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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

High pressure-temperature electrical conductivity of magnesiowustite as a function of iron oxide concentration

The electrical conductivity of (Mg, Fe)O magnesiowustite containing 9 and 27.5 mol pct FeO has been measured at simultaneously high pressures (30-32 GPa) and temperatures using a diamond anvil cell heated with a continuous wave Nd:YAG laser and an external resistance heater. The conductivity depends strongly on the FeO concentration at both ambient and high pressures. At the pressures and temperatures of about 30 GPa and 2000 K, conditions expected in the lower mantle, the magnesiowustite containing 27.5 percent FeO is 3 orders of magnitude more conductive than that containing 9 percent FeO. The activation energy of magnesiowustite decreases with increasing iron concentration from 0.38 (+ or - 0.09) eV at 9 percent FeO to 0.29 (+ or - 0.05) eV at 27.5 percent FeO.

Li, Xiaoyuan↗
NASA NTRS1986

Electrically conductive, black thermal control coatings for space craft application. II - Silicone matrix formulation

Five black electrically conductive thermal-control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consisted of organic and inorganic systems applied on titanium and aluminum surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation and convective and conductive heating from -196 to 538 C. Mechanical, physical, thermal, electrical, and optical characteristics, formulation, mixing, application, surface preparation of substrates, and a method of determining electrical resistance are presented for the silicone matrix formulation designated as GF-580.

Hribar, V. F.↗
NASA NTRS1975

Effective electrical conductivity of a nonuniform plasma

A simple nonuniformity model for calculating effective electrical conductivity and Hall parameter is proposed. The model shows that the effective conductivity can be significantly reduced by nonuniformities in the Hall parameter, even if the local conductivity is uniform.

Nichols, L. D.↗
NASA NTRS1978

Electrical conductivity measurements from the STRATCOM 8 experiment

A blunt probe experiment for measuring electrical conductivity was flown with the STRATCOM 8 instrument package. Data were obtained by the instrument throughout the entire measurement period. A preliminary analysis of the data indicates an enhancement in conductivity associated with the krypton discharge ionization lamp, particularly in negative conductivity. The conductivity values and their altitude dependence are consistent with previous balloon and rocket results.

Mitchell, J. D.↗
NASA NTRS1979

Electrical conductivity of the lunar interior - Theory, error sources, and estimates

Estimates of the electrical conductivity of the lunar interior were previously obtained by comparison of magnetometer data at the lunar surface and in near lunar space. In studies based on solar wind observations, IR was assumed that fields induced in the lunar interior by time-varying external fields are confined by the solar wind within the lunar interior on the dayside and within a cylindrical plasma cavity on the nightside. In the present paper, the induced fields are calculated for a more realistic conical plasma cavity geometry.

Goldstein, B. E.↗
NASA NTRS1984

The electrical conductivity of the upper mantle as estimated from satellite magnetic field data

The electrical conductivity of the upper mantle is estimated from low-latitude magnetic field variations caused by large fluctuations in the equatorial ring current. The data base is derived from magnetic field magnitude data measured by satellites OGO 2, 4, and 6, which offer better global coverage than land-based observatories. The procedures of analysis consist of: (1) separation of the disturbance field into internal and external parts relative to the surface of the earth, (2) estimation of an electromagnetic response function Q(omega) which relates the internally generated magnetic field variations to the external variations due to the ring current, and (3) interpretation of the estimated response function using theoretical response functions for assumed conductivity profiles. Special consideration is given to possible oceanic and ionospheric effects. Best estimates of the geomagnetic response function Q(omega) for 0.2 to 2.0 cpd indicate an upper mantle conductivity of the order of 0.01 S/m.

Didwall, E. M.↗
NASA NTRS1981

Electrical conductivity and electron-spin resonance in oxidatively stabilized polyacrylonitrile subjected to elevated temperature

Electrical conductivity and electron spin resonance measurements are presented for oxidatively stabilized polyacrylonitrile (PAN) fibers subjected to heat treatment at temperatures ranging from 700 to 950 K. Conductivity measurements made at temperatures between 77 and 523 K reveal that PAN fibers heat treated in vacuum behave as semiconductors, with a room-temperature conductivity dominated by the contributions of impurity states, with an activation energy of 88 kcal/mole. A decrease in conductivity is observed upon air which is attributed to a decrease in the electron-phonon scattering time. ESR spectra indicate that conducting pathways having metallic properties are formed at temperatures as low as 715 K, although the contribution of these pathways to the room-temperature conductivity is extremely small next to the contribution of localized spin centers.

Lerner, N. R.↗