽  
E. Łusakowska ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Growth Conditions ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Zinc Blende

Bulk laser damage of large-size KDP crystals obtained at various crystal growth conditions

1994 ◽  
Author(s):  
Marina I. Kolybayeva ◽  
Igor M. Pritula ◽  
Viacheslav M. Puzikov ◽  
Vitaly I. Salo ◽  
Serge V. Garnov ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Growth Conditions ◽  
Laser Damage ◽  
Large Size ◽  
Kdp Crystals

Development of model-based control for Bridgman crystal growth

2004 ◽  
Vol 266 (1-3) ◽  
pp. 182-189 ◽  
Author(s):  
Paul Sonda ◽  
Andrew Yeckel ◽  
Prodromos Daoutidis ◽  
Jeffrey.J. Derby
Keyword(s):  
Crystal Growth ◽  
Model Based Control ◽  
Model Based ◽  
Bridgman Crystal Growth

Research on Effects of Mo Element on the Magnetic Properties of 1J79 Alloy

2010 ◽  
Vol 160-162 ◽  
pp. 1787-1790
Author(s):  
Jing Cao ◽  
Yong Feng Wang ◽  
Chun Xue Wei
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Crystal Growth ◽  
Saturation Magnetization ◽  
Electron Probe ◽  
Electric Arc ◽  
Experimental Results ◽  
Vibrating Sample Magnetometer ◽  
Electron Probe Microanalyzer ◽  
Mo Content

1J79 alloy was prepared by vacuum electric arc smelting．The crystal growth and the content of impurity was observed by electron probe microanalyzer，and magnetic properties were measured by vibrating sample magnetometer(VSM)．Experimental results show that inclusions in the alloy are fewer and fewer, composition becomes more uniform with the increases of the Mo content, and grain size also becomes larger and larger with the increases of Mo content, to reduce coercivity. The small amount of Mo addition is useful to improve the saturation magnetization and reduce coercivity．

Reactive crystal growth in two dimensions: Silicon nitride on Si(111)

1995 ◽  
Vol 51 (24) ◽  
pp. 17891-17901 ◽  
Author(s):  
E. Bauer ◽  
Y. Wei ◽  
T. Müller ◽  
A. Pavlovska ◽  
I. S. T. Tsong
Keyword(s):  
Crystal Growth ◽  
Silicon Nitride ◽  
Two Dimensions
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