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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Oxide morphology and spalling model for NiAl

A scanning electron microscope equipped with an energy dispersive spectrographic unit was used to study in detail the Al2O3 oxide morphology and oxide-metal interface of a nickel-rich NiAl alloy (Ni-42 at% Al) with a view toward providing information relevant to spalling theories in the MCrAlY system. In addition, the kinetics of spalling was studied for critical evaluation of one of the step-process spall models and for collection of pertinent experimental data. Cyclic oxidation tests were run in 1-atm air at about 1100 C, and isothermal specimens were examined from 2 min to 200 hr of exposure. It is shown that oxide spalling occurs primarily at the oxide-metal interface in an intergranular mode, that crystallographic Kirkendall voids arise as a result of oxidation, and that the fractional area of spalled oxide varies widely in cyclic tests but increases with the square of oxide thickness for isothermal tests. A spall model is developed in the form of a summation series.

Smialek, J. L.↗
NASA NTRS1977

Fracture surface characteristics of off-axis composites

The fracture surface characteristics of off-axis high-modulus graphite-fiber/epoxy composite specimens were studied using a scanning electron microscope (SEM). The specimens were subjected to tensile loading at various angles (0-90 deg) to the fiber direction. SEM photomicrographs of the fractured surfaces revealed three different load angle regions with distinct fracture characteristics. Based on these revelations, criteria were established which can be used to characterize fracture surfaces with respect to a predominant 'single-stress' fracture mode.

Sinclair, J. H.↗
NASA NTRS1975

Surface morphology and chemistry of rusty particle 60002,108

Scanning electron microscope, energy dispersive X-ray, and microprobe analyses of the surface of rusty colored particle 60002,108 from deep core 60002 reveal the particle to be basically metallic Ni-Fe that probably grew in contact with silicate minerals, principally plagioclase and pyroxene, and was later partially oxidized and hydrated. A yellowish wrinkled and 'shatter cone' like granular material that is either iron oxide or oxyhydrate may have formed while the particle was in the lunar environment. Ruby-red mounds of lawrencite formed, and the reaction of lawrencite, metallic Ni-Fe, and water vapor resulted in aprons of iron oxyhydrate that surrounds these mounds and flows out over the preexisting yellowish granular substrate. The observations do not allow one to distinguish unequivocally between the initiation of hydration of the ruby-red lawrencite mounds in the lunar environment followed by reaction in the terrestrial and/or spacecraft environment or only reaction in the terrestrial and/or spacecraft environment. The relationship of the lawrencite-rich mounds to the yellowish granular substrate favors the first possibility.

Carter, J. L.↗
NASA NTRS1978

Studies of Brazilian meteorites. XIV - Mineralogy, petrology, and chemistry of the Conquista, Minas Gerais, chondrite

The Conquista chondrite is described and classified as an H4. The mineral composition is reported. H-group classification is based on described microscopic, electron microprobe, and bulk chemical studies. The evidence for petrologic type 4 classification includes the pronounced well-developed chondritic texture; the slight compositional variations in constituent phases; the high Ca contents of pyroxene and the presence of pigeonite; glassy to microcrystalline interstitial material rich in alkalis and SiO2; and twinned low-Ca clinopyroxene.

Keil, K.↗
NASA NTRS1978

A Schottky-barrier solar cell on sliced polycrystalline GaAs

Antireflecting-metal-oxide-semiconductor (AMOS) technology has been applied to sliced wafers of polycrystalline GaAs having grain sizes of about 100 microns. Simulated AM1 sunlight efficiencies up to 14% were obtained, and studies using the scanning electron microscope showed that grain boundaries have a minimal effect on short-circuit current density. However, current-voltage characteristics show some influence on open-circuit voltage.

Yeh, Y. C. M.↗
NASA NTRS1980

Solar-cell defect analyzer

Laser-Scanning System pinpoints imperfections in solar cells. Entire solar panels containing large numbers of cells can be scanned. Although technique is similar to use of scanning electron microscope (SEM) to locate microscopic imperfections, it differs in that large areas may be examined, including entire solar panels, and it is not necessary to remove cover glass or encapsulants.

Gauthier, M. K.↗
NASA NTRS1978

Rocket effluent: Its ice nucleation activity and related properties

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

Parungo, F. P.↗
NASA NTRS1979

Characterization of the adsorption of water vapor and chlorine on microcrystalline silica

The characterization of water adsorption on silica is necessary to an understanding of how hydrogen chloride interacts with silica. The adsorption as a function of outgas temperatures of silica and as a function of the isotherm temperature was studied. Characterization of the silica structure by infrared analysis, X-ray diffraction and differential scanning calorimetry, surface area determinations, characterization of the sample surface by electron spectroscopy for chemical analysis (ESCA), and determinations of the heat of immersion in water of silica were investigated. The silica with a scanning electron microscope was examined.

Skiles, J. A.↗
NASA NTRS1979

GaAs solar cell development

The four (AlGa)As-GaAs solar cells were fabricated and will be delivered for radiation damage testing using 1 MeV electrons. These cells were LPE grown at 700 C for 4 minutes. The junction depth was measured to be 0.3 micron using a secondary electron microscope. The radiation model for the shallow junction cells was verified. Some mesa diodes were also fabricated and will be irradiated along with the cells for parallel evaluations of their electrical characteristics.

Source record↗
NASA NTRS1977

Analysis of aerospace nickel-cadmium battery cells

Various steps followed in analyzing the electrolyte, separator, and electrodes are reviewed. Specific emphasis is given to scanning electron microscopic and metallographic analysis of the plates. Cadmium migration is defined, its effects and causes are examined, and methods for its reduction in cells are suggested.

Eliason, R. R.↗
NASA NTRS1979

Investigation of medium and high temperature phase change materials

A detailed description of the programs for acquisition and analysis of the test results is given. Basically it concerns three programs. The TEST program controls the recording of the test data. With the THELLI program it is possible to follow the temperature curve recorded for each individual thermoelement during the test. With the AUSW program the test data can be analyzed, to determine, for example, the melting point and the start of melting. The first results of the service life tests are discussed. From these it is attempted to draw inferences for the subsequent tests. An attempt is made to focus on the determination of the area-related mass loss, the reduction in thickness and the corrosion rate as well as optical and scanning electron microscope evaluation.

Heine, D.↗
NASA NTRS1979

Adhesive material transfer in the erosion of an aluminum alloy

In order to study the basic mechanisms of erosion, hardened steel balls were shot into annealed 6061 Al alloy targets at velocity of up to 150 m/sec. The projectiles were collected and examined by a scanning electron microscope combined with energy-dispersive X-ray analyzer and it was found that target material in substantial amounts is adhesively transferred to the projectile. The transferred material forms on the projectile surface a layer the thickness of which increases with increases in impact velocity.

Salik, J.↗
NASA NTRS1979

Comparative evaluation of woven graphite-epoxy composites

A comparative evaluation of some of the mechanical properties of woven graphite-epoxy composites are discussed. In particular, the types of weaves and the resin contents were chosen for comparison. The types of weaves selected are plain weave, satin weave, and tridirectional weave. The composites made of the fabrics are compared to composites made from unidirectional tapes under static and fatigue loading. During static loading, acoustic emission events were monitored. Also, examinations of fracture surfaces and polished sections both away from the fracture surface, and of virgin specimens under an electron microscope are discussed.

Hanagud, S.↗
NASA NTRS1978

Radiation sensitivity of quartz crystal oscillators experiment for the Long Duration Exposure Facility /LDEF/

A proposed experiment, which has been selected by NASA for inclusion in the Long Duration Exposure Facility (LDEF), is discussed. The objective of the experiment is to obtain information relevant to predicting and improving the radiation sensitivity of quartz oscillators. Specifically, the effect of exposing various grades of quartz oscillators to an orbital environment will be compared with observations obtained using the transmission electron microscope which suggest that the technique may be used to classify quartz-crystals according to their radiation sensitivity.

Venables, J. D.↗
NASA NTRS1978

Rocket effluent size distributions made with a cascade quartz crystal microbalance

Airborne particulate size distribution measurements were made in the stabilized ground cloud from a Titan III C rocket just after launch from the Kennedy Space Center on May 12, 1977. The measurements were made from aboard a small twin engine aircraft instrumented with particle and gas sensors. The plume was followed for about 1 hour while making multiple passes through the cloud at varying altitudes. The results obtained with a ten-stage cascade quartz crystal microbalance impactor show that the mass concentration as a function of particle diameter is bimodal with the first maximum between 0.05 micrometers and 0.1 micrometers and the second maximum between 0.8 and 1.0 micrometer. Scanning electron microscope analysis were performed on the material collected and show distinctly different kinds of particles in the two modes.

Woods, D. C.↗
NASA NTRS1978

Rocket effluent - Its ice nucleation activity and related properties

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager I and II launches. The aerosol's morphology, concentration and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a subfreezing thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei. Their consequences for potential inadvertant weather modification demand additional study.

Parungo, F. P.↗
NASA NTRS1978

Fractographic analysis of gaseous hydrogen induced cracking in 18Ni maraging steel

Electron microscope fractographic analysis supplemented an extensive study of the kinetics of gaseous hydrogen assisted cracking in 18Ni maraging steel. Temperature determined the crack path morphology in each steel which, in turn, was directly related to the temperature dependence of the crack growth rate. Crack growth in the low temperature regime proceeded along prior austenite grain boundaries. Increasing the temperature above a critical value produced a continuously increasing proportion of transgranular quasi-cleavage associated with lath martensite boundaries. The amount of transgranular cracking was qualitatively correlated with the degree of temperature-induced deviation from Arrhenius behavior. Fractographic observations are interpreted in terms of hypothesized mechanisms for gaseous hydrogen embrittlement. It is concluded that hydrogen segregation to prior austenite and lath martensite boundaries must be considered as a significant factor in developing mechanisms for gaseous embrittlement of high strength steels.

Gangloff, R. P.↗
NASA NTRS1979

Comparative evaluation of woven graphite-epoxy composites

A comparative evaluation of some of the mechanical properties of woven graphite-epoxy composites have been discussed in this report. In particular the types of weaves and the resin contents have been chosen for comparison. The types of weaves selected are plain weaves, satin weave and tri-directional weave. The composites made of these fabrics have been compared to composites made from unidirectional tapes under static and fatigue loading. During static loading acoustic emission events have been monitored. Also, examinations of fracture surface and polished sections of specimens away from the fracture surface under an electron microscope have been discussed.

Hanagud, S.↗