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All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Curating NASA's Past, Present, and Future Astromaterial Sample Collections

The Astromaterials Acquisition and Curation Office at NASA Johnson Space Center (hereafter JSC curation) is responsible for curating all of NASA's extraterrestrial samples. JSC presently curates 9 different astromaterials collections in seven different clean-room suites: (1) Apollo Samples (ISO (International Standards Organization) class 6 + 7); (2) Antarctic Meteorites (ISO 6 + 7); (3) Cosmic Dust Particles (ISO 5); (4) Microparticle Impact Collection (ISO 7; formerly called Space-Exposed Hardware); (5) Genesis Solar Wind Atoms (ISO 4); (6) Stardust Comet Particles (ISO 5); (7) Stardust Interstellar Particles (ISO 5); (8) Hayabusa Asteroid Particles (ISO 5); (9) OSIRIS-REx Spacecraft Coupons and Witness Plates (ISO 7). Additional cleanrooms are currently being planned to house samples from two new collections, Hayabusa 2 (2021) and OSIRIS-REx (2023). In addition to the labs that house the samples, we maintain a wide variety of infra-structure facilities required to support the clean rooms: HEPA-filtered air-handling systems, ultrapure dry gaseous nitrogen systems, an ultrapure water system, and cleaning facilities to provide clean tools and equipment for the labs. We also have sample preparation facilities for making thin sections, microtome sections, and even focused ion-beam sections. We routinely monitor the cleanliness of our clean rooms and infrastructure systems, including measurements of inorganic or organic contamination, weekly airborne particle counts, compositional and isotopic monitoring of liquid N2 deliveries, and daily UPW system monitoring. In addition to the physical maintenance of the samples, we track within our databases the current and ever changing characteristics (weight, location, etc.) of more than 250,000 individually numbered samples across our various collections, as well as more than 100,000 images, and countless "analog" records that record the sample processing records of each individual sample. JSC Curation is co-located with JSC's Astromaterials Research Office, which houses a world-class suite of analytical instrumentation and scientists. We leverage these labs and personnel to better curate the samples. Part of the cu-ration process is planning for the future, and we refer to these planning efforts as "advanced curation". Advanced Curation is tasked with developing procedures, technology, and data sets necessary for curating new types of collections as envi-sioned by NASA exploration goals. We are (and have been) planning for future cu-ration, including cold curation, extended curation of ices and volatiles, curation of samples with special chemical considerations such as perchlorate-rich samples, and curation of organically- and biologically-sensitive samples.

Zeigler, R. A.↗
NASA NTRS1972

GLC of amino acids - A survey of contamination.

Analyses of biological substances and geochemical samples, of both terrestrial and extraterrestrial origin, are reported for amino acids at the 1-10 nanogram per gram level achieved by gas-liquid and ion-exchange chromatographic methods. These studies have shown that nanogram quantities of amino acids, present in water extracts of geochemical samples or in other samples of low amino acid concentration, can be successfully determined only if the researcher is well aware of the possible sources of contamination.

Rash, J. J.↗
NASA NTRS1971

Chemical composition of lunar anorthosites and their parent liquids.

Data obtained in a trace element analysis of some anorthosite and anorthositic fragments are presented. The low Mg concentrations of the Apollo 15 anorthosite and the KREEP anorthosite reflect the mineralogical purity of these samples. They are so pure that their composition can be taken as that of liquidus plagioclases. Some of the characteristics of the parent liquids of these plagioclases can be calculated from the liquid-plagioclase distribution coefficients.

Hubbard, N. J.↗
NASA NTRSDate not supplied

Investigating Commercial Off-The-Shelf (COTS) Glovebox and Support Components Compared to Custom Curatorial Laboratories

There is a need envisioned to investigate the application of commercial off-the-shelf (COTS) systems as tools that could be used within commercial preliminary curation as the expected space economy is supported and begins to take flight. NASA is involved with supporting and developing the space economy [1] and therefore it’s feasible that at some point, a commercial space company would bring back materials and either store initially, or permanently, within COTS equipment as a stand-in for custom curation laboratories. While utilizing opportunities to explore this capability at NASA-Johnson Space Center (JSC) during the establishment of other laboratories [2] it was realized that cleanliness and/or other properties could be evaluated for these COTS systems during their installation in advanced research facilities that are not ISO-class rated clean rooms. Several aspects of a COTS-Curation system were explored including various gloves for curation manipulation within a negative pressure glovebox (Fig.1), Balazs organic and inorganic contaminant levels testing prior to glovebox ever being used, mode swapping comparison of recirculation vs. single pass, constant monitoring of oxygen (O2) and moisture (H2O) levels in various conditions, etc. To acquire inorganic and organic compound loads inside the glovebox, Balazs wafer testing and gas sampling were implemented. These are standardized analytical tests provided by Balazs™ NanoAnalysis, a division of Air Liquide USA. Deployment of 8-inch silicon wafer witness plates for 24-hours in an undisturbed environment capture the organic compound load and inorganic trace metal contents which can be obtained by Vapor Phase Decomposition Inductively Coupled Plasma Mass Spectrometry (VPD ICP-MS). Balazs gas sample analysis was also performed for better measurements of volatile organic compounds (VOC) in glovebox air analyzed by Thermal Desorption Gas Chromatography Mass Spectrometry (TD GC-MS). These analytical testings were carried out in a controlled ultra high pure (UHP) gaseous nitrogen (N2)-purged environment where oxygen and moisture contents were continuously monitored at certain temperature and pressure. The preliminary outcomes of these testings are promising. The COTS systems appear to maintain the steady-state controlled environment for days, if not weeks, with uninterrupted gaseous N2-supply which was operated from a standard medium pressure LN2 250L 230L dewar, exchanged as needed. The outgassing load can be maintained by selecting the glove materials that have the least outgassing and particle shedding performances. Further experiments will be considered to validate the preliminary findings. While this project is exploratory, it is not intended as an endorsement by NASA Curation for approved materials or usage for advanced curatorial activities. NASA does not endorse nor promote any one particular product or company. References: [1] McCubbin F. M. et al. (2019) Space Science Reviews 215:A48. [2] Lewis, E.K. et. al (2024) LPSC LV, Abstract #2457.

Curation↗
NASA NTRS1988

Observations on the dynamics of electromagnetically levitated liquid metals and alloys at elevated temperatures

Electromagnetic levitation and heating of small (0.5 to 1.0 gm) samples of Cu, Ni, and Ni-base alloys were performed in inert atmospheres. These experiments were recorded by high-speed photography using both regular film and video methods. Initial studies revealed interesting dynamics of the droplets that included axisymmetric oscillation, rotation, and oscillation mode changes. An attempt is made to explain the behavior using available models.

Hansen, G. P.↗
NASA NTRS2008

Comparison of CERES-MODIS Stratus Cloud Properties with Ground-Based Measurements at the DOE ARM Southern Great Plains Site

Overcast stratus cloud properties derived for the Clouds and the Earth's Radiant Energy system (CERES) Project using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data are compared with observations taken at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site from March 2000 through December 2004. Retrievals from ARM surface-based data were averaged over a 1-hour interval centered at the time of each satellite overpass, and the CERES-MODIS cloud properties were averaged within a 30-km x 30 km box centered on the ARM SGP site. Two datasets were analyzed: all of the data (ALL) which include multilayered, single-layered, and slightly broken stratus decks and a subset, single-layered unbroken decks (SL). The CERES-MODIS effective cloud heights were determined from effective cloud temperature using a lapse rate method with the surface temperature specified as the 24-h mean surface air temperature. For SL stratus, they are, on average, within the ARM radar-lidar estimated cloud boundaries and are 0.534 +/- 0.542 km and 0.108 +/- 0.480 km lower than the cloud physical tops and centers, respectively, and are comparable for day and night observations. The mean differences and standard deviations are slightly larger for ALL data, but not statistically different to those of SL data. The MODIS-derived effective cloud temperatures are 2.7 +/- 2.4 K less than the surface-observed SL cloud center temperatures with very high correlations (0.86-0.97). Variations in the height differences are mainly caused by uncertainties in the surface air temperatures, lapse rates, and cloud-top height variability. The biases are mainly the result of the differences between effective and physical cloud top, which are governed by cloud liquid water content and viewing zenith angle, and the selected lapse rate, -7.1 K km(exp -1). Based on a total of 43 samples, the means and standard deviations of the differences between the daytime Terra and surface retrievals of effective radius r(sub e), optical depth, and liquid water path for SL stratu are 0.1 +/- 1.9 micrometers (1.2 +/- 23.5%), -1.3 +/- 9.5 (-3.6 +/-26.2%), and 0.6 +/- 49.9 gm (exp -2) (0.3 +/- 27%), respectively, while the corresponding correlation coefficients are 0.44, 0.87, and 0.89. For Aqua, they are 0.2 +/- 1.9 micrometers (2.5 +/- 23.4%), 2.5 +/- 7.8 (7.8 +/- 24.3%), and 28.1 +/- 52.7 gm (exp -2) (17.2 +/- 32.2%), as well as 0.35, 0.96, and 0.93 from a total of 21 cases. The results for ALL cases are comparable. Although a bias in R(sub e) was expected because the satellite retrieval of effective radius only represents the top of the cloud, the surface-based radar retrievals revealed that the vertical profile of r(sub e) is highly variable with smaller droplets occurring at cloud top in some cases. The larger bias in optical depth and liquid water path for Aqua is due, at least partially, to differences in the Terra and Aqua MODIS visible channel calibrations. methods for improving the cloud-top height and microphysical property retrievals are suggested.

Dong, Xiquan↗
NASA NTRS2018

Heating Experiments of the Tagish Lake Meteorite: Investigation of the Effects of Short-Term Heating on Chondritic Organics

We present in this study the effects of short-term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmo thermometers. The kinetics of short-term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites - potential analogues of the target asteroid Ryugu of the Hayabusa2 mission - which had experienced post-hydration, short-duration local heating. In an attempt to understand the effects of short-term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X-ray microscopy utilizing X-ray absorption near edge structure spectroscopy, and ultra-performance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 degrees Centigrade for 96 hours, as the OM maturity trend was influenced by the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s-sigma σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long-term internal heating.

Chan, Queenie Hoi Shan↗
NASA NTRS1971

Apollo 14 - Nature and origin of rock types in soil from the Fra Mauro formation.

Compositions of glasses in the Apollo 14 soil correspond to four types of Fra Mauro basalts, to mare basalts and soils, and, in minor amounts, to gabbroic anorthosite and potash granite. The Fra Mauro basalts can be related by simple low pressure crystal-liquid fractionation that implies a parent composition like that of Apollo 14 sample 14310.

Aitken, F. K.↗
NASA NTRS1978

The use of an ion-beam source to alter the surface morphology of biological implant materials

An electron bombardment, ion thruster was used as a neutralized-ion beam sputtering source to texture the surfaces of biological implant materials. Scanning electron microscopy was used to determine surface morphology changes of all materials after ion-texturing. Electron spectroscopy for chemical analysis was used to determine the effects of ion texturing on the surface chemical composition of some polymers. Liquid contact angle data were obtained for ion textured and untextured polymer samples. Results of tensile and fatigue tests of ion-textured metal alloys are presented. Preliminary data of tissue response to ion textured surfaces of some metals, polytetrafluoroethylene, alumina, and segmented polyurethane were obtained.

Weigand, A. J.↗
NASA NTRS1977

KREEP petrogenesis revisited

An experimentally determined crystallization sequence for a composition similar to the LKFM breccias and experimentally determined crystal/liquid distribution coefficients are used to calculate the evolution of the abundances of several key elements during the crystallization of LKFM liquids. Results indicate that the LKFM breccias are not themselves precursors to Apollo 15 igneous KREEP, but that compositions slightly poorer in Ti and Fe might be. Consideration of the evolution of Ti and Sm abundances during the differentiation of proposed whole-moon compositions suggests that it may be necessary to appeal to 'unorthodox' mechanisms such as magma hybridization or interaction of magma with genetically unrelated minerals within the lunar crust to produce KREEP-rich liquids having the observed Ti/Sm. It is concluded that the compositions of samples with Sm contents greater than those in LKFM are dominated by igneous processes, while samples with lower Sm contents may be mixtures of an anorthositic component, a Mg-rich Sm-poor component, and a component similar in composition to LKFM.

Mckay, G. A.↗
NASA NTRS1985

Free-surface phenomena under low- and zero-gravity conditions

A free surface experiment using a liquid doped with a fluorescent dye under sheet illumination is summarized. The work includes the selection of a CCD camera for use during the design stages of the experiment as well as a preliminary demonstration of this technique in the production of a contour map of a liquid-liquid interface with better than 0.1 mm resolution. With a different data sampling and storage procedure, the image processing is reduced to a simple thresholding procedure which can be done in hardware.

Hesselink, L.↗
NASA NTRS1985

Statistical mechanics of light elements at high pressure. VII - A perturbative free energy for arbitrary mixtures of H and He

A model free energy is presented which accurately represents results from 45 high-precision Monte Carlo calculations of the thermodynamics of hydrogen-helium mixtures at pressures of astrophysical and planetophysical interest. The free energy is calculated using free-electron perturbation theory (dielectric function theory), and is an extension of the expression given in an earlier paper in this series. However, it fits the Monte Carlo results more accurately, and is valid for the full range of compositions from pure hydrogen to pure helium. Using the new free energy, the phase diagram of mixtures of liquid metallic hydrogen and helium is calculated and compared with earlier results. Sample results for mixing volumes are also presented, and the new free energy expression is used to compute a theoretical Jovian adiabat and compare the adiabat with results from three-dimensional Thomas-Fermi-Dirac theory. The present theory gives slightly higher densities at pressures of about 10 megabars.

Hubbard, W. B.↗
NASA NTRS1989

Surface composition of solid-rocket exhausted aluminum oxide particles

Particulate samples of aluminum oxide were collected on Teflon filters from the exhaust plume of the Space Shuttle (STS-61A, October 30, 1985) over the altitude interval 4.6-7.6 km immediately after launch. These particles were analyzed using SEM, energy-dispersive X-ray analysis, electron spectroscopy for chemical analysis, X-ray fluorescent spectroscopy, and conventional wet-chemical techniques. The samples were 0.6-1.0 percent surface-chlorided (chlorided meaning predominantly aluminum chlorides and oxychlorides, possibly including other adsorbed forms of chloride) by weight. This level of chloriding is about one-third of the amount determined previously from laboratory-prepared alumina and surface site samples of solid-rocket-produced alumina (SRPA) after both had been exposed to moist HCl vapor at temperatures down to ambient. This level is equivalent to previous laboratory results with samples exposed to moist HCl at temperatures above the boiling point of water. It is suggested that the present lower chloriding levels, determined for samples from a 'dry' Shuttle exhaust cloud, underscore the importance of a liquid water/hydrochloric acid phase in governing the extent of surface chloriding of SRPA. The reduced chloriding is not trivial with respect to potential physical/chemical modification of the SRPA particle surfaces and their corresponding interaction with the atmosphere.

Cofer, Wesley R., III↗
NASA NTRS2000

Modeling Specular Exchange Between Concentric Cylinders in a Radiative Shielded Furnace

The objective of this research is to develop and validate mathematical models to characterize the thermal performance of a radiative shielded furnace, the University of Alabama in Huntsville (UAH) Isothermal Diffusion Oven. The mathematical models are validated against experimental data obtained from testing the breadboard oven in a terrestrial laboratory environment. It is anticipated that the validation will produce math models capable of predicting the thermal performance of the furnace over a wide range of operating conditions, including those for which no experimental data is available. Of particular interest is the furnace core temperature versus heater power parametric and the transient thermal response of the furnace. Application to a microgravity environment is not considered, although it is conjectured that the removal of any gravity dependent terms from the math models developed for the terrestrial application should yield adequate results in a microgravity environment. The UAH Isothermal Diffusion Oven is designed to provide a thermal environment that is conducive to measuring the diffusion of high temperature liquid metals. In addition to achieving the temperatures required to melt a sample placed within the furnace, reducing or eliminating convective motions within the melt is an important design consideration [1]. Both of these influences are reflected in the design of the furnace. Reducing unwanted heat losses from the furnace is achieved through the use of low conductivity materials and reflective shielding. As evidenced by the highly conductive copper core used to house the sample within the furnace, convective motions can be greatly suppressed by providing an essentially uniform thermal environment. An oven of this design could ultimately be utilized in a microgravity environment, presumably as a experiment payload. Such an application precipitates other design requirements that limit the resources available to the furnace such as power, mass, volume, and possibly even time. Through the experimental and numerical results obtained, the power requirements and thermal response time of the breadboard furnace are quantified.

Schunk, Richard Gregory↗
NASA NTRS2002

Amino acids in the Tagish Lake Meteorite

High-performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and CI carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the CI Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated fiom a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P- or D-type asteroids. If the Tagish Lake meteorite was indeed derived fiom these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.

Kminek, G.↗
NASA NTRS2019

Polarimetric Retrievals of Cloud Droplet Number Concentrations

Cloud droplet number concentration (Nd) is an important parameter of liquid clouds and is crucial to understanding aerosol-cloud interactions. It couples boundary layer aerosol composition, size and concentration with cloud reflectivity. It affects cloud evolution, precipitation, radiative forcing, global climate and, through observation, can be used to partially monitor the first indirect effect. With its unique combination of multi-wavelength, multi-angle, total and polarized reflectance measurements, the Research Scanning Polarimeter (RSP) retrieves Nd with relatively few assumptions. The approach involves measuring cloud optical thickness, mean droplet extinction cross-section and cloud physical thickness. Polarimetric observations are capable of measuring the effective variance, or width, of the droplet size distribution. Estimating cloud geometrical thickness is also an important component of the polarimetric Nd retrieval, which is accomplished using polarimetric measurements in a water vapor absorption band to retrieve the amount of in-cloud water vapor and relating this to physical thickness. We highlight the unique abilities and quantify uncertainties of the polarimetric approach. We validate the approach using observational data from the North Atlantic and Marine Ecosystems Study (NAAMES). NAAMES targets specific phases in the seasonal phytoplankton lifecycle and ocean-atmosphere linkages. This study provides an excellent opportunity for the RSP to evaluate its approach of sensing Nd over a range of concentrations and cloud types with in situ measurements from a Cloud Droplet Probe (CDP). The RSP and CDP, along with an array of other instruments, are flown on the NASA C-130 aircraft, which flies in situ and remote sensing legs in sequence. Cloud base heights retrieved by the RSP compare well with those derived in situ (R=0.83) and by a ceilometer aboard the R.V. Atlantis (R=0.79). Comparing geometric mean values from 12 science flights throughout the NAAMES-1 and NAAMES-2 campaigns, we find a strong correlation between Nd retrieved by the RSP and CDP (R=0.96). A linear least squares fit has a slope of 0.92 and an intercept of 0.3 cm−3. Uncertainty in this comparison can be attributed to cloud 3D effects, nonlinear liquid water profiles, multilayered clouds, measurement uncertainty, variation in spatial and temporal sampling, and assumptions used within the method. Radiometric uncertainties of the RSP measurements lead to biases on derived optical thickness and cloud physical thickness, but these biases largely cancel out when deriving Nd for most conditions and geometries. We find that a polarimetric approach to sensing Nd is viable and the RSP is capable of accurately retrieving Nd for a variety of cloud types and meteorological conditions.

Droplet concentration↗
NASA NTRSDate not supplied

The Search for Chiral Asymmetry as a Potential Biosignature in Samples from Mars

The search for evidence of extraterrestrial life in our solar system has been guided by our under-standing of terrestrial biology and its associated biosignatures. The observed homochirality in all life on Earth, that is, the predominance of “left-handed” or L-amino acids and “right-handed” or D-sugars, is a unique property of life that is crucial for molecular recognition, enzymatic function, information storage and structure, and is thought to be a prerequisite for the origin or early evolution of life. Therefore, the detection of L- or D-excesses of chiral amino acids or sugars could be a powerful indicator of extant or extinct life on Mars or other habitable environments in our solar system. However, studies of primitive meteorites have revealed that they contain extraterrestrial amino acids and sugar acids with large enantiomeric excesses (60% and higher) that resulted from non-biological processes [1], complicating the use of chiral asymmetry by itself as a definitive biosignature. The exploration of habitable environments on Mars, including an assessment of the preservation potential for complex organics of either abiotic or biological origin, is an objective of both current and future Mars missions. Now with the unambiguous detection of indigenous organic matter in sedimentary rocks by the Sample Analysis at Mars (SAM) instrument suite on Mars [2-5], NASA’s Curiosity rover has found evidence of the preservation of potential chemical biosignatures in the martian near surface. Although amino acids have not yet been identified by in situ measurements on Mars [5], indigenous achiral amino acids have been identified in one martian meteorite [6]. It is expected that amino acid racemization would be very slow and any chiral or isotopic signatures from an extinct martian biota could be preserved for billions of years, given the extremely cold and dry surface conditions [7]. The ESA/Roscosmos ExoMars mission scheduled for launch next year includes the Rosalind Franklin rover designed to acquire samples from a depth of ~2 m and deliver them to a suite of instruments, including the Mars Organic Molecule Analyzer (MOMA). The MOMA instrument contains a wet chemistry experiment designed specifically for the detection of amino acids and measurement of their enantiomeric compositions [8]. The complexity and limited duration of spaceflight operations, and the known analytical challenges associated with in situ extraction and characterization of trace reduced organic com-pounds in ancient rocks, make it challenging to determine the origins of martian organic matter found to date. Coordinated state-of-the-art laboratory measurements of returned samples from Mars that include spatially resolved chemical, mineralogical, bulk and molecule-specific isotopic, and enantiomeric measurements will be required to firmly establish whether the complex organic matter detected on Mars derives from bio-tic or abiotic processes. Ultimately, Mars Sample Return of rock cores collected by NASA’s Perseverance rover may be our best chance of identifying chemical biosignatures, including any chiral amino acid asymmetry resulting from a past or present martian biota, if one ever existed on Mars. Here we review our current knowledge of the distributions, and enantiomeric and isotopic com-positions of amino acids found in meteorites compared to terrestrial biochemistry. We also propose a set of measurement criteria that should be used to help establish the sources of any amino acids detected in samples returned from Mars using state-of-the-art gas and liquid chromatography mass spectrometry techniques [1].

D P Glavin↗
NASA NTRS1985

Containerless Processing of Undercooled Melts

The physical mechanisms controlling liquid undercooling were studied for application to solidification processing methods. The undercooling potential of containerless processing was assessed on droplet samples of high melting temperature metals drop tube and drop tower facilities and in a laboratory-scale apparatus. New insight into nucleation and crystal growth will be obtained in undercooled liquids of high melting temperature iron and nickel-base systems. The processing parameters include melt superheat, droplet size and particle statistics and droplet surface coating. The solidification behavior is determined by thermal analysis and by structural and metallographic characterization.

Perepezko, J. H.↗