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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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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Modeling the evolution of Sm and Eu abundances during lunar igneous differentiation

The current work presents models for the evolution of europium and samarium abundances during lunar igneous processes. The effect of probable variations in lunar temperature and oxygen fugacity, mineral-liquid distribution coefficients, and the crystallization or melting progression are considered in the model calculations. Changes in the proportions of crystallizing phases strongly influence the evolution of trace element abundances during fractional crystallization, and models must include realistic estimates of the major phase equilibria during crystallization. The results are applied to evaluating the possibility of generating KREEP-rich materials by lunar igneous processes.

Weill, D. F.↗
NASA NTRS1975

Petrogenesis of KREEP

Solid/liquid distribution coefficients (weight basis) were experimentally determined for a number of trace elements for olivine, orthopyroxene, plagioclase and ilmenite. Values of distribution coefficients were measured at 1200 C and a f sub O2 of 10 to the -13.0 power for liquids similar in composition to the olivine-opx-plagioclase peritectic in the pseudoternary system (Fe,Mg)2SiO4-CaAl2Si2O8-SiO2. Values were also measured at 1140 C and a f sub O2 of 10 to the -12.8 power for liquids similar in composition to high-Ti mare basalts. Major and trace element partitioning and relevant phase equilibria were used to investigate possible parent-daughter relationships between a number of highland samples and highly evolved KREEP-rich materials. Out of about 80 highlands samples tested, 33 were found to be possible parents to the KREEP-rich materials. The average composition of these samples is very similar to that of the Low-K Fra Mauro basalt (LKFM). A model is proposed to explain the production of LKFM-type material and more evolved members of the KREEP suite.

Mckay, G. A.↗
NASA NTRS1976

Petrogenesis of KREEP

Solid/liquid distribution coefficients were experimentally determined for a number of trace elements for olivine, orthopyroxene, plagioclase and ilmenite. Major- and trace-element partitioning and relevant phase equilibria are used to study possible parent-daughter relationships between a number of highland samples and highly evolved KREEP-rich materials. A model is proposed in which low-K Fra Mauro basalt type material was produced by fractionation of large amounts of olivine and lesser amounts of plagioclase from undifferentiated lunar material at about 4.4 AE.

Mckay, G. A.↗
NASA NTRS1978

Crystallization of a lunar magma ocean

The results of applying the presently most detailed thermal model to the cooling, crystallization and differentiation of a lunar magma ocean are used to delineate its general features, i.e., those features that are model independent within reasonable variations in ocean characteristics. Two primitive lunar compositions are used to illustrate the effect of different compositions and phase equilibria on the solidification time and mineralogy of magma oceans. The magma ocean thermal model led to some inferences about the thermal evolution of the outer portion of the moon modeled as isolated magma pods rather than as a magma ocean.

Minear, J. W.↗
NASA NTRS1978

The bearing of spinel cataclasites on the crust-mantle structure of the moon

Subsolidus thermodynamic calculations have been made to define the temperature and pressure conditions required to equilibrate lunar spinel cataclasites (olivine + high alumina orthopyroxene + pleonaste spinel + plagioclase + or - cordierite) that occur as clasts in 15445, 73263, and 72435. The results, which are subject to modification by improved thermodynamic data and experiment, indicate that those samples that are cordierite-free and of high Mg/(Mg + Fe) were derived from the lower crust and possibly from a high-velocity zone of the uppermost mantle. However, the cordierite-bearing type in 72435,8 /low Mg/(Mg + Fe)/ resided in the upper levels of the crust prior to excavation by impact. Consideration of the relevant supersolidus phase equilibria indicates that the whole-rock chemistry of all spinel cataclasites can only be explained by pleonaste spinel accumulation. These materials are interpreted to be primordial cumulate rocks formed during the differentiation of the lunar magma ocean.

Herzberg, C. T.↗
NASA NTRS1979

Advanced methods for preparation and characterization of infrared detector materials

Crystal growth of Hg sub 1-x Cd sub x Te and density measurements of ingot slices are discussed. Radial compositional variations are evaluated from the results of infrared transmission edge mapping. The pseudo-binary HgTe-CdTe phase diagram is examined with reference to differential thermal analysis measurements. The phase equilibria calculations, based on the 'regular association solution' theory (R.A.S.) are explained and, using the obtained R.A.S. parameters, the activities of Hg, Cd, and Te vapors and their partial pressures over the pseudo-binary melt are calculated.

Lehoczy, S. L.↗
NASA NTRS1980

Trace elements as quantitative probes of differentiation processes in planetary interiors

The characteristic trace element signature that each mineral in the source region imparts on the magma constitutes the conceptual basis for trace element modeling. It is shown that abundances of trace elements in extrusive igneous rocks may be used as petrological and geochemical probes of the source regions of the rocks if differentiation processes, partition coefficients, phase equilibria, and initial concentrations in the source region are known. Although compatible and incompatible trace elements are useful in modeling, the present review focuses primarily on examples involving the rare-earth elements.

Drake, M. J.↗
NASA NTRS1981

Two-phase models of quasar emission line regions

It is demonstrated that the emitting gas in clouds of quasar emission line regions must be confined by a hot intercloud medium, provided only that the heating mechanisms are strong enough to drive the low-density intercloud gas above a few tens of millions degrees K. The study of the thermal properties of the gas presented includes heating by photoionization, Compton scattering, suprathermal particles, absorption of radio frequency radiation, cloud friction, thermal conduction, and shocks. Cooling curves for photoionized gases are presented, and phase diagrams analogous to the pressure-temperature diagrams used in studying the interstellar medium are constructed for various conditions. It is shown that two-phase equilibria occur over a wide range of mean density, but over a much narrower range of pressure. The implications of these results for the emission line region are discussed, and it is shown that the emission clouds may be short-lived.

Krolik, J. H.↗
NASA NTRS1983

A two-pyroxene thermometer

Experimentally determined pyroxene phase relations at 800-1200 C are combined with calculated phase equilibria for the Di-En and Hd-Fs joins to yield a graphical two-pyroxene thermometer that should be suitable for a wide variety of rocks from the earth, the moon, and meteorites. The thermometer can be used directly with natural pyroxenes having low contents of Al and other minor components. Samples having higher contents of 'other' components require special projection onto the Ca-Mg-Fe pyroxene quadrilateral; Wo, En, and Fs as normally calculated will not yield correct temperatures. The special projection is required to approximate the activities of those components in natural pyroxenes. Whereas the effects of pressure are nonnegligible, they can be corrected for. It is pointed out that use of the thermometer for slowly cooled rocks may pose special problems if the pyroxenes have undergone granule exsolution (coalescence of exsolved material to form separate grains).

Lindsley, D. H.↗
NASA NTRS1984

Lunar sample analysis

Results are presented from an extensive series of new high resolution scanning electron microscope studies of the very primative group of meteorites known as unequilibrated chondrites. These include quantitative analyses of micrometer sized phases and interpretation in terms of relevant phase equilibria. Several new meteorite minerals including high chromium metal, have been discovered.

Housley, R. M.↗
NASA NTRS1984

Trace element abundances in megacrysts and their host basalts - Constraints on partition coefficients and megacryst genesis

Rare earth and other trace element abundances are determined in megacrysts of clinopyroxene, orthopyroxene, amphibole, mica, anorthoclase, apatite and zircon, as well as their host basalts, in an effort to gather data on mineral/melt trace element partitioning during the high pressure petrogenesis of basic rocks. Phase equilibria, major element partitioning and isotopic ratio considerations indicate that while most of the pyroxene and amphibole megacrysts may have been in equilibrium with their host magmas at high pressures, mica, anorthoclase, apatite, and zircon megacrysts are unlikely to have formed in equilibrium with their host basalts. It is instead concluded that they were precipitated from more evolved magmas, and have been mixed into their present hosts.

Irving, A. J.↗
NASA NTRS1986

High pressure cosmochemistry applied to major planetary interiors: Experimental studies

The overall goal of this project is to determine properties of the H-He-C-N-O system, as represented by small molecules composed of these elements, that are needed to constrain theoretical models of the interiors of the major planets. Much of our work now concerns the H2O-NH3 system. This project is the first major effort to measure phase equilibria in binary fluid-solid systems in diamond anvil cells. Vibrational spectroscopy, direct visual observations, and X-ray crystallography of materials confined in externally heated cells are our primary experimental probes. We also are collaborating with the shockwave physics group at Lawrence Livermore Laboratory in studies of the equation of state of a synthetic Uranus fluid and molecular composition of this and other H-C-N-O materials under planetary conditions.

Nicol, M. F.↗
NASA NTRS1988

Characteristics and carbon stable isotopes of fluids in the Southern Kerala granulites and their bearing on the source of CO2

Carbon dioxide-rich inclusions commonly occur in the banded charnockites and khondalites of southern Kerala as well as in the incipient charnockites formed by desiccation of gneisses along oriented zones. The combined high density fluid inclusion isochores and the range of thermometric estimates from mineral assemblages indicate entrapment pressures in the range of 5.4 to 6.1 Kbar. The CO2 equation of state barometry closely compares with the 5 plus or minus 1 Kbar estimate from mineral phases for the region. The isochores for the high density fluid inclusions in all the three rock types pass through the P-T domain recorded by phase equilibria, implying that carbon dioxide was the dominating ambient fluid species during peak metamorphic conditions. In order to constrain the source of fluids and to evaluate the mechanism of desiccation, researchers undertook detailed investigations of the carbon stable isotope composition of entrapped fluids. Researchers report here the results of preliminary studies in some of the classic localities in southern Kerala namely, Ponmudi, Kottavattom, Manali and Kadakamon.

Santosh, M.↗
NASA NTRS1989

An alternate hypothesis for the origin of Angra dos Reis - Porphyry, not cumulate

The Angra dos Reis achondrite is a unique meteorite of potentially great importance for understanding the origins of the solar system and of the terrestrial planets. It is proposed that the meteorite, which consists of megacrysts of Al-Ti augite (fassaite) in skeletal or cellular shapes, olivine, and possibly whitlockite in a fine-grained groundmass of the same materials plus spinel, is a porphyritic igneous rock modified by metamorphism. In this interpretation, the megacrysts represent cellular-textured phenocrysts, and the fine-grain groundmass represents crystallized or devitrified magma. Phase equilibria suggest that Angra dos Reis-like compositions could grow phenocrysts of fassaite pyroxene, olivine, and whitlockite. These same compositions could crystallize, without crystal sorting or accumulation, to an almost monomineralic fassaite pyroxenite.

Treiman, A. H.↗
NASA NTRS1989

The convective liquidus in a solidifying magma chamber - A fluid dynamic investigation

An experimental study of the solidification of a layer of paraffin cooled from above is reported. When the fluid is superheated, convection sets in at the beginning of cooling but rapidly decreases in intensity. Once the layer has lost its superheat, convection ceases and further cooling is by conduction. The interior temperature then remains constant until encountered by the upper crust. The convective liquidus is defined as the temperature threshold below which convection is very weak or nonexistent. In natural basaltic systems the convective liquidus, although strictly unknown, may be very close to the true liquidus. Rapid convection may therefore not be a dominant process during the crystallization of many magmna chambers; instead, convection is part of an overall intimate balance between phase equilibria, crystal growth, and heat transfer.

Brandeis, Genevieve↗
NASA NTRS1990

Reaction zone microstructure in a Ti3Al + Nb/SiC composite

A composite of Ti-25Al-13Nb (atomic percent) matrix with a continuous SiC fiber (SCS-6) reinforcement was fabricated by hot pressing powder cloths and mats of fiber. The fiber/matrix reaction zone was studied using scanning electron microscopy (SEM) and transmission electron microscopy/analytical electron microscopy (TEM/AEM) techniques. The extent of reaction was determined, phases were identified, and solute partitioning among the phases was determined. It was found that the matrix had reacted only with a portion of the carbon-rich outer layer of the SCS-6 fiber. The reaction zone contained two concentric zones which are distinguished by the presence of different carbide phases. Both zones contained a hexagonal Si-bearing phase, and one of the zones also contained some fine scattered porosity. The results are discussed with reference to available phase equilibria data.

Baumann, S. F.↗
NASA NTRS1991

Electrolysis of lunar soil to produce oxygen and metals

The discussion of melt electrolysis consists of three sections. The implications of the chemistry and physics of fluxed and raw melts on melt electrolysis are discussed first. This includes discussion of the factor that influence melt resistivity, melt viscosity, oxygen production efficiency, and the theoretical energy required to produce oxygen. Second, the implications of phase equilibria and solubilities in silicate melts on the selection of materials for container and electrodes are discussed. The implications of proposed container and electrode materials on melt composition and how this effects expected resistivities, viscosities, as outlined in the first section are discussed. Finally, a general discussion of the basic features of both the fluxed and unfluxed melt electrolysis is given, including their advantages and disadvantages and how they compare with alternative processes.

Colson, Russell O.↗