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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Lightweight, Durable, and Multifunctional Electrical Insulation Material Systems for High Voltage Applications

Newly developed multilayer structures of well-known polymer insulation materials significantly improved dielectric breakdown voltage, VB, or dielectric strength, K, if well-bonded, when compared to those of single material insulations or the commercial SOA systems, such as Teflon-Kapton-Teflon (TKT), at the same overall thickness. To date, the greatest improvement of the new structures from a few candidate materials, including various types of Kapton PIs and PFA or PET as bond layer (BL), was about 61% higher than that of the Kapton PI alone films, 40.1 vs. 24.9 kV, which was translated to 86.3% decrease in insulation thickness, thus significant volume and weight reduction of the final system. However, it was of interest to note that most improvements of the multilayer structures occurred at thicker overall thicknesses, above ~ 0.15 mm. Extensive analyses also showed that K of the multilayer structures increased with (i) decreasing individual layer thickness regardless of material type, (ii) increasing total accumulated thickness of PI or overall PI/BL ratio, and (iii) increasing number of interface or total number of layers, but only above the aforementioned overall thickness limit. Increases in VB of the multilayer structures were directly correlated with damage evolution and failure mode. With further material-design-process optimizations of the multilayer structures, it was expected to achieve other multifunctionalities, such as high partial discharge (PD) resistance, improved durability, EMI shielding, and high thermal dissipation in addition to high dielectric strength. These new structures can be used in various high voltage and high temperature applications, such as future hybrid or all electric aircraft wiring and power transmission as well as many other non-aerospace high power cables, electronic parts and components, printed circuit board, and so forth. The multilayer insulation system can be easily processed and manufactured with various conductor types via calendaring, compression-molding, stamping, laminating, vacuum-bagging and autoclaving, or 3D printing, even for complex 3-D components. Based on their unique structural configurations and potential capabilities, the new insulation system was identified as micro-multilayer multifunctional electrical insulation (MMEI). Patent application of the MMEI concept and current design configurations was filed for a 1-year provisional application (OAI-58834, Serial No.: 62/659,234), pending conversion to a U.S. utility application. This paper presents details of the MMEI structures, their dielectric performance analyses, potential mechanisms, and commercial scaleup feasibility assessment.

Multifunctional↗
DOE OSTI2020

Sudden-Discharge Cycling Characteristics and Millisecond Dynamic Behaviors of a HTS Stainless-Steel Insulated Double-Pancake Coil With Thin Copper Plates

We have tested an intermediate-sized HTS stainless-steel (co-wound) insulated double pancake coil (~132 turns per coil) and discovered dynamic effects during sudden discharge on both millisecond and second scales. For soft break, the power supply is turned off suddenly but the shunt resistor (164 milliohm) is still connected; for hard break, a high voltage contactor is used to suddenly open the circuit so that the leads are completely open. Hard break is dangerous to traditionally insulated LTS magnets, but the SS-insulated HTS DPC retained integrity over ¡80 charge-discharge cycles. Voltage decay curves for soft and hard breaks are studied on short and long timescales. On long timescales, we observe the expected exponential decay and measure the time constant to calculate contact resistance. On short timescales, we observe highly dynamic effects: a hyper-exponential decay suggesting that the inductance or contact resistance is suddenly changing with time, likely an indication of the RL circuit forming. Moreover, peak voltage immediately (ms) after the sudden discharge were collected and compared. It is found that the peak voltage in soft-discharge is proportional to the applied current, while the those in hard-break has a unique pattern and tends to stay flat even though the applied current increases.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1983

Neutron-transmutation-doped germanium bolometers

Six slices of ultra-pure germanium were irradiated with thermal neutron fluences between 7.5 x 10 to the 16th and 1.88 x 10 to the 18th per sq cm. After thermal annealing the resistivity was measured down to low temperatures (less than 4.2 K) and found to follow the relationship rho = rho sub 0 exp(Delta/T) in the hopping conduction regime. Also, several junction FETs were tested for noise performance at room temperature and in an insulating housing in a 4.2 K cryostat. These FETs will be used as first stage amplifiers for neutron-transmutation-doped germanium bolometers.

Palaio, N. P.↗
NASA NTRS2003

NASA Tech Briefs, September 2003

Topics include: Oxygen-Partial-Pressure Sensor for Aircraft Oxygen Mask; Three-Dimensional Venturi Sensor for Measuring Extreme Winds; Swarms of Micron-Sized Sensors; Monitoring Volcanoes by Use of Air-Dropped Sensor Packages; Capacitive Sensors for Measuring Masses of Cryogenic Fluids; UHF Microstrip Antenna Array for Synthetic- Aperture Radar; Multimode Broad-Band Patch Antennas; 164-GHz MMIC HEMT Frequency Doubler; GPS Position and Heading Circuitry for Ships; Software for Managing Parametric Studies; Software Aids Visualization of Computed Unsteady Flow; Software for Testing Electroactive Structural Components; Advanced Software for Analysis of High-Speed Rolling-Element Bearings; Web Program for Development of GUIs for Cluster Computers; XML-Based Generator of C++ Code for Integration With GUIs; Oxide Protective Coats for Ir/Re Rocket Combustion Chambers; Simplified Waterproofing of Aerogels; Improved Thermal-Insulation Systems for Low Temperatures; Device for Automated Cutting and Transfer of Plant Shoots; Extension of Liouville Formalism to Postinstability Dynamics; Advances in Thrust-Based Emergency Control of an Airplane; Ultrasonic/Sonic Mechanisms for Drilling and Coring; Exercise Device Would Exert Selectable Constant Resistance; Improved Apparatus for Measuring Distance Between Axles; Six Classes of Diffraction-Based Optoelectronic Instruments; Modernizing Fortran 77 Legacy Codes; Active State Model for Autonomous Systems; Shields for Enhanced Protection Against High-Speed Debris; Scaling of Two-Phase Flows to Partial-Earth Gravity; Neutral-Axis Springs for Thin-Wall Integral Boom Hinges.

Source record↗
DOE OSTI2024

Stabilizing lithium superoxide formation in lithium-air batteries by Janus chalcogenide catalysts

Solid lithium peroxide (Li 2 O 2 ) is the major discharge product in Li-air batteries. However, the electronically insulating nature of Li 2 O 2 tends to affect the battery’s performance such as the polarization gap and cyclability. On the other hand, lithium superoxide (LiO 2 ), generated through a one-electron transfer process, offers greater electronic conductivity, lower charge transfer resistance, and thus reduced charge potential. Nevertheless, LiO 2 long-term stabilization as a final product remains a significant challenge. Here, in this study, we present the molybdenum (Mo)-based Janus chalcogenide family featuring asymmetric structures as a new generation of cathode catalysts for Li-air batteries. These catalysts demonstrate remarkable efficacy in stabilizing LiO 2 discharge products, even under high current densities of 5000 mA/g (corresponding to 0.5 mA/cm 2 ). Our density functional calculations provide an understanding of why the asymmetric Mo-Janus chalcogenides result in LiO 2 formation whereas the symmetric Mo-dichalcogenides produce Li 2 O 2 as the discharge product. These results pave the way to explore a new generation of advanced catalysts for superoxide-based Li-air batteries.

Chalcogenide↗
DOE OSTI2022

Thermal and thermoelectric properties of an antiferromagnetic topological insulator MnBi 2 Te 4

The discovery of an intrinsic antiferromagnetic topological insulator (AFMTI) in MnBi 2 Te 4 has attracted intense attention, most of which lies in its electrical properties. Here in this paper, we report electronic, thermal, and thermoelectric transport studies of this newly found AFMTI. The temperature and magnetic field dependence of its resistivity, thermal conductivity, and Seebeck coefficient indicate strong coupling between charge, lattice, and spin degrees of freedom in this system. Furthermore, MnBi 2 Te 4 exhibits a large anomalous Nernst signal, which is associated with nonzero Berry curvature of the field-induced canted antiferromagnetic state.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Electrical research on solar cells and photovoltaic materials

The flat-plate solar cell array program which increases the service lifetime of the photovoltaic modules used for terrestrial energy applications is discussed. The current-voltage response characteristics of the solar cells encapsulated in the modules degrade with service time and this degradation places a limitation on the useful lifetime of the modules. The most desirable flat-plate array system involves solar cells consisting of highly polarizable materials with similar electrochemical potentials where the cells are encapsulated in polymers in which ionic concentrations and mobilities are negligibly small. Another possible mechanism limiting the service lifetime of the photovoltaic modules is the gradual loss of the electrical insulation characteristics of the polymer pottant due to water absorption or due to polymer degradation from light or heat effects. The mechanical properties of various polymer pottant materials and of electrochemical corrosion mechanisms in solar cell material are as follows: (1) electrical and ionic resistivity; (2) water absorption kinetics and water solubility limits; and (3) corrosion characterization of various metallization systems used in solar cell construction.

Orehotsky, J.↗
NASA NTRS1999

Non-Equilibrium Superconductivity and Magnetic Pair Breaking in Perovskite Half-Metallic Ferromagnet-Insulator-Superconductor (F-I-S) Heterostructures

The effect of spin-polarized quasiparticle currents on the critical current density (J-c) of cuprate superconductors is studied in perovskite F-I-S heterostructures as a function of insulator thickness and of underlying magnetic materials. A pulsed current technique is employed to minimize extraneous Joule heating on the superconductor. At temperatures near T-c, F-I-S samples with insulator thicknesses\1e2nm show precipitous decrease in J_c as current injection (I_m) is increased. In contrast, J_c in a controlled sample with a substituted non-magnetic material (N-I-S) exhibit no dependence on I_m. Similarly, a F-I-S sample with a 10 mn insulating barrier also show little J_c effect versus I_m. At low temperatures with I_m = 0, significant suppression of J-c is observed only in the thin barrier F-I-S samples, although T_c and the normal-state resistivity of all samples are comparable. These phenomena can be attributed to the Cooper pair breaking induced by externally-injected and internally-reflected spin-polarized quasiparticle currents. We estimate an order of magnitude range for the spin diffusion length of 100 nm to 100\ mum.

Fu, C.-C.↗
NASA NTRS2001

Passive Gas-Gap Heat Switches for Use in Adiabatic Demagnetization Refrigerators

We have designed, built, and tested a gas gap heat switch that works passively, without the need for a separate, thermally activated getter. This switch uses He-3 condensed as a thin film on alternating plates of copper. The switch is thermally conductive at temperatures above about 0.2 K, and is insulating if either end of the switch is below about 0.15 K. The "on" conductance (7 mW/K at 0.25K) is limited by the surface area and gap between the copper leaves, the saturated vapor pressure of the He-3, and the Kapitza boundary resistance between the He-3 and the copper. The "off" conductance is determined by the helium containment shell which physically supports the two conductive ends. We have also designed and are building passive gas gap heat switches which will passively turn off near 1 K and 4 K. For these switches we rely on the rapidly changing vapor pressure of He-4 above neon or copper substrates, respectively, when the coverage is less than one monolayer. The different binding energies of the He-4 to the neon or copper give rise to the different temperatures where the switches transition between the on and off states.

Shirron, P. J.↗
DOE OSTI2023

Application of the van der Pauw method for electrical conductivity measurements at high temperatures using an insulating compressing ring

High quality data on the high temperature electrical properties of ceramics, particularly oxides, is of great value for material selection, design, and modeling for a broad range of emerging applications. Utilizing the mismatch in the coefficient of thermal expansion between two materials, a purely mechanical method for establishing electrical contact in the van der Pauw geometry to measure the bulk resistivity of ceramic disks at high temperatures is presented. Measurements of a reference material, 20 mol. % Gd-doped cerium oxide, are presented up to 1000 °C. The viability of electrical measurements up to a maximum temperature of 1600 °C is also considered. Measurements are performed using multiple techniques and compared to literature values finding excellent agreement. Finally, the approach described in this work enables the van der Pauw method to be applied to many ceramic materials over a wide range of temperatures and environments.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Melt-grown semi-insulating Mn:β-Ga 2 O 3 single crystals exhibiting unique visible absorptions and luminescence

In this study, several acceptor dopants have been explored in β-Ga 2 O 3 to produce semi-insulating substrates and epitaxial films. Fe and Mg make up the majority of research thus far; however, other transition metals provide potential alternatives for optimized performance. β-Ga 2 O 3 bulk single crystals were grown by the Czochralski and vertical gradient freeze methods with a nominal dopant concentration of 0.25 at. % Mn. Ultraviolet-visible-near infrared spectroscopy and photoluminescence revealed polarization- and orientation-dependent optical absorptions (pleochroism) coupled with an orange luminescence. All samples were electrically insulating, on the order of 10 9 –10 11 ohm cm at room temperature, indicative of acceptor doping. Actual dopant concentrations of the intentionally doped transition metal and background impurities were determined via glow discharge mass spectrometry, indicating the macroscale segregation behavior. High-temperature resistivity measurements indicated an experimental acceptor level of 1.7 ± 0.2 eV. Hydrogenation of samples resulted in an increase in the orange luminescence and O–H stretching modes observable in the infrared spectrum. Density functional theory calculations were performed to determine the likely site-occupancy and acceptor level of Mn in the bandgap.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fractional Quantum Anomalous Hall Effect

The realization of the fractional quantum anomalous Hall effect (FQAHE) in a zero-field fractional Chern insulator is a new advancement in condensed matter physics, resulting from the interplay among strong correlations, topology, and spontaneous time-reversal symmetry breaking in lattice systems. In this review, we highlight the experimental and theoretical progress toward achieving FQAHE in two material platforms: twisted bilayer MoTe 2 and rhombohedral-stacked multilayer graphene. These systems host narrow topological bands with nontrivial Chern numbers, enabling interaction-driven fractionalized states analogous to the fractional quantum Hall effect, but without external magnetic fields. We discuss how spontaneous ferromagnetism, moiré lattice reconstruction, and band topological effects underpin the emergence of FQAHE in twisted MoTe 2 . We describe experimental discoveries of zero-field fractional Chern insulators in both transport and optical experiments, as well as signatures of composite Fermi liquids and higher-energy Chern band, which may shed light on engineering nonabelian states. In rhombohedral graphene/hexagonal boron nitride moiré superlattices, we review the recent observations of fractionally quantized Hall resistance, connections between FQAHE and extended quantum anomalous Hall phases, and the coexistence of superconductivity and FQAHE. Furthermore, these discoveries not only deepen our understanding of strongly correlated topological matter but also open new frontiers for exploring nonabelian anyons, fault-tolerant quantum computation, and topological opto-spintronics free of magnetic fields.

bilayer↗
NASA NTRS1972

Design and fabrication of wraparound contact silicon solar cells

Both dielectric insulation and etched junction contact techniques were evaluated for use in wraparound contact cell fabrication. Since a suitable process for depositing the dielectrics was not achieved, the latter approach was taken. The relationship between loss of back contact and power degradation due to increased series resistance was established and used to design a simple contact configuration for 10 ohm-cm etched wraparound junction contact N/P cells. A slightly deeper junction significantly improved cell curve shape and the associated loss of current was regained by using thinner contact grid fingers. One thousand cells with efficiencies greater than 10.5% were fabricated to demonstrate the process.

Scott-Monck, J. A.↗
DOE OSTI2021

Towards cubic symmetry for Ir 4 + : Structure and magnetism of the antifluorite K 2 IrBr 6

Here, crystal structure, electronic state of Ir 4 + , and magnetic properties of the antifluorite compound K 2 IrBr 6 are studied using high-resolution synchrotron x-ray diffraction, resonant inelastic x-ray scattering (RIXS), thermodynamic and transport measurements, and ab initio calculations. The crystal symmetry is reduced from cubic at room temperature to tetragonal below 170 K and eventually to monoclinic below 122 K. These changes are tracked by the evolution of the noncubic crystal-field splitting Δ measured by RIXS. Nonmonotonic changes in Δ are ascribed to the competing effects of the tilt, rotation, and deformation of the IrBr 6 octahedra as well as tetragonal strain on the electronic levels of Ir 4 + . The Néel temperature of T N = 11.9 K exceeds that of the isostructural K 2 IrCl 6 , and the magnitude of frustration on the fcc spin lattice decreases. We argue that the replacement of Cl by Br weakens electronic correlations and enhances magnetic couplings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Metal-Insulation REBCO Pancake Coil With Solder Surface Shunt: Testing and Modeling

Rare-earth barium copper oxide (REBCO) high-temperature superconducting (HTS) magnets can generate very high magnetic fields with superior engineering current density and robust mechanical integrity. The no-insulation (NI) winding technique, including its metal-insulation (MI) variant, enables “self-protection” against localized overheating through inter-turn current sharing, improving defect tolerance and allowing temporary current overloads. In REBCO pancake coils, the current-sharing path is predominantly confined to the edges of the REBCO tapes due to insulating buffer layers. Applying a surface shunt using solder can effectively enhance current sharing in NI/MI coils via the REBCO tape edges. Here, in this paper, we present both experimental and numerical research on the current distribution in surface-shunt metal-insulation (SSMI) REBCO pancake coils. We tested a stainless steel co-wound MI REBCO double-pancake coil, before and after applying a soldered surface shunt, in a saturated liquid nitrogen bath. The SSMI coil was modeled using the H-formulation and rotated anisotropic resistivity to study its dynamic behavior, including inter-turn current sharing and intra-turn screening currents. Benchmarked by experimental data, the numerical model is able to study the defect tolerance of the SSMI coil during energization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Multiphysics Co-Optimization Design and Analysis of Double-Side Cooled Silicon Carbide-Based Power Module: Preprint

With the rapid growth of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), much more rigorous design targets have been set for automotive power electronics, including high power density, high reliability, and low cost. Novel power module and inverter technologies based on wide bandgap (WEG) semiconductors have been developed to meet these design targets, while providing optimal power semiconductor operating temperature and promising thermomechanical performance. Compared with conventional cooling techniques which are normally applied only on one side of power module, double-side cooling approach is now believed to be the solution to enable high power density and low thermal resistance of WEG semiconductor-based power electronics. In this work, we develop a three-phase power module that is double-sided cooled using dielectric fluid jet impingement. In each phase, four silicon carbide (SiC) power semiconductors are bonded to copper busbars without electrical insulation layers. A finite element analysis (FEA) model is created for thermal and thermomechanical analysis. Based on FEA modeling results, we select particular dimensions for a parametric study to optimize thermal and mechanical performance. Using a multi-objective genetic algorithm (MOGA)-based optimization method, we have minimized the maximum junction temperature and thermal stresses within the power module. The multiphysics co-optimization approach has enabled an efficient design process of power modules with greatly reduced computational cost, as compared to conventional processes that rely on exhaustive numerical simulations and iterations.

ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1976

Smoke generator

A smoke generator is disclosed which is particularly suitable for mounting on the wing tips of an aircraft and for conducting airflow studies. The device includes a network of thermally insulated tubes for carrying a fluid which is used to produce smoke. The fluid, which need not be combustible, is heated above its vaporization temperature by electric current which is passed through the fluid conduit tubes, so that the tubes serve both as fluid conduits and resistance heating elements. Fluid supply and monitoring systems and electrical control systems are also disclosed.

Rogers, J. R.↗
NASA NTRS1991

Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

Johnson, Gregory A.↗