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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Environmental charging of spacecraft-tests of thermal control materials for use on the global positioning system flight space vehicle. Part 2: Specimen 6 to 9

The NASA/USAF program on the Environmental Charging of Spacecraft Surfaces consists, in part, of experimental efforts directed toward evaluating the response of materials to the environmental charged particle flux. Samples of thermal blankets of the type to be used on the Global Positioning System Flight Space Vehicles were tested to determine their response to electron flux. The primary result observed was that no discharges were obtained with the quartz-fiber-fabric-covered multilayer insulation specimen. The taped aluminized polyester grounding system used on all specimens did not appear to grossly deteriorate with time; however, the specimens require specific external pressure to maintain constant grounding system resistance.

Stevens, N. J.↗
NASA NTRS1993

Welding Wires To Thin Thermocouple Films

Parallel-gap resistance welding yields joints surviving temperatures of about 1,000 degrees C. Much faster than thermocompression bonding. Also exceeds conductive-paste bonding and sputtering thin films through porous flame-sprayed insulation on prewelded lead wires. Introduces no foreign material into thermocouple circuit and does not require careful control of thickness of flame-sprayed material.

Holanda, Raymond↗
NASA NTRS1985

Enhanced adhesion of films to semiconductors or metals by high energy bombardment

Films (12) of a metal such as gold or other non-insulator materials are firmly bonded to other non-insulators such as semiconductor substrates (10), suitably silicon or gallium arsenide by irradiating the interface with high energy ions. The process results in improved adhesion without excessive doping and provides a low resistance contact to the semiconductor. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters. The process can be utilized to apply very small, low resistance electrodes (78) to light-emitting solid state laser diodes (60) to form a laser device 70.

Tombrello, Thomas A.↗
DOE OSTI2021

Two-terminal electronic charge resistance switching device

A two-terminal memory device and methods for its use are provided. In the device, a bottom electrode is electrically continuous with a first operating terminal, and a control gate electrode is electrically continuous with a second operating terminal. A stack of insulator layers comprising a hopping conduction layer and a tunnel layer is contactingly interposed between the bottom electrode and the control gate electrode. The tunnel layer is thinner than the hopping conduction layer, and it has a wider bandgap than the hopping conduction layer. The hopping conduction layer consists of a material that supports electron hopping transport.

Marinella, Matthew↗
DOE OSTI2022

A Gapped Phase in Semimetallic T d -WTe 2 Induced by Lithium Intercalation

The Weyl semimetal WTe 2 has shown several correlated electronic behaviors, such as the quantum spin Hall effect, superconductivity, ferroelectricity, and a possible exciton insulator state, all of which can be tuned by various physical and chemical approaches. A new electronic phase in WTe 2 induced by lithium intercalation is discovered. The new phase exhibits an increasing resistivity with decreasing temperature and its carrier density is almost two orders of magnitude lower than the carrier density of the semimetallic T d phase, probed by in situ Hall measurements as a function of lithium intercalation. The theoretical calculations predict the new lithiated phase to be a potential charge density wave (CDW) phase with a bandgap of ≈0.14 eV, in good agreement with the in situ transport data. The new phase is structurally distinct from the initial T d phase, characterized by polarization-angle-dependent Raman spectroscopy, and large lattice distortions close to 6% are predicted in the new phase. This finding of a new gapped phase in a 2D semimetal demonstrates electrochemical intercalation as a powerful tuning knob for modulating electron density and phase stability in 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Vanadium oxide coatings to self-regulate current sharing in high-temperature superconducting cables and magnets

High-temperature superconductors such as REBa 2 Cu 3 O 7-δ (REBCO, RE = rare earth) enable high-current cables and high-field magnets. By removing the turn-to-turn insulation in a magnet application, recent experiments demonstrated that REBCO magnets can self-protect against catastrophic damage during a superconducting-to-normal transition (quench), i.e., when the stored magnetic energy rapidly converts to heat. The current can bypass the hot spot during a quench, thereby reducing the localized heat dissipation. The removal of the insulation between turns, however, leads to excessive eddy currents during current ramping, thereby forcing a much-prolonged magnet charging time. To address this issue, we investigate vanadium oxide (VO x ) coatings as a temperature-dependent self-switching medium that automatically manages current sharing. VO x coatings (with 1.70 ≤ × ≤ to 2.07) were deposited by reactive cathodic arc deposition, initially on insulating glass to determine the electrical properties, and later on commercial REBCO tapes. The coatings are x-ray amorphous but with a short-range crystalline ordering according to Raman spectrometry. The resistivity of VO x decreased by at least three orders of magnitude when the temperature increased from 80 to 300 K. The coating process is compatible with commercial REBCO tapes as evidenced by the negligible change in the critical current caused by the coating process. Here, the results from current sharing experiments and circuit analysis suggest that the VO x coating can effectively self-regulate current sharing in REBCO magnets, suppress excessive eddy currents, and enable self-protection during quenches.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Charge state transition levels of Ni in $β$-Ga 2 O 3 crystals from experiment and theory: An attractive candidate for compensation doping

Nickel-doped β-Ga 2 O 3 crystals were investigated by optical absorption and photoconductivity, revealing Ni-related deep levels. Here, the photoconductivity spectra were fitted using the phenomenological Kopylov and Pikhtin model to identify the energy of the zero-phonon transition (thermal ionization), Franck–Condon shift, and effective phonon energy. The resulting values are compared with the predicted ones by first-principle calculations based on the density functional theory (DFT). An acceptor level (0/-) of 1.9 eV and a donor level (+/0) of 1.1 eV above the valence band minimum are consistently determined for Ni Ga , which preferentially incorporates on the octahedrally coordinated Ga site. Temperature-dependent resistivity measurements yield a thermal activation energy of ~2.0 eV that agrees well with the determined Ni acceptor level. Conclusively, Ni is an eminently suitable candidate for compensation doping for producing semi-insulating β-Ga 2 O 3 substrates due to the position of the acceptor level (below and close to the mid-bandgap).

36 MATERIALS SCIENCE↗
NASA NTRS1981

Developments in Fibrous Refractory Composite Insulation

A family of high strength per unit density fibrous insulation materials has undergone preliminary development for heat-shielding advanced, reusable entry vehicles. These materials have a range of temperature capabilities dependent on composition. They have an unusually high thermal-shock resistance, an unusually high strain-to- failure, low thermal conductivity, and good morphological stability. One composition within the family, 22% aluminoborosilicate fiber (0.19 g/cc), has been successfully produced in a pilot plant and scaled up to full production. This fiber's additional strength makes it a desirable composition; it will be used on the third and fourth Space Shuttle vehicles. Another composition, 15% aluminoborosilicate fiber (0.14 g/cc) , has been adopted for use on limited parts of the third vehicle and as a replacement for the 0.14 g/cc density, rigid silica RSI on the fourth.

Leiser, Daniel B.↗
NASA NTRS2010

NASA Tech Briefs, January 2010

Topics covered include: Cryogenic Flow Sensor; Multi-Sensor Mud Detection; Gas Flow Detection System; Mapping Capacitive Coupling Among Pixels in a Sensor Array; Fiber-Based Laser Transmitter for Oxygen A-Band Spectroscopy and Remote Sensing; Low-Profile, Dual-Wavelength, Dual-Polarized Antenna; Time-Separating Heating and Sensor Functions of Thermistors in Precision Thermal Control Applications; Cellular Reflectarray Antenna; A One-Dimensional Synthetic-Aperture Microwave Radiometer; Electrical Switching of Perovskite Thin-Film Resistors; Two-Dimensional Synthetic-Aperture Radiometer; Ethernet-Enabled Power and Communication Module for Embedded Processors; Electrically Variable Resistive Memory Devices; Improved Attachment in a Hybrid Inflatable Pressure Vessel; Electrostatic Separator for Beneficiation of Lunar Soil; Amorphous Rover; Space-Frame Antenna; Gear-Driven Turnbuckle Actuator; In-Situ Focusing Inside a Thermal Vacuum Chamber; Space-Frame Lunar Lander; Wider-Opening Dewar Flasks for Cryogenic Storage; Silicon Oxycarbide Aerogels for High-Temperature Thermal Insulation; Supercapacitor Electrolyte Solvents with Liquid Range Below -80 C; Designs and Materials for Better Coronagraph Occulting Masks; Fuel-Cell-Powered Vehicle with Hybrid Power Management; Fine-Water-Mist Multiple-Orientation-Discharge Fire Extinguisher; Fuel-Cell Water Separator; Turbulence and the Stabilization Principle; Improved Cloud Condensation Nucleus Spectrometer; Better Modeling of Electrostatic Discharge in an Insulator; Sub-Aperture Interferometers; Terahertz Mapping of Microstructure and Thickness Variations; Multiparallel Three-Dimensional Optical Microscopy; Stabilization of Phase of a Sinusoidal Signal Transmitted Over Optical Fiber; Vacuum-Compatible Wideband White Light and Laser Combiner Source System; Optical Tapers as White-Light WGM Resonators; EPR Imaging at a Few Megahertz Using SQUID Detectors; Reducing Field Distortion in Magnetic Resonance Imaging; Fluorogenic Cell-Based Biosensors for Monitoring Microbes; A Constant-Force Resistive Exercise Unit; GUI to Facilitate Research on Biological Damage from Radiation; On-Demand Urine Analyzer; More-Realistic Digital Modeling of a Human Body; and Advanced Liquid-Cooling Garment Using Highly Thermally Conductive Sheets.

Source record↗
DOE OSTI2026

Unraveling Grain Boundary Instability in Dense Proton-Conducting Oxides

The long-term stability of protonic ceramic electrolysis cell (PCEC) materials under high-steam operating conditions remains a critical barrier to device commercialization. Here, we investigate the fundamental degradation mechanisms of dense BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ (BCZYYb) electrolytes operated at 550 °C, 50% H 2 O in air. Over 1,000 h, the total electrolyte conductivity decreases by 11.1%, driven primarily by a >130% increase in grain-boundary resistivity. Post-mortem analyses reveal that damage is localized to near-surface grain boundaries extending ∼50 μm into the dense electrolyte pellet. This surface localization indicates that degradation is likely to be severe in thin, device-level electrolytes. Degradation is primarily attributed to chemo-mechanical grain-boundary weakening arising from hydration-induced chemical expansion, culminating in the formation of intergranular cracks oriented parallel to the pellet surface. These internal cracks subsequently react with steam and/or CO 2 , leading to the formation of nanoscale insulating phases, including Ba(OH) 2 , nanocrystalline BaCO 3 , and amorphous Ce/Zr/Y/Yb-containing oxides or hydroxycarbonates. After an initial degradation period of approximately 200 h, the overall conductivity stabilizes. Incorporating NiO sintering aids reduces grain-boundary density by an order of magnitude under identical sintering conditions. Although addition of NiO increases the initial resistivity by >160% at 550 °C, it substantially suppresses grain-boundary instability and mitigates chemical degradation. These findings underscore the urgent need for chemical and/or physical stabilization of BCZYYb electrolytes and offer design guidelines to enable durable, high-performance PCECs.

08 HYDROGEN↗
NASA NTRS2004

Grounding Headphones for Protection Against ESD

A simple alternative technique has been devised protecting delicate equipment against electrostatic discharge (ESD) in settings in which workers wear communication headsets. In the original setting in which the technique was devised, the workers who wear the headsets also wear anti-ESD grounding straps on their wrists. The alternative technique eliminates the need for the wrist grounding straps by providing for grounding through the headsets. In place of the electrically insulating foam pads on the headsets, one installs pads made of electrically conductive foam like that commonly used to protect electronic components. Grounding wires are attached to the conductive foam pads, then possibly to the shielding cable which may be grounded to the backshell on the connector. The efficacy of this technique in protecting against ESD has been verified in experiments. The electrical resistance of the pads is a few megohms - about the same as that of a human body between the fingers of opposite hands and, hence, low enough for grounding. The only drawback of the technique is that care must be taken to place the foam pads in contact with the user s skin: any hair that comes between the foam pads and the skin must be pushed aside because hair is electrically insulating and thus prevents adequate grounding.

Peters, John↗
DOE OSTI2024

Understanding and Manipulating Counterion Condensation within Charged Polymer Electrolytes for Selective and Low Resistant Membrane Separations

Polymeric ion-exchange membranes are found at the heart of numerous electrochemical systems spanning separations (electrodialysis and membrane capacitive deionization) and energy conversion and storage (flow batteries, fuel cells, and electrolyzers). The ion-exchange membrane separators need to be ion conducting but electron insulating, and in many scenarios selective for a particular ion to conduct. Because of their polymeric nature, the molecular architectures of ion-exchange membranes lack the molecular precision found in many inorganic materials. Plus, they contain numerous structural defects that impede ionic transport. As a result of their poor structure, it has been difficult to carefully probe the underlying physics that governs ion transport in ion-exchange membranes. We investigated counterion condensation phenomena in ion-exchange membranes and correlated it to bulk ionic charge transport and selectivity in precisely defined and long-range ordered materials afforded through the principles of directed self-assembly. A multi-faceted approach spanning i.) advanced metrology, two-dimensional atomic force microscopy, x-ray scattering, and ion-exchange equilibria, and ii.) molecular simulations (classical molecular dynamics and ab-inito molecular dynamics) that bridge multiple time and length scales, were employed to correlate the extent of counterion condensation to ionic conductivity and selectivity. After uncovering the extent of the condensation phenomena in this project, new macromolecular chemistries were employed to manipulate the ion pairing interactions of the condensed counterions to tethered ions on the polymer backbone so more facile and selective conduction rates can be attained. The research has aided in the rational design of polymeric ion-exchange membrane separators with high current density for electrochemical systems and subsequently better energy efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2024

From nonmetal to strange metal at the stripe-percolation transition in La 2 - x Sr x CuO 4

The nature of the normal state of cuprate superconductors continues to stimulate considerable speculation. Of particular interest has been the linear temperature dependence of the in-plane resistivity in the low-temperature limit, which violates the prediction for a Fermi liquid. We present measurements of anisotropic resistivity in La$_{2–x}$Sr$_x$CuO$_4$ that confirm the strange-metal behavior for crystals with doped-hole concentration $p = x > p^* \sim 0.19$ and contrast with the nonmetallic behavior for $p < p^*$. We propose that the changes at $p^*$ are associated with a first-order transition from doped Mott insulator to conventional metal; the transition appears as a crossover due to intrinsic dopant disorder. We consider results from the literature that support this picture; in particular, we present a simulation of the impact of the disorder on the first-order transition and the doping dependence of stripe correlations. Below $p^*$, the strong electronic interactions result in charge and spin stripe correlations that percolate across the CuO 2 planes; above $p^*$, residual stripe correlations are restricted to isolated puddles. Here we suggest that the $T$-linear resistivity results from scattering of quasiparticles from antiferromagnetic spin fluctuations within the correlated puddles. This is a modest effect compared to the case at $p < p^*$, where the data suggest that there are no coherent quasiparticles in the normal state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Role of Surface Termination in the Metal–Insulator Transition of V 2 O 3 (0001) Ultrathin Films

Surface termination is known to play an important role in determining the physical properties of materials. It is crucial to know how surface termination affects the metal–insulator transition (MIT) of V 2 O 3 films for both fundamental understanding and its applications. By changing growth parameters, we achieved a variety of surface terminations in V 2 O 3 films that are characterized by low-energy electron diffraction (LEED) and photoemission spectroscopy techniques. Depending upon the terminations, our results show that MIT can be partially or fully suppressed near the surface region due to the different fillings of the electrons at the surface and subsurface layers and the change of screening length compared to the bulk. Across MIT, a strong redistribution of spectral weight and its transfer from a high-to-low-binding energy regime is observed in a wide energy scale. Our results show that the total spectral weight in the low-energy regime is not conserved across MIT, indicating a breakdown of the “sum rules of spectral weight”, signature of a strongly correlated system. Such a change in spectral weight is possibly linked to the change in hybridization, lattice volume (i.e., effective carrier density), and the spin degree of freedom in the system that occurs across MIT. We find that MIT in this system is strongly correlation-driven, where the electron–electron interactions play a pivotal role. Furthermore, our results provide better insight into the understanding of the electronic structure of strongly correlated systems and highlight the importance of accounting for surface effects during interpretation of the physical property data mainly using surface-sensitive probes, such as surface resistivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Spatial Atomic Layer Deposition of Aluminum Oxide as a Passivating Hole Contact for Silicon Solar Cells

In this work, tunneling aluminum oxide (Al 2 O 3 ) passivation layers are demonstrated to be a candidate for hole collecting, passivating contacts when coupled with a boron-doped surface. Here, these very thin Al 2 O 3 films (1.5-3 nm) are deposited using spatial atomic layer deposition (ALD) on boron diffused (110-115 Ω –1 ) hydrophilic surfaces operating as metal-insulator-semiconductor (MIS) contacts. Emitter saturation current density values of approximately ≈57 fA cm 2 are achieved for Al 2 O 3 film thicknesses of 2 nm before metallization. At this same thickness, contact resistivity values of 33 mΩ cm 2 are obtained after metallization. Most importantly, the boron diffusion, wet chemical surface preparation, and spatial ALD of Al 2 O 3 used to create these MIS structures were all performed with industrially relevant equipment on Cz wafers.

14 SOLAR ENERGY↗
DOE OSTI2025

Stabilization of Preternatural Barium Oxidation States as an Unexpected Byproduct of β-Decay: Discovery of a New Halide Semiconductor Alloy

137 Cs has a wide range of roles in the nuclear industry. The solid material, safely encapsulated in CsCl as 137 CsCl, is stored as fission product waste from nuclear power production and legacy waste from nuclear weapons production; it has also served as a radiation source in food and sewage irradiators as well as medical devices. However, because of the solubility of the chloride salt and the relatively high specific activity of 137 Cs, damaged or broken capsules can lead to severe radiological accidents. Safe capsule design and material recycling are complicated by the unclear structural evolution during β-decay, which remains ambiguous due to the differing oxidation states of Cs (1+) and Ba (2+). Here, in this study, we use first-principles calculations to investigate the evolving structure–property relationships of Cs 1–x Ba x Cl during β-decay. Despite the well-established 2+ formal oxidation state of alkali-earth metals, we find that Ba 1+ can be stabilized in the form of a mixed-valence alloy at low concentrations. Specifically, we identify three regimes for the β-decay of 137 Cs into CsCl: Ba-doped CsCl (Ba ≤ 14%), wherein Ba has the expected 2+ oxidation state; Cs–Ba–Cl alloys, where Ba has a mix of the usual Ba 2+ and highly unusual Ba 1+ oxidation state in the form of a quasi-disordered mixed-valence alloy (Ba = 25%); and phase separation into a CsCl + BaCl 2 + Ba (m) mechanical mixture, where Ba reverts to its expected 2+ oxidation state (Ba > 25%). Surprisingly, the Cs 0.75 Ba 0.25 Cl mixed-valence alloy is a narrow indirect band gap semiconductor (1.05 eV) despite the insulating nature of both CsCl and BaCl 2 . It also exhibits strongly excitonic polarized optical properties, has glass-like ultralow thermal conductivity (directional average of 0.21 W/mK at 300 K), and shows greater resistance to deformation under both tensile and volumetric strengths compared with the original CsCl structure (e.g., shear and Young’s modulus of 9.04 and 31.62 GPa, respectively). These findings imply that transmutation of 137 Cs leads to highly unusual chemical bonding that stabilizes Ba 1+ in local regions of the quasi-disordered Cs 0.25 Ba 0.75 Cl, resulting in anomalous physical properties. Moreover, this discovery provides valuable insight for safe nuclear waste capsule design, which can aid in preventing environmental or human exposure to radioactive materials.

Fuhr, Addis S. [Oak Ridge National Laboratory (ORN↗
DOE OSTI2022

Temperature-Following Thermal Barrier Coatings for High Efficiency Engines (Final Report)

HRL Laboratories and General Motors (GM), pursued this effort to increase the efficiency of internal combustion engines (ICEs) by developing and implementing temperature-following thermal barrier coatings (TBCs) to decrease heat loss from the combustion chamber. HRL developed microsphere TBCs based on hollow high-temperature alloy spheres with average diameter of 50 μm and wall thickness ~1 μm (microspheres) that achieve unprecedented low thermal conductivity and heat capacity (10X lower than the state of the art) while offering exceptional environmental and mechanical resistance.> In current ICEs, approximately 29% of the fuel’s energy is lost to the cooling system and about 22% goes into moving the car. By limiting heat losses from the combustion chamber with insulating coatings, fuel energy can be redirected into additional piston work and into the exhaust stream. The additional energy that goes into the exhaust stream can be turned into useful work through the use of an exhaust energy recovery device, such as turbocompounding and/or through driving a turbocharger to increase the power density of the engine allowing downsizing. Insulating coatings for piston crowns have been pursued in the past, but previous materials—typically ceramics—exhibited low thermal conductivity but retained high heat capacity. Such materials reduce heat losses but stabilize at a high surface temperature. The high surface temperature heats the incoming gases, which lowers volumetric efficiency and increases propensity for knock, resulting in degraded engine performance. This program developed an innovative new material that combines low thermal conductivity with low heat capacity. These unique properties allow it to follow rapid changes in gas temperature during each combustion cycle. A metallic microsphere TBC has been demonstrated that exhibits increased surface temperature during the combustion period, resulting in reduced heat transfer losses, while still returning to a low surface temperature during the gas exchange period. A 10X lower thermal conductivity and heat capacity than state-of-the-art thermal barrier coatings has been demonstrated. These unprecedented thermal properties are achieved through the coating architecture, which consists of closed pores on the microscale and exhibits a total porosity of 90% to 95%. By selecting a high-temperature nickel alloy as the coating material, the ductility and strength of metals can be harnessed to achieve much better durability and damage tolerance than brittle ceramic coatings can achieve.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1983

Intumescent coating development

A program was completed at the University of Dayton Research Institute in which polyimide and phenolic intumescent coatings were evaluated as supplemental thermal insulation for the sprayed-on foam insulation on the aft bulkhead of the space shuttle external tank. The purpose of the intumescent coating was to provide additional thermal protection during lift-off in order to replace the ablative heat resistant layer with a lighter weight material for increased payload in the shuttle.

Sayler, I. O.↗