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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

A Particle-in-Cell Simulation for the Traveling Wave Direct Energy Converter (TWDEC) for Fusion Propulsion

A Particle-in-cell simulation model has been developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC) applied to the conversion of charged fusion products into electricity. In this model the availability of a beam of collimated fusion products is assumed; the simulation is focused on the conversion of the beam kinetic energy into alternating current (AC) electric power. The model is electrostatic, as the electro-dynamics of the relatively slow ions can be treated in the quasistatic approximation. A two-dimensional, axisymmetric (radial-axial coordinates) geometry is considered. Ion beam particles are injected on one end and travel along the axis through ring-shaped electrodes with externally applied time-varying voltages, thus modulating the beam by forming a sinusoidal pattern in the beam density. Further downstream, the modulated beam passes through another set of ring electrodes, now electrically oating. The modulated beam induces a time alternating potential di erence between adjacent electrodes. Power can be drawn from the electrodes by connecting a resistive load. As energy is dissipated in the load, a corresponding drop in beam energy is measured. The simulation encapsulates the TWDEC process by reproducing the time-dependent transfer of energy and the particle deceleration due to the electric eld phase time variations.

Chap, Andrew↗
DOE OSTI2024

Reducing Ohmic Resistances in Membrane Capacitive Deionization Using Micropatterned Ion-Exchange Membranes, Ionomer Infiltrated Electrodes, and Ionomer-Coated Nylon Meshes

Membrane capacitive deionization (MCDI) is an emerging water desalination platform that is compact, electrified, and does not require high-pressure piping. Herein, highly conductive poly(phenylene alkylene) ion-exchange membranes (IEMs) are micropatterned with different surface geometries for MCDI. The micropatterned membranes increase the interfacial area with the liquid stream leading to a 700 mV reduction in cell voltage when operating at constant current (2 mA cm -2 ; 2000 ppm NaCl feed) while improving the energy normalized adsorbed salt (ENAS) value by 1.4 times. Combining the micropatterned poly(phenylene alkylene) IEMs with poly(phenylene alkylene) ionomer-filled electrodes reduces the cell voltage by 1000 mV and improves the ENAS values by 2.3 times relative to the base case. This reduction in cell voltage allows for higher current density operation (i.e., 3–4 mA cm -2 ) . The reduction in cell voltage is ascribed to the ameliorating ohmic resistances related to ion transport at the membrane-process stream interface and in the carbon cloth electrode. Finally, porous ionic conductors are implemented into the spacer channel with flat and micropatterned IEM configurations and ionomer infiltrated electrodes. For the configuration with flat IEMs, the porous ionic conductor improves ENAS values across the current density regime (2–4 mA cm -2 ), while for micropatterned IEMs it gets improved only at 4 mA cm -2 .

42 ENGINEERING↗
NASA NTRS2011

Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

Nawaz, Anuscheh↗
NASA NTRS2003

Miniature Inchworm Actuators Fabricated by Use of LIGA

Miniature inchworm actuators that would have relatively simple designs have been proposed for applications in which there are requirements for displacements of the order of microns or tens of microns and for the ability to hold their positions when electric power is not applied. The proposed actuators would be members of the class of microelectromechanical systems (MEMS), but would be designed and fabricated following an approach that is somewhat unusual for MEMS. Like other MEMS actuators, the proposed inchworm actuators could utilize thermoplastic, bimetallic, shape-memory-alloy, or piezoelectric actuation principles. The figure depicts a piezoelectric inchworm actuator according to the proposal. As in other inchworm actuators, linear motion of an extensible member would be achieved by lengthening and shortening the extensible member in synchronism with alternately clamping and releasing one and then the other end of the member. In this case, the moving member would be the middle one; the member would be piezoelectric and would be shortened by applying a voltage to it. The two outer members would also be piezoelectric; the release of the clamps on the upper or lower end would be achieved by applying a voltage to the electrodes on the upper or lower ends, respectively, of these members. Usually, MEMS actuators cannot be fabricated directly on the side walls of silicon wafers, yet the geometry of this actuator necessitates such fabrication. The solution, according to the proposal, would be to use the microfabrication technique known by the German acronym LIGA - "lithographie, galvanoformung, abformung," which means lithography, electroforming, molding. LIGA involves x-ray lithography of a polymer film followed by selective removal of material to form a three-dimensional pattern from which a mold is made. Among the advantages of LIGA for this purpose are that it is applicable to a broad range of materials, can be used to implement a variety of designs, including those of structures >1 mm high, affords submicron precision, and is amenable to mass production at relatively low unit cost. Fabrication of the proposed actuators would involve some technological risks - in particular, in the integration of electrode connection lines and placement of actuator elements. It will also be necessary to perform an intensive study of the feasibility of growing piezoelectric crystals onto LIGA molds.

Yang, Eui-Hyeok↗
DOE OSTI2025

Spin-filter tunneling detection of antiferromagnetic resonance with electrically tunable damping

Antiferromagnetic spintronics offers the potential for higher-frequency operations and improved insensitivity to magnetic fields compared to ferromagnetic spintronics. However, previous electrical techniques to detect antiferromagnetic dynamics have utilized large, millimeter-scale bulk crystals. In this work, we demonstrate direct electrical detection of antiferromagnetic resonance in structures on the few-micrometer scale using spin-filter tunneling in platinum ditelluride (PtTe 2 )/bilayer chromium sulfide bromide (CrSBr)/graphite junctions in which the tunnel barrier is the van der Waals antiferromagnet CrSBr. This sample geometry allows not only efficient detection but also electrical control of the antiferromagnetic resonance through spin-orbit torque from the PtTe 2 electrode. The ability to efficiently detect and control antiferromagnetic resonance enables detailed studies of the physics governing these high-frequency dynamics.

Cham, Thow Min Jerald [Cornell University, Ithaca,↗
NASA NTRS1984

A mathematical model for the iron/chromium redox battery

A mathematical model has been developed to describe the isothermal operation of a single anode-separator-cathode unit cell in a redox-flow battery and has been applied to the NASA iron/chromium system. The model, based on porous electrode theory, incorporates redox kinetics, mass transfer, and ohmic effects as well as the parasitic hydrogen reaction which occurs in the chromium electrode. A numerical parameter study was carried out to predict cell performance to aid in the rational design, scale-up, and operation of the flow battery. The calculations demonstrate: (1) an optimum electrode thickness and electrolyte flow rate exist; (2) the amount of hydrogen evolved and, hence, cycle faradaic efficiency, can be affected by cell geometry, flow rate, and charging procedure; (3) countercurrent flow results in enhanced cell performance over cocurrent flow; and (4) elevated temperature operation enhances cell performance.

Fedkiw, P. S.↗
DOE OSTI2025

Concavity-based local erosion and sphere-size-based local dilation applied to lithium-ion battery electrode microstructures for particle identification

Performance metrics of lithium-ion batteries can be extracted from the analysis of electrode microstructures nanoscale imaging. The characterization workflow can involve a challenging particle identification, or instance segmentation, step. In this work, we propose a new identification method based on an original transformation: a sphere-size-based local dilation followed by a concavity-based local erosion, that is local morphology closing. The new transformation is much more efficient than the global morphology closing, with correct identification achieved with only 1.7 % dilation volume and 2.6 % erosion volume on a test geometry, compared to 39.2 % and more than 50 %, respectively, with its global counterpart. The new method has been then benchmarked versus other identification algorithms (watershed and pseudo coulomb repulsive field) on a real electrode microstructure with equal or better segmentation achieved.

25 ENERGY STORAGE↗
NASA NTRS1991

YBa2Cu3O(7-delta)/Au/Nb sandwich geometry SNS weak links on c-axis oriented YBa2Cu3O(7-delta)

Sandwich geometry superconductor/normal metal/superconductor structures have been fabricated on LaAlO3 and cubic zirconia with laser-ablated, c-axis-oriented YBa2Cu3O(7-delta) base electrodes, 100-600 A of Au, and Nb counter electrodes, all formed in situ without breaking vacuum. Junctions range in size from 5 to 50 micron on a side. Four probe I-V measurements at 4.2 K show RnA products as low as 6 x 10 to the -9th sq cm and critical current densities up to 5.2 kA/sq cm. AC Josephson steps were observed with the application of 10-GHz radiation. The temperature dependence of Jc and the observation of the AC Josephson effect suggest that true supercurrents are present and that they do indeed represent the characteristics of the YBa2Cu3O(7-delta)/Au/Nb structure. The best results were obtained when the devices were annealed at about 450 C in O2 for 30 min after Au deposition.

Foote, M. C.↗
NASA NTRS1992

Radiative transfer in the electrode region of an arc heater

Radiation from hot gases in the electrode region of an arc heater are discussed. Major original contributions are made: (1) an analytical expression for the radiative heat flux, for an axisymmetric geometry and a grey reflecting wall, is derived, (2) the expression is rendered analytically differentiable/integrable by using appropriate techniques to remove the singularities, and (3), finally a two band model is devised to compute the radiative heat load at the walls in NASA Ames' jet facility. The advantage of using these techniques is that the time taken for the numerical integration is considerably reduced and computation of a 39 x 39 axisymmetric geometry becomes manageable. Fluid equations, representative of a high current arc heater, are numerically solved for an axisymmetric geometry. The computed average heat load of 400 Watts/sq cm using the two band model agrees well with the experimental estimates made at NASA Ames' facility.

Durgapal, P.↗
DOE OSTI2025

Rheo–Electric Foundations and Engineering of Carbon Slurry Flow Electrodes

Flowable carbon slurry electrodes promise continuous, scalable electrochemical desalination and energy storage when their rheology (flow and stability) and electronic connectivity are jointly optimized. This report integrates six complementary thrusts that we executed under the Laboratory Directed Research and Development (LDRD) project: (i) a fast, ex situ, centrifuge-compatible method to quantify pellet (packed slurry) electronic conductivity, with a validated cell constant (“shape factor”) and quantitative structure–property insights for carbon mixtures; (ii) a controlled circulation study showing that peristaltic pumping can irreversibly alter particle size and morphology over laboratory-relevant durations; (iii) development of a miniature jet pump that preserves particle integrity while achieving entrainment ratios of 2–4 at practical flow rates; (iv) a comprehensive mapping of how a representative non-ionic surfactant (Tween 20) collapses the carbon gel network, separating network-percolation losses from intrinsic particle contact resistance; (v) in-situ visualization revealing how gravitational settling and flow-driven mixing compete to control charge transport, with dynamic bed layers preventing saturation while achieving 30-fold local concentration enhancement; and (vi) a simple, widely adoptable fabrication route to structured, gas-nitrided titanium nitride (TiN) titanium current collectors that dramatically lower interfacial losses and enable geometry-driven performance gains. Together, these results provide a coherent toolchain and design rules to accelerate formulation screening, de-risk device prototyping, and standardize characterization for carbon slurry electrodes in flow-electrode capacitive deionization (FCDI), electrochemical flow capacitor (EFC), and related systems.

25 ENERGY STORAGE↗
NASA NTRS1981

Pumping power considerations in the designs of NASA-Redox flow cells

Pressure drop data for six different cell geometries of various flow port, manifold, and cavity dimensions are presented. The redox/energy/storage system uses two fully soluble redox couples as anode and cathode fluids. Both fluids are pumped through a redox cell, or stack of cells, where the electrochemical reactions take place at porous carbon felt electrodes. Pressure drop losses are therefore associated with this system due to the continuous flow of reactant solutions. The exact pressure drop within a redox flow cell is directly dependent on the flow rate as well as the various cell dimensions. Pumping power requirements for a specific set of cell operating conditions are found for various cell geometries once the flow rate and pressure drop are determined. These pumping power requirements contribute to the overall system parasitic energy losses which must be minimized, the choice of cell geometry becomes critical.

Hoberecht, M. A.↗
NASA NTRS1981

Wedge-and-strip anodes for centroid-finding position-sensitive photon and particle detectors

The paper examines geometries employing position-dependent charge partitioning to obtain a two-dimensional position signal from each detected photon or particle. Requiring three or four anode electrodes and signal paths, images have little distortion and resolution is not limited by thermal noise. An analysis of the geometrical image nonlinearity between event centroid location and the charge partition ratios is presented. In addition, fabrication and testing of two wedge-and-strip anode systems are discussed. Images obtained with EUV radiation and microchannel plates verify the predicted performance, with further resolution improvements achieved by adopting low noise signal circuitry. Also discussed are the designs of practical X-ray, EUV, and charged particle image systems.

Martin, C.↗
NASA NTRS1991

YBa2Cu3O(7-x)/Au/Nb device structures

Fabrication and testing of planar and edge geometry YBaCuO/Au/Nb superconductor/normal-metal/superconductor (SNS) device structures is described. Weak-link devices of this type serve as sensitive probes of the electrical quality of the YBaCuO/Au interface. The devices are fabricated using laser-ablated, in situ, c-axis-oriented YBaCuO thin films, with both annealed and unannealed YBaCuO/Au interfaces. The planar SNS structures are formed by sequential, in situ deposition of YBaCuO, Au, and Nb, followed by etching, planarization, and wiring electrode definition to produce junctions ranging from 5 to 20 micron on a side. Resulting RnA products are 1-10 x 10 to the -8th ohm-sq cm with critical current densities up to 5 kA/sq cm. For the edge geometry devices, the YBaCuO film edges are patterned using Ar ion milling, followed by a low energy ion cleaning step and in situ deposition of Au and Nb. Devices with areas in the 10 to the -7th to 10 to the -8th sq cm range have been fabricated with RnA products lower than 10 to the -8th ohm-sq cm and critical current densities up to 3kA/sq cm. Both types of devices show ac Josephson steps under microwave irradiation. The best results have been obtained with annealed YBaCuO/Au interfaces.

Hunt, B. D.↗
NASA NTRS2002

Production of Ultra-Light Normal Incidence Mirrors

Mirrors fabrication for large aperture telescopes is an important aspect in space exploration programs. One of the cost effective techniques to obtain such mirrors is electroplating of Ni-Co alloys from sulfamate solution. The Center for Irradiation of Materials at Alabama A&M University - Research Institute has been involved in a NASA-MSFC project for producing ultra-light Ni-Co alloy mirrors since the summer of year 2000. The goal of this project is to obtain ultra-light, high strength electroformed large aperture normal incidence replicated mirrors, (weighting less than 5 kg/m2), free of stress, with a good figure and reproducible thickness variation. In order to simplify the control of parameters such as temperature gradient, concentration gradient, distribution of the electric field lines and flow control, the proposed geometry involves a cylindrical main tank contained in another cylindrical tank, which plays the role of a weir. Designs were created to accommodate the new horizontal position of the mandrel and the pipes fitting through the outer tank's lid. The inner tank contains the working electrodes and a series of sensors for monitoring temperature, flow, stress and pH. The outer tank holds the electric heaters, the filters and a part of the piping system. Another two tanks complete the setup and serve for rinsing/preheating and equilibrating the electroplating bath. This paper will describe advantages of the new experimental setup and the parameters achieved in the electroplating bath for the proposed geometry.

Jones, Ruth↗
NASA NTRS1981

Effect of thrust chamber configuration on MPD arcjet performance

The performance of quasisteady multimegawatt MPD thrusters is significantly affected by anode thickness, location, and orifice radius, and by cathode length. Terminal voltage oscillations and electrode erosion are deferred until higher currents by anodes at more downstream locations and of smaller orifice radius and by cathodes of greater length. Without an optimized geometry, specific impulses of 3300 s and thrust efficiencies up to 31% are implied by the best data.

King, D. Q.↗
DOE OSTI2025

Design and Preliminary Experimental Results on a Uniform-Field Test Fixture for Power Flow Experiments

Electrodes that produce a uniform electric field across their surfaces are desired for a variety of high-voltage systems including spark-gap switches and transversely excited atmospheric lasers. Here, the implementation of uniform-field electrodes to a parallel-plate load is described for the study of vacuum power flow under pulsed-power applications. We begin with an overview of general uniform-field geometries, and provide an open-source program that generates these geometries as described by Ernst. Following that, a modification to an existing power-flow experimental platform, that adopts a uniform-field geometry, is introduced and its utility is described. Lastly, preliminary experimental results are presented and future steps are outlined.

Capacitors↗
NASA NTRS1972

Area influences and floating potentials in Langmuir probe measurements.

Analysis of the influence of a relatively small reference electrode on a Langmuir probe measurement of plasma density and temperature. The analysis employs the collisionless theory of Laframboise for spherical and cylindrical probes and in a completely general way includes a broad range of electron densities and temperatures, as well as all possible values of ion mass and multiplicity of ionization. It is shown that a ratio alpha of reference-electrode area to probe area of 10,000 will guarantee no distortion of the measurement as a result of a shifting reference-electrode potential. It is further shown that the constraint on alpha can be relaxed by approximately two orders of magnitude when the charge-normalized ion mass is decreased from 200 to 1 amu and the ratio of reference-electrode radius to Debye length is decreased from 100 to 0. An additional result of the analysis is the dependence of a probe's floating potential on its geometry and radius, as well as on the properties of the plasma. A discussion of the latter result reveals in a striking manner the significant differences between the ion-current responses of spherical and cylindrical probes.

Szuszczewicz, E. P.↗
NASA NTRS1986

Discharge cell for optogalvanic spectroscopy having orthogonal relationship between the probe laser and discharge axis

A method and apparatus for an optogalvanic spectroscopy system are disclosed. Orthogonal geometry exists between the axis of a laser probe beam and the axis of a discharge created by a pair of spaced apart and longituduinally aligned high voltage electrodes. The electrodes are movable to permit adjustment of the location of a point in the discharge which is to irradiated by a laser beam crossing the discharge region. The cell dimensions are selected so that the cross section of the discharge region is substantly comparable in size to the cross section of the laser beam passing orthogonally through the discharge region.

Webster, C. R.↗