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NASA NTRS1993

Materials science on parabolic aircraft: The FY 1987-1989 KC-135 microgravity test program

This document covers research results from the KC-135 Materials Science Program managed by MSFC for the period FY87 through FY89. It follows the previous NASA Technical Memorandum for FY84-86 published in August 1988. This volume contains over 30 reports grouped into eight subject areas covering acceleration levels, space flight hardware, transport and interfacial studies, thermodynamics, containerless processing, welding, melt/crucible interactions, and directional solidification. The KC-135 materials science experiments during FY87-89 accomplished direct science, preparation for space flight experiments, and justification for new experiments in orbit.

Curreri, Peter A.↗

NASA NTRS1993

Liquidus temperatures in the Ti-Al system

Liquidus temperatures were determined for the titanium-aluminum system at compositions ranging from 41 to 62 at. pct Al. The measurements were obtained by inducing solidification of slightly undercooled melts under containerless processing conditions using electromagnetic levitation. Absolute temperatures were determined by optical pyrometry in combination with independent measurements of spectral emissivities by laser polarimetry. The present liquidus temperatures are in agreement with two sets of literature values and are consistent with a set of solid-state literature data. These values exceed those selected in one recent proposed phase diagram revision by about 30 K and are as much as 40 to 60 K higher than those in another proposed revision.

Anderson, C. D.↗

NASA NTRS1994

Heating And Positioning In A Microwave Cavity

Two reports describe theoretical and experimental studies of microwave dielectrophoretic positioning of spherical sample of lossy dielectric material in microwave resonant cavity and heating of positioned sphere by electro-magnetic field. Studies part of continuing effort to develop techniques for containerless processing of materials in microgravity. Previous studies in this series described in "Microwave Dielectrophoretic Levitation in Microgravity" (NPO-18824).

Jackson, Henry W.↗

NASA NTRS1992

Determination of the viscous acoustic field for liquid drop positioning/forcing in an acoustic levitation chamber in microgravity

The development of acoustic levitation systems has provided a technology with which to undertake droplet studies as well as do containerless processing experiments in a microgravity environment. Acoustic levitation chambers utilize radiation pressure forces to position/manipulate the drop. Oscillations can be induced via frequency modulation of the acoustic wave, with the modulated acoustic radiation vector acting as the driving force. To account for tangential as well as radial forcing, it is necessary that the viscous effects be included in the acoustic field. The method of composite expansions is employed in the determination of the acoustic field with viscous effects.

Lyell, Margaret J.↗

NASA NTRS1993

Liquidus temperature and optical properties measurement by containerless techniques

Reactive alloy liquidus temperatures measured by conventional, contained techniques are often in error due to reactions with containers and gaseous impurities. This paper describes a new liquidus temperature measurement technique that avoids these problems by employing containerless processing. This technique relies on precise and accurate noncontact temperature measurements (NCTM), which are made possible by spectral emissivity values. The spectral emissivities, epsilon(sub lambda), are measured along with the optical properties (real, n, and imaginary, k, components of the index of refraction) using polarimetric techniques on electromagnetically levitated specimens. Results from work done at Vanderbilt University and Intersonics on the Ti-Al system are presented to demonstrate the above techniques.

Anderson, Collin D.↗

NASA NTRS1995

NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

Johnson, D. R.↗

NASA NTRS1996

Material Reseach

Containerless processing experiments in space and in ground-based facilities such as the Drop Tube Facility at Marshall Space Flight Center provide a unique capabilty to study materials processing phenomena without the influence of walls on nucleation processes. This research will further develop that capability by new experiments with immesible systems. Nucleation and undercooling phenomena will be monitored using infra-red temperature measurements.

Workman, Gary L.↗

NASA NTRS1995

STS-94 Day 09 Highlights

On this ninth day of the STS-94 mission, the flight crew, Cmdr. James D. Halsell, Jr., Pilot Susan L. Still, Payload Cmdr. Janice E. Voss, Mission Specialists Michael L. Gernhardt and Donald A. Thomas, and Payload Specialists Gregory T. Linteris and Roger K. Crouch spend their morning in the Spacelab module working on several experiments. Thomas has been working with the Large Isothermal Furnace (LIF), a vacuum-heating furnace designed to heat large samples uniformly; the Middeck Glovebox (MGBX) unit; and the Internal Flows in a Free Drop Experiment (IFFD). The IFFD experiment involves containerless processing of materials using acoustic positioning techniques.

Source record↗

NASA NTRS1995

Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

Johnson, D. R.↗

NASA NTRS1995

A Method Based on Radiative Cooling for Detecting Structural Changes in Undercooled Metallic Liquids

We introduce a structure-sensitive parameter for undercooled melts which can be measured in containerless processing experiments. We have established that the ratio, R(T), of hemispherical total emissivity epsilon(sub T)(T) to constant-pressure specific heat c(sub p)(T) can serve as an indicator which is sensitive to any changes in short range atomic order in undercooled metallic melts. R(T) (triple bonds) epsilon(sub T)(T)/c(sub p)(T) values for nickel, zirconium, and silicon have been obtained using the high temperature electrostatic levitator while the levitated melts were undergoing purely radiative cooling into the deeply undercooled region. R(T) plots for undercooled liquid nickel and zirconium indicate no significant change in short-range structure from their melting temperatures to 15% undercooling. In contrast, liquid silicon shows marked short-range structural changes beginning above its melting temperature and extending throughout the undercooled region. The short-range structure of liquid silicon is related to the highly-directional covalent bonding which characterizes its solid form. The nickel and zirconium data show that epsilon(sub T) varies linearly with T, in support of metal emissivity theories.

Rulison, Aaron J.↗

NASA NTRS1998

On the Cu-Nb Phase Diagram and Solidified Microstructures

Container and containerless processing was employed to determine liquidus temperatures and to examine microstructural development in the Cu-Nb system. The Cu-Nb phase diagram of an S-shaped, near-horizontal liquidus, has been confirmed by both the temperature-time profiles and resultant microstructures with only Nb dendrites in a Cu matrix, which were obtained from crucible experiments under clean conditions. However, the microstructural pathways of Cu-Nb alloys are particularly sensitive to processing variables. By the addition of oxygen impurities or rapid solidification, droplet-shaped morphology was observed for some compositions, implying occurrence of a liquid-phase separation. The effects of impurities and cooling rates are analyzed in connection with a stable and metastable liquid miscibility gap, respectively.

Li, D.↗

NASA NTRS2001

Mechanisms for the Crystallization of Zblan

The heavy metal fluoride glasses represent a class of reasonably good glass forming compositions with very unique infrared optical properties that have been of interest to researchers for 20 years. The most extensively studied glass with the most potential for practical applications is ZBLAN which contains the fluorides of zirconium, barium, lanthanum, aluminum, and sodium. It has a broad transmission range (0.3-6 um), low index of refraction (about 1.43), low dispersion, low Raleigh scattering, ultra-low thermal 2 dispersion, and potential ultra-low signal attenuation. Potential applications include fiber amplifiers, fiber optic gyroscopes, delivery systems for laser cutting, drilling and surgery, radiation resistant data links, nonlinear optical systems, and ultra-low-loss repeater-less transcontinental and transoceanic optical fiber. Potential markets for these materials are in the tens of billions of dollars per year. Optical fiber from this system possess excellent transmission characteristics in the IR, but the glass is somewhat susceptible to nucleation and crystallization. The theoretical intrinsic loss coefficient for ZBLAN at 2 microns is 0.00 1 dB/Km. Extrinsic losses, however, cause significant attenuation. The lowest loss coefficient measured is 0.7 dB/Km. This compares with the loss coefficient for fiber optic grade fused silica glass of 0.2 dB/Km. The extrinsic losses in ZBLAN have been attributed to 1) impurities which might be lowered by containerless processing and 2) to scattering from micro-crystallites that form during glass preform production or during fiber drawing.

Ethridge, Edwin C.↗

NASA NTRS2002

Thermophysical Property Measurements in the MSFC ESL

Electrostatic Levitation (ESL) is an advanced technique for containerless processing of metals, ceramics, and semiconductors. Because no container is required, there is no contamination from reaction with a crucible, allowing processing of high temperature, highly reactive melts. The high vacuum processing environment further reduces possible contamination of the samples. Finally, there is no container to provide heterogeneous nucleation sites, so the undercooled range is also accessible for many materials. For these reasons, ESL provides a unique environment for measuring thermophysical properties of liquid materials. The properties that can be measured in ESL include density, surface tension, viscosity, electrical and thermal conductivity, specific heat, phase diagram, TTT- and CCT- curves, and other thermodynamic properties. In this paper, we present data on surface tension and viscosity, measured by the oscillating drop technique, and density, measured by an automated photographic technique, measured in the ESL at NASA Marshall Space Flight Center.

Hyers, R. W.↗

NASA NTRS2002

First Commerical Operations on the International Space Station

As part of NASA's mission of furthering the commercial development of space, the Space Product Development Office has sponsored the flight of seven commercial payloads to the International Space Station (ISS) during calendar year 2001. Most of these payloads, which are among the first users of this new laboratory, build upon successful commercial investigations that previously were restricted to the limited flight duration of the Space Shuttle. These commercial operations range from multi-media, in the form of Dreamtime, to biotechnology such as in Advanced Astroculture, to advanced materials such as Zeolite Crystal Growth. Industry investment in the commercial program has continued to remain high, while awaiting long term access to space, which the ISS provides. While the majority of early commercial use of the ISS is in the area of biotechnology, there is a significant shift towards commercial materials research over the next two years. In order to take fall advantage of the ISS, much of the commercial hardware is designed to be left on Station, while the Shuttle brings samples up and down. This not only makes good use of this valuable space resource, it has the added benefit of having commercial hardware available on the ISS for scientific users. In order to provide benefit to the entire NASA microgravity program, the scientific community on a space available basis can use a variety of commercial apparatus at very low cost. In addition to the solution crystal growth capability of Creosote Crystal Growth, in 2002 containerless processing will be available in the form of Space-DRUMS, and in 2003, thermophysical properties research can be performed in the Vulcan furnace. The first commercial operations on the ISS provides not only a much needed capability to the commercial development of space program, it also has the potential to augment the science program as well.

Nall, Mark E.↗

NASA NTRS2002

Spin-Up Instability of a Levitated Molten Drop in MHD-Flow Transition to Turbulence

When an alternating magnetic field interacts with induced eddy currents in a conducting body, there will be a repulsive force between the body and the driving coil system generating the field. This repulsive force is the basis of electromagnetic levitation, which allows containerless processing of different materials. The eddy currents in the conducting body also generate Joule heating. Axial rotation of electromagnetically levitated objects is a common observation in levitation systems and often an undesirable side effect of such experiments on 1-g and -g. There have been recent efforts to use magnetic damping and suppress this tendency of body rotation. The first report of rotation in EML drops was attributed to a slight asymmetry of the shape and location of the levitation coils could change the axis and speed of rotation. Other theories of sample rotation include a frequency difference in the traveling electromagnetic waves and a phase difference in two different applied fields of the same frequency. All of these different mechanisms share the following characteristics: the torque is small, constant for constant field strength, and very weakly dependent on the sample's temperature and phase (solid or liquid). During experiments on the MSL-1 (First Microgravity Science Laboratory) mission of the Space Shuttle (STS-83 and STS-94, April and July 1997), a droplet of palladium-silicon alloy was electromagnetically levitated for viscosity measurements. For the non-deforming droplet, the resultant MHD flow inside the drop is inferred from motion of impurities on the surface. These observations indicate formation of a pair of co-rotating toroidal flow structures inside the spheroidal levitated drop that undergo secondary flow instabilities. As rise in the fluid temperature rises, the viscosity falls and the internal flow accelerates and becomes oscillatory; and beyond a point in the experiments, the surface impurities exhibit non-coherent chaotic motion signifying emergence of turbulence inside the drop. In this work, a background of these set of observations will be given followed by a presentation of our results on the digital particle tracking analysis that has been performed on a number of available videos. The analysis indicates that the levitated drop attains a constant rotational speed during the melting phase and formation of the co-rotating axi-symmetric laminar toroidal structures. However, the rate of axial rotation increases dramatically during the deformation of the toroidal structures anti their breakup into chaotic entities. This new data suggests an interaction between the flow inside the levitated molten drop and the driving coils in the experiments. Possible mechanisms for this interaction will be reviewed. The data will also be used to make an assessment of existing theories on droplet rotation.

Abedian, B.↗

NASA NTRS2004

Enhanced Damping for Capillary Bridge Oscillation Using Velocity Feedback

The stability of cylindrical liquid bridges in reduced gravity is affected by ambient vibrations of the spacecraft. Such vibrations are expected to excite capillary modes of the bridge. The lowest-order unstable mode is particularly susceptible to vibration as the length of the bridge approaches the stability limit. This low-order mode is known as the (2,0) mode and is an axisymmetric varicose mode of one wavelength in the axial direction. In this work, an optical system is used to detect the (2,0)-mode amplitude. The derivative of the error signal produced by this detector is used to produce the appropriate voltages on a pair of ring electrodes which are concentric with the bridge. A mode-coupled Maxwell stress profile is thus generated in proportional to the modal velocity. Depending on the sign of the gain, the damping of the capillary oscillation can be either increased or decreased. This effect has been demonstrated in Plateau-tank experiments. Increasing the damping of the capillary modes on free liquid surfaces in space could be beneficial for containerless processing and other novel technologies. [work supported by NASA]

Wei, Wei↗

NASA NTRS2004

Science Using an Electrostatic Levitation Furnace in the MUCAT Sector at the APS

The original motivation for the construction of the BESL prototype was to obtain the first proof of a 50-year-old hypothesis regarding the solidification of liquid metals. Since the 1950s it has been known that under proper conditions liquid metals can be cooled below their melting temperature (undercooled) without crystallizing to the stable solid phase. In 1952 Frank proposed that this was because the atoms in the metallic liquid were arranged with the symmetry of an icosahedron, a Platonic solid consisting of 20 tetrahedra (4-sided pyramid-shaped polyhedra) arranged around a common center. Since this local atomic order is incompatible with the long-range translational periodicity of crystal phases, a barrier is formed to the formation of small regions of the crystal phase, the nucleation barrier. A proof of Frank's hypothesis required a direct correlation between measured icosahedral order in the undercooled liquid and the nucleation barrier. The tendency of sample containers to catalyze nucleation obscured this relation, requiring containerless techniques. Combining containerless processing techniques for electrostatically levitated droplets (ESL) with x-ray synchrotron methods, a team from Washington University, St. Louis, MO, NASA Marshall Space Flight Center, and MUCAT at the APS demonstrated an increasing icosahedral order in TiZrNi liquids with decreasing temperature below the melting temperature. The increased icosahedral order caused the transformation of the liquid to a metastable icosahedral quasicrystal phase, instead of the stable tetrahedrally-coordinated crystal intermetallic, giving the first clear demonstration of the connection between the nucleation barrier and the local structure of the liquid, verifying Frank's hypothesis for this alloy.

Goldman, A.↗

NASA NTRS2004

Enhanced Damping for Capillary Bridge Oscillation Using Velocity Feedback

Wei, Wei↗