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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Preliminary description and interpretation of Apollo 14 cores 14211/10

Core 14211/10 is a 2 cm-diameter double drive tube that was collected within the smooth plains area of the Apollo 14 landing site. Rock fragments in the core appear to be derived from the smooth plains area because the coring site is beyond ejecta range of Cone Crater and is within the expected continuous ejecta of two large craters in the plains. The characteristics of the glassy soil breccia zone between 12.5 and 15.5 cm indicate that this zone represents the bottom of a glass-lined crater. At least some of the dark agglutinate and glass-rich soils at the top of the core are mature, by FMR measurements, and show maturation interrelationships between particle types. Hence, this dark interval is interpreted as a gardened zone.

Nagle, J. S.↗
NASA NTRS1979

Some effects of gas adsorption on the high temperature volatile release behavior of a terrestrial basalt, tektite and lunar soil

Mass pyrograms obtained from high-temperature, mass psectrometric pyrolysis of a glassy theoleiitic submarine basalt and a tektite, ground in air to less than 64 microns, have shown N2 and SO release patterns very similar to those from the pyrolysis of mature lunar soil fines. The N2 and CO release behavior from the terrestrial samples reproduces the biomodal, high-temperature (approximately 700 and 1050 C) features from the lunar samples. Unground portions of the basalt and tektite show no release of N2 and CO during pyrolysis. Grinding also alters the release behavior and absolute amounts of H2O and CO2. It is suggested that adsorption of atmospheric gases in addition to solar wind implantation of ions may account for the wide range of values in previously reported concentrations of carbon and nitrogen from lunar fines.

Graham, D. G.↗
NASA NTRS1979

Volcano-ice interactions on Mars

Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.

Allen, C. C.↗
NASA NTRS1980

Visible and ultraviolet /800-130 nm/ extinction of vapor-condensed silicate, carbon, and silicon carbide smokes and the interstellar extinction curve

The extinction curves from 800 to 130 nm (1.25-7.7/micron) of amorphous silicate smokes nominally of olivine and pyroxene composition, carbon smokes, and crystalline SiC smokes are presented. The SiC smoke occurred in the low-temperature (beta) cubic structural form. The SiC smoke showed an absorption edge which occurred at significantly longer wavelengths than the calculated extinction profile of the hexagonal SiC form previously used to calculate the interstellar extinction profile. Neither SiC nor amorphous silicates show an extinction band similar to the observed 6.6/micron astronomical extinction band. The infrared absorption peaks for the silicate and SiC samples near 10 microns and 11-13 microns, respectively, were also measured. The ultraviolet to infrared extinction ratio for the amorphous silicate samples is similar to the observed astronomical extinction ratio. The measured extinction ratios for SiC smokes are significantly below the interstellar extinction ratio. The extinction peak of the carbon smokes occurred at 4.0 and 4.25/micron, for samples of mean radii 13 and 6 nm, respectively. The extinction profile is distinctly different from that predicted for graphite grains of the same size, and is similar to that predicted for glassy carbon grains.

Stephens, J. R.↗
NASA NTRS1980

Effect of W and WC on the oxidation resistance of yttria-doped silicon nitride

The effect of tungsten and tungsten carbide contamination on the oxidation and cracking in air of yttria-doped silicon nitride ceramics is investigated. Silicon nitride powder containing 8 wt % Y2O3 was doped with 2 wt % W, 4 wt % W, 2 wt % WC or left undoped, and sintered in order to simulate contamination during milling, and specimens were exposed in air to 500, 750 and 1350 C for various lengths of time. Scanning electron and optical microscopy and X-ray diffraction of the specimens in the as-sintered state reveals that the addition of W or WC does not affect the phase relationships in the system, composed of alpha and beta Si3N4, melilite and an amorphous phase. Catastrophic oxidation is observed at 750 C in specimens containing 2 and 4 wt % W, accompanied by the disappearance of alpha Si3N4 and melilite from the structure. At 1350 C, the formation of a protective glassy oxide layer was observed on all specimens without catastrophic oxidation, and it is found that pre-oxidation at 1350 C also improved the oxidation resistance at 750 C of bars doped with 4 wt % W. It is suggested that tungsten contamination from WC grinding balls may be the major cause of the intermediate-temperature cracking and instability frequently observed in Si3N4-8Y2O3.

Schuon, S.↗
NASA NTRS1981

Physical aging in graphite epoxy composites

The matrix dominated mechanical behavior of a graphite epoxy composite was found to be affected by sub Tg annealing. Postcured + or - 45 deg 4S specimens of Thornel 300 graphite/Narmco 5208 epoxy were quenched from above Tg and given a sub Tg annealing at 140 C for times up to 10 to the 5th power min. The ultimate tensile strength, strain to break, and toughness of the composite material were found to decrease as functions of sub Tg annealing time. No weight loss was observed during the sub Tg annealing. The time dependent change in mechanical behavior is explained on the basis of free volume changes that are related to the physical aging of the nonequilibrium glassy network epoxy. The results imply possible changes in composite properties with service time.

Kong, E. S. W.↗
NASA NTRS1980

Trace elements in ocean ridge basalt glasses - Implications for fractionations during mantle evolution and petrogenesis

Seven documented and fresh glassy selvages from ocean floor basalt pillows were analyzed for trace elements including Ag, Au, Bi, Br, Ni, Pd, and Zn using radiochemical activation analysis. Glasses from DSDP leg 24, site 238 in the Indian Ocean have a trace element pattern which reflects secondary processes at a shallow depth. Chemical fractionations in petrogenesis of tholeiitic basalts indicate that (Ir, Os), Au, Pd, Ni, and Re are strongly fractionated in igneous processes; the unfractionated chondritic mantle pattern thus imposes constraints on mantle evolution models. Finally, the limited Rb/Cs fractionation in oceanic tholeiites reflects the low abundance of volatiles and hydrous silicates in normal ocean ridge basalts.

Hertogen, J.↗
NASA NTRS1980

Nature of the fossil evidence - Moon and meteorites

The nature of the fossil evidence to be found in extraterrestrial materials concerning the history of solar activity is reviewed. The various types of lunar rocks and meteorites containing evidence of exposure to solar radiations are distinguished, including igneous rocks, breccias, glassy agglutinates, single mineral crystals, carbonaceous meteorites, and the Antarctic meteorites, some of which fell to earth as much as a million years ago. The characteristic effects of energetic particles from space in materials are then examined, including ion implantation and surface radiation damage to a depth of several hundred A by the solar wind, radioactivity, electron trapping and track production induced by solar flares to depths from millimeters to centimeters, and spallation due to galactic cosmic rays at depths from centimeters to meters. Complications in the interpretation of radiation exposure histories represented by dynamic surface processes, the nonsolar origin of some trapped elements, and difficulties in determining the duration and epoch of surface exposure of individual crystals are also noted.

Walker, R. M.↗
NASA NTRS1981

Long-term influence of physical aging processes in epoxy matrix composites

Selected mechanical properties of (plus or minus 45 degree sub 4s) graphite/epoxy composites were found to be affected by sub T sub g annealing. Postcured specimens of Thornel 300 graphite/Narmco 5208 epoxy were sub T sub G annealed at 413 K (140 C) for ca. 10 to the first through 10 to the fifth powers min., with a prior quenching from above T sub g. The ultimate tensile strength, strain-to-break, and toughness of the composite were found to decrease as a function of sub T sub g annealing time. The time-dependent change in properties can be explained on the basis of physical aging which is related to free volume changes in the non-equilibrium glassy state of network epoxies. The results imply possible changes in composite properties with service time.

Kong, E. S. W.↗
NASA NTRS1982

Liquid drop technique for generation of organic glass and metal shells

It was found that liquid drop techniques are very useful in several diverse areas. For producing very uniform metallic, organic, inorganic and, on particular, glassy shells, the liquid jet method is the most reproducible and exceptionally useful of all the techniques studied. The technique of capillary wave synchronization of the break-up of single and multiple component jets was utilized to produce uniform sized liquid drops and solid particles, and hollow liquid and solid shells. The technique was also used to encapsulate a number of liquids in impermeable spherical shells. Highly uniform glass shells were made by generating uniform drops of glass forming materials in an aqueous solution, subsequently evaporating the water, and then fusing and blowing the remaining solids in a high temperature vertical tube furnace. Experimental results are presented and the critical problems in further research in this field are discussed.

Hendricks, C. D.↗
NASA NTRS1982

SIRTF - The Shuttle Infrared Telescope Facility

The Shuttle Infrared Telescope (SIRTF) is a 1-m class cryogenically cooled telescope to be operated from the shuttle as a facility for infrared astronomy. By exploiting the very low infrared background of space, SIRTF will achieve 100 to 1000 times the sensitivity currently attainable at infrared wavelengths between 2 and 200 microns. The scientific requirements of SIRTF, the current design concept, and the scientific capabilities of the systems are reviewed. We also review recent experimental results showing that mirrors made of glassy materials may be suitable for use in large cryogenic telescopes such as SIRTF.

Werner, M. W.↗
NASA NTRS1982

Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

The undercooling behavior of large spheroids of Pd40Ni40P40 was investigated. By surface etching, supporting the specimens on a fused silica substrate, and successive heating and cooling, crystallization can be eliminated, presumable due to the removal of surface heterogeneities. By this method samples up to 3.2g with a 0.53 mm minor diameter, were made entirely glassy, except for some superficial crystals comprising less than 0.5% of the volume. These experiments show that a cooling rate of approximately 1 K/sec is adequate to avoid copious homogeneous nucleation in the alloy, and that by eliminating or reducing the effectiveness of heterogeneous nucleation sites, it is possible to form bulk samples of this metallic glass with virtually unlimited dimensions.

Spaepen, F.↗
NASA NTRS1981

Sub-T/g/ annealing studies of advanced epoxy-matrix graphite-fiber-reinforced composites

Annealing at temperatures below the glass transition temperature (sub-T/g/ annealing) in structural epoxy network glasses is found to affect long-term mechanical properties of symmetrically (+ or - 45 deg) reinforced 16-lamina graphite/epoxy composites. Post-cured specimens of Thornel 300 graphite/Narmco 5208 epoxy are sub-T(g) annealed at 140 C for about 10, 100, 1000, 10,000, and 100,000 min with a prior quenching above T(g). The ultimate tensile strength, strain-to-break, and static toughness of the composite materials are found to decrease as a function of sub-T(g) annealing time, while no weight loss is observed. Time-dependent changes in properties are explained by a physical aging concept based on free-volume decreases in the nonequilibrium glassy state of network epoxies, and results imply that changes in composite properties may occur with the service time.

Kong, E. S. W.↗
NASA NTRS1981

An overview of the nonequilibrium behavior of polymer glasses

It is pointed out that research efforts are at present being directed in two areas, one comprising experimental studies of this phenomenon in various glassy polymer systems and the other involving the development of a quantitative theory capable of satisfactorily predicting aging behavior for a variety of polymer materials under different conditions. Recent work in both these areas is surveyed. The basic principles of nonequilibrium behavior are outlined, with emphasis placed on changes in material properties with annealing below the glass transition temperature. Free volume theory and thermodynamic theory are discussed.

Tant, M. R.↗
NASA NTRS1980

Bulk compositions of chondrules in the Allende meteorite

The bulk chemistries of 33 chondrules from the Allende meteorite were determined by electron microbeam analyses and the modal recombination model. Chondrules were selected on the basis of a petrographic study of 2755 inclusions, of which 997 are chondrules, classified as recrystallized olivine chondrules, euhedral olivine chondrules, anhedral olivine chondrules, glassy/skeletal olivine chondrules, barred olivine chondrules, and pyroxene type chondrules. The data indicate that nonequilibrium metastable paths of crystallization were followed, a model which is supported by olivine-liquid (glassy mesostases) relationships. Variations in olivine morphology are related to cooling rate, degree of supercooling, normative olivine, and calculated viscosities. The chondrules in Allende were derived from highly undersaturated ultramafic melts in which Fe-Ni-S-O immiscible liquids were produced. The chondrule suite exhibits systematic variations in volatile loss, and this relationship is used to support a melting event (however, neither the nature of this event nor the mechanism of melt formation is established).

Simon, S. B.↗
NASA NTRS1982

Carbon in the Allende meteorite - Evidence for poorly graphitized carbon rather than carbyne

A carbon-rich acid residue from the Allende carbonaceous chondrite was examined by high-resolution transmission electron microscopy (HRTEM) and also by analytical electron microscopy. A TEM mount of this residue that has previously been reported to contain carbyne forms of carbon was shown to contain sheet silicate contaminants. These sheet silicate grains give electron diffraction patterns similar to those reported for carbynes, thus raising questions about the previous report of carbynes in this residue. Furthermore, two crystals from a glacier microspherule, which had previously been identified as carbyne VIII, were shown by microanalysis to be talc. In view of these observations it is suggested that identifications of carbyne by electron diffraction should be supported by microanalyses of the individual grains. HRTEM investigations of the Allende carbon indicate that it is a poorly crystalline graphite, structurally similar to 'glassy' carbon

Smith, P. P. K.↗
NASA NTRS1982

A new LL3 chondrite, Allan Hills A79003, and observations on matrices in ordinary chondrites

Allan Hills A79003 is an LL3 chondrite with a petrologic subtype of 3.4 + or - 0.2. Contrary to previous suggestions, it is not paired with other Allan Hills specimens. It contains haxonite, (Fe,Ni)23C6; shock-melted, 'fizzed' metal-troilite intergrowths; and translucent, glassy-looking Huss matrix (fine-grained, Fe-rich silicate matrix), in addition to the normal opaque and recrystallized varieties of Huss matrix. Some chondrules are partly coated with opaque matrix, others with translucent matrix. Translucent matrix is more uniform in composition and contains less S, CaO and FeO and more MgO than the opaque variety. Both kinds of matrix rimmed chondrules before consolidation of the meteorite.

Scott, E. R. D.↗
NASA NTRS1982

Bulk formation of a metallic glass - Pd40Ni40P20

Molten spheroids of Pd40Ni40P20, of up to 0.53-cm minor diameter, were slowly cooled (1.4 K/s) on a fused silica surface under 10 to the -6 torr vacuum to a form which was entirely glassy except for some superficial crystallinity comprising less than 0.5% of the volume. The occurrence of crystallization was eliminated by subjecting the specimens to surface etching followed by a succession of heating and cooling cycles. The absence of crystallization in bulk was confirmed by X-ray diffraction, transmission electron microscopy, and calorimetry. Using the last technique, the heat of crystallization of the glass was measured to be 5.3 + or - 0.3 kJ/g atom.

Drehman, A. J.↗