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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Advanced Lithium-ion Batteries with High Specific Energy and Improved Safety for Nasa's Missions

High Energy Materials ( Cathodes, anodes and high voltage and safe electrolyte are required to meet the needs of the future space missions. A. Cathodes: The layered layered composites of of Li2MnO3 and LiMO2 are promising Power capability of the materials, however requires further improvement. Suitable morphology is critical for good performance and high tap (packing) density. Surface coatings help in the interfacial kinetics and stability. B. Electrolytes: Small additions of Flame Retardant Additives improves flammability without affecting performance (Rate and cycle life). 1.0 M in EC+EMC+TPP was shown to have good performance against the high voltage cathode; Performance demonstrated in large capacity prototype MCMB- LiNiCoO2 Cells. Formulations with higher proportions are looking promising. Still requires further validation through abuse tests (e.g., on 18650 cells).

NASA Missions↗
NASA NTRS1975

Supersonic CO electric-discharge lasers

Laser modeling activity is described which involved addition of an option allowing N2 as a second diatomic gas. This option is now operational and a few test cases involving N2/CO mixtures were run. Results from these initial test cases are summarized. In the laboratory, a CW double-discharge test facility was constructed and tested. Features include: water-cooled removable electrodes, O-ring construction to facilitate cleaning and design modifications, increased discharge length, and addition of a post-discharge observation section. Preliminary tests with this facility using N2 yielded higher power loadings than obtained in the first-generation facility. Another test-section modification, recently made and as yet untested, will permit injection of secondary gases into the cathode boundary layer. The objective will be to vary and enhance the UV emission spectrum from the auxiliary discharge, thereby influencing the level of photoionization in the main discharge region.

Hason, R. K.↗
NASA NTRS1978

Observations of a double-layer in a hot-cathode discharge

The meniscus region of a hot cathode discharge was selected for an analysis of the nonlinear interaction of a convectively amplifying wave with a background plasma. A potential step, resulting from rectification of the wave fields is observed, and it is noted that predicted values for the step are in good agreement with empirical data. Attention is given to the determination of plasma parameters (using a Langmuir probe placed in front of the cathode) in terms of their relation to the pondermotive force.

Levine, J. S.↗
NASA NTRS2007

Potential Fluctuations and Energetic Ion Production in Hollow Cathode Discharges

Ions with energies significantly in excess of the applied discharge voltage have been reported for many years in hollow cathode discharges. Models of dc potential hills downstream of the cathode and instabilities in postulated double layers in the cathode orifice have been proposed to explain this, but have not been substantiated. Measurements of the dc and rf plasma density and potential profiles near the exit of hollow cathodes by miniature fast-scanning probes suggests that turbulent ion acoustic fluctuations and ionization instabilities in the cathode plume significantly increase the energy of the ions that flow from this region. Increases in the discharge current and/or decreases in the cathode gas flow enhance the amplitude of the fluctuations and increase the number and energy of the energetic ions, which increases the erosion rate of the cathode electrodes. The transition from the quiescent 'spot mode' to the noisy 'plume mode' characteristic of these discharges is found to be a gradual transition of increasing fluctuation amplitudes.

keeper↗
NASA NTRS1983

Comparison of the characteristics of potential drop and current-driven double layers

The characteristics of double layers driven by an applied potential drop and by an injected current into a plasma are compared. In the latter case the potential drop across the double layer appears because of the formation of a virtual cathode. The double layers formed by the two mechanisms show striking similarities with regard to their structure, temporal evolution, and dynamics. However, in the case of current-driven double layers a large energization of ions trapped in the virtual cathode region is observed. Such a large energization of trapped ions is not seen in the case of the potential-drop driven double layers. The interrelation between the field-aligned currents and potential drops for the auroral plasma is discussed. For current-driven double layers, it is found that the current density is proportional to the 1/2 power of the potential drop.

Singh, N.↗
NASA NTRS2007

MoO3 Cathodes for High-Temperature Lithium Thin-Film Cells

MoO3 has shown promise as a cathode material that can extend the upper limit of operating temperature of rechargeable lithium thin-film electrochemical cells. Cells of this type are undergoing development for use as energy sources in cellular telephones, wireless medical sensors, and other, similarly sized portable electronic products. The LiCoO2 and LiMn2O4 cathodes heretofore used in these cells exhibit outstanding cycle lives (of the order of hundreds of thousands of cycles) at room temperature, but operation at higher temperatures reduces their cycle lives substantially: for example, at a temperature of 150 C, cells containing LiCoO2 cathodes lose half their capacities in 100 charge/discharge cycles. The superiority of MoO3 as a cathode material was demonstrated in experiments on lithium thin-film cells fabricated on glass slides. Each cell included a layer of Ti (for adhesion to the glass slide), a patterned layer of Pt that served as a cathode current collector, a cathode layer of MoO3, a solid electrolyte layer of Li3.3 PO3.8 N0.22 ("LiPON"), and an anode layer of Li. All the layers were deposited by magnetron sputtering except for the Li layer, which was deposited by thermal evaporation. These cells, along with similar ones containing LiCoO2 cathodes, were subjected to several tests, including measurements of specific capacity in charge/discharge cycling at a temperature of 150 C. The results of these measurements, plotted in the figure, showed that whereas specific capacity of the cells containing LiCoO2 cathodes faded to about half its initial value after only 100 cycles, the specific capacity of the cells containing the MoO3 cathodes faded only slightly during the first few hundred cycles and thereafter not only recovered to its initial value but continued to increase up to at least 5,500 cycles.

West, William↗
NASA NTRS2024

Reliable and Efficient Electrochemical Recovery of O 2 from Metabolic CO 2 at the International Space Station (ISS)

Maximum O 2 recovery from metabolic carbon dioxide (CO 2 ) is desired for future long-duration missions beyond Low Earth Orbit (LEO). The O 2 recovery for the Environmental Control and Life Support System (ECLSS) at the International Space Station (ISS), presently limited to 50% (Sabatier), must be highly reliable and efficient and recover a minimum of 75% oxygen (O 2 ) from metabolic CO 2 . An alternative technology development effort currently underway at NASA Marshall Space Flight Center (MSFC) via a Microfluidic Electrochemical Reactor (MFECR) approach has the potential to increase O 2 recovery significantly and reduce the complexity of the ECLSS O 2 recovery at the ISS as it would replace three pieces, the CO 2 Reduction Assembly (CRA) (Sabatier reactor), the Oxygen Generation Assembly (OGA), and the Plasma Pyrolysis Assembly (PPA). The MFECR's electrochemical process generates ethylene (C 2 H 4 ) and carbon moxide (CO) instead of methane (CH 4 ) (Sabatier) as a byproduct, eliminating the need for further dehydrogenation through the PPA. As in the OGA, the MFECR's electrochemical process generates O 2 and hydrogen (H 2 ) from the water electrolysis process. MSFC and the University of Texas in Arlington (UTA) have jointly designed and fabricated an MFECR's single cell that operates at ambient conditions and utilizes a proprietary catalysis highly selective on reducing CO 2 to C 2 H 4 and CO at the cathode. This MFECR's single cell consists of gas diffusion layers at the cathode and anode for respective intake of CO 2 and output of O 2 from the catalytic layer. This approach is expected to substantially improve the ISS ECLSS sustainability and reduce power and weight requirements as the MFECR would replace three units currently installed in the ISS. In this paper, the authors discuss the outcome of preliminary tests, the current development, and the evaluation efforts on different alternatives for the cathode and the anode configurations, the setup of the MFECR at an engineering development unit (EDU) scale, and the O 2 recovery performance, and evaluation efforts on different alternatives on not only the configuration and setup of the MFECR at an Engineering Design Unit (EDU) scale but also the selection of component materials.

Jesus A Dominguez↗
NASA NTRS1971

High contrast cathode ray tube

A layer of material is described, which contains fine grains of phosphor material stimulated by electrons to produce visible radiation. The layer, which also contains fine grains of cobalt oxide, is deposited on the glass screen of a cathode ray tube to provide high contrast, by absorbing most of the visible radiation which is directed to the layer through the screen, while not materially affecting the visible light which the phosphor material produces in response to the electron stimulation.

Lisovicz, E. J.↗
NASA NTRS1977

Relation of morphology of electrodeposited zinc to ion concentration profile

The morphology of electrodeposited zinc was studied with special attention to the ion concentration profile. The initial concentrations were 9M hydroxide ion and 1.21M zincate. Current densities were 6.4 to 64 mA/sq cm. Experiments were run with a horizontal cathode which was observed in situ using a microscope. The morphology of the zinc deposit was found to be a function of time as well as current density; roughly, the log of the transition time from mossy to large crystalline type deposit is inversely proportional to current density. Probe electrodes indicated that the electrolyte in the cathode chamber was mixed by self inducted convection. However, relatively large concentration gradients of the involved species existed across the boundary layer of the cathode. Analysis of the data suggests that the morphology converts from mossy to large crystalline when the hydroxide activity on the cathode surface exceeds about 12 M. Other experiments show that the pulse discharge technique had no effect on the morphology in the system where the bulk concentration of the electrolyte was kept homogeneous via self induced convection.

May, C. E.↗
NASA NTRS2005

Energetic ion production and electrode erosion in hollow cathode discharges

Ions with energies significantly in excess of the discharge voltage have been reported in high current hollow cathode discharges. Models of DC potential hills downstream of the cathode and ion acoustic instabilities in a double layer postulated in the cathode orifice have been proposed to explain these energetic ions, but have not been substantiated in experiments.

ion thruster↗
NASA NTRS1977

Use of Auger spectroscopy in the evaluation of thermionic cathodes

Auger spectroscopy has been used to evaluate the properties of 'good' and 'poor' impregnated tungsten cathodes used in high-power microwave wave tubes. The results were interpreted to analyze failure modes in cathodes removed from TWT's because of poor emission characteristics. Most of the poor cathodes evaluated in this program were obtained from fabricated electron guns that had been employed and discarded from the 200-W TWT tubes developed for the Communication Technology Satellite program. The results of these measurements have shown there are at least two types of failure modes that one observes with poor cathodes. They are (1) chemical contamination of the cathode surface and (2) low partial layer barium coverage of the cathode surface.

Forman, R.↗
NASA NTRS1969

Cathodochromic storage device

A memory and display device has been developed by combing a fast phosphor layer with a cathodochromic layer in a cathode ray tube. Images are stored as patterns of electron beam induced optical density in the cathodo-chromic material. The stored information is recovered by exciting the backing, fast phosphor layer with a constant current electron beam and detecting the emitted radiation which is modulated by absorption in the cathodochromic layer. The storage can be accomplished in one or more TV frames (1/30 sec each). More than 500 TV line resolution and close to 2:1 contrast ratio are possible. The information storage time in a dark environment is approximately 24 hours. A reconstituted (readout) electronic video signal can be generated continuously for times in excess of 10 minutes or periodically for several hours.

Bosomworth, D. R.↗
NASA NTRS1989

Electronic structure of BaO/W cathode surfaces

The local electronic structure of the emissive layer of barium dispenser thermionic cathodes is investigated theoretically using the relativistic scattered-wave approach. The interaction of Ba and O with W, Os, and W-Os alloy surfaces is studied with atomic clusters modeling different absorption environments representative of B- and M-type cathodes. Ba is found to be strongly oxidized, while O and the metal substrate are in a reduced chemical state. The presence of O enhances the surface dipole and Ba binding energy relative to Ba on W. Model results for W-Os alloy substrates show only relatively small changes in Ba and O for identical geometries, but very large charge redistributions inside the substrate, which are attributed to the electronegativity difference between Os and W. If Os is present in the surface layer, the charge transfer from Ba to the substrate and the Ba binding energy increase relative to W. Explanations are offered for the improved electron emission from alloy surfaces and the different emission enhancement for different alloy substrates.

Muller, Wolfgang↗
NASA NTRS1992

Plasma dynamics on current-carrying magnetic flux tubes

A 1D numerical simulation is used to investigate the evolution of a plasma in a current-carrying magnetic flux tube of variable cross section. A large potential difference, parallel to the magnetic field, is applied across the domain. The result is that density minimum tends to deepen, primarily in the cathode end, and the entire potential drop becomes concentrated across the region of density minimum. The evolution of the simulation shows some sensitivity to particle boundary conditions, but the simulations inevitably evolve into a final state with a nearly stationary double layer near the cathode end. The simulation results are at sufficient variance with observations that it appears unlikely that auroral electrons can be explained by a simple process of acceleration through a field-aligned potential drop.

Swift, Daniel W.↗
NASA NTRS1984

Plasma response to the injection of an electron beam

The results of Vlasov-Poisson-solver numerical simulations of the detailed temporal response of a Maxwellian plasma to the sudden injection of an electron beam are presented in graphs and maps and discussed. Phenomena characterized include ion bursts, electron shocks and holes, plasma heating and expulsion, density gradients; cavitons, deep-density-front and solitary-pulse propagation down the density gradient, and Bunemann-mode excitation leading to formation of a virtual cathode and double layers which are at first monotonic or have low-potential-side dips or high-potential-side bumps and become strong as the electron-current density decreases. The strength of the double layer is found to be roughly proportional to the beam energy.

Singh, N.↗
NASA NTRS2011

Effect of Reverse Bias Stress on Leakage Currents and Breakdown Voltages of Solid Tantalum Capacitors

The majority of solid tantalum capacitors are produced by high-temperature sintering of a fine tantalum powder around a tantalum wire followed by electrolytic anodization that forms a thin amorphous Ta2O5 dielectric layer and pyrolysis of manganese nitrite on the oxide to create a conductive manganese dioxide electrode. A contact to tantalum wire is used as anode terminal and to the manganese layer as a cathode terminal of the device. This process results in formation of an asymmetric Ta -- Ta2O5 -- MnO2 capacitor that has different characteristics at forward (positive bias applied to tantalum) and reverse (positive bias applied to manganese cathode) voltages. Reverse bias currents might be several orders of magnitude larger than forward leakage currents so I-V characteristics of tantalum capacitors resemble characteristics of semiconductor rectifiers. Asymmetric I-V characteristics of Ta -- anodic Ta2O5 systems have been observed at different top electrode materials including metals, electrolytes, conductive polymers, and manganese oxide thus indicating that this phenomenon is likely related to the specifics of the Ta -- Ta2O5 interface. There have been multiple attempts to explain rectifying characteristics of capacitors employing anodic tantalum pentoxide dielectrics. A brief review of works related to reverse bias (RB) behavior of tantalum capacitors shows that the mechanism of conduction in Ta -- Ta2O5 systems is still not clear and more testing and analysis is necessary to understand the processes involved. If tantalum capacitors behave just as rectifiers, then the assessment of the safe reverse bias operating conditions would be a relatively simple task. Unfortunately, these parts can degrade with time under reverse bias significantly, and this further complicates analysis of the I-V characteristics and establishing safe operating areas of the parts. On other hand, time dependence of reverse currents might provide additional information for investigation of the processes under reverse bias conditions. In practice, there were instances when, due to unforeseen events, the system operated at conditions when capacitors experience periodically a relatively small reverse bias for some time followed by normal, forward bias conditions. In such a case an assessment should be made on the degree to which these capacitors are degraded by application of low-voltage reverse bias, and whether this degradation can be reversed by normal operating conditions. In this study, reverse currents in different types of tantalum capacitors were monitored at different reverse voltages below 15%VR and temperatures in the range from room to 145 C for up to 150 hours to get better understanding of the degradation process and determine conditions favorable to the unstable mode of operation. The reversibility of RB degradation has been evaluated after operation of the capacitors at forward bias conditions. The effect of reverse bias stress (RBS) on reliability at normal operating conditions was evaluated using highly accelerated life testing at voltages of 1.5VR and 2 VR and by analysis of changes in distributions of breakdown voltages. Possible mechanisms of RB degradation are discussed.

Teverovsky, Alexander A.↗
NASA NTRS2012

NASA Tech Briefs, November 2012

The topics include: Visual System for Browsing, Analysis, and Retrieval of Data (ViSBARD); Time-Domain Terahertz Computed Axial Tomography NDE System; Adaptive Sampling of Time Series During Remote Exploration; A Tracking Sun Photometer Without Moving Parts; Surface Temperature Data Analysis; Modular, Autonomous Command and Data Handling Software with Built-In Simulation and Test; In-Situ Wire Damage Detection System; Amplifier Module for 260-GHz Band Using Quartz Waveguide Transitions; Wideband Agile Digital Microwave Radiometer; Buckyball Nucleation of HiPco Tubes; FACT, Mega-ROSA, SOLAROSA; An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications; Engineered Multifunctional Surfaces for Fluid Handling; Polyolefin-Based Aerogels; Adjusting Permittivity by Blending Varying Ratios of SWNTs; Gravity-Assist Mechanical Simulator for Outreach; Concept for Hydrogen-Impregnated Nanofiber/Photovoltaic Cargo Stowage System; DROP: Durable Reconnaissance and Observation Platform; Developing Physiologic Models for Emergency Medical Procedures Under Microgravity; Spectroscopic Chemical Analysis Methods and Apparatus; Low Average Sidelobe Slot Array Antennas for Radiometer Applications; Motion-Corrected 3D Sonic Anemometer for Tethersondes and Other Moving Platforms; Water Treatment Systems for Long Spaceflights; Microchip Non-Aqueous Capillary Electrophoresis (MicronNACE) Method to Analyze Long-Chain Primary Amines; Low-Cost Phased Array Antenna for Sounding Rockets, Missiles, and Expendable Launch Vehicles; Mars Science Laboratory Engineering Cameras; Seismic Imager Space Telescope; Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations; A Posteriori Study of a DNS Database Describing Super critical Binary-Species Mixing; Scalable SCPPM Decoder; QuakeSim 2.0; HURON (HUman and Robotic Optimization Network) Multi-Agent Temporal Activity Planner/Scheduler; MPST Software: MoonKommand

Source record↗
NASA NTRS2012

Wide Operating Temperature Range Electrolytes for High Voltage and High Specific Energy Li-Ion Cells

A number of electrolyte formulations that have been designed to operate over a wide temperature range have been investigated in conjunction with layered-layered metal oxide cathode materials developed at Argonne. In this study, we have evaluated a number of electrolytes in Li-ion cells consisting of Conoco Phillips A12 graphite anodes and Toda HE5050 Li(1.2)Ni(0.15)Co(0.10)Mn(0.55)O2 cathodes. The electrolytes studied consisted of LiPF6 in carbonate-based electrolytes that contain ester co-solvents with various solid electrolyte interphase (SEI) promoting additives, many of which have been demonstrated to perform well in 4V systems. More specifically, we have investigated the performance of a number of methyl butyrate (MB) containing electrolytes (i.e., LiPF6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + MB (20:20:60 v/v %) that contain various additives, including vinylene carbonate, lithium oxalate, and lithium bis(oxalato)borate (LiBOB). When these systems were evaluated at various rates at low temperatures, the methyl butyrate-based electrolytes resulted in improved rate capability compared to cells with all carbonate-based formulations. It was also ascertained that the slow cathode kinetics govern the generally poor rate capability at low temperature in contrast to traditionally used LiNi(0.80)Co(0.15)Al(0.05)O2-based systems, rather than being influenced strongly by the electrolyte type.

Li-ion Battery↗