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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Grain size analysis and high frequency electrical properties of Apollo 15 and 16 samples

The particle size distribution of eleven surface fines samples collected by Apollo 15 and 16 was determined by the method of measuring the sedimentation rate in a column of water. The fact that the grain size distribution in the core samples shows significant differences within a few centimeters variation of depth is important for the understanding of the surface transportation processes which are responsible for the deposition of thin layers of different physical and/or chemical origin. The variation with density of the absorption length is plotted, and results would indicate that for the case of meter wavelength radar waves, reflections from depths of more than 100 meters generally contribute significantly to the radar echoes obtained.

Gold, T.↗
NASA NTRS1974

Surface electrical properties experiment, Part 3

A complete unified discussion of the electromagnetic response of a plane stratified structure is reported. A detailed and comprehensive analysis of the theoretical parts of the electromagnetic is given. The numerical problem of computing numbers of the electromagnetic field strengths is discussed. It is shown that the analysis of the conductive media is not very far removed from the theoretical analysis and the numerical difficulties are not as accute as for the low-loss problem. For Vol. 1, see N75-15570; for Vol. 2 see N75-15571.

Source record↗
NASA NTRS1974

Electrical properties of sample 70215 - Low-frequency corrections

Dielectric permittivity, loss tangent, and direct current conductivity of solid sample 70215,14 were measured at temperatures ranging from 100 to 373 K and vacuums of .01 to .1 microtorr; alternating current measurements were made in the 30 Hz to 100 kHz frequency range. It is concluded that dc conductivity undergoes a three order-of-magnitude change between lunar day and lunar night. The assumption is made that strong k' increments at the lower frequencies are partially induced by electrode and dc conductivity effects. Corrections were applied to the experimental data; corrected results suggest relaxation processes occurring at frequencies below 1 kHz.

Alvarez, R.↗
NASA NTRS1977

Optical and electrical properties of ion beam textured Kapton and Teflon

Results are given for ion beam texturing of polyimide (Kapton) and fluorinated ethylene propylene (Teflon) by means of a 30-cm diam electron bombardment argon ion source. Ion beam-textured Kapton and Teflon surfaces are evaluated for various beam energies, current densities, and exposure times. The optical properties and sheet resistance are measured after each exposure. Provided in the paper are optical spectral data, resistivity measurements, calculated absorptance and emittance measurements, and surface structure SEM micrographs for various exposures to argon ions. It is found that Kapton becomes conducting and Teflon nonconducting when ion beam-textured. Textured Kapton exhibits large changes in the transmittance and solar absorptance, but only slight changes in reflectance. Surface texturing of Teflon may allow better adherence of subsequent sputtered metallic films for a high absorptance value. The results are valuable in spacecraft charging applications.

Mirtich, M. J.↗
NASA NTRS1982

Measuring the Electrical Properties of Epoxies

Two techniques rapidly determine low-frequency resistivity of conductive epoxies and high-frequency dielectric properties of insulating epoxies. Conductive epoxy is molded in channels in plastic block. Four-point ohmmeter is used to apply current and sense voltage; it reads out resistance. Because mold has precise and stable dimensions, it produces accurate consistent measurements.

Sergent, J. E.↗
NASA NTRS1982

In situ measurements of thunderstorm electrical properties

An airplane sensor to measure the charge, size and two dimensional shape of precipitation particles and large cloud particles was developed. The basic design of the instrument includes: the transducers and analog electronics, the analog to digital conversion electronics and a microprocessor based system to run the electronics and load the digital data onto magnetic tape. Prototype instrumentation for the proposed lightning mapper satellite was tested by flying it in a U-2 aircraft over severe storms in Oklahoma. Flight data are compared to data from ground based instruments.

Marshall, T. C.↗
NASA NTRS1983

Correlation of solar cell electrical properties with material characteristics of silicon cast by the ubiquitous crystallization process

Solar cells were fabricated using a conservative 'baseline' process on 1-3 Omega-cm p-type silicon from ingots cast by the ubiquitous crystallization process. Conversion efficiencies of the cells were measured, as well as spectral response and minority carrier diffusion length. Adjacent slices from the same ingot were studied for their grain size, dislocation distribution, and impurity distribution. Cell performance was related to the observed structural features, as well as to the chemical structure of the ingot.

Hyland, S.↗
NASA NTRS1984

Effect of Ion Sputtering on Interface Chemistry and Electrical Properties of an Gaas (100) Schottky Contacts

Auger and electron photoelectron spectroscopy were used to measure the extent of As depletion during 1 keV to 5 keV argon sputtering of GaAs surfaces. This depletion was correlated with a general decrease in the barrier height of the rectifying Au contact deposited in situ. However, nondestructive angle resolved XPS measurements showed As was depleted at the outer surface more by 1 keV than 3 keV argon. These effects are explained based on a combined work effective work function model and creation of a donor like surface damage layer. The donor layer was correlated with As depletion by sputtering. Deep level trap formation and annealing of sputtering effects were studied.

Wang, Y. X.↗
NASA NTRS1984

Effect of ion sputtering on interface chemistry and electrical properties of Au GaAs(100) Schottky contacts

The effects of sputtering n-type (100)GaAs with 1 to 5 keV argon ions have been studied in ultrahigh vacuum. Auger electron and X-ray photoelectron spectroscopies have been used to characterize the surface before and after sputtering. Gold Schottky contacts were prepared in situ to avoid contamination at the metal/semiconductor interface. The data show that sputtering depletes the surface in As, and the extent of depletion increased as the ion energy was increased. However, angular-resolved photoelectron data showed As was enriched on the outer atom layer by 5 keV but depleted by 1 keV Ar(+) sputtering. Current and capacitance versus voltage data showed that sputtering always lowered the Schottky barrier height and generally increased the ideality factor. However, the barrier height after 3 keV sputtering was higher than after 1 keV sputtering. Those effects are explained based on a combined effective work function model and creation of a donorlike surface damage layer. The donor layer was correlated with As depletion by sputtering. Deep level trap formation and annealing of sputtering effects were studied.

Wang, Y.-X.↗
NASA NTRS1984

Electrical properties of metal-doped pyridine-derived polyimide films

A series of polyimide films containing pyridine coordinating groups doped with cobalt or nickel ions has been examined. Using 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, films were prepared in combination with 4,4'-oxydianiline, 4,4'-dianiline sulfide, 3,3'-bis(aminopyridine) sulfide and 2,2'-dioxyphenelenebis (5,5'-aminopyridine). Room temperature volume resistivities have been found to decrease slightly with sulfur and pyridine containing diamines relative to diamines which do not contain these functionalities. Doping with cobalt and nickel additives results in further lowering of room temperature volume resistivity. Preliminary temperature profiling experiments have shown that volume resistivity decreases as T(g) is approached.

Khor, E.↗
NASA NTRS1985

Electrical properties of TGS crystals grown by a new technique

The cooled sting technique used to grow triglycine sulphate (TGS) crystals is investigated. The sting procedure, which achieves supersaturation by cooling the seed crystal mounted on the sting is described and a diagram is provided. Temperature differentials of 1.5 and 1.0 C are optimum for growing (001) and (010) orientation TGS seeds. The data obtained are compared with previous data and good correlation is shown; it is inferred that TGS crystals of any orientation can be grown at a uniform rate of 1 mm/day using this technique.

Batra, A. K.↗
NASA NTRS1986

Water permeation and electrical properties of pottants, backings, and pottant/backing composites

It is reported that the interface between plastic film back covers and ethylene vinyl acetates (EVA) or polyvinyl butyral (PVB) in photovoltaic modules can influence water permeation, and electrial properties of the composites such as leakage current and dielectric constant. The interface can either be one of two dissimilar materials in physical contact with no intermixing, or the interface can constitute a thin zone which is an interphase of the two materials having a gradient composition from one material to the other. The former condition is described as a discrete interface. A discrete interface model was developed to predict water permeation, dielectric strength, and leakage current for EVA, ethylene methyl acrylate (EMA), and PVB coupled to Tedlar and mylar films. Experimental data was compared with predicted data.

Orehotsky, J.↗