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  • 1
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    Non-contact temperature measurement of a falling drop (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The 105 meter drop tube at NASA-Marshall has been used in a number of experiments to determine the effects of containerless, microgravity processing on the undercooling and solidification behavior of metals and alloys. These experiments have been limited, however, because direct temperature measurement of the falling drops has not been available. Undercooling and nucleation temperatures are calculated from thermophysical properties based on droplet cooling models. In most cases these properties are not well known, particularly in the undercooled state. This results in a large amount of uncertainty in the determination of nucleation temperatures. If temperature measurement can be accomplished then the thermal history of the drops could be well documented. This would lead to a better understanding of the thermophysical and thermal radiative properties of undercooled melts. An effort to measure the temperature of a falling drop is under way. The technique uses two color pyrometry and high speed data acquisition. The approach is presented along with some preliminary data from drop tube experiments. The results from droplet cooling models is compared with noncontact temperature measurements.
    Keywords: MATERIALS PROCESSING
    Type: JPL, Proceedings of the Second Noncontact Temperature Measurement Workshop; p 183-202
    Format: application/pdf
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  • 2
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    NASA-sponsored containerless processing experiments (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An outline is presented of containerless processing and facilities at Intersonics which is sponsored by NASA. There are electromagnetic, acoustic, and aerodynamic levitation facilities. There are also laser beam and arc lamp heating systems along with state of the art noncontact temperature and optical property measurement facilities. Nonintrusive diagnostic techniques with Laser Induced Fluorescence and mass spectrometer are also available. Controlled atmosphere processing, gas quenching, and proven microgravity processing technology is part of the Intersonics capabilities.
    Keywords: MATERIALS PROCESSING
    Type: JPL, Proceedings of the First Workshop on Containerless Experimentation in Microgravity; p 57-76
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  • 3
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    Very high temperature chemistry: Science justification for containerless experimentation in space (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A summary is presented of the justification for application of containerless processing in space to high temperature science. Low earth orbit offers a gravitational environment that allows samples to be positioned in an experimental apparatus by very small forces. Well controlled experiments become possible on reactive materials at high temperatures in a reasonably quiescent state and without container contamination. This provides an opportunity to advance the science of high temperature chemistry that can only be realized with a commitment by NASA to provide advanced facilities for in-space containerless study of materials at very high temperature.
    Keywords: MATERIALS PROCESSING
    Type: JPL, Proceedings of the First Workshop on Containerless Experimentation in Microgravity; p 54-56
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  • 4
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    Undercooling studies on Nb-Pt and Nb-Si alloys using the 105 meter drop tube (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Niobium-platinum samples of compositions ranging from 16 to 32 at. pct have been undercooled to as much as 540 K in the low gravity, containerless environment of a 105 meter drop tube. Undercooling was terminated in the Nb-Pt samples by the nucleation and growth of the Nb3Pt phase. In the 16-18 at. pct Pt samples, this resulted in samples which are completely Nb3Pt, in contrast to both the equilibrium phase diagram and the nonundercooled samples which formed with Nb dendrites and interdendritic Nb3Pt. Undercoolings for the Nb-Si samples were up to 670 K, which corresponds to 27 percent of the liquidus temperature or 80 percent of the estimated hypercooling limit. In the Nb-Si system, a coupled zone was identified as well as a metastable extension of the solubility limit of Si in Nb due to deep undercooling.
    Keywords: MATERIALS PROCESSING
    Type: Advances in Space Research (ISSN 0273-1177); 8; 12, 1
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  • 5
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    Undercooling of niobium-germanium alloys in a 100 meter drop tube (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The undercoolings of pure Nb and Nb-Ge alloys are examined using the 100-m drop tube of the Marshall Space Flight Center. The temperatures of the samples prior to release were measured, and IR detectors were utilized to monitor recalescence from solidification. It is observed that the Nb and Nb-Ge samples undercooled to the homogeneous nucleation limit. The data reveal that all the samples displayed a dendritic primary phase, except for alloys nucleating in the beta-phase field, which had a cellular phase. The composition of these phases are studied using EDXA; it is detected that the composition of the phases corresponds to the Jorda (1978) phase diagram.
    Keywords: MATERIALS PROCESSING
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  • 6
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    Determination of Nucleation Kinetic Parameters of Metallic Melts Using Electrostatic Levitation Techniques (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Results from electrostatic levitation studies using zirconium specimens will be presented. Analysis of the data permits the determination of nucleation kinetic parameters.
    Keywords: Solid-State Physics
    Type: 15th International Symposium on Experimental Methods for Microgravity Materials Science; Mar 06, 2003 - Mar 09, 2003; San Diego, CA; United States
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  • 7
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    Undercooling of bulk high temperature metals in the 100 meter drop tube (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The 100-meter drop tube at NASA Marshall Space Flight Center provides an excellent opportunity to study the effects of containerless, microgravity processing in metals and alloys. In a series of experiments high melting temperature pure metals were melted in an electron beam furnace and dropped in vacuum. Sample sizes ranged from 0.175 to 1.2 grams. Large undercoolings on the order of 18 percent of the melting temperature were observed in Ti, Zr, Nb, Mo, Rh, Ta, and Pt. Undercoolings of 5 to 18 percent T(m) were observed in Ru and Ir. These undercooling results are consistent, repeatable, and occur in a high percentage of experiments. The experimental technique will be presented as well as the resultant microstructures of undercooled drops. The data will be discussed with respect to nucleation theory.
    Keywords: MATERIALS PROCESSING
    Type: Materials processing in the reduced gravity environment of space; Dec 01, 1986 - Dec 03, 1986; Boston, MA; United States
    Format: text
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  • 8
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    Applications of containerless processing in the studies of metals and alloys (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The use of containerless processing in nucleation and microstructural studies of alloys is reviewed in terms of approaches and recent results. Drop-tube studies of niobium based on a statistical approach are discussed, and experiments are described which permit the study of the solidification front across the surface of a specimen. The various alloys studied are reviewed in terms of facilitated observations of metastability, chemical homogeneity, and microstructural refinement. Heterogeneous nucleation is reported for a preexponential factor of 10 exp 27 and a critical free energy of 46-56kT. The theoretical relationship between undercooling and solidification velocity correlates with containerless test observations at large solute concentrations. Containerless processing is effective for studying the properties of liquid metals or accessing the metastable thermodynamic regime.
    Keywords: MATERIALS PROCESSING
    Type: AIAA/IKI Microgravity Science Symposium; May 13, 1991 - May 17, 1991; Moscow; USSR
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  • 9
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    The Solidification Velocity of Undercooled Nickel and Titanium Alloys with Dilute Solute (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The study of solidification velocity is important for two reasons. First, understanding the manner in which the degree of undercooling of the liquid and solidification velocity affect the microstructure of the solid is fundamental. Second, there is disagreement between theoretical predictions of the relationship between undercooling and solidification velocity and experimental results. Thus, the objective of this research is to accurately and systematically quantify the solidification velocity as a function of undercooling for dilute nickel-and titanium-based alloys. The alloys chosen for study cover a wide range of equilibrium partition coefficients, and the results are compared to current theory.
    Keywords: Solid-State Physics
    Type: 2002 Microgravity Materials Science Conference; 63-73; NASA/CP-2003-212339
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  • 10
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    Undercooling of pure metals in a containerless, microgravity environment (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The 105-m drop tube at NASA/Marshall Space Flight Center has been used in a series of undercooling experiments on pure metals. Ti, Zr, Nb, Mo, Rh, Hf, Ta, and Pt were undercooled 17-20 percent of the melting temperature in a containerless, microgravity environment. Ir and Ru were undercooled to 13 percent Tm. Sample sizes ranged from 175 to 880 mg.
    Keywords: MATERIALS PROCESSING
    Type: Applied Physics Letters (ISSN 0003-6951); 49; 1342-134
    Format: text
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