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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

The structure and microphysical properties of the clouds of Venus

Results are presented from the processing and interpretation of measurement data in the descent capsules of the automatic stations Venera-9 and Venera-10 for the characteristics of light scattering in the atmosphere of Venus by means of onboard nephelometers. A model for the aerosol component in the planet's atmosphere in the altitude range 62-14 km is proposed.

Marov, M. Y.↗
NASA NTRS1980

The effect of preparation conditions on the structure and mechanical properties of reaction-sintered silicon nitride

The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.

Heinrich, J.↗
NASA NTRS1980

The assembly and properties of protobiological structures - The beginnings of cellular peptide synthesis

New data indicate that lysine-rich proteinoids have the ability to catalyze the synthesis of peptide bonds from a variety of amino acids and ATP. This capacity is evident in aqueous solution, in suspension of phase-separated complexes of lysine-rich proteinoid with acidic proteinoids, and in suspension of phase-separated particles composed of lysine-rich proteinoids with polynucleotides. Since the proteinoid complexes can contain other catalytic activities, including ability to catalyze internucleotide bond formation, it is inferred that the first protocells on earth already had a number of biological types of activity.

Fox, S. W.↗
NASA NTRS1982

The metallurgical structure and mechanical properties at low temperature of Nitronic 40 with particular reference to its use in the construction of models for cryogenic wind tunnels

Nitronic 40 was chosen for the construction of Pathfinder I, an R & D model for use in the National Transonic Facility, because of its good mechanical properties at cryogenic temperatures. Nitronic 40 contains delta ferrite and is in a sensitized condition. Heat treatments carried out to remove residual stresses also caused further sensitization. Experiments showed that heat treatment followed by cryoquenching removed the sensitization without creating residual stresses. Heat treatment at temperatures of 2200 F was used to remove the delta ferrite but with little success and at the cost of massive grain growth. The implications of using degraded Nitronic 40 for cryogenic wind tunnel models are discussed, together with possible acceptance criteria.

Wigley, D. A.↗
NASA NTRS1982

Effects of cobalt on structure, microchemistry and properties of a wrought nickel-base superalloy

The effect of cobalt on the basic mechanical properties and microstructure of wrought nickel-base superalloys has been investigated experimentally by systematically replacing cobalt by nickel in Udimet 700 (17 wt% Co) commonly used in gas turbine (jet engine) applications. It is shown that the room temperature tensile yield strength and tensile strength only slightly decrease in fine-grained (disk) alloys and are basically unaffected in coarse-grained (blading) alloys as cobalt is removed. Creep and stress rupture resistances at 760 C are found to be unaffected by cobalt level in the blading alloys and decrease sharply only when the cobalt level is reduced below 8 vol% in the disk alloys. The effect of cobalt is explained in terms of gamma prime strengthening kinetics.

Jarrett, R. N.↗
NASA NTRS1982

Modeling the thermal structure and magnetic properties of the crust of active regions with application to the Rio Grande rift

Experiments in Curie depth estimation from long wavelength magnetic anomalies are summarized. The heart of the work is equivalent-layer-type magnetization models derived by inversion of high-elevation, long wavelength magnetic anomaly data. The methodology is described in detail in the above references. A magnetization distribution in a thin equivalent layer at the Earth's surface having maximum detail while retaining physical significance, and giving rise to a synthetic anomaly field which makes a best fit to the observed field in a least squares sense is discussed. The apparent magnetization contrast in the equivalent layer is approximated using an array of dipoles distributed in equal area at the Earth's surface. The dipoles are pointed in the direction of the main magnetic field, which carries the implicit assumption that crustal magnetization is dominantly induced or viscous. The determination of the closest possible dipole spacing giving a stable inversion to a solution having physical significance is accomplished by plotting the standard deviation of the solution parameters against their spatial separation for a series of solutions.

Source record↗
NASA NTRS1987

Jupiter's ring system - New results on structure and particle properties

Jupiter's diffuse ring system is upon reexamination of Voyager images noted to be composed of a relatively bright narrow ring and an inner toroidal halo as well as the 'gossamer' exterior ring, while the previously suspected inner disk is missing. Several narrow, bright features are visible in the main ring, and are suggested to be related in some way to Adrastea and Metis. The smallest ring particles and the dark, rough, red largest bodies both have total optical depths of 1-6 x 10 to the -6th. After arising at the bright ring's inner boundary, the halo rapidly expands inward to a 20,000-km thickness, and disappears at a radius of 90,000 km halfway between the main ring and the planet's cloudtops.

Showalter, Mark R.↗
NASA NTRS1988

Effect of substrate preparation on the structure and chemisorption properties of Pd/MgO model catalyst

Pd/MgO model catalysts are prepared by vapor deposition of Pd particles on MgO thin films which are deposited, at different temperatures, on UHV cleaved mica. MgO films and Pd particles are characterized in situ by Auger electron spectroscopy and energy-loss spectroscopy and ex situ by transmission electron microscopy. Succesive temperature programmed desorption (TPD) of CO shows a different evolution of the morphology of the Pd particles deposited on MgO films prepared at low and high temperature. In addition, on MgO prepared at low temperature, the smallest particles show a continuous decay of CO adsorption during TPD due to contamination by support species.

Henry, C. R.↗
NASA NTRS1990

Effect of shock pressure on the structure and superconducting properties of Y-Ba-Cu-O in explosively fabricated bulk metal-matrix composites

While it is now well established that copper-oxide-based powder, or virtually any other ceramic superconductor powder, can be consolidated and encapsulated within a metal matrix by explosive consolidation, the erratic superconductivity following fabrication has posed a major problem for bulk applications. The nature of this behavior was found to arise from microstructural damage created in the shock wave front, and the residual degradation in superconductivity was demonstrated to be directly related to the peak shock pressure. The explosively fabricated or shock loaded YBa2Cu3Ox examples exhibit drastically altered rho (or R) - T curves. The deterioration in superconductivity is even more noticeable in the measurement of ac magnetic susceptibility and flux exclusion or shielding fraction which is also reduced in proportion to increasing peak shock pressure. The high-frequency surface resistance (in the GHz range) is also correspondingly compromised in explosively fabricated, bulk metal-matrix composites based on YBa2Cu3O7. Transmission electron microscopy (including lattice imaging techniques) is being applied in an effort to elucidate the fundamental (microstructural) nature of the shock-induced degradation of superconductivity and normal state conductivity. One focus of TEM observations has assumed that oxygen displaced from b-chains rather than oxygen-vacancy disorder in the basal plane of oxygen deficient YBa2Cu3Ox may be a prime mechanism. Shock-wave displaced oxygen may also be locked into new positions or interstitial clusters or chemically bound to displaced metal (possibly copper) atoms to form precipitates, or such displacements may cause the equivalent of local lattice cell changes as a result of stoichiometric changes. While the shock-induced suppression of T(sub c) is not desirable in the explosive fabrication of bulk metal-matrix superconductors, it may be turned into an advantage if the atomic-scale distortion can be understood and controlled as local flux pinning sites.

Murr, L. E.↗