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Results for “Bi-Sn”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Directional Solidification of Bi-Sn on USMP-4

The experiments used MEPHISTO hardware to study the solidification and melting behavior of bismuth alloyed with 1 at% tin. Three samples, each approximately 900 mm long and 6mm in diameter, were used. A portion of each sample also included a 2 mm diameter growth capillary, to assist in the formation of a single grain. One sample provided the Seebeck voltage generated during melting and freezing processes. Another provided temperature data and Peltier pulsed demarcation of the interface shape for post flight analysis. The third sample provided resistance and growth velocity measurements, as well as additional thermal data. The third sample was also quenched at the end of the mission to preserve the composition of the liquid near the interface for post flight determination. A total of 450mm of directionally solidified samples were preserved for post mission structural and compositional characterization. Substantial differences were observed in the Seebeck signal between the ground-based experiments and the space-based experiments. The temperature gradient in the liquid for the ground-based experiments was significantly lower than the temperature gradient in the liquid for the space-based experiments.

Abbaschian, Reza↗
NASA NTRS1995

Numerical simulation of heat and mass transport during space crystal growth with MEPHISTO

The MEPHISTO space experiments are collaborative United States and French investigations aimed at understanding the fundamentals of crystal growth. Microgravity experiments were conducted aboard the USMP-1 and -2 missions on STS-52 and 62 in October 1992 and March 1994 respectively. MEPHISTO is a French designed and built Bridgman type furnace which uses the Seebeck technique to monitor the solid/liquid interface temperature and Peltier pulsing to mark the location and shape of the solid/liquid interface. In this paper the Bridgman growth of Sn-Bi and Bi-Sn under terrestrial and microgravity conditions is modeled using the finite element code, FIDAP*. The numerical model considers fully coupled heat and mass transport, fluid motion and solid/liquid phase changes in the crystal growth process. The primary goals of this work are: to provide a quantitative study of the thermal buoyancy-induced convection in the melt for the two flight experiments; to compare the vertical and horizontal growth configurations and systematically evaluate the effects of various gravity levels on the solute segregation. Numerical results of the vertical and horizontal Bridgman growth configurations are presented.

Yao, Minwu↗
NASA NTRS2001

Morphological Stability of Faceted Interfaces

The major focus of this investigation is to study the fundamentals of layer spreading mechanisms during growth of doped Ge (a facet forming material), and to determine the conditions for morphological instability of vicinal solid-liquid interfaces. The investigation will also lead to the determination of the effect of dopants on the layer growth kinetics, step free energy, and dopant capture by the advancing ledges. The theoretical treatment of growth of faceted interfaces indicates that the kinetics of a step on a growing vicinal interface considerably depends on its angle of inclination, the melt concentration, and characteristics of flow currents in the melt. The morphological stability of the interface also depends on these parameters, as well as on the density and spreading velocity of the steps. However, the treatment of the instability of the interface by the layer growth mechanism is rather difficult because it requires exact knowledge of the thermal and solutal fields, hydrodynamics of the melt, and supercooling at the interface. The results of recent space experiments of the principal investigator involving directional solidification of faceted Bi-Sn alloys have shown that the morphological stability of various crystallographic orientations is significantly affected by the anistropy in interfacial properties of the faceted alloy in general, and the interface kinetics in particular. These findings have also raised many important and fundamental questions, particularly with respect to the behavior of interfacial steps, which need to be addressed via additional groundbased and microgravity experiments. For the present investigation we will use a novel crystal growth technique which provides axial heat flux close to the solid-liquid boundary. The Axial Heat Processing (AHP) technique allows for precise control and determination of the heat and mass transfer close to the crystallization front, and the establishment of a planar interface over the entire cross-section of the growing crystal.

Abbaschian, Reza↗
NASA NTRS2003

Effects of Traveling Magnetic Field on Dynamics of Solidification

The Lorentz body force induced in electrically conducting fluids can be utilized for a number of materials processing technologies. An application of strong static magnetic fields can be beneficial for damping convection present during solidification. On the other hand, alternating magnetic fields can be used to reduce as well as to enhance convection. However, only special types of time dependent magnetic fields can induce a non-zero time averaged Lorentz force needed for convection control. One example is the rotating magnetic field. This field configuration induces a swirling flow in circular containers. Another example of a magnetic field configuration is the traveling magnetic field (TMF). It utilizes axisymmetric magnetostatic waves. This type of field induces an axial recirculating flow that can be advantageous for controlling axial mass transport, such as during solidification in long cylindrical tubes. Incidentally, this is the common geometry for crystal growth research. The Lorentz force induced by TMF can potentially counter-balance the buoyancy force, diminishing natural convection, or even setting up the flow in reverse direction. Crystal growth process in presence of TMF can be then significantly modified. Such properties as the growth rate, interface shape and macro segregation can be affected and optimized. Melt homogenization is the other potential application of TMF. It is a necessary step prior to solidification. TMF can be attractive for this purpose, as it induces a basic flow along the axis of the ampoule. TMF can be a practical alloy mixing method especially suited for solidification research in space. In the theoretical part of this work, calculations of the induced Lorentz force in the whole frequency range have been completed. The basic flow characteristics for the finite cylinder geometry are completed and first results on stability analysis for higher Reynolds numbers are obtained. A theoretical model for TMF mixing is also developed. In the experimental part, measurements of flow induced by TMF in a column of mercury (Hg) are presented. Also, an alloy mixing of Bi-Sn of the eutectic composition is demonstrated. A traveling magnetic field of 4mT at 3kHz applied for 120 minutes is found to be sufficient to homogenize an alloy enclosed in a 1cm diameter and 12 cm long tube.

Source record↗
DOE OSTI2020

Materials Data on SnBi by Materials Project

SnBi crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Sn is bonded in a 5-coordinate geometry to five equivalent Sn and six equivalent Bi atoms. There are a spread of Sn–Sn bond distances ranging from 3.13–3.48 Å. There are a spread of Sn–Bi bond distances ranging from 3.33–3.62 Å. Bi is bonded in a 10-coordinate geometry to six equivalent Sn and four equivalent Bi atoms. There are two shorter (3.39 Å) and two longer (3.43 Å) Bi–Bi bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SnBi3 by Materials Project

SnBi3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sn is bonded in a body-centered cubic geometry to eight equivalent Bi atoms. All Sn–Bi bond lengths are 3.42 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a body-centered cubic geometry to four equivalent Sn and four equivalent Bi atoms. All Bi–Bi bond lengths are 3.42 Å. In the second Bi site, Bi is bonded in a body-centered cubic geometry to eight equivalent Bi atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sn3Bi by Materials Project

BiSn3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Sn is bonded to eight equivalent Sn and four equivalent Bi atoms to form SnSn8Bi4 cuboctahedra that share corners with twelve equivalent SnSn8Bi4 cuboctahedra, edges with eight equivalent BiSn12 cuboctahedra, edges with sixteen equivalent SnSn8Bi4 cuboctahedra, faces with four equivalent BiSn12 cuboctahedra, and faces with fourteen equivalent SnSn8Bi4 cuboctahedra. All Sn–Sn bond lengths are 3.46 Å. All Sn–Bi bond lengths are 3.46 Å. Bi is bonded to twelve equivalent Sn atoms to form BiSn12 cuboctahedra that share corners with twelve equivalent BiSn12 cuboctahedra, edges with twenty-four equivalent SnSn8Bi4 cuboctahedra, faces with six equivalent BiSn12 cuboctahedra, and faces with twelve equivalent SnSn8Bi4 cuboctahedra.

36 MATERIALS SCIENCE↗