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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Aspects of the mechanisms of smoke generation by burning materials

An investigation of smoke generation during the burning of natural and synthetic solid materials (relevant to fire safety problems), under simulated fire conditions, is presented. Smoke formation mechanisms, including flaming and nonflaming combustion, are reviewed, and the complex physical, chemical, and electrical processes, important in smoke particulate production, are identified. With reference to the smoke formation mechanisms, measured experimental data are discussed, and include effects of ventilation gas temperature, dependence on material composition, and chemical analysis of smoke particulates. Significant differences in smoke characteristics are observed between flaming and nonflaming conditions, which is attributed to specific differences in controlling mechanisms and resultant ways leading to particulate formation. The effects of polymer substrate properties and effects of additives for a given substrate on smoke properties are also discussed in terms of basic processes. It is shown that many of the measured trends can be interpreted by considering postulated mechanisms of particulate formation.

Bankston, C. P.↗
NASA NTRS1980

Development of a digital data base for reflectance-related soil information

A digital soils data base established for inclusion of soil reflectance data, physical, chemical, and engineering measurements, and site information is discussed. Initial data are taken from 500 soil samples covering the spectral range of 0.5 to 2.3 microns. Information obtained from each observation includes spectral data, and identification records with the soil and spectral observation parameters. The LARSPEC software system is available to retrieve and manipulate information, and scattergrams of identification and spectral data allow the initiation of statistical analyses of soil data. In addition, soil characteristics, graphical displays of reflectance spectra, and identification information examples are given.

Stoner, E. R.↗
NASA NTRS1981

Workshop on Early Crustal Genesis: Implications from Earth

Ways to foster increased study of the early evolution of the Earth, considering the planet as a whole, were explored and recommendations were made to NASA with the intent of exploring optimal ways for integrating Archean studies with problems of planetary evolution. Major themes addressed include: (1) Archean contribution to constraints for modeling planetary evolution; (2) Archean surface conditions and processes as clues to early planetary history; and (3) Archean evidence for physical, chemical and isotopic transfer processes in early planetary crusts. Ten early crustal evolution problems are outlined.

Phinney, W. C.↗
NASA NTRS1982

Comparisons of different plate treatments and designs: Analysis

The design and process changes on cell performance and life were studied. The merits of each design were analyzed physically, chemically, and electrochemically. A teardown analysis of each cell was carried out. On opening the cell it was found that the cell pack was moist with the electrolyte, the extent varying from one cell to another. The cell components, the positives, the negatives, and the separators, could be separated easily for cell pack of an uncycled cell. The separators from the uncycled cell were clean and white. In the case of cycled cells the separators were stuck to the surface of the negative plates. During the removal of these separators from the negative plates invariably a thin layer of the separator material was strongly adhering to the surface of the negative plates and could not be removed as easily as in the case of the uncycled cells. The separators had dark patches due to cadmium migration.

Kunigahelli, V.↗
NASA NTRS1980

Thermal evolution of Ganymede and Callisto - Effects of solid-state convection and constraints from Voyager imagery

The imaging experiments of the Voyager 1 and 2 fly-by missions have provided a large amount of information about the nature of the surfaces of the Galilean satellites. The present investigation is concerned with the development of models regarding the thermal evolution of Ganymede and Callisto, taking into account the approach of parameterized convection. Attention is given to the physical, chemical, and geological data which are available as constraints on the thermal evolution of Ganymede and Callisto. Both satellites appear to possess surfaces composed of silicates and ice. However, their surface features are distinctly different from each other. In the discussion of thermal evolution models, attention is given to ice-dominant rheology, silicate-dominant rheology, and aspects of phase changes and solid-state convection.

Thurber, C. H.↗
NASA NTRS1983

A comparison of volcanic eruption processes on earth, moon, Mars, Io and Venus

The physical, chemical, and atmospheric characteristics of the silicate planets and satellites are surveyed in terms of their effects on the volcanic evolution of the surfaces of these bodies. The equations relating the parameters affecting magma ascent through the crust and eruption are analyzed, and three major types of eruption are characterized: effusive, steady explosive, and unsteady explosive. This analytical framework is then used to predict the nature of volcanic activity on each of the planets and satellites, and the predictions are compared with actual observations. Outstanding problems are discussed, with emphasis on the need for a general model of planetary interior dynamics applicable to bodies with varying degrees of interior viscosity, mantle activity, and lithospheric plate tectonics.

Wilson, L.↗
NASA NTRS1983

Photodeposition of aluminum oxide and aluminum thin films

Uniform films of Al2O3 have been photodeposited using an excimer laser operating at 248 nm (KrF) or at 193 nm (ArF) and trimethylaluminum and N2O as the reactants. Deposition rates were typically 2000 A/min and the physical, chemical, and electrical properties of the photodeposited Al2O3 films are comparable to films deposited using conventional techniques. Properties of photodeposited aluminum films are also presented.

Solanki, R.↗
NASA NTRS1984

Metallic glass as a temperature sensor during ion plating

The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

Miyoshi, K.↗
NASA NTRS1983

Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

Lathrop, J. W.↗
NASA NTRS1982

Geological implications of impacts of large asteroids and comets on the earth

The present conference discusses such topics as large object fluxes in near-earth space and the probabilities of terrestrial impacts, the geological record of impacts, dynamics modeling for large body impacts on continents and oceans, physical, chemical, and biological models of large impacts' atmospheric effects, dispersed impact ejecta and their signatures, general considerations concerning mass biological extinctions, the Cretaceous/Tertiary boundary event, geochemical signatures in the stratigraphic record, and other phanerozoic events. Attention is given to terrestrial impact rates for long- and short-period comets, estimates of crater size for large body impact, a first-order estimate of shock heating and vaporization in oceanic impacts, atmospheric effects in the first few minutes after an impact, a feasibility test for biogeographic extinction, and the planktonic and dinosaur extinctions.

Silver, L. T.↗
NASA NTRS1984

Colloidally separated samples from Allende residues - Noble gases, carbon and an ESCA-study

Results are presented which strengthen the hypothesis of heterogeneity among the carbon- and nitrogen-bearing phases of the Allende meteorite. These data also highlight the possibility of performing physical separations yielding samples in which some of the noble gas- and carbon-bearing phases are extraordinarily predominant over others. The conclusion, based on mass and isotope balance arguments, that a significant portion of the carbonaceous matter in Allende is likely to be gas-poor or gas-free need not weaken the case for carbonaceous carriers for the major noble gas components. The concept that acid-soluble carbonaceous phases contain a multiplicity of components, each of which may have formed under a multiplicity of different physical-chemical conditions, is reemphasized by the results of the present study.

Ott, U.↗
NASA NTRS1984

Global habitability and earth remote sensing

Since 1960, when NASA launched the Tiros satellite to study the atmosphere of the earth, great advances have been made in the study of the earth system by means of remote sensing. It is felt that the time has come for assembling the separate pieces into a coherent whole. Work has, therefore, been conducted to develop a concept called 'global habitability'. The objective of the considered program is to investigate long-term physical, chemical, and biological trends and changes in the earth's environment, including its atmosphere, land masses, and oceans. The program is specifically concerned with a study of the effects of natural and human activities on the earth's environment, and with the future effects on biological productivity and habitability of the earth by man and by other species.

Tilford, S. G.↗
NASA NTRS1985

Preparation and Characterization of HgxCd1-xTe

Experimental studies of growth of Hgx Cd1-xTe important as infrared detector material: Studies part of greater effort to determine effects of processing conditions on chemical, physical, and electrical properties of this material.

Broerman, J.↗
NASA NTRS1984

Magnetic constraints on early lunar evolution revisited: Limits on accuracy imposed by methods of paleointensity measurements

It is impossible to carry out conventional paleointensity experiments requiring repeated heating and cooling to 770 C without chemical, physical or microstructural changes on lunar samples. Non-thermal methods of paleointensity determination have been sought: the two anhysteretic remanent magnetization (ARM) methods, and the saturation isothermal remanent magnetization (IRMS) method. Experimental errors inherent in these alternative approaches have been investigated to estimate the accuracy limits on the calculated paleointensities. Results are indicated in this report.

Banerjee, S. K.↗
NASA NTRS1984

The Interaction of Global Biochemical Cycles

The global biosphere in an exceedingly complex system. To gain an understanding of its structure and dynamic features, it is necessary not only to increase the knowledge about the detailed processes but also to develop models of how global interactions take place. Attempts to analyze the detailed physical, chemical and biological processes in this context need to be guided by an advancement of understanding of the latter. It is necessary to develop a strategy of data gathering that severs both these purposes simultaneously. The following papers deal with critical aspects in the global cycles of carbon, nitrogen, phosphorus and sulfur in details as well as the cycle of water and the flow of energy in the Earth's environment. The objective is to set partly the foundation for the development of mathematical models that allow exploration of the coupled dynamics of the global cycles of carbon, nitrogen, phosphorus, sulfur, as well as energy and water flux.

Moore, B., III↗
NASA NTRS1984

Global biogeochemical cycles: Studies of interaction and change, some views on the strategy of approach

The global biosphere is an exceedingly complex system. To gain an understanding of its structure and dynamic features, it is necessary to increase knowledge about the detailed processes, but also to develop models of how global interactions take place. Attempts to analyze the detailed physical, chemical and biological processes need, in this context, to be guided by an advancement of understanding of the latter. It is necessary to develop a strategy of data gathering that serves both these purposes simultaneously. climate research during the last decade may serve as a useful example of how to approach this difficult problem in a systematic way. Large programs for data collection may easily become rigid and costly. While realizing the necessity of a systematic and long lasting effort of observing the atmosphere, the oceans, land and life on Earth, such a program must remain flexible enough to permit the modifications and even sometimes improvisations that are necessary to maintain a viable program.

Bolin, B.↗
NASA NTRS1984

Laboratory Investigations

The primary objectives were to examine the site-specific physical, chemical, and biological factors that impact construction, durability and performance of the proposed 5-MW (sub e) solar pond system at the Salton Sea. The interactions of the water, salt, and soil of the site and on material compatibility were examined. Potential interactions of the water/brine and soil are particularly important because the pond will utilize the naturally occurring clays as a bottom seal. Although there is a considerable and growing solar pond literature, little written information deals with the important site-specific investigations of water, salt, and soil. Therefore, technical effort was directed toward identifying the factors that should be investigated and determining methods of investigation. As a result, a by-product was the development of an approach for site-specific investigations and some specific methodologies. This development should continue in order to establish a generic approach for evaluating the suitability of any site for the construction of large-scale solar ponds.

Source record↗
NASA NTRS1984

Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

Research on the reliability of terrestrial solar cells was performed to identify failure/degradation modes affecting solar cells and to relate these to basic physical, chemical, and metallurgical phenomena. Particular concerns addressed were the reliability attributes of individual single crystalline, polycrystalline, and amorphous thin film silicon cells. Results of subjecting different types of crystalline cells to the Clemson accelerated test schedule are given. Preliminary step stress results on one type of thin film amorphous silicon (a:Si) cell indicated that extraneous degradation modes were introduced above 140 C. Also described is development of measurement procedures which are applicable to the reliability testing of a:Si solar cells as well as an approach to achieving the necessary repeatability of fabricating a simulated a:Si reference cell from crystalline silicon photodiodes.

Lathrop, J. W.↗