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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Experiments On Transparent Conductive Films For Spacecraft

Report describes experiments on thin, transparent, electrically conductive films made, variously, of indium tin oxide covered by magnesium fluoride (ITO/MgF2), aluminum-doped zinc oxide (AZO), or pure zinc oxide (ZnO). Films are candidates for application to such spacecraft components, including various optoelectronic devices and window surfaces that must be protected against buildup of static electric charge. On Earth, such films useful on heat mirrors, optoelectronic devices, gas sensors, and automotive and aircraft windows.

Perez-Davis, Marla E.↗
NASA NTRS2019

Saponite Dissolution Experiments and Implications for Mars

Recent work suggests that the mineralogical sequence of the Murray formation at Gale crater may have resulted from diagenetic alteration after sedimentation, or deposition in a stratified lake with oxic surface and anoxic bottom waters. Fe-containing clay minerals are common both at Gale crater, and throughout the Noachian-aged terrains on Mars. These clay minerals are primarily ferric (Fe3+), and previous work suggests that these ferric clay minerals may result from alteration of ferrous (Fe2+) smectites that were oxidized after deposition. The detection of trioctahedral smectites at Gale crater by CheMin suggests Fe2+ smectite was also deposited during the early Hesperian. However, due to their sensitivity to oxygen, Fe2+ smectites are difficult to analyze on Earth and very few saponite dissolution rates exist in the literature. To the best of our knowledge, no experiments have measured the dissolution rates of ferrous saponites under oxidizing and reducing conditions. In order to better understand the characteristics of water-rock interaction at Gale crater, particularly the oxidation state, we report our results to date on ongoing syntheses of ferrous and magnesium saponites and dissolution experiments of natural saponite under ambient conditions. Future experiments will include the dissolution of synthetic ferric, ferrous, and magnesium saponites under oxidizing and anoxic conditions at a range of pH values.

Luu, N. C.↗
NASA NTRS2003

High Resistivity Transparent/Conductive Coatings for Space Applications: Problems and Possible Improvements

We have prepared transparent films with a sheet relativity of 10(exp 1) to 10(exp 12) ohm/square by co-depositing a transparent conducting oxide (TCO) with magnesium fluoride, using two independently controlled RF magnetron sputter guns to facilitate adjustment of the film composition, Co-deposited indium tin oxide (ITO) and MgF2 on quartz and flexible polymeric substrate exhibited reasonably stable sheet resistivity over several months' time, with substantially lower optical reflectance than that of pure ITO. However, exposure to low-intensity blue light reduces sheet resistivity by as much as two orders of magnitude. Our results suggest this photoconductivity effect may be present in all InO(x)-based materials. We find that sheet resistivity can by "tuned" by admitting a small amount of high-purity air during deposition offering the possibility of closed loop process control.

Cashman, Thomas↗
NASA NTRS1996

Transparent, Conductive Coatings Developed for Arc-Proof Solar Arrays

Transparent, conductive thin-film coatings have many potential applications where a surface must be able to dissipate electrical charges without sacrificing its optical properties. Such applications include automotive and aircraft windows, heat mirrors, optoelectronic devices, gas sensors, and solar cell array surfaces for space applications. Many spacecraft missions require that solar cell array surfaces dissipate charges in order to avoid damage such as electronic upsets, formation of pinholes in the protective coatings on solar array blankets, and contamination due to deposition of sputtered products. In tests at the NASA Lewis Research Center, mixed thin-films of sputter-deposited indium tin oxide (ITO) and magnesium fluoride (MgF2) that could be tailored to the desired sheet resistivity, showed transmittance values of greater than 90 percent. The samples evaluated were composed of mixed, thin-film ITO/MgF2 coatings, with a nominal thickness of 650 angstroms, deposited onto glass substrates. Preliminary results indicated that these coatings were durable to vacuum ultraviolet radiation and atomic oxygen. These coatings show promise for use on solar array surfaces in polar low-Earth-orbit environments, where a sheet resistivity of less than 10(exp 8)/square is required, and in geosynchronous orbit environments, where a resistivity of less than 10(exp 9)/square is required.

Source record↗
NASA NTRS2001

Combustion of Metals in Carbon Dioxide and Reduced-Gravity Environments

Ongoing exploration and future mission2001110444 s to Mars have given impetus to research on the use of natural resources of the planet. Since carbon dioxide (CO2) constitutes approximately 95% of the Mars atmosphere and since it reacts directly and vigorously with several metals, this investigation focuses on metal-CO2 reactions as a possible combination for rocket-propellant production and energy generation. Magnesium (Mg) has been initially selected as the metal fuel owing to its low ignition temperature and high specific impulse and burning rate in CO2. Our studies in this field started with low gravity (g) combustion tests of Mg in O2, CO2, and CO. Reduced gravity provided a clear picture of the burning phenomena by eliminating the intrusive buoyant flows in high-temperature metal reactions and by removing the destructive effect of gravity on the shape of molten metal samples. Suspended cylindrical metal samples of 2, 3, and 4-mm in diameter and length were radiatively ignited in low-g to generate free-floating samples exhibiting a spherically symmetric flame with increasing metal-oxide accumulation in an outer shell. For the Mg-CO2 combination, burning times twice as long as in normal-g and five times longer than in Mg-O2 flames were observed, revealing a diffusion-controlled reaction. The burning time is proportional to the square of the sample diameter. In tests conducted with pure CO, combustion was not possible without constant heating of the sample due to the formation of a thick carbon-containing coating around the Mg sample generated by surface reactions. The following work presents two new studies that attempt to explain some of the low-g experimental observations. First, a simplified one-dimensional, quasi-steady numerical model is developed to obtain temperature, species concentrations, and burning rates of the spherically symmetric diffusion flame around the Mg sample burning in O2 and CO2. Second, a Planar Laser Induced Fluorescence (PLIF) technique is implemented to provide spatially resolved measurements of magnesium oxide (MgO) in the reaction zone of Mg samples burning in O2 and CO2. These experiments reveal fundamental differences between the two combustion systems.

Branch, M. C.↗
NASA NTRS1967

Fogging technique used to coat magnesium with plastic

Cleaning process and a fogging technique facilitate the application of a plastic coating to magnesium plates. The cleaning process removes general organic and inorganic surface impurities, oils and greases, and oxides and carbonates from the magnesium surfaces. The fogging technique produces a thin-filmlike coating in a clean room atmosphere.

Mroz, T. S.↗
NASA NTRS1963

Lunar Rocks as a Source of Oxygen

A thermodynamic study of the thermal stability of conventional terrestrial minerals in a hypothetical lunar atmosphere has opened some interesting speculation. Much of the Earth's crust is composed of oxides of silicon, aluminum, magnesium, and related compounds. These crust components may be as much a product of the Earth's atmosphere as vegetation and animal life. Though inanimate and long considered imperishable, these materials are stable under conditions of an atmosphere equivalent to 34 ft of water at sea level and persist under adverse conditions of moisture and temperature to altitudes of roughly 29,000 ft above sea level. The oxygen content averages 21% ) and the oxygen partial pressure would be roughly 1/5 atm.

Poole, H. G.↗
NASA NTRSDate not supplied

Gaseous By-Product of Thermal Vacuum Processing of Lunar Highland Simulant

Scientists at Kennedy Space Center are advancing technologies to achieve oxygen extraction on the Lunar surface. One such technology is Molten Regolith Electrolysis (MRE) in which regolith simulant is melted under high temperatures to perform oxygen extraction through electrolysis of the melt pool. A study was conducted to understand the molten formation and proper-ties of Lunar Highlands Simulants (LHS-1) under high vacuum environments ranging between 10-6 Torr. These studies include investigating the regolith melt behavior and by-product gas analysis systems to prepare for pilot plant development and operations. The off-gassing rates and pressure build-up, gaseous compounds, and material compatibility may be a risk to MRE systems. The KSC findings are reported here for inclusion into future mis-sion architecture and operational planning. The four stages of the experiment were vacuum, resistive heating, regolith melt and gas detection. The regolith mass of 70 g was melted in a 40 cm tall x 50 cm diameter vacuum chamber at temperature increase rate 47 ℃ /min and ramp rate of 1 ampere/3 min up to an 18-amp maximum. The test is conducted for about 60 minutes and the constituent gases produced during heating of regolith is monitored with a re-sidual gas analyzer. During the molten formation, primary off-gassing volatiles included water vapor (18 amu), a peak at 44 amu (FeO2 – expected), and atomic oxygen (16 amu), among a series of other compounds that could create compatibility issues such as magnesium, chlorine, and silicon oxide. These results add to the knowledge required for successful oxygen extraction on the moon.

Molten Regolith Electrolysis↗
NASA NTRS1974

Single Crystal Membranes

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Stormont, R. W.↗
NASA NTRS1967

Magnesium-zinc reduction is effective in preparation of metals

Uranium, thorium, and plutonium are effectively prepared by magnesium-zinc reduction, using uranium oxides, thorium dioxide, and plutonium dioxide as starting materials. This technique is also useful in performing reduction of metals such as zirconium and titanium.

Knighton, J. B.↗
NASA NTRS1988

Microgravity nucleation and particle coagulation experiments support

Researchers at NASA Goddard Space Flight Center have embarked on a program to study the formation and growth of cosmic grains. This includes experiments on the homogeneous nucleation of refractory vapors of materials such as magnesium, lead, tin, and silicon oxides. As part of this program, the Chemical Engineering Department of the University of Virginia has undertaken to develop a math model for these experiments, to assist in the design and construction of the apparatus, and to analyze the data once the experiments have begun. Status Reports 1 and 2 addressed the design of the apparatus and the development of math models for temperature and concentration fields. The bulk of this report discusses the continued refinement of these models, and the assembly and testing of the nucleation chamber along with its ancillary equipment, which began in the spring of 1988.

Lilleleht, L. U.↗
NASA NTRS2019

Compositional and Microstructural Effects in the Protection of SiC Components in Water Vapor

Greater gas turbine engine efficiency is a major goal in aeronautics research often pursued through increased engine operating temperatures. However, it is necessary to replace the current hot-stage alloy components with more thermally robust parts, such as promising Silicon-based ceramics and composites. Unfortunately, these materials are still susceptible to the effects of oxidation, water vapor, and (Calcium-Magnesium-Alumino-Silicate) CMAS interaction, among other issues at high temperature. To mitigate these effects, environmental barrier coating (EBC) materials are employed to help control the rate of degradation to the underlying composite. Often, a thermally grown oxide (TGO) layer forms between the EBC and the composite which can act as a point of failure. The current study focuses on the combined effects of water vapor, composite composition, and microstructure in TGO formation on protected and unprotected SiC samples which have been produced under different processing conditions.

Kowalski, Benjamin↗
NASA NTRS2009

Production of Oxygen from Lunar Regolith by Molten Oxide Electrolysis

This paper describes the use of the molten oxide electrolysis (MOE) process for the extraction of oxygen for life support and propellant, and silicon and metallic elements for use in fabrication on the Moon. The Moon is rich in mineral resources, but it is almost devoid of chemical reducing agents, therefore, molten oxide electrolysis is ideal for extraction, since the electron is the only practical reducing agent. MOE has several advantages over other extraction methods. First, electrolytic processing offers uncommon versatility in its insensitivity to feedstock composition. Secondly, oxide melts boast the twin key attributes of highest solubilizing capacity for regolith and lowest volatility of any candidate electrolytes. The former is critical in ensuring high productivity since cell current is limited by reactant solubility, while the latter simplifies cell design by obviating the need for a gas-tight reactor to contain evaporation losses as would be the case with a gas or liquid phase fluoride reagent operating at such high temperatures. Alternatively, MOE requires no import of consumable reagents (e.g. fluorine and carbon) as other processes do, and does not rely on interfacing multiple processes to obtain refined products. Electrolytic processing has the advantage of selectivity of reaction in the presence of a multi-component feed. Products from lunar regolith can be extracted in sequence according to the stabilities of their oxides as expressed by the values of the free energy of oxide formation (e.g. chromium, manganese, Fe, Si, Ti, Al, magnesium, and calcium). Previous work has demonstrated the viability of producing Fe and oxygen from oxide mixtures similar in composition to lunar regolith by molten oxide electrolysis (electrowinning), also called magma electrolysis having shown electrolytic extraction of Si from regolith simulant. This paper describes recent advances in demonstrating the MOE process by a joint project with participation by NASA KSC and MSFC, and Ohio State University and MIT. Progress in measuring cell efficiency for oxygen production, development of non reacting electrodes, and cell feeding and withdrawal will be discussed.

Curreri, Peter A.↗
NASA NTRS2017

Environmental Barrier Coatings for Ceramic Matrix Composites - An Overview

SiC/SiC Ceramic Matrix Composites (CMCs) are increasingly being considered as structural materials for advanced power generation equipment because of their light weight, higher temperature capability, and oxidation resistance. Limitations of SiC/SiC CMCs include surface recession and component cracking and associated chemical changes in the CMC. The solutions pursued to improve the life of SiC/SiC CMCs include the incorporation of coating systems that provide surface protection, which has become known as an Environmental Barrier Coating (EBC). The development of EBCs for the protection of gas turbine hot section CMC components was a continuation of coating development work for corrosion protection of silicon-based monolithics. Work on EBC development for SiC/SiC CMCs has been ongoing at several national laboratories and the original gas turbine equipment manufacturers. The work includes extensive laboratory, rig and engine testing, including testing of EBC coated SiC/SiC CMCs in actual field applications. Another EBC degradation issue which is especially critical for CMC components used in aircraft engines is the degradation from glassy deposits of calcium-magnesium-aluminosilicate (CMAS) with other minor oxides. This paper addresses the need for and properties of external coatings on SiC/SiC CMCs to extend their useful life in service and the retention of their properties.

EBC↗
NASA NTRS1981

Corrosion resistant thermal barrier coating

A thermal barrier coating system for protecting metal surfaces at high temperature in normally corrosive environments is described. The thermal barrier coating system includes a metal alloy bond coating, the alloy containing nickel, cobalt, iron, or a combination of these metals. The system further includes a corrosion resistant thermal barrier oxide coating containing at least one alkaline earth silicate. The preferred oxides are calcium silicate, barium silicate, magnesium silicate, or combinations of these silicates.

Levine, S. R.↗