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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Origin of iron meteorite groups IAB and IIICD

Several low Ni-iron meteorites previously classified with group IAB are reclassified with group IIICD because of lower Ge, Ga, W, and Ir concentrations and higher As concentrations. The low Ni extreme of IIICD is now 62 mg/g, and that of IAB is 64 mg/g. It is proposed that the meteorites of both groups formed as individual shock melts on a chondritic parent body. The differences in log element-log Ni slopes of the daughter irons demonstrate that there were detailed differences in the composition and size of phases in the parental material (e.g., more Ni in the sulfides or metal of IAB, or more Ge and Ir in the oxides of IIICD).

Wasson, J. T.↗
NASA NTRS1981

Corrosion of 310 stainless steel in H2-H2O-H2S gas mixtures: Studies at constant temperature and fixed oxygen potential

Corrosion of SAE 310 stainless steel in H2-H2O-H2S gas mixtures was studied at a constant temperature of 1150 K. Reactive gas mixtures were chosen to yield a constant oxygen potential of approximately 6 x 10 to the minus 13th power/cu Nm and sulfur potentials ranging from 0.19 x 10 to the minus 2nd power/cu Nm to 33 x 10 to the minus 2nd power/cu Nm. The kinetics of corrosion were determined using a thermobalance, and the scales were analyzed using metallography, scanning electron microscopy, and energy dispersive X-ray analysis. Two corrosion regimes, which were dependent on sulfur potential, were identified. At high sulfur potentials (p sub S sub 2 less than or equal to 2.7 x 10 to the minus 2nd power/cu Nm) the corrosion rates were high, the kinetics obeyed a linear rate equation, and the scales consisted mainly of sulfide phases similar to those observed from pure sulfication. At low sulfur potentials (P sub S sub 2 less than or equal to 0.19 x 10 to the minus 2nd power/cu Nm) the corrosion rates were low, the kinetics obeyed a parabolic rate equation, and scales consisted mainly of oxide phases.

Rao, D. B.↗
NASA NTRS1981

High-efficiency thin-film GaAs solar cells, phase2

Thin GaAs epi-layers with good crystallographic quality were grown using a (100) Si-substrate on which a thin Ge epi-interlayer was grown by CVD from germane. Both antireflection-coated metal oxide semiconductor (AMOS) and n(+)/p homojunction structures were studied. The AMOS cells were fabricated on undoped-GaAs epi-layers deposited on bulk poly-Ge substrates using organo-metallic CVD film-growth, with the best achieved AM1 conversion efficiency being 9.1%. Both p-type and n(+)-type GaAs growth were optimized using 50 ppm dimethyl zinc and 1% hydrogen sulfide, respectively. A direct GaAs deposition method in fabricating ultra-thin top layer, epitaxial n(+)/p shallow homojunction solar cells on (100) GaAs substrates (without anodic thinning) was developed to produce large area (1 sq/cm) cells, with 19.4% AM1 conversion efficiency achieved. Additionally, an AM1 conversion efficiency of 18.4% (17.5% with 5% grid coverage) was achieved for a single crystal GaAs n(+)/p cell grown by OM-CVD on a Ge wafer.

Yeh, Y. C. M.↗
NASA NTRS1980

Genesis of the Smartville arc-ophiolite, Sierra Nevada foothills, California

Rare earth element analyses of metavolcanic rocks from the Smartville, Calif. ophiolite divide the uniform suite of pillowed and massive lavas into the lower part consisting of massive, brecciated tholeiites, an intrusive dike-sill complex, and part of a plutonic suite. The tholeiites are light REE depleted with a (Ce)N range of 6.5 to 26.0 and (Yb)N of 6.0 to 30.0; it is suggested that the tholeiites were produced by partial melting of a LREE depleted source similar to MORB. The upper part of the volcanic pile is comprised of basaltic-andesitic flows and interbedded coarse to fine volcanic sediments; these 'calc-alkaline' rocks are light REE enriched with the (Ce)N range of 17.0-28.0 and (Yb)N of 8.0 to 12.0. Finally, petrographic investigations of volcanic sediments and sulfide ore deposits in the lava show that the ophiolite formed near a group of active submarine and subareal volcanoes.

Menzies, M.↗
NASA NTRS1980

Are sulfur isotope ratios sufficient to determine the antiquity of sulfate reduction

Possible limitations on the use of sulfur isotope ratios in sedimentary sulfides to infer the evolution of microbial sulfate reduction are discussed. Current knowledge of the ways in which stable sulfur isotope ratios are altered by chemical and biological processes is examined, with attention given to the marine sulfur cycle involving various microbial populations, and sulfur reduction processes, and it is noted that satisfactory explanations of sulfur isotope ratios observed in live organisms and in sediments are not yet available. It is furthermore pointed out that all members of the same genus of sulfate reducing bacteria do not always fractionate sulfur to the same extent, that the extent of sulfur fractionation by many sulfate-reducing organisms has not yet been determined, and that inorganic processes can also affect sulfur isotope fractionation values. The information currently available is thus concluded to be insufficient to determine the time of initial appearance of biological sulfate reduction.

Ashendorf, D.↗
NASA NTRS1980

The generation of electron hole pairs in very thin solar cells possessing an optical back-surface reflector

It is pointed out that very thin solar cells (1 micron thick or less) as, for example, amorphous silicon or cadmium sulfide cells, possessing a back surface reflector should be regarded as Fabry-Perot cavities as far as the generation of electron-hole pairs by light is concerned. The generation rate of electron-hole pairs as a function of distance from the front surface exhibits characteristic interference patterns which are not negligible and must be accounted for in an analysis of the performance of such a cell.

Von Roos, O.↗
NASA NTRS1981

Gaseous constituents in the plume from eruptions of Mount St. Helens

Measurements in the stratosphere of gaseous constituents in the plume of Mount St. Helens were obtained during five flights of the NASA U-2 aircraft between 19 May and 17 June 1980. Mixing ratios from gas chromatographic measurements on samples acquired about 24 hours after the initial eruption show considerable enhancement over nonvolcanic concentrations for sulfur dioxide (more than 1000 times), methyl chloride (about 10 times), and carbon disulfide (more than 3 times). The mixing ratio of carbonyl sulfide was comparable to nonvolcanic mixing ratios although 3 days later it was enhanced two to three times. Ion chromatography measurements on water-soluble constituents are also reported. Very large concentrations of chloride, nitrate, and sulfate ions were measured, implying large mixing ratios for the water-soluble gaseous constituents from which the anions are derived. Measurements of radon-222 present in the plume are also reported.

Inn, E. C. Y.↗
NASA NTRS1981

Lead isotopic studies of the Samail ophiolite, Oman

The isotopic composition of Pb and the concentrations of U, Th, and Pb are determined for samples from massive sulfides and lithologic units of the Samail ophiolite. It is shown that the magma that formed the ophiolite was probably derived from a depleted mantle, similar in Pb isotopic composition to the source area of mid-ocean ridge basalt. The gross geochemical characteristics of the mantle sources have remained almost unchanged for the last 100 million years. It is also shown that the U-Th-Pb systematics of the Samail formation indicate that local vertical heterogeneity in the oceanic crust can result from crystal fractionation and metasomatism at, and near, an oceanic spreading center.

Chen, J. H.↗
NASA NTRS1980

The surface composition of Amalthea

It is proposed that charged particles from the Jovian magnetosphere, contaminants such as sulfur from Io, and high-velocity micrometeoritic matter, combine to darken, redden, and alter the surface of Amalthea revealed by Voyager; whose few isolated bright spots have a distinct greenish spectrum. A major finding of this analysis is that available spectral reflectance data contain little information about the bulk composition of the satellite. The effects of contamination by sulfur and its allotropes are shown to redden a variety of bulk compositions: carbonaceous material, refractory minerals, iron and iron sulfides, and moderate temperature silicates. The bright, greenish spots probably identify locations in which atypical alteration processes occur, such as variations in the amount of contaminant sulfur in micrometeoritic glasses or in the relative abundances of certain sulfur allotropes.

Gradie, J.↗
NASA NTRS1981

Metal and associated phases in Bishunpur, a highly unequilibrated ordinary chondrite

Bishunpur is one of the most unequilibrated ordinary chondrites, and preserves a relatively unaltered record of solar nebular processes. A survey of three polished thin sections of Bishunpur revealed that metal occurs in three textural domains: (1) in the matrix, (2) within chondrules and (3) in coatings on chondrules. A table provides a textural classification of the various metal types found in Bishunpur and their composition. Electron-microprobe analyses are discussed, and similarities between Bishunpur metal and opaques and those in carbonaceous chondrites are considered. Attention is given to low-Ni kamacite grains in chondrule olivine, Si-bearing chondrule metal, spheroidal metal in chondrules, metal and sulfide-bearing rims, coarse matrix metal, and fine matrix metal formation.

Rambaldi, E. R.↗
NASA NTRS1980

An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces

A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

Shanabarger, M. R.↗
NASA NTRS1982

Analysis of volatile metabolites in biological fluids as indicators of prodromal disease condition

The volatile profile cannot be defined as a single class of substances, rather it is a broad spectrum of materials of different polarities characterized by having a boiling-point in the low to medium range (up to approximately 300 C) and the fact that the compounds are suitable for gas chromatography without derivatization. The organic volatile profiles are very complex mixtures of metabolic byproducts, intermediates, and terminal products of enzymatic degradations composed mainly of alcohols, ketones, aldehydes, pyrazines, sulfides, isothiocyanates, pyrroles, and furans. The concentration of organic volatiles in biological fluids covers a wide range with many important components present at trace levels. The complexity of the organic volatile fraction requires the use of capillary columns for their separation.

Zlatkis, A.↗
NASA NTRS1981

Advances in space power research and technology at the National Aeronautics and Space Administration

Progress and plans in various areas of the NASA Space Power Program are discussed. Solar cell research is narrowed to GaAs, multibandgap, and thin Si cells for arrays in planar and concentrator configurations, with further work to increase cell efficiency, radiation hardness, develop flexible encapsulants, and reduce cost. Electrochemical research is concentrating on increasing energy and power density, cycle and wet stand life, reliability and cost reduction of batteries. Further development of the Ni-H2 battery and O2-H2 fuel cell to multihundred kW with a 5 year life and 30,000 cycles is noted. Basic research is ongoing for alkali metal anodes for high energy density secondary cells. Nuclear thermoelectric propulsion is being developed for outer planets exploration propulsion systems, using Si-Ge generators, and studies with rare earth chalcogenides and sulfides are mentioned. Power Systems Management seeks to harmonize increasing power supply levels with inner and outer spacecraft environments, circuits, demands, and automatic monitoring. Concomitant development of bipolar transistors, an infrared rectenna, spacecraft charging measurement, and larger heat pipe transport capacity are noted.

Mullin, J. P.↗
NASA NTRS1981

Cumberland Falls chondritic inclusions - Mineralogy/petrology of a forsterite chondrite suite

The mineralogy and petrology of a suite of chondritic inclusions from the Cumberland Falls aubrite are investigated in order to clarify the relation of the inclusions to each other, forsterite chondrites, and the aubrites. Thin sections of nine chondritic inclusions and the achondritic matrix of Cumberland Falls were examined in reflected light, then analyzed for up to 12 elements by electron microprobe techniques. Minerals detected in abundant quantities include low-Ca pyroxene, olivine, plagioclase, kamacite, taenite, schreibersite, troilite, ferroan alabandite and daubreelite; diospide, oldhamite and a Ti-rich sulfide are found in one or two inclusions. The mineralogic compositions indicate similar degrees of reduction for the inclusions in the Cumberland Falls meteorites and in four meteorites identified as forsterite chondrites (Kakangari, Mt. Morris, Pontlyfni and Winona). The inclusions are found to be of a primitive composition, corresponding to petrological types 2 or 3, while the identification of jadeitic pyroxene in nearly all inclusions indicates a substantial degree of shock. The results suggest that the inclusions formed from nebular material that condensed and accreted over a broad redox range, and experienced tertiary shock in a collision with an enstatite meteorite in which the Cumberland Falls meteorite formed.

Neal, C. W.↗
NASA NTRS1982

Mineralogical aspects of terrestrial weathering effects in chondrites from Allan Hills, Antarctica

The work reported here represents a first attempt at comparing the mineralogical aspects of weathering effects in selected Antarctic chondrites with those present in a petrologically similar chondrite which was weathered in the Arizona desert. The methods of analysis employed include X-ray diffractometry, differential thermal analysis, and reflectance spectrophotometry. It is found that the dominant weathering products in the rocks are complex, multiple-phase, hydrous ferric oxides which formed by alteration of Ni-Fe metal and sulfide particles under the influence of liquid water. The Fe-oxide weathering products may comprise approximately 15-20 wt % of the most intensely weathered samples although the same samples contain not more than 5% goethite as the only well-crystallized hydrous ferric oxide.

Gooding, J. L.↗
NASA NTRS1982

Stable NRM and mineralogy in Allende - Chondrules

The main objective of the present investigation is related to a description of the magnetic and mineralogic contrasts between chondrules which have a natural remanent magnetization (NRM) vector that is ultrastable during alternating field (AF) demagnetization, and those which have unstable NRM vectors when subjected to the same treatment. The results presented in the present investigation together with new magnetic results from Allende listed in a summary provided by Wasilewski (1981) are used as a basis to argue that the stable NRM in Allende was acquired during a sulfidation event. Attention is given to magnetic phases in Allende, experimental results obtained in magnetic studies conducted with 20 chondrules, and a magnetization model for Allende.

Wasilewski, P. J.↗
NASA NTRS1981

High spectral resolution airborne spectrometry

An airborne spectroradiometer system developed at Columbia University has been providing new spectral data for use in remote sensing for natural resources. The system has been improved by addition of a solid state silicon detector array, and has been extended into the infrared by addition of a 64 element lead sulfide detector array. The infrared data in the 2000 to 2500 nm region especially holds large potential for mineral and oil exploration.

Collins, W.↗
NASA NTRS1982

The redox potential of boron nitride and implications for its use as a crucible material in experimental petrology

The suitability of boron nitride for use as a crucible material in silicate and oxygen-bearing metal sulfide systems has been investigated. Boron nitride is unsatisfactory for use with many silicate systems because its presence in combination with a source of oxygen establishes the oxygen fugacity at values below that of the assemblage quartz + fayalite + iron, reducing transition metal ions such as Ni(2+) and Fe(2+) to the metallic state. B2O3, resulting from the oxidation of BN, acts as a flux to promote formation of melt.

Wendlandt, R. F.↗