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  • 1
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    Voltammetric studies of porous molybdenum electrodes for the alkali metal thermoelectric converter (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from about 600 to 1000 K revealed a series of redox processes within the AMTEC operational voltage range which can be used to establish the electronic and ionic conductivities of these electrodes. Improved estimates of the free energies of formation of Na2Mo3O6, NaMoO2, and Na3MoO4 are obtained. Evidence is provided for the slow corrosive attack by Na2MoO4 on molybdenum. The ionic conductivity of Na2MoO4 is found to be sufficiently large at temperatures of greater than 700 K to explain the observed electrochemical phenomena in addition to the enhanced sodium transport in AMTEC electrodes below the freezing point of Na2MoO4.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 133; 2253-225
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  • 2
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    All NbN tunnel junction fabrication (1987)
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    Publication Date: 2011-08-19
    Description: The development of SIS tunnel junctions based on NbN for mixer applications in the submillimeter range is reported. The unique technological challenges inherent in the development of all refractory-compound superconductor-based tunnel junctions are highlighted. Current deposition and fabrication techniques are discussed, and the current status of all-NbN tunnel junctions is reported.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: International Journal of Infrared and Millimeter Waves (ISSN 0195-9271); 8; 1243-124
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  • 3
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    The role of oxygen in porous molybdenum electrodes for the alkali metal thermoelectric converter (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model for chemical reactions in porous molybdenum electrodes is presented which is based on thermochemical and kinetic data, known sodium-molybdenum-oxygen chemistry, X-ray diffraction analysis of molybdenum and molybdenum oxide electrodes, and the electrochemical behavior of the cell. Enhanced sodium transport through the electrode in its optimum performance state is found to be due to the high sodium ion conductivity of molten Na2MoO4 in the pores, and the electrical conduction to the molybdenum matrix by Na2Mo3O6. The decline of electrode performance is shown to be due to a combination of loss mechanisms for the Na-Mo-O compounds including reduction at short circuit, disproportionation of Na2Mo3O6 at open circuit, and the evaporation of Na2MoO4 at elevated temperature. It is suggested that operation of the cell at moderate voltage of about 0.5 V corresponding to maximum power may be a more stable condition for the porous electrode than open-circuit stand or short-circuit, where degradation reactions are heightened.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 133; 1587-159
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  • 4
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    Room temperature deposition of superconducting NbN for superconductor-insulator-superconductor junctions (1986)
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    Publication Date: 2011-08-19
    Description: The deposition of stoichiometric B1-crystal-structure (111) NbN films on glass or sapphire substrates by reactive dc magnetron sputtering is reported. High-purity Ar-N2 mixtures are used in the apparatus described by Thakoor et al. (1985), and typical deposition parameters are given as background pressure about 10 ntorr, voltage -325 V, current 1 A, deposition rate 1.35 nm/s, film thickness 500 nm, P(Ar) 5-17 mtorr, initial P(N2) 2-6 mtorr, and room temperature. The N2 consumption-injection characteristics are studied and found to control NbN formation using well-conditioned Nb targets. Films with transition temperatures 15-16 K are obtained at P(Ar) = 12.9 + or - 0.2 mtorr and P(N2) = 3.7 + or - 0.1 mtorr. SIS junctions of area about 0.001 sq cm fabricated using the NbN films are shown to have I-V characteristics with nonlinearity parameter about 110 and NbN superconducting-gap parameter Delta = about 2.8 meV.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 4; 528-531
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  • 5
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    Resistive synaptic interconnects for electronic neural networks (1987)
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    Publication Date: 2011-08-19
    Description: The use of the alpha-Ge(1-x):Al(x) and alpha-Ge(1-x):Cu(x) alloys and Pt/Al2O3 cermet thin films as resistive interconnects for binary synaptic memory arrays is evaluated. The fabrication of the 10-20 microns long, 10 microns wide, and 0.1 micron thick interconnects from the alloys and cermet is described. The current-voltage and switching characteristics of the as-deposited films and the patterned test structure are studied. The resistivity, uniformity, stability, and compatibility of the interconnects are examined. It is observed that alpha-Ge(1-x):Cu(x) alloys have a wide resistivity range and low temperature coefficients of resistance; however, their long-term stability is limited due to their low crystallization temperature. It is detected that the alpha-Ge(1-x):Al(x) alloys have higher crystallization temperatures and their resistivity is not greatly affected by large changes in metal content. The Pt/Al2O3 samples display excellent stability, easy fabrication, and control of resistivity with metal content.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 5; 1407-141
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  • 6
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    Electronic hardware implementations of neutral networks (1987)
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    Publication Date: 2011-08-19
    Description: This paper examines some of the present work on the development of electronic neural network hardware. In particular, the investigations currently under way at JPL on neural network hardware implementations based on custom VLSI technology, novel thin film materials, and an analog-digital hybrid architecture are reviewed. The availability of such hardware will greatly benefit and enhance the present intense research effort on the potential computational capabilities of highly parallel systems based on neural network models.
    Keywords: CYBERNETICS
    Type: Applied Optics (ISSN 0003-6935); 26; 5085-509
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  • 7
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    Manganese oxide microswitch for electronic memory based on neural networks (1989)
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    Publication Date: 2011-08-19
    Description: A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Vacuum Science and Technology B (ISSN 0734-211X); 7; 450-454
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  • 8
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    Binary synaptic connections based on memory switching in a-Si:H for artificial neural networks (1987)
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    Publication Date: 2011-08-19
    Description: A scheme for nonvolatile associative electronic memory storage with high information storage density is proposed which is based on neural network models and which uses a matrix of two-terminal passive interconnections (synapses). It is noted that the massive parallelism in the architecture would require the ON state of a synaptic connection to be unusually weak (highly resistive). Memory switching using a-Si:H along with ballast resistors patterned from amorphous Ge-metal alloys is investigated for a binary programmable read only memory matrix. The fabrication of a 1600 synapse test array of uniform connection strengths and a-Si:H switching elements is discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 9
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    Observation of adsorbate-induced surface states by elastic electron tunneling spectroscopy (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Electronic structure induced by adsorbates at the interface of Al/AlOx/Au tunnel junctions has been observed by elastic electron tunneling spectroscopy. Strong structures appearing in the tunneling spectra above approximately 1 eV after exposure to I, Hg, Bi, and organohalides, have been interpreted in terms of adsorbate-induced surface states. The spectroscopic capabilities of elastic electron tunneling spectroscopy may be useful in the area of chemical detection. In the broader sense, the observation of adsorbate-induced unoccupied electronic states below the vacuum energy, makes elastic electron tunneling spectroscopy a potentially useful technique for the study of surfaces.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Applied Physics (ISSN 0021-8979); 58; 2266-226
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  • 10
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    Alkali Metal Thermoelectric Conversion (AMTEC) for space nuclear power systems (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Performance parameters of the Alkali Metal Thermoelectric Converter (AMTEC) for a 100 kW electric power system have been calculated at four technological levels assuming a heat pipe-cooled nuclear reactor heat source. The most advanced level considered would operate between 1180 K converter temperature and 711 K radiator temperature at 16 percent efficiency, and would weigh 1850 kg with a radiator area of 43 sq m. In addition, electrode research studies for the AMTEC systems have been conducted utilizing an experimental test cell of Bankston et al. (1983) and Mo and several Mo-Ti electrodes. It was found that the Mo-Ti electrodes offered no improvement in lifetime characteristics over the pure Mo electrodes, however, oxygen treatment of a degraded Mo electrode restored its specific power output to 90 percent of its original specific power and maintained this level for 60 hr, thus offering a potential for lifetime stability.
    Keywords: ENERGY PRODUCTION AND CONVERSION
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