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At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Sulfur poisoning of hydrocarbon oxidation by palladium

Using a differential bed recycle reactor the oxidation of ethane and diethyl ketone by a Pd catalyst was studied at the 0-30 ppm level in air. In both cases first order kinetics were observed. The ethane oxidation rate was characterized n the Arrhenius form by a pre-exponential of 1.0 x 10 to the 8th power cm/sec and an E sub a of 27 kcal/mole. The diethyl ketone oxidation rate was characterized by a pre-exponential of 5.7 x -1000 cm/sec and E sub a of 14 kcal/mole. Poisoning of ethan oxidation was also investigated by hydrogen sulfide and to a smaller extent by the refrigerants Freon 22 and Gentron 142-B. Poisoning by Gentron 142-B was much more severe than by hydrogen sulfide. Kinetic experiments indicated that only the pre-exponential was changing.

Baumgartner, A. J.↗
NASA NTRS1977

Collection and analysis of organic gases from natural ecosystems - Application to poultry manure

Combined gas chromatography-mass spectrometry was used to identify volatile compounds generated from chicken manure and collected in Poropak QS-Carbosieve B traps. Various alcohols, ketones, esters, and carboxylic acids together with dimethyl sulfide and dimethyl disulfide were detected when the wastes were incubated in an argon atmosphere. Significant amounts of dimethyl sulfide and dimethyl disulfide but few other compounds were found when the manure was incubated in air

Smith, M. S.↗
NASA NTRS1977

Manufacture and engine test of advanced oxide dispersion strengthened alloy turbine vanes

Oxide-Dispersion-strengthened (ODS) Ni-Cr-Al alloy systems were exploited for turbine engine vanes which would be used for the space shuttle thermal protection system. Available commercial and developmental advanced ODS alloys were evaluated, and three were selected based on established vane property goals and manufacturing criteria. The selected alloys were evaluated in an engine test. Candidate alloys were screened by strength, thermal fatigue resistance, oxidation and sulfidation resistance. The Ni-16Cr (3 to 5)Al-ThO2 system was identified as having attractive high temperature oxidation resistance. Subsequent work also indicated exceptional sulfidation resistance for these alloys.

Bailey, P. G.↗
NASA NTRS1978

Evaluation of volcano-style field ionization source and field emitting cathodes for mass spectrometry and applications

A volcano-style field ionization source was tested with eight different gases: hydrogen, helium, ammonia, methane, argon, neon, water vapor, and hydrogen sulfide. For ammonia, hydrogen sulfide, and water, the ionization efficiency of the field ionization source was determined as a function of the electrical potential difference between the ionizer and its counterelectrode. The ionization efficiencies for the other gases were too low to be measured in the present apparatus. The operating characteristics of a field emission cathode, were studied, in the presence of the same eight gases at pressures up to 0.00001 torr. The presence of the gases caused little or no significant change in the electron emission from the cathodes. Results indicate that the field emission cathode has advantages over electrically heated cathodes as a source of an electron beam in spacecraft mass spectrometers.

Buttrill, S. E., Jr.↗
NASA NTRS1978

Are the stratospheric dust particles meteor ablation debris or interplanetary dust?

Natural and laboratory created fusion crusts and debris from artificial meteor samples were used to develop criteria for recognizing meteor ablation debris in a collection of 5 to 50 micron particles from the stratosphere. These laboratory studies indicate that meteor ablation debris from nickel-iron meteoroids produce spherules containing taenite, wuestite, magnetite, and hematite. These same studies also indicate that ablation debris from chondritic meteoroids produce spheres and fragmentary debris. The spheres may be either silicate rich, containing zoned olivine, magnetite, and glass, or sulfide rich, containing iron oxides (e.g., magnetite, wuestite) and iron sulfides (e.g., pyrrhotite, pentlandite). The fragmentary debris may be either fine-grained aggregates of olivine, magnetite, pyroxene, and occasionally pyrrhotite (derived from the meteorite matrix) or individual olivine and pyroxene grains (derived from meteorite inclusions).

Blanchard, M. B.↗
NASA NTRS1978

X-ray photoelectron spectroscopic study of surface chemistry of dibenzyl disulfide on steel under mild and severe wear conditions

X-ray photoelectron spectroscopy was used to characterize the chemical composition of 304 stainless steel surfaces run in oil containing dibenzyl disulfide under both mild and severe wear conditions. In severe wear a sulfide was formed at the expense of the normal oxide. This was due to either chemical attack on the oxide or reaction with clean metal exposed by the wear process. In the mild wear scars there was no evidence of either sulfide or mercaptide. The oxide, however, was approximately twice as thick as the normal oxide on an unworn surface. The change in surface chemistry was primarily a function of wear rate rather than load.

Wheeler, D. R.↗
NASA NTRS1978

Concentration-response data on toxicity of pyrolysis gases from some natural and synthetic polymers

Concentration-response data are presented on the toxic effects of the pyrolysis gases from some natural and synthetic polymers, using the toxicity screening test method developed at the University of San Francisco. The pyrolysis gases from wool, red oak, Douglas fir, polycaprolactam, polyether sulfone, polyaryl sulfone, and polyphenylene sulfide appeared to exhibit the concentration-response relationships commonly encountered in toxicology. Carbon monoxide seemed to be an important toxicant in the pyrolysis gases from red oak, Douglas fir, and polycaprolactam, but did not appear to have been the principal toxicant in the pyrolysis gases from polyether sulfone and polyphenylene sulfide.

Hilado, C. J.↗
NASA NTRS1975

Morphology and composition of chalcopyrite, chromite, Cu, Ni-Fe, pentlandite, and troilite in vugs of 76015 and 76215

Vugs from 76015 and 76215 are lined with euhedral crystals of plagioclase, pyroxene, ilmenite, Ni-Fe, and troilite. Smaller crystals of chromite, pentlandite, and chalcopyrite occur on the surface of the troilite in 76015. Wire Cu and dendritic-metallic Cu occurs with metallic Ni-Fe and troilite in some vugs of 76215. Troilite in both samples may have crystallized from an immiscible sulfide liquid. With falling temperature, chalcopyrite, and pentlandite may have exsolved from the troilite in 76015. By contrast, metallic Cu may have formed in 76215 by thermal breakdown of a bornite, troilite, and Ni-Fe assemblage which originally crystallized from a low-Ni immiscible sulfide liquid.

Carter, J. L.↗
NASA NTRS1975

The source of sublimates on the Apollo 15 green and Apollo 17 orange glass samples

Elemental analyses of the thin film of micromounds which coat the surfaces of Apollo 15 green glass and Apollo 17 orange glass are reported. It is thought that Zn, Ga, Pb, Cu, Tl, S, F, and Cl condensed as a sublimate on the outside surface of these glass particles in lava fountains about 3.4 and 3.6 b.y. ago (Apollos 15 and 17, respectively). The heavy metals enriched in these samples may have been mobilized in a halide- and sulfide-rich vapor, while the source of these elements and of the glass may be a sulfide- and halide-rich pyroxenite inside the moon. The isotopic composition of lead on the surface of individual particles was determined, and the composition is considered with respect to the evolution of the source region. The lead on the surfaces is similar to lead that has been mixed into other soils and breccias at nearby sites.

Meyer, C., Jr.↗
NASA NTRS1977

Space-based solar power conversion and delivery systems study. Volume 4: Energy conversion systems studies

Solar cells and optical configurations for the SSPS were examined. In this task, three specific solar cell materials were examined: single crystal silicon, single crystal gallium arsenide, and polycrystalline cadmium sulfide. The comparison of the three different cells on the basis of a subsystem parametric cost per kW of SSPS-generated power at the terrestrial utility interface showed that gallium arsenide was the most promising solar cell material at high concentration ratios. The most promising solar cell material with no concentration, was dependent upon the particular combination of parameters representing cost, mass and performance that were chosen to represent each cell in this deterministic comparative analysis. The potential for mass production, based on the projections of the present state-of-the-art would tend to favor cadmium sulfide in lieu of single crystal silicon or gallium arsenide solar cells.

Source record↗
NASA NTRS1979

Surface chemistry of iron sliding in air and nitrogen lubricated with hexadecane and hexadecane containing dibenzyl-dilsulfide

Wear experiments were conducted on iron sliding in hexadecane and hexadecane plus one weight percent dibenzyl dilsulfide (DBDS) in atmospheres of air and nitrogen at room temperature. The wear scars and the wear debris were analyzed by X-ray photoelectron spectroscopy. The presence of air reduced wear but increased friction, while DBDS reduced friction but had little effect on wear except that the wear increased somewhat when DBDS was used in air. Wear scar analysis indicated that oxygen and sulfur competed chemically for the surface, with the oxide predominating. Low wear was associated with a thick oxide layer and low friction with a thin predominantly sulfide layer. Analysis of the wear debris indicated the presence of a sulfate in the high wear case (hexadecane plus DBDS in air), and showed the presence of an organic sulfide in the low wear case (Hexadecane plus DBDS in nitrogen).

Wheeler, D. R.↗
NASA NTRS1978

Melt inclusions in Luna 24 soil fragments

Optical examinations of 28 slides of Luna 24 soil fragments revealed melt inclusions in grains of olivine, plagioclase, spinel, and ilmenite as well as interstitial inclusions. In contrast with Apollo samples, the Luna 24 samples contain sulfide melt inclusions, which indicates that saturation with respect to an iron sulfide melt took place throughout much of the crystallization history, even while olivine was crystallizing. The Luna 24 silicate-melt inclusions have recorded a more extensive differentiation toward higher iron magmas than have the Apollo inclusions, but they have also recorded some inexplicably low aluminum values.

Roedder, W.↗
NASA NTRS1979

Oxidation of CS2 and COS - sources for atmospheric SO2

The oxidation of COS and CS2 by reaction with hydroxyl radicals is investigated as a possible source of atmospheric SO2 in remote marine regions. Calculations of the vertical profiles of SO2 were performed based on a one-dimensional photochemical model of the formation and destruction of SO2 by various processes for observed O3, CO, CH4 and H2O profiles at 15 deg S. Variations in the rate of SO2 destruction, the chosen deposition velocity and the loss due to aerosols are shown to lead to similar SO2 profiles, which indicate higher mixing ratios at high altitude, while the oxidation of dimethyl sulfide or hydrogen sulfide can not account for the profiles observed. Possible diffuse sources of CS2 and COS are indicated, and it is concluded that the oxidation of COS and possibly CS2 may provide an explanation for the existence of a uniform background level of SO2.

Logan, J. A.↗
NASA NTRS1980

Improved PFB operations: 400-hour turbine test results

A pressurized fluidized bed (PFB) coal-burning reactor was used to provide hot effluent gases for operation of a small gas turbine. Preliminary tests determined the optimum operating conditions that would result in minimum bed particle carryover in the combustion gases. Solids were removed from the gases before they could be transported into the test turbine by use of a modified two stage cyclone separator. Design changes and refined operation procedures resulted in a significant decrease in particle carryover, from 2800 to 93 ppm (1.5 to 0.05 grains/std cu ft), with minimal drop in gas temperature and pressure. The achievement of stable burn conditions and low solids loadings made possible a 400 hr test of small superalloy rotor, 15 cm (6 in.) in diameter, operating in the effluent. Blades removed and examined metallographically after 200 hr exhibited accelerated oxidation over most of the blade surface, with subsurface alumina penetration to 20 micron m. After 400 hours, average erosion loss was about 25 micron m (1 mil). Sulfide particles, indicating hot corrosion, were present in depletion zones, and their presence corresponded in general to the areas of adherent solids deposit. Sulfidation appears to be a materials problem equal in importance to erosion.

Rollbuhler, R. J.↗
NASA NTRS1980

Development of advanced thermoelectric materials, phase A

Work performed on the chemical system characterized by chrome sulfide, chrome selenide, lanthanum selenide, and lanthanum sulfide is described. Most materials within the chemical systems possess the requisites for attractive thermoelectric materials. The preparation of the alloys is discussed. Graphs show the Seebeck coefficient, electrical resistivity, and thermal conductivity of various materials within the chemical systems. The results of selected doping are included.

Source record↗
NASA NTRS1980

The origin and evolution of sulfur in an Archean volcano-sedimentary basin, Deer Lake area, Minnesota

Rocks of the Deer Lake area, northcentral Minnesota, consist of Archean (age greater than 2.6 billion years) metasediments and metavolcanics intruded by mafic layered sills. Geologic and sulfur isotopic data suggest that sulfides in the sediments are bacteriogenic, having formed in response to the activity of sulfate reducing bacteria during diagenesis. Deposition of the sediments appears to have occurred in a deep marine basin with restricted circulation of sea water. The bulk of the sulfur in the igneous rocks is of deep seated origin, but basal contacts of the sills show evidence of assimilation of biogenic sulfur from the intruded sediments. This assimilation of biogenic sulfur is the primary geochemical control of local Cu-Ni sulfide mineralization.

Nicol, D. L.↗
NASA NTRS1979

Microbial Sulfate Reduction Measured by an Automated Electrical Impedance Technique

Electrical impedance measurements are used to investigate the rates of sulfate reduction by pure cultures of and sediments containing sulfur-reducing bacteria. Changes in the electrical impedance ratios of pure cultures of Desulfovibrio aestuarii and samples of reduced sediments from San Francisco Bay were measured by a Bactometer 32, and sulfate reduction was followed by measuring the incorporation of (S-35) sulfate into metal sulfides. The growth of the bacteria in pure culture is found to result in an increase of 0.2200 in the impedance ratio within 24 h, accompanied by increases in protein, ATP, sulfide and absorptance at 660 nm, all of which are inhibited by the addition of molybdate. Similar responses were observed in the sediments, although impedance ratio responses were not completely inhibited upon the addition of molybdate, due to the presence of nonsulfate-respiring microorganisms. Experiments conducted with sterile media and autoclaved sediments indicate that the presence of H2S together with iron is responsible for the impedance effect, and sulfate reduction rates ranging between 0.85 and 1.78 mmol/l per day are estimated for the sediments by the impedance technique.

Oremland, R. S.↗
NASA NTRS1980

A study of chondrule rims and chondrule irradiation records in unequilibrated ordinary chondrites

A study of the possibility that chondrules may have had an independent existence in space was made by searching for unusual track densities in chondrules and by an investigation of the compositions of chondrule rims from thirteen unequilibrated ordinary chondrites. No unusual radiation was found; observed track densities can be explained in terms of cosmic ray exposure ages of the respective meteorites. Fine-grained rims that surround chondrules in unequilibrated ordinary chondrites are heterogeneous in composition consisting of iron sulfide and a silicate phase; fine-grained rims of the kind observed in primitive type 3 ordinary chondrites are absent in higher petrographic grades, but more crystalline, coarse-grained, and lacy sulfide rims are observed. This can be explained by chondrules having had an independent existence in space during which they acquired rims by condensation on their surfaces or by accretion of fine particles.

Allen, J. S.↗