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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Microscopic investigation of cavitation erosion damage in metals

The results of research to identify the cavitation erosion damage mechanisms at the microscopic level for three metals (aluminum, stainless steel, and titanium) representing a range of properties and microstructure are presented. The metals were exposed to cavitation generated in distilled water by a 20-kHz ultrasonic facility operating at a vibration amplitude of 2 mils. Representative properties of the metals and experimental details are summarized. Replicas of the eroded surfaces of the specimens obtained periodically during exposure were examined with a transmission electron microscope to follow progression of the erosion damage and identify dominant erosion mechanisms as a function of exposure time. Eroded surfaces of selected specimens were also examined with a scanning electron microscope to assist in the interpretation.

Hackworh, J. V.↗
NASA NTRS1994

The contribution of vapor deposition to amorphous rims on lunar soil grains

Recent analysis analytical electron microscope study of lunar soils showed that the approximately 60-nm-wide amorphous rims surrounding many lunar soils grains exhibit distinct compositional differences from their hosts. On average, the amorphous rim compositions reflect the local bulk soil composition with the exceptions of Si and S, which are enriched relative to the bulk soil. These chemical trends led us to propose that the amorphous rims were in fact deposits of impact-generated vapors produced during regolith gardening, a hypothesis that runs contrary to the generally accepted view that the rims are produced through amorphization of the outer parts of mineral grains by interaction with the solar wind. Analytical data are reported for amorphous rims on individual minerals in lunar soils in order to show that the magnitude of the chemical differences between rim and host are so great that they require a major addition of foreign elements to the grain surfaces. The average composition of amorphous rims is listed as a function of host mineralogy as determined in microtone thin sections using energy-dispersive X-ray spectrometry in the transmission electron microscope. As the host mineral becomes chemically more complex, the chemical differences are not as clear. The average rim compositions are remarkably similar and are independent of the host grain mineralogy. Whether there are 'sputtering' or radiation effects superimposed on the vapor-deposited material can be debated. We do not explicitly exclude the effects of radiation damage as a contributing factor to the formation of amorphous rims; we are merely emphasizing the major role played by condensed vapors in the formation of amorphous rims on lunar soil grains.

Keller, L. P.↗
NASA NTRS2010

Experimental Investigation of Space Radiation Processing in Lunar Soil Ilmenite: Combining Perspectives from Surface Science and Transmission Electron Microscopy

Energetic ions mostly from the solar wind play a major role in lunar space weathering because they contribute structural and chemical changes to the space-exposed surfaces of lunar regolith grains. In mature mare soils, ilmenite (FeTiO3) grains in the finest size fraction have been shown in transmission electron microscope (TEM) studies to exhibit key differences in their response to space radiation processing relative to silicates [1,2,3]. In ilmenite, solar ion radiation alters host grain outer margins to produce 10-100 nm thick layers that are microstructurally complex, but dominantly crystalline compared to the amorphous radiation-processed rims on silicates [1,2,3]. Spatially well-resolved analytical TEM measurements also show nm-scale compositional and chemical state changes in these layers [1,3]. These include shifts in Fe/Ti ratio from strong surface Fe-enrichment (Fe/Ti >> 1), to Fe depletion (Fe/Ti < 1) at 40-50 nm below the grain surface [1,3]. These compositional changes are not observed in the radiation-processed rims on silicates [4]. Several mechanism(s) to explain the overall relations in the ilmenite grain rims by radiation processing and/or additional space weathering processes were proposed by [1], and remain under current consideration [3]. A key issue has concerned the ability of ion radiation processing alone to produce some of the deeper- penetrating compositional changes. In order to provide some experimental constraints on these questions, we have performed a combined X-ray photoelectron spectroscopy (XPS) and field-emission scanning transmission electron (FE-STEM) study of experimentally ion-irradiated ilmenite. A key feature of this work is the combination of analytical techniques sensitive to changes in the irradiated samples at depth scales going from the immediate surface (approx.5 nm; XPS), to deeper in the grain interior (5-100 nm; FE-STEM).

Christoffersen, R.↗
NASA NTRS2014

X-Ray Absorption near Edge Structure Spectroscopic Study of Hayabusa Category 3 Carbonaceous Particles

Analyses with a scanning transmission x-ray microscope (STXM) using x-ray absorption near edge structure (XANES) spectroscopy were applied for the molecular characterization of two kinds of carbonaceous particles of unknown origin, termed category 3, which were collected from the Hayabusa spacecraft sample catcher. Carbon-XANES spectra of the category 3 particles displayed typical spectral patterns of heterogeneous organic macromolecules; peaks corresponding to aromatic/olefinic carbon, heterocyclic nitrogen and/or nitrile, and carboxyl carbon were all detected. Nitrogen-XANES spectra of the particles showed the presence of N-functional groups such as imine, nitrile, aromatic nitrogen, amide, pyrrole, and amine. An oxygen-XANES spectrum of one of the particles showed a ketone group. Differences in carbon- and nitrogen-XANES spectra of the category 3 particles before and after transmission electron microscopic (TEM) observations were observed, which demonstrates that the carbonaceous materials are electron beam sensitive. Calcium-XANES spectroscopy and elemental contrast mapping identified a calcium carbonate grain from one of the category 3 particles. No fluorine-containing molecular species were detected in fluorine-XANES spectra of the particles. The organic macromolecular features of the category 3 particles were distinct from commercial and/or biological ‘fresh (non-degraded)’ polymers, but the category 3 molecular features could possibly reflect degradation of contaminant polymer materials or polymer materials used on the Hayabusa spacecraft. However, an extraterrestrial origin for these materials cannot currently be ruled out.

Asteroides↗
NASA NTRS2013

Laboratory Instruments Available to Support Space Station Researchers at Marshall Space Flight Center

A number of research instruments are available at NASA's Marshall Space Flight Center (MSFC) to support ISS researchers and their investigations. These modern analytical tools yield valuable and sometimes new informative resulting from sample characterization. Instruments include modern scanning electron microscopes equipped with field emission guns providing analytical capabilities that include angstron-level image resolution of dry, wet and biological samples. These microscopes are also equipped with silicon drift X-ray detectors (SDD) for fast yet precise analytical mapping of phases, as well as electron back-scattered diffraction (EBSD) units to map grain orientations in crystalline alloys. Sample chambers admit large samples, provide variable pressures for wet samples, and quantitative analysis software to determine phase relations. Advances in solid-state electronics have also facilitated improvements for surface chemical analysis that are successfully employed to analyze metallic materials and alloys, ceramics, slags, and organic polymers. Another analytical capability at MSFC is a mganetic sector Secondary Ion Mass Spectroscopy (SIMS) that quantitatively determines and maps light elements such as hydrogen, lithium, and boron along with their isotopes, identifies and quantifies very low level impurities even at parts per billion (ppb) levels. Still other methods available at MSFC include X-ray photo-electron spectroscopy (XPS) that can determine oxidation states of elements as well as identify polymers and measure film thicknesses on coated materials, Scanning Auger electron spectroscopy (SAM) which combines surface sensitivity, spatial lateral resolution (approximately 20 nm), and depth profiling capabilities to describe elemental compositions in near surface regions and even the chemical state of analyzed atoms. Conventional Transmission Electron Microscope (TEM) for observing internal microstructures at very high magnifications and the Electron Probe Micro-analyzer (EPMA) for very precise microanalysis are available as needed by the researcher. Space Station researchers are invited to work with MSFC in analyzing their samples using these techniques.

Panda, Binayak↗
NASA NTRS1970

Matrix characteristics and origin of lunar breccia samples no. 12034 and 12073

The transmission electron microscope was used to investigate the nature of the matrix in two samples of lunar breccia. This matrix is composed largely of tiny (0.5 microns) grains of unaltered glass which are plastically fitted against one another, and tightly welded to the clastic fragments with which they are in contact. The breccias have an open framework of angular clastic particles composed mainly of anorthositic, basaltic and glassy fragments. Most of the anorthositic fragments have been shock metamorphosed. Over half of the glassy clasts, and also the former diaplectic glass particles produced from shocked plagioclase, were partly or wholly devitrified before inclusion in the present breccias. It is concluded that each breccia was deposited from a hot basesurge cloud of impact debris, and the tiny bits of glass in the matrix condensed from rock that was volatilized by the heat of major meteorite impact.

Waters, A. C.↗
NASA NTRS1972

Surface studies on Surveyor 3 tubing sections

Sections C and E of the unpainted, polished aluminum tubing from the strut of the radar altimeter and Doppler velocity sensor were examined in a transmission electron microscope for micrometeorite damage and ion bombardment. Both sections were contaminated and eroded on one side; it is suggested that these conditions were caused by sandblasting by lunar dust and retrorocket plume contamination during Surveyor 3 landing. Microcraters of different configurations were found on the bright sides of the tubes. Several degrees of violence were involved in the formation of the craters, and the particle size could be responsible for some differences. All micropits found were on the bright areas and data indicate 0.2 hypervelocity impact/sq cm and 2/sq cm for other types of craters. The greatest degree of damage resulted from particle impact and was limited to a maximum depth of 2 microns.

Buvinger, E. A.↗
NASA NTRS1973

An Exploratory Study of the Microstructure of Mullite Fibers

The microstructures of mullite composition fibers were examined by transmission electron microscopic techniques and by X-ray diffraction analyses. Both spun and monofilament fiber structures contained little porosity, nor did the degree of porosity change after heating the monofilament to 1205 C for one half hour. Thermal exposure produced crystallite growth and nucleation from the amorphous phase in all three of the spun fibers. After 116 hours at 1426 C, the crystallites of the standard spun fibers became contiguous. In addition, the surface crystallites of these fibers were found to be more than twice as large as the interior crystallites.

Santoro, G.↗
NASA NTRS1974

Summary of in situ epitaxial nucleation and growth measurements

In situ nucleation and growth measurements of Ag and Au on single-crystal PbSe thin films were made using a transmission electron microscope. Properties studied were polymorphism, crystalline perfection, and the stoichiometric composition of the initial and the autoepitaxially thickened PbSe substrates. The quantitative nucleation and cluster growth measurements were limited to low-saturation conditions. The epitaxial orientations are discussed, and evidence is presented as to the stage of deposition at which the epitaxial order for Ag is introduced. Strong substrate/overgrowth interaction manifested itself by alloying and interdiffusion.

Poppa, H.↗
NASA NTRS1974

On the irradiation history and origin of gas-rich meteorites

Transmission electron microscope study of the track density gradients and irradiation geometries of track-rich grains and chondrules in sections of Fayetteville and Kapoeta, and in sections of lunar breccias and grains from lunar soil. A substantial fraction (50 to 90%) of the meteoritic track-rich grains and chondrules show evidence of having been irradiated anisotropically in their different faces, as would be expected for irradiation on the surface of a parent body. The observations thus support the hypothesis that the irradiation of these grains and chondrules took place on the regoliths of asteroidal-sized bodies. Measurements of steepest track density gradients indicate that, while there are finite differences between spectra exhibited by individual gas-rich meteorites, the average solar flare spectral shapes have been similar over the last 4 b.y. or so.

Rajan, R. S.↗
NASA NTRS1977

Effects of high temperature and e-beam irradiation on the stability of refractory thin films

Refractory thin films of Al2O3, ZrO2, MgO, ThO2, and BN have been investigated in situ in an UHV transmission electron microscope. The electron transparent refractory films were prepared by electron-beam evaporation, anodization, RF sputtering, and thinning of bulk crystal materials. The study concentrates on monitoring the thermal and mechanical stability of the films, phase and structural changes, and electron irradiation effects as a function of film-preparation conditions. With increasing temperatures, five different crystallographic phases were observed for both anodized and electron-beam-evaporated alumina films. Zirconia films exhibited two phase transitions upon heating to 1200 C and electron-irradiation-induced crystallization of ZrO2 even at room temperature. MgO, ThO2, and BN films did not undergo any noticeable phase transformation but ruptured due to sintering below 1200 C.

Lee, E. H.↗
NASA NTRS1977

Shock-produced olivine glass - First observation

Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, /Mg(0.88)Fe(0.12)/2SiO4, recovered from peak pressures of about 56 billion pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of olivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 billion pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.

Jeanloz, R.↗
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

Chemical and structural studies of 'Brownlee' particles

Several techniques were applied to the study of small particles (around 10 microns) collected in the upper atmosphere by U-2 aircraft. The major element chemistry of roughly 1/3 of the particles is similar to that of chondritic meteorites, although considerable variation of element ratios is observed from particle to particle, and even within a given particle. All particles of 'chondritic' composition are polycrystalline aggregates. About half have fully re-entrant structures; the remaining ones have more compact structures ranging from platey to spherical morphologies. Micro-crystallites with various internal structures are observed in the size range from less than 100 A to several microns. Although tracks are clearly observed in transmission electron microscope examination of terrestrial analog crystals, no tracks of solar flare origin have yet been identified in the U-2 particles. Induced fission track analysis of one aggregate shows that the U concentration is less than 15 ppbm, lending support to the extraterrestrial origin hypothesis.

Flynn, G. J.↗
NASA NTRS1979

Investigations of submicron sized metal particles in glass coatings of lunar breccia 15286

Almost all the submicron metal particles in the glass coating of breccia 15286 are rounded and contain two phases, metal and sulfide (FeS). The Ni content of the metal phase as determined by scanning transmission electron microscope X-ray analysis ranged from 9.4 to 15.5 wt %. The sulfide was nearly stoichiometric troilite containing up to 1.3 wt % Ni. The close chemical and microstructural similarities between the coarse (greater than 1-micron) and the submicron sized metal indicate a common origin probably as meteoritic debris. Metal-silicate melt experiments under controlled oxygen partial pressured indicate that the metal particles may have formed from a fine dispersion of immiscible metal-sulfide droplets into an impact-generated silicate melt.

Mehta, S.↗