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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Crack nucleation in Fe-3% Si in a hydrogen environment

An investigation has been made of the grain-size and strain-rate dependence of the crack nucleation process in iron-3% silicon polycrystals tested in a low-pressure hydrogen environment. The results are compared with similar observations made in an air environment and are discussed in terms of the role of hydrogen on the process of crack nucleation in iron.

Kamdar, M. H.↗
NASA NTRS1975

Glass-Si heterojunction solar cells

An increase in efficiency from 2% to over 7% was achieved by a solar cell that used polycrystal silicon heterojunction with SnO2 glass. For Single crystal substrates, efficiencies close to 10% were measured. These cells had the same structures as polycrystalline cells. Work on p+/n heterojunction using In2O3 glass resulted in cells of 3% efficiency on polycrystalline material and 4% efficiency on single crystal material.

Ahrons, R. W.↗
NASA NTRS1976

Effect of interfacial oxide layers on the current-voltage characteristics of Al-Si contacts

Aluminum-silicon contacts with very thin interfacial oxide layers and various surface impurity concentrations are studied for both n and p-type silicon. To determine the surface impurity concentrations on p(+)-p and n(+)-n structures, a modified C-V technique was utilized. Effects of interfacial oxide layers and surface impurity concentrations on current-voltage characteristics are discussed based on the energy band diagrams from the conductance-voltage plots. The interfacial oxide and aluminum layer causes image contrasts on X-ray topographs.

Porter, W. A.↗
NASA NTRS1977

Analysis of GaAs and Si solar energy hybrid systems

Various silicon hybrid systems are modeled and compared with a gallium arsenide hybrid system. The hybrid systems modeled produce electric power and also thermal power which can be used for heating or air conditioning. Various performance indices are defined and used to compare the system performance: capital cost per electric power out; capital cost per total power out; capital cost per electric power plus mechanical power; annual cost per annual electric energy; and annual cost per annual electric energy plus annual mechanical work. These performance indices indicate that concentrator hybrid systems can be cost effective when compared with present day energy costs.

Heinbockel, J. H.↗
NASA NTRS1978

Observed and theoretical profiles of the Si II lines at lambda 1814

Emission line spectra observed at the limb of the solar disc are presented for transitions of singly ionized silicon at lambdas 1816.93, 1817.45 and 1808.01. The profiles show self-reversals in the line cores. A non-LTE analysis for a simplified model of the silicon ion is presented, and calculated line profiles are compared with the observations. The study indicates that some modification of the Vernazza et al. (1973) model of the solar chromosphere in the transition region is needed to reconcile the calculated and observed profiles.

Finn, G. D.↗
NASA NTRS1979

The Si ribbon crystal for the solar battery using the horizontal pull method

A method utilizing a device to spray noble gases to cool the site of silicon crystal growth is described. The salient points are: (1) soft and uniform cooling was possible, (2) the length of the boundary surface of growth along the growth direction was made long over a wide width compared to the thickness, and (3) this made it possible to effectively remove the heat produced from solification. By using forced gas spraying on the solution surface in contact with the points of crystal growth, growth at the points of growth is enhanced and the rate of growth is speeded up.

Norifuji, H.↗
NASA NTRS1980

Analysis of GaAs and Si solar cell arrays for earth orbital and orbit transfer missions

Silicon and gallium arsenide arrays were studied and compared for low earth orbit (LE), geosynchronous orbit (GEO), and LEO to GEO electric propulsion orbit transfer missions. The sensitivities of total cost to parameters such as mission duration, array cost, cover glass thickness, and concentration ratio were determined along with cost tradeoffs between silicon and gallium arsenide arrays for selected mission classes. Results indicate that development of the technology for low cost, light weight concentrators should be increased and that cost reduction efforts for gallium arsenide cells be pursued.

Jeffries, K. D.↗
NASA NTRS1980

Conceptual design study of concentrator enhanced solar arrays for space applications. 2kW Si and GaAs systems at 1 AU

The effect of concentration level on the specific power for a deployable, thin, gallium arsenide cell array in geosynchronous orbit for 10 years in conjunction with a two dimensional flat plate trough concentrator (V trough) and also with a multiple flat plate concentrator was investigated as well as the effects for a conventional silicon cell array on a rigid substrate. For application to a thin GaAs array at 1 AU for 10 years, the V trough produces a 19% benefit in specific power and a dramatic reduction in array area, while the multiple flat plate collector design is not only of no benefit, but is a considerable detriment. The benefit it achieves by reducing array area is duplicated by the 2D design. For the silicon array on a rigid substrate, improvement in performance due to a concentrator with ordinary mirror coating is quite small: 9% increase in specific power, and 13% reduction in array area. When the concentrator mirrors are coated with an improved cold mirror coating, somewhat more significant results are obtained: 31% specific power improvement; and 27% area reduction. In both cases, a 10 year exposure reduces BOL output by 23%.

Source record↗
NASA NTRS1980

Melting relations and elemental distribution of portion of the system Fe-S-Si-O to 32 KB with planetary application

The melting relations and distribution of K and Cs in portions of the system was determined at high pressures. Ferrosilite is stable as a primary phase at high pressures because of the incongruent melting of ferrosilite to quartz plus liquid and the boundary between the one and two liquid fields on the joint Fe(1-x) O-FeS-SiO2 shifts away from silica with increasing pressures. Potassium K was found to have limited solubility in metal sulfide liquids at pressures up to 45 kb. The speculation that K may dissolve significantly in metal-metal sulfide liquids after undergoing first order isomorphic transition was tested by determining the distribution of Cs between sulfide and silicate liquids as an analogy to K. At 45 kb, 1400 C and 27 kb, 1300 C only limited amounts of Cs were detected in quench sulfide liquids even at pressures beyond the isomorphic transition of Cs.

Huang, W. L.↗