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  • ENERGY PRODUCTION AND CONVERSION
  • 1990-1994  (9)
  • 1975-1979
  • 1993  (9)
  • 1
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    Advances in direct oxidation methanol fuel cells (1993)
    In:  CASI
    Details
    Publication Date: 2016-05-14
    Description: Fuel cells that can operate directly on fuels such as methanol are attractive for low to medium power applications in view of their low weight and volume relative to other power sources. A liquid feed direct methanol fuel cell has been developed based on a proton exchange membrane electrolyte and Pt/Ru and Pt catalyzed fuel and air/O2 electrodes, respectively. The cell has been shown to deliver significant power outputs at temperatures of 60 to 90 C. The cell voltage is near 0.5 V at 300 mA/cm(exp 2) current density and an operating temperature of 90 C. A deterrent to performance appears to be methanol crossover through the membrane to the oxygen electrode. Further improvements in performance appear possible by minimizing the methanol crossover rate.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center, Space Electrochemical Research and Technology; p 181-191
    Format: application/pdf
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  • 2
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    Electrochemical impedance spectroscopy of lithium-titanium disulfide rechargeable cells (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The two-terminal alternating current impedance of Li/TiS2 rechargeable cells was studied as a function of frequency, state-of-charge, and extended cycling. Analysis based on a plausible equivalent circuit model for the Li/TiS2 cell leads to evaluation of kinetic parameters for the various physicochemical processes occurring at the electrode/electrolyte interfaces. To investigate the causes of cell degradation during extended cycling, the parameters evaluated for cells cycled 5 times were compared with the parameters of cells cycled over 600 times. The findings are that the combined ohmic resistance of the electrolyte and electrodes suffers a tenfold increase after extended cycling, while the charge-transfer resistance and diffusional impedance at the TiS2/electrolyte interface are not significantIy affected. The results reflect the morphological change and increase in area of the anode due to cycling. The study also shows that overdischarge of a cathode-limited cell causes a decrease in the diffusion coefficient of the lithium ion in the cathode.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 140; 7; p. 1854-1861.
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Air Force Ni-Cd cell qualification program update (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The generic qualification of aerospace nickel-cadmium cells is discussed. The test program includes the following: all available manufacturers, all available designs, cells from the previous program, and high and low orbit life cycling. It is the purpose of this program to characterize the beginning of life performance.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Marshall Space Flight Center, The 1992 NASA Aerospace Battery Workshop; p 319-35
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    NASA TECHNICAL REPORTS
  • 4
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    Bipolar rechargeable lithium battery for high power applications (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Viewgraphs of a discussion on bipolar rechargeable lithium battery for high power applications are presented. Topics covered include cell chemistry, electrolytes, reaction mechanisms, cycling behavior, cycle life, and cell assembly.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Marshall Space Flight Center, The 1992 NASA Aerospace Battery Workshop; p 719-74
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  • 5
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    Status of the development of rechargeable lithium cells (1993)
    In:  CASI
    Details
    Publication Date: 2016-05-14
    Description: The progress in the development of the ambient temperature lithium - titanium disulfide rechargeable cell under development at the Jet Propulsion Laboratory is described in this paper. Originally aimed at achieving a specific energy of 100 Wh/kg, 'AA' cells have demonstrated 125 Wh/kg at the C/3 discharge rate. The results of evaluating cell design parameters are discussed and cycling test data are also included in the paper. Safety tests results at various over-charge and over discharge conditions and rates proved to be uneventful. The test results of cell with built-in overcharge mechanism proved the concept was feasible. Replacing the lithium foil electrode with a Li(x)C resulted in a capacity at 1mA/cm(exp 2) of 200 mAh/gm and 235 mAh/gm at 0.167 mA.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center, Space Electrochemical Research and Technology; p 85-95
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  • 6
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    The International Telecommunications Satellite (INTELSAT) Solar Array Coupon (ISAC) atomic oxgyen flight experiment: Techniques, results and summary (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Techniques and results of the ISAC flight experiment are presented, and comparisons between flight tests results and ground based testing are made. The ISAC flight experiment, one component of a larger INTELSAT 6 rescue program, tested solar array configurations and individual silver connects in ground based facilities and during STS-41 (Space Shuttle Discovery). In addition to the INTELSAT specimens, several materials, for which little or no flight data exist, were also tested for atomic oxygen reactivity. Dry lubricants, elastomers, polymeric materials, and inorganic materials were exposed to an oxygen atom fluence of 1.2 x 10(exp 20) atoms. Many of the samples were selected to support Space Station Freedom design and decision-making.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: CNES, Fifth International Symposium on Materials in a Space Environment; p 331-348
    Format: text
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  • 7
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    High power density proton exchange membrane fuel cells (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center, Space Electrochemical Research and Technology; p 149-166
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  • 8
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    Near-ambient solid polymer fuel cell (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Fuel cells are extremely attractive for extraterrestrial and terrestrial applications because of their high energy conversion efficiency without noise or environmental pollution. Among the various fuel cell systems the advanced polymer electrolyte membrane fuel cells based on sulfonated fluoropolymers (e.g., Nafion) are particularly attractive because they are fairly rugged, solid state, quite conductive, of good chemical and thermal stability and show good oxygen reduction kinetics due to the low specific adsorption of the electrolyte on the platinum catalyst. The objective of this program is to develop a solid polymer fuel cell which can efficiently operate at near ambient temperatures without ancillary components for humidification and/or pressurization of the fuel or oxidant gases. During the Phase 1 effort we fabricated novel integral electrode-membrane structures where the dispersed platinum catalyst is precipitated within the Nafion ionomer. This resulted in electrode-membrane units without interfacial barriers permitting unhindered water diffusion from cathode to anode. The integral electrode-membrane structures were tested as fuel cells operating on H2 and O2 or air at 1 to 2 atm and 10 to 50 C without gas humidification. We demonstrated that cells with completely dry membranes could be self started at room temperature and subsequently operated on dry gas for extended time. Typical room temperature low pressure operation with unoptimized electrodes yielded 100 mA/cm(exp 2) at 0.5V and maximum currents over 300 mA/cm(exp 2) with low platinum loadings. Our results clearly demonstrate that operation of proton exchange membrane fuel cells at ambient conditions is feasible. Optimization of the electrode-membrane structure is necessary to assess the full performance potential but we expect significant gains in weight and volume power density for the system. The reduced complexity will make fuel cells also attractive for smaller and portable power supplies and as replacement for batteries.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-195939 , NAS 1.26:195939
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  • 9
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    Non-destructive, ultra-low resistance, thermally stable contacts for use on shallow junction InP solar cells (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Contact formation to InP is plagued by violent metal-semiconductor intermixing that takes place during the contact sintering process. Because of this the InP solar cell cannot be sintered after contact deposition. This results in cell contact resistances that are orders of magnitude higher than those that could be achieved if sintering could be performed in a non-destructive manner. We report here on a truly unique contact system involving Au and Ge, which is easily fabricated, which exhibits extremely low values of contact resistivity, and in which there is virtually no metal-semiconductor interdiffusion, even after extended sintering. We present a description of this contact system and suggest possible mechanisms to explain the observed behavior.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-TM-106228 , E-7946 , NAS 1.15:106228 , IEEE Photovoltaic Specialists Conference; May 10, 1993 - May 14, 1993; Louisville, KY; United States
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