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Results for “transitional metals”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Electron microscopy and diffraction of layered, superconducting intercalation complexes.

Several layered, transition metal dichalcogenide intercalation complexes with unique superconducting properties have been examined by high-resolution electron microscopy and electron diffraction. Details of the crystalline lattice and of the lattice imperfections have been directly resolved. The results can be correlated with the available X-ray diffraction and chemical data, and they confirm and extend the postulated models.

Fernandez-Moran, H.↗
NASA NTRS1971

Inorganic photochromic and cathodochromic recording materials.

Discussion of studies at RCA Laboratories of the properties of rare-earth-doped CaF2, transition-metal-doped SrTiO3 and iron- or sulfur-doped sodalite as photochromic materials which change color during light or electron beam exposures. Particular attention is given to their photochromic characteristics in single-crystal and powder forms and to their cathodochromic properties in powder form. Details are given on the photochromic mechanisms, spectra, optical density, thermal decay rates, and coloring and bleaching efficiency of their single crystals and on the diffuse reflectance spectra, saturated photochromic contrast ratio, switching and erase sensitivities, and cathodochromic excitation of their photochromic powders. The many attractive characteristics of these materials when used in display storage systems are indicated.

Duncan, R. C., Jr.↗
NASA NTRS1973

A new optical recording medium

Method has been developed for doping lithium niobiate crystals with transition metal to increase rate at which crystal can record optical data. Discovery may facilitate development of system for analog storage of TV frames, printed pages, photographs, and other visual information.

Aronson, H.↗
NASA NTRS1974

The formation of goethite and hydrated clay minerals on Mars

Laboratory studies reported by Huguenin (1973) on the kinetics and mechanism of the photostimulated oxidation of magnetic and preliminary laboratory data on the weathering of silicates, reported herein, are applied to Mars. Basalts in the Martian dark areas are predicted to alter to hydrated Fe(2 plus or minus) depleted clay minerals, minor goethite, and minor to trace amounts of transition metal oxides such as TiO2, MnO2, and Cr2O3 at a rate of 10 to the minus 1.5 plus or minus 1.5 micron/yr. Some Ca-Mg carbonates are also expected to be formed. The clay minerals are predicted to be more silica-rich than the silicate source material, SiO2 contents of 60% or higher being expected, and strongly depleted in Fe(2+). The oxygen, OH, and H2O contents of the bulk weathering product are predicted to be significantly greater than those of the dark-area source materials, whereas the relative bulk metal abundances should be the same.

Huguenin, R. L.↗
NASA NTRS1974

A review of the deformation behavior of tungsten at temperatures less than 0.2 of the melting point /K/

The deformation behavior of tungsten at temperatures below 0.2 times the absolute melting temperature is reviewed with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition. It is concluded that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. Future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of alloys of tungsten and other transition metal alloys.

Stephens, J. R.↗
NASA NTRS1976

Superconductive neuristor R-junction

Device incorporating specially-configured pure metal transition region can be developed to simulate a nerve cell. Combination of such cells may be formed to simulate an eye or brain and can be used in recognizing characters and other visual images.

Reible, S. A.↗
NASA NTRS1976

The 55 K specific heat anomaly in palladium hydride

A specific heat anomaly in PdH and PdD has been observed by Aston et al. (1957) close to 55 K. Its position was found to be independent of hydrogen concentration and its magnitude to be linear in hydrogen concentration. Ferguson's (1965) and Brodowsky's (1972) explanations of the anomaly are shown to be unsatisfactory. This is true also for the detailed mechanical statistical model proposed by Staford and McLellan (1974) for interstitial solid solutions of hydrogen in transition metals. It is shown that Gopal's (1966) simple Schottky model of specific heat anomaly, which considers a system of several levels with Boltzmann statistics, provides much better agreement with experiment than the more elaborate models, both in magnitude and in predicting a linear dependence on hydrogen concentration.

Jacobi, N.↗
NASA NTRS1977

Solar photolysis of water

Hydrogen is produced by the solar photolysis of water in a first photooxidation vessel with a transparent wall in the presence of a water soluble photooxidizable reagent and an insoluble hydrogen recombination catalyst. Simultaneously oxygen is produced in a second photoreduction reactor with a transparent wall in the presence of an insoluble photoreduction reagent catalyst. When spent, the solution from the first reactor is fed into the second reactor. A reaction occurs in the dark in which the redox reagents are regenerated, and the regenerated photooxidation reagent solution is recycled to the first reactor. The photoreduction-catalyst is a bifunctional reagent catalyst including a transition metal salt together with a hydroxyl or chlorohydroxyl decomposition catalyst of high area.

Ryason, P. R.↗
NASA NTRS1976

Power Sources Symposium, 27th, Atlantic City, N.J., June 21-24, 1976, Proceedings

A lithium-chlorine rechargeable battery is considered along with an FeS electrode development for a secondary Li5Si-FeS battery, the sodium-sulfur battery, nickel battery systems for electric vehicles, reactions in lithium thionyl chloride cells, progress in the development of lithium inorganic batteries, a stable electrolyte for Li/SO2 reserve cells, and rechargeable lithium transition metal sulfide batteries. Attention is also given to thermal runaway tests on nickel-cadmium aircraft batteries, the development of nickel-zinc batteries for aircraft, an evaluation of sealed lead acid batteries for aircraft applications, the charging of sealed lead-acid batteries, hydrogen recombination in sealed nickel-cadmium cells, the characteristics of nickel-hydrogen flight cells, the lithium-iodine cell, low power methanol fuel cells, and a nuclear battery hybrid configuration study.

Source record↗
NASA NTRS1977

Electronic absorption spectra of lunar minerals

Techniques for obtaining information on the crystal chemistry of transition-metal ions from measurement of the electronic absorption spectra of lunar minerals are reviewed along with the theory of spectral interpretation. Typical polarized absorption spectra are examined for lunar pyroxenes, pyroxferroite, olivine, and plagioclase feldspars. Oxidation states of Fe, Ti, and Cr in lunar minerals are discussed, and conditions under which they crystallized are considered. It is shown how information on the gross mineralogy and petrology of different regions of the moon's surface may be extracted from remote reflectivity measurements of that surface.

Vaughan, D. J.↗
NASA NTRS1977

Molecular cluster theory of CO chemisorption on a nickel /100/ surface

Self-consistent Hartree-Fock-Slater molecular cluster models for the chemisorption of carbon monoxide on a (100) transition metal surface are presented. Energy levels and charge distribution for the CO:Ni5 cluster in C sub 4v symmetry are obtained, and the variation of binding energies with height of the CO molecule above the surface of nickel is studied in detail. Comparison is made with experimental binding energy spectra and with the multiple-scattering results of Batra and Bagus. The redistribution in energy of free-atom valence levels is studied by means of local-densities-of-states diagrams.

Ellis, D. E.↗
NASA NTRS1978

Solar photolysis of water

A cyclic process is described for the solar photolysis of water, including a first stage in which water is reduced in the presence of a Eu(+2) photooxidizable reagent producing hydrogen and spent oxidized Eu(+3) reagent. The spent reagent Eu(+3) is reduced by means of a transition metal ligand complex reductant, RuL(+3) in a photoexcited state, such as a ruthenium pyridyl complex. Due to competing reactions between the photolysis and regeneration products, the photooxidation reaction must be separated from the regeneration in space and time by supporting the reagent and/or the reductant on solid supports and utilizing pH, wavelength and flow control to maximize hydrogen and oxygen production.

Ryason, P. R.↗
NASA NTRS1978

Catalysts for electrochemical generation of oxygen

Single crystal surfaces of platinum and gold and transition metal oxides of the spinel type were studied to find more effective catalysts for the electrolytic evolution of oxygen and to understand the mechanism and kinetics for the electrocatalysis in relation to the surface electronic and lattice properties of the catalyst. The single crystal studies involve the use of low energy electron diffraction (LEED) and Auger electron spectroscopy as complementary tools to the electrochemical measurements. Modifications to the transfer system and to the thin-layer electrochemical cell used to facilitate the transfer between the ultrahigh vacuum environment of the electron surface physics equipment and the electrochemical environment with a minimal possibility of changes in the surface structure, are described. The electrosorption underpotential deposition of Pb onto the Au(111), (100) and (110) single crystal surfaces with the thin-layer cell-LEED-Auger system is discussed as well as the synthesis of spinels for oxygen evolution studies.

Hagans, P.↗
NASA NTRS1979

Friction and wear of single-crystal manganese-zinc ferrite

Sliding friction experiments were conducted with single crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110) on matched crystallographic planes exhibit the lowest coefficient of friction, indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages of (110) planes are observed on the ferrite surfaces as a result of sliding.

Miyoshi, K.↗
NASA NTRS1979

Feasibility study for a secondary Na/S battery

The feasibility of a moderate temperature Na battery was studied. This battery is to operate at a temperature in the range of 100-150 C. Two kinds of cathode were investigated: (1) a soluble S cathode consisting of a solution of Na2Sn in an organic solvent and (2) an insoluble S cathode consisting of a transition metal dichalcogenide in contact with a Na(+)ion conducting electrolyte. Four amide solvents, dimethyl acetamide, diethyl acetamide, N-methyl acetamide and acetamide, were investigated as possible solvents for the soluble S cathode. Results of stability and electrochemical studies using these solvents are presented. The dialkyl substituted amides were found to be superior. Although the alcohol 1,3-cyclohexanediol was found to be stable in the presence of Na2Sn at 130 C, its Na2Sn solutions did not appear to have suitable electrochemical properties.

Abraham, K. M.↗
NASA NTRS1979

Association of nucleotides with homoionic clays

The binding of nucleotides to homoionic clays is studied as a possible mechanism for the concentration and catalysis of biological or prebiotic materials on the prebiotic earth. Samples of radioactively labeled adenosine and thymidine nucleotides were mixed in solutions with bentonite, kaolinite or Dowex-50 particles in which all exchangeable sites were occupied by Na, Mg, Ca, Mn, Fe, Cu or Zn ions. The binding of nucleotides to homoionic clays is observed, with adenosine nucleotides favored over thymidine, bentonite as the best absorber, and greater binding to clays homoionic in transition metal ions. Results indicate that the oligomerization of nucleotides may be possible by this mechanism, however difficulties in nucleotide variability and base pairing may arise due to the observed preference for purines at the adsorption sites.

Odom, D. G.↗
NASA NTRS1979

Friction and wear of single-crystal manganese-zinc ferrite

Sliding friction experiments were conducted with single-crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110 line type) on matched crystallographic planes exhibit the lowest coefficient of friction indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages are observed on the ferrite surfaces as a result of sliding.

Miyoshi, K.↗
NASA NTRS1979

Method of purifying metallurgical grade silicon employing reduced pressure atmospheric control

A method in which a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, as well as certain transition metals including nickel, iron, and manganese is described. The tube is then evacuated and heated to a temperature within a range of 800 C to 1400 C. A stream of gas comprising a reactant, such as silicon tetrafluoride, is continuously delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. The reactant which included carbon monoxide gas and impurities such as iron and nickel react to form volatile carbonyls.

Ingle, W. M.↗