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  • 1
    Electronic Resource
    Electronic Resource
    Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 410-416 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optinum performance as AMTEC electrodes at thicknesses less than 1.0 μm when used with molybdenum or nickel current collector grids. Power densities of 0.40 W cm−2 for 0.5 μm molybdenum films at 1200 K and 0.35 W cm−2 for 0.5 μm tungsten films at 1180 K were obtained at electrode maturity after 40–90 h. Sheet resistances of magnetron sputter deposited films on sodium beta″-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3–0.4 μm. The a.c. impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness 〈2.0 μm, is not utilized efficiently unless a fairly fine (∼1×1mm) current collector grid is employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01093756
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    Paper (German National Licenses)
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  • 2
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    Kinetics and transport at AMTEC electrodes. I - The interfacial impedance model (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Mixed mass-transport and kinetic control of sodium ion reduction at porous inert electrodes on sodium beta-double-prime alumina solid electrolyte (BASE) ceramic in a high-temperature electrochemical cell has been observed and modeled. The high ionic conductivity of BASE and the reversibility of the liquid sodium/BASE anodic half-cell led to assignment of potential-dependent (nonohmic) resistances to kinetic and mass-transport processes associated with the porous electrode. The morphology of these electrodes and typical sodium gas pressures are consistent with Knudsen, or free-molecular, flow through the electrode.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 137; 1709-171
    Format: text
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  • 3
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    Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Applied Electrochemistry (ISSN 0021-891X); 18; 410-416
    Format: text
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  • 4
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    Effects of Na2MoO4 and Na2WO4 on molybdenum and tungsten electrodes for the alkali metal thermoelectric converter (AMTEC) (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The effects of adding Na2MoO4 and Na2WO4 to porous Mo and W electrodes, respectively, on the performance and impedance characteristics of the electrodes in an alkali metal thermoelectric converter (AMTEC) were investigated. It was found that corrosion of the porous electrode by Na2MoO4 or Na2WO4 to form Na2MO3O6 and WO2, respectively, and recrystallization of the Mo or W as the salt evaporates, result in major morphological changes including a loss of columnar structure and a significant increase in porosity. This effect is more pronounced in Na2MoO4/Mo electrodes, due to the lower stability of Na2MoO4.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 135; 2736-274
    Format: text
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  • 5
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    High power density performance of WPt and WRh electrodes in the alkali metal thermoelectric converter (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The properties of the alkali metal thermoelectric converter (AMTEC) are discussed together with those of an efficient AMTEC electrode. Three groups of electrodes were prepared and tested for their performance as AMTEC electrodes, including WPt-T3, WRh-B1, and WRh-B2. The best electrodes of both WPt and WRh types typically exhibited low porosity, and thickness greater than 0.8 micron, which indicated that transport in these electrodes does not occur by a purely free-molecular flow mode. The observed values of the exchange current were found to be within the range of those observed for oxide-free Mo electrodes under similar conditions.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 136; 893
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  • 6
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    AMTEC electrode development (1987)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-alumina solid electrolyte. Progress is reported on a long life, high power, porous electrode. Two electrode compositions were identified which have the potential for long life operation at power densities above 0.5 W/sq cm. Longer lifetime testing is being initiated. Successful optimization and demonstration of very long lifetimes for these electrodes will be a major step toward establishing the feasibility of AMTEC space power systems.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: New Mexico Univ., Transactions of the Fourth Symposium on Space Nuclear Power Systems; p 299-301
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  • 7
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    Experimental observation of electrochemical rate limitations affecting sodium ion-electron recombination at electrodes of the alkali metal thermoelectric converter at T about 1200 K (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper considers a model of the internal impedances of thin porous Mo and W alkali metal thermoelectric converter (AMTEC), in which the kinetic parameters associated with the reaction of the beta-double-prime alumina solid electrolite (BASE)/porous metal/gas three-phase boundary can be evaluated. Impedance data in the frequency range 0.01-100,000 Hz were collected over a range of AMTEC cell operating voltages for small-area thin porous Mo and W electrodes, yielding apparent charge transfer resistances at a series of cell potentials/currents. The ohmic resistance in the AMTEC cell could be broken down and characterized with three parameters: the BASE ionic resistance, the electrode film sheet resistance, and the contact/lead resistance, all of which could be calculated or measured independently and used to calculate power curves in good agreement with observed power curves. It is shown that these calculations can be used to predict the properties of electrodes with optimized parameters or to detect enhanced transport modes.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Symposium on High Temperature Materials Chemistry - IV; Oct 19, 1987 - Oct 23, 1987; Honolulu, HI; United States
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  • 8
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    Recent advances in Alkali Metal Thermoelectric Converter (AMTEC) electrode performance and modeling (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-double prime-alumina solid electrolyte (BASE). This paper describes progress on the remaining scientific issue which must be resolved to demonstrate AMTEC feasibility for space power systems: a stable, high power density electrode. Two electrode systems have recently been discovered at JPL that now have the potential to meet space power requirements. One of these is a very thin sputtered molybdenum film, less than 0.5 micron thick, with overlying current collection grids. This electrode has experimentally demonstrated stable performance at 0.4-0.5 W/sq cm for hundreds of hours. Recent modeling results show that at least 0.7 W/sq cm can be achieved. The model of electrode performance now includes all loss mechanisms, including charge transfer resistances at the electrode/electrolyte interface. A second electrode composition, cosputtered platinum/tungsten, has demonstrated 0.8 W/sq cm for 160 hours. Systems studies show that a stable electrode performance of 0.6 W/sq cm will enable high efficiency space power systems.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Space structures, power, and power conditioning; Jan 11, 1988 - Jan 13, 1988; Los Angeles, CA; United States
    Format: text
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