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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Screening of redox couples and electrode materials

Electrochemical parameters of selected redox couples that might be potentially promising for application in bulk energy storage systems were investigated. This was carried out in two phases: a broad investigation of the basic characteristics and behavior of various redox couples, followed by a more limited investigation of their electrochemical performance in a redox flow reactor configuration. In the first phase of the program, eight redox couples were evaluated under a variety of conditions in terms of their exchange current densities as measured by the rotating disk electrode procedure. The second phase of the program involved the testing of four couples in a redox reactor under flow conditions with a varity of electrode materials and structures.

Giner, J.↗
NASA NTRS1977

Relation of morphology of electrodeposited zinc to ion concentration profile

The morphology of electrodeposited zinc was studied with special attention to the ion concentration profile. The initial concentrations were 9M hydroxide ion and 1.21M zincate. Current densities were 6.4 to 64 mA/sq cm. Experiments were run with a horizontal cathode which was observed in situ using a microscope. The morphology of the zinc deposit was found to be a function of time as well as current density; roughly, the log of the transition time from mossy to large crystalline type deposit is inversely proportional to current density. Probe electrodes indicated that the electrolyte in the cathode chamber was mixed by self inducted convection. However, relatively large concentration gradients of the involved species existed across the boundary layer of the cathode. Analysis of the data suggests that the morphology converts from mossy to large crystalline when the hydroxide activity on the cathode surface exceeds about 12 M. Other experiments show that the pulse discharge technique had no effect on the morphology in the system where the bulk concentration of the electrolyte was kept homogeneous via self induced convection.

May, C. E.↗
NASA NTRS1978

Copernicus observations of interstellar matter in the direction of HR 1099

Results are reported for high-resolution Copernicus U1 and V2 scans of the bright RS CVn spectroscopic binary HR 1099. The observations reveal strong UV emission lines at L-alpha and Mg II h and k from the stars as well as interstellar H I and D I L-alpha absorption lines and interstellar Mg II h and k absorption in the direction of the binary system. Column densities, bulk velocities, and temperatures are derived for the interstellar features. A comparison of the derived number density of interstellar H I with data for the nearby star Epsilon Eri indicates an inhomogeneous distribution of interstellar hydrogen along the line of sight. The range of values obtained for the D/H ratio is shown to be consistent with results of other studies. A depletion factor of at least 5 with respect to the solar abundance is estimated for the interstellar magnesium.

Anderson, R. C.↗
NASA NTRS1978

Petrographic and petrological studies of lunar rocks

Thin sections and polished electron probe mounts of Apollo 15 glasscoated breccias 15255, 15286, 15466, and 15505 were examined optically and analyzed by sem/microprobe. Sections from breccias 15465 and 15466 were examined in detail, and chemical and mineralogical analyses of several larger lithic clasts, green glass, and partly crystallized green glass spheres are presented. Area analyses of 33 clasts from the above breccias were also done using the SEM/EDS system. Mineralogical and bulk chemical analyses of clasts from the Apollo 15 glass-coated breccias reveal a diverse set of potential rock types, including plutonic and extrusive igneous rocks and impact melts. Examination of the chemistry of the clasts suggests that many of these clasts, like those found in 61175, are impact melts. Their variability suggests formation by several small local impacts rather than by a large basin-forming event.

Winzer, S. R.↗
NASA NTRS1984

Titanium isotopic anomalies in meteorites

Studies of Ti isotopic compositions have shown that virtually every Ca-Al-rich Allende inclusion contains anomalous Ti. The present investigation is concerned with the results of a study of Ti isotopic compositions in meteorites. One objective of the study is to evaluate the possibility of a relation between oxygen and Ti anomalies, while another objective is to explore questions regarding the origin of the Ti anomalies. A summary of the major experimental findings of the study of Ti isotopic compositions is also presented. It is noted that an assessment of the implications of the Ti results favors a chemical memory type of model in which products from various nucleosynthetic sources survive in mineral grains. Isotopic heterogeneities are then preserved due to incomplete mixing and/or equilibriation with the bulk of solar system matter. Strong arguments are found to exist against a pure late supernova injection model.

Niemeyer, S.↗
NASA NTRS1990

Triton, Pluto and Charon

On the eve of the Voyager encounter with Neptune and Triton, the knowledge of the surface and atmosphere of the satellite has made some progress. Methane, and perhaps molecular nitrogen, appears to dominate the surface and atmospheric chemistry. Sketchy evidence suggests changes in the disposition and state of the volatile materials on this body in the past few years, perhaps in response to the extreme seasons. Pluto and its satellite Charon are at last revealed in some detail, chiefly resulting from observations of the mutual transits and occultations of 1985-1990. A stellar occultation by Pluto in 1988 has given the first detailed information on the planet's atmosphere. The density of the Pluto-Charon system indicates a bulk composition consisting of silicates and water ice, suggesting formation directly from the solar nebula.

Cruikshank, D. P.↗
NASA NTRS1991

An instrument for spatial conductivity measurements of high Tc superconducting (HTSC) materials

High T(sub c) Superconducting (HTSC) thin films are suggested for use in a number of aerospace applications such as an IR bolometer and as electromagnetic shielding. As part of its flight assurance role, the Materials Branch of the Goddard Space Flight Center has initiated development of an instrument capable of measuring variations in conductivity for flat samples using an eddy current testing device and an X-Y positioning table. This instrument was used to examine bulk HTSC samples. System changes that would enable characterization of thin film materials are discussed.

Vansant, T.↗
NASA NTRS1992

Marine Magnetic Data Holdings of World Data Center-a for Marine Geology and Geophysics

The World Data Center-A for Marine Geology and Geophysics is co-located with the Marine Geology & Geophysical Data Center, Boulder, CO. Fifteen million digital marine magnetic trackline measurements are managed within the GEOphysical DAta System (GEODAS). The bulk of these data were collected with proton precision magnetometers under Transit Satellite navigational control. Along-track sampling averages about 1 sample per kilometer, while spatial density, a function of ship's track and survey pattern, range from 4 to 0.02 data points/sq. km. In the near future, the entire geophysical data set will be available on CD-ROM. The Marine Geology and Geophysics Division (World Data Center-A for MGG), of the National Geophysical Data Center, handles a broad spectrum of marine geophysical data, including measurements of bathymetry, magnetics, gravity, seismic reflection subbottom profiles, and side-scan images acquired by ships throughout the world's oceans. Digital data encompass the first three, while the latter two are in analog form, recorded on 35mm microfilm. The marine geophysical digital trackline data are contained in the GEODAS data base which includes 11.6 million nautical miles of cruise trackline coverage contributed by more than 70 organizations worldwide. The inventory includes data from 3206 cruises with 33 million digital records and indexing to 5.3 million track miles of analog data on microfilm.

Sharman, George F.↗
NASA NTRS1992

Modification of primordial ices by cosmic rays as simulated by cyclotron irradiation

Frozen CH4 and CH4/Ar mixtures closed into metal cuvettes and open to the vacuum were irradiated at 15 and 77 K with 10 - 20 MeV p and He-3(2+) ions in order to simulate the effect of cosmic rays on solid organic matter in space. Ices exposed to vacuum represent surfaces of icy systems whereas closed systems stand for bulk ices. The products were analyzed by MS, SEM, RBS, ERDA, H-1-NMR, HPLC, GC-MS, NEXAFS, and FT-IR. Volatile products consisted of a mixture of low molecular species, e.g., C2H2, C2H4, C2H6, and long linear aliphatic and olefinic compounds. The formation of polycyclic aromatic hydrocarbons (PAH's) and related species in solid CH4 is due to a multi-center reaction within one collision cascade and is governed by energy density effects with critical linear energy transfer values L(sub T) between 2 and 10 keV/micron. Open ices exhibit preferential hydrogen release resulting in an increased carbonization as compared to more hydrogen rich molecules protected inside large icy bodies.

Kaiser, R. I.↗
NASA NTRS2005

Hydrogen Abundances in Metal Grains from the Hammadah Al Hamra (HaH) 237 Metal-rich Chondrite: A Test of the Nebular-Formation Theory

The Bencubbin-like (CB) chondrites are metal-rich, primitive meteorites [1,2]. Some of these chondrites (HaH 237, QUE 94411) contain compositionally zoned metal grains with near-chondritic bulk compositions. Thermodynamic modeling of the zoning patterns in these grains suggests that they were formed by condensation in a region of the solar nebula with enhanced dust/gas ratios and a total pressure of 10(exp -4) bars at temperatures between 1400 - 1500 K [3]. If these predictions are correct than the metal grains would have been exposed to abundant H2 gas, which comprises the bulk of nebular systems. Since Fe-based alloys can absorb significant quantities of H, metal grains formed in the solar nebula should contain measurable abundances of H.

Lauretta, D. S.↗
NASA NTRS2008

Thermoelectric Properties of Self Assemble TiO2/SnO2 Nanocomposites

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 (mu)W/m sq K at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Dynys, Fred↗
NASA NTRS2008

Thermoelectric Properties of Self Assembled TiO2/SnO2 Nanocomposites

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 W/mK2 at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Dynys, Fred↗
NASA NTRS2008

Using Aerogel-Based Insulation Material To Prevent Foam Loss on the Liquid-Hydrogen Intertank

Uninsulated areas on cryogenic propellant tanks and feedlines cause moisture in the air to condense or ice to form. Flange joints, bracket supports, expansion bellows, and other cavities are uninsulated by design. These areas cannot be sealed because conventional thermal insulation materials would restrict mechanical articulations. Aerogel-based thermal insulation systems are able to seal critical locations such as the liquid-oxygen (LO2) feedline bellows. A new thermal insulation system was also necessary between the intertank wall, flange, and the liquid-hydrogen (LH2) tank dome, where there is a cavity (or crevice) with an exposed 20-K surface. When nitrogen gas is used for purging within the intertank volume, it condenses on this cold surface. Some solid nitrogen may also form on the colder side of the crevice. Voids or discontinuities within the foam can pressurize and cause areas of foam to weaken and break off, reducing thermal efficiency and creating potentially dangerous debris. To prevent this foam loss, we developed a thermal insulation system using bulk-fill aerogel material and demonstrated it with a one-tenth-scale model of the LH2 intertank flange area

Source record↗
NASA NTRS2015

Mechanical Properties of Air Plasma Sprayed Environmental Barrier Coating (EBC) Materials

Development work in Environmental Barrier Coatings (EBCs) for Ceramic Matrix Composites (CMCs) has focused considerably on the identification of materials systems and coating architectures to meet application needs. The evolution of these systems has occurred so quickly that modeling efforts and requisite data for modeling lag considerably behind development. Materials property data exists for many systems in the bulk form, but the effects of deposition on the critical properties of strength and fracture behavior are not well studied. We have plasma sprayed bulk samples of baseline EBC materials (silicon, ytterbium disilicate) and tested the mechanical properties of these materials to elicit differences in strength and toughness. We have also endeavored to assess the mixed-mode fracture resistance, Gc, of silicon in a baseline EBC applied to SiCSiC CMC via four point bend test. These results are compared to previously determined properties of the comparable bulk material.

Ceramic Matrix Composites (CMC's)↗
NASA NTRS1965

Three-dimensional wire-mesh capacitor system measures fluid density

Gaging system automatically measures the bulk density of a stored, electrically nonconductive fluid containing varying portions of liquid and vapor. The system employs a three-dimensional wire-mesh capacitor whose capacitance varies with the bulk density of the fluid dielectric medium between the capacitor plates.

Source record↗
NASA NTRS1991

A new approximate sum rule for bulk alloy properties

A new, approximate sum rule is introduced for determining bulk properties of multicomponent systems, in terms of the pure components properties. This expression is applied for the study of lattice parameters, cohesive energies, and bulk moduli of binary alloys. The correct experimental trends (i.e., departure from average values) are predicted in all cases.

Bozzolo, Guillermo↗
NASA NTRS1992

A new approximate sum rule for bulk alloy properties

A new, approximate sum rule is introduced for determining bulk properties of multicomponent systems, in terms of the pure components properties. This expression is applied for the study of lattice parameters, cohesive energies, and bulk moduli of binary alloys. The correct experimental trends (i.e., departure from average values) are predicted in all cases.

Bozzolo, Guillermo↗