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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
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↗
NASA NTRS2019

Polymer Infused Composite Metal Foam as a Potential Aircraft Leading Edge Material

The leading edge of the aircraft wings must be free from three-dimensional disturbances caused by insect adhesion, ice accretion, and particle wear in order to improve flight performance, safety, and fuel efficiency of the aircraft. An innovative solution was explored in this work by infusing stainless steel composite metal foam (SS CMF) with a hydrophobic epoxy resin system. S-S CMF was made with 100% stainless steel using a powder metallurgy technique. The infused epoxy filled the macro- and microporosities, unique to SS CMF’s structure, creating a product with a density similar to that of aluminum. The contact angle, wear rate, erosion resistance, and insect adhesion of the novel infused composite metal foam were measured and compared to aluminum, epoxy and stainless steel. The infusion process was determined to fill up to 88% of the pores within the SS CMF and was found to reduce wettability and insect residue accretion. The contact angle of the infused SS CMF was 43% higher than its parent material, stainless steel, and 130% higher than aluminum. Insect residue maximum height and areal coverage were reduced by 60 and 30%, respectively, compared to aluminum. Grit blast experiments to simulate erosion resulted in a greater roughness increase for aluminum than for the parent epoxy resin or the resin-infused SS CMF. These results suggest that the durability and performance of infused SS CMF was superior compared to aluminum, which is the current leading edge material of choice. Based on the promising results under relevant wear and erosion conditions, it is concluded that the infused SS CMF can offer a potential tailored replacement to aluminum leading edge material.

Jacob C. Marx↗
DOE OSTI2021

Differences in c-Si Solar Cell Metallization and Susceptibility to Series Resistance Degradation

In this case study, we investigate a degradation mode occurring at the cell level in fielded multi-Si modules. Affected cells in the module show a progressive, series-resistance-related power degradation observed in module- and cell-level IV curves along with EL and PL imaging at the module, cell, and cell core sample scale. SEM and elemental analysis via EDS reveal a difference in the oxides in the silver paste used in screen printing of the finger contacts. This suggests that the cells were screen printed with different silver paste compositions and possibly firing conditions. One of these combinations leads to degradation of the contact at the interface between the cell and contact finger, causing severe series resistance across the cell that continues to progress over time.

acetic acid↗
DOE OSTI2020

Assessment of AFM - KPFM and SSRM for Measuring and Characterizing Materials Aging Processes

Atomic Force Microscopy (AFM), in conjunction with Peak Force Kelvin Probe Force Microscopy (PF-KPFM) and Peak Force Scanning Spreading Resistance Microscopy (PF-SSRM), was used to assess changes on thin metal films that underwent accelerated aging. The AFM technique provides a relatively easy, non-destructive methodology that does not require high-vacuum facilities to obtain nanometer-scale spatial resolution of surface chemistry changes. Surface morphology, roughness, contact potential difference, and spreading resistance were monitored to qualitatively identify effects of aging-morphology changes and oxidation of Au, Al, Cu thin film standards as well as diffusion of CuAu and AlAu thin film stacks at 65C under dried nitrogen flow conditions. AFM PF-KPFM and PF-SSRM modes have been exercised, refined and have proven to be viable and necessary early aging detection tools.

36 MATERIALS SCIENCE↗
NASA NTRS1983

GaAs solar cells for concentrator systems in space

Cells for operation in space up to more than 100 suns were made, and an AMO efficiency of 21% at 100 suns with these cells was obtained. The increased efficiency resulted not only from the higher open circuit voltage associated with the higher light intensity (higher short circuit current); it also benefitted from the increase in fill factor caused by the lower relative contribution of the generation recombination current to the forward bias current when the cell's operating current density is increased. The experimental cells exhibited an AMO efficiency close to 16% at 200 C. The prospect of exploiting this capability for the continuous annealing of radiation damage or for high temperature missions (e.g., near Sun missions) remains therefore open. Space systems with concentration ratios on the order of 100 suns are presently under development. The tradeoff between increased concentration ratio and increased loss due to the cell's series resistance remains attractive even for space applications at a solar concentrator ratio of 100 suns. In the design of contact configuration with low enough series resistance for such solar concentration ratios, the shallow junction depth needed for good radiation hardness and the thin AlGaAs layer thickness needed to avoid excessive optical absorption losses have to be retained.

Loo, R. Y.↗
NASA NTRS1989

Solid-state non-volatile electronically programmable reversible variable resistance device

A solid-state variable resistance device (10) whose resistance can be repeatedly altered by a control signal over a wide range, and which will remain stable after the signal is removed, is formed on an insulated layer (14), supported on a substrate (12) and comprises a set of electrodes (16a, 16b) connected by a layer (18) of material, which changes from an insulator to a conductor upon the injection of ions, covered by a layer (22) of material with insulating properties which permit the passage of ions, overlaid by an ion donor material (20). The ion donor material is overlaid by an insulating layer (24) upon which is deposited a control gate (26) located above the contacts. In a preferred embodiment, the variable resistance material comprises WO.sub.3, the ion donor layer comprises Cr.sub.2 O.sub.3, and the layers sandwiching the ion donor layer comprise silicon monoxide. When a voltage is applied to the gate, the resistance between the electrode contacts changes, decreasing with positive voltage and increasing with negative voltage.

Ramesham, Rajeshuni↗
DOE OSTI2026

Low-cost, Highly Efficient and Fast Thermally Pressed Scalable Carbon-based Planar Perovskite Solar Cells

This Final Technical Report summarizes work completed under Award Number DEEE0009833, titled "Low-cost, Highly Efficient and Fast Thermally Pressed Scalable Carbon-based Planar Perovskite Solar Cells." The project addressed the central technical problem that carbon-electrode perovskite solar cells (C-PSCs) can reduce electrode costs and improve environmental durability, but they have historically lagged noble-metalcontact devices due to poor carbon/perovskite contact, high carbon-electrode resistance, imperfect hole extraction, and insufficient operational stability. The Statement of Project Objectives (SOPO), therefore, required systematic engineering of thermally pressed carbon-based planar perovskite solar cells by improving the carbon/perovskite interface quality, improving carbon-electrode conductivity, and further increasing device stability. The work advanced understanding of carbon-based perovskite photovoltaics by connecting device performance to three coupled mechanisms: interfacial recombination at the perovskite/hole-transport-layer/carbon stack; lateral and vertical transport losses in carbon contacts; and instability driven by moisture, heat, illumination, ion migration, and slow/variable manufacturing steps.

14 SOLAR ENERGY↗
NASA NTRS1985

Rolling-Contact Rheostat

Contact noise in rheostats and potentiometers reduced by rolling contact design. Smooth rolling action eliminates sporadic variations in resistance caused by bouncing and stick/slip motion of conventional sliding contacts.

Ruoff, C. F.↗
NASA NTRS2008

Making Superconducting Welds between Superconducting Wires

A technique for making superconducting joints between wires made of dissimilar superconducting metals has been devised. The technique is especially suitable for fabrication of superconducting circuits needed to support persistent electric currents in electromagnets in diverse cryogenic applications. Examples of such electromagnets include those in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems and in superconducting quantum interference devices (SQUIDs). Sometimes, it is desirable to fabricate different parts of a persistent-current-supporting superconducting loop from different metals. For example, a sensory coil in a SQUID might be made of Pb, a Pb/Sn alloy, or a Cu wire plated with Pb/Sn, while the connections to the sensory coil might be made via Nb or Nb/Ti wires. Conventional wire-bonding techniques, including resistance spot welding and pressed contact, are not workable because of large differences between the hardnesses and melting temperatures of the different metals. The present technique is not subject to this limitation. The present technique involves the use (1) of a cheap, miniature, easy-to-operate, capacitor-discharging welding apparatus that has an Nb or Nb/Ti tip and operates with a continuous local flow of gaseous helium and (2) preparation of a joint in a special spark-discharge welding geometry. In a typical application, a piece of Nb foil about 25 m thick is rolled to form a tube, into which is inserted a wire that one seeks to weld to the tube (see figure). The tube can be slightly crimped for mechanical stability. Then a spark weld is made by use of the aforementioned apparatus with energy and time settings chosen to melt a small section of the niobium foil. The energy setting corresponds to the setting of a voltage to which the capacitor is charged. In an experiment, the technique was used to weld an Nb foil to a copper wire coated with a Pb/Sn soft solder, which is superconducting. The joint was evaluated as part of a persistent-current circuit having an inductance of 1 mH. A current was induced in a loop, and no attenuation of the current after a time interval 1,000 s was discernible in a measurement having a fractional accuracy of 10(exp -4): This observation supports the conclusion that the weld had an electrical resistance <10(exp -10) omega.

Penanen, Konstantin I.↗
NASA NTRS1972

Development of GaAs solar cells

Solar cells and mesa diodes were fabricated by the implantation of zinc or beryllium ions into n-type gallium arsenide. Annealing temperatures above 750 C (zinc) or 650 C (beryllium) were found to produce 50% to 100% activation of the implanted ions. Junction depths of about 0.4 micron were produced by 600 keV zinc implants or 70 keV beryllium implants. P-layer sheet resistance was about 150 ohms for 2 x 10 to the 15th power cm/2 zinc or 1 x 10 to the 15th power cm/2 beryllium implants. This is sufficiently low for efficient solar cell fabrication. Contacting procedures were improved to yield reproducibly adherent, low resistance front and back contacts.

Source record↗
DOE OSTI2026

Atomic- and Molecular-Scale Interphase Engineering for High-Performance Solid-State Batteries

Solid-state batteries (SSBs) promise a decisive advance beyond conventional Li-ion systems, yet their development remains constrained by persistent solid–solid interfacial instabilities that degrade performance and durability. Interfaces between solid electrolytes and both cathodes and Li metal often exhibit poor wettability, limited physical contact, and high charge–transfer resistance, leading to chemical decomposition, mechanical failure, and impedance growth. Overcoming these limitations requires interphase engineering with atomic-scale precision—capabilities that conventional coating methods cannot reliably deliver. Atomic layer deposition (ALD) and molecular layer deposition (MLD) uniquely meet this need by enabling ultrathin, conformal, and composition-tunable films that stabilize reactive surfaces, suppress parasitic reactions, and regulate Li-metal morphology. Importantly, this Perspective highlights ALD/MLD systems that have already demonstrated effectiveness in liquid-electrolyte cells and discusses how these validated strategies can be deliberately translated to solid-state architectures. By grounding future directions in experimentally proven concepts rather than speculative hypotheses, we outline how atomic- and molecular-scale design principles can accelerate the development of robust, high-performance SSB technologies.

atomic and molecular layer deposition↗
DOE OSTI2025

Integration of hydrophobic gas diffusion layers for zero-gap electrolyzers to enable highly energy-efficient CO 2 electrolysis to C 2 products

Electrochemical CO 2 reduction (eCO2R) is an attractive route for mitigating global CO 2 emissions while producing value-added chemicals. Ethylene is one product of eCO2R and is an essential industrial precursor with a global market of $230 billion. The large-scale implementation of C 2 H 4 -selective CO 2 electrolyzers remains challenging because of low energy efficiencies. In this work, we develop the design principles necessary for incorporating an expanded polytetrafluoroethylene (ePTFE) electrode into a zero-gap electrolyzer while simultaneously developing an integrated electrical front contact that reduces the ohmic resistances inherent to electrically insulating gas diffusion layers. By co-designing the catalyst layer, gas diffusion medium, and operating conditions for a zero-gap ePTFE gas diffusion electrode (GDE), we achieved a full-cell voltage of 2.5 V at 200 mA cm −2 at 25 cm 2 geometric area cell with Faradaic efficiencies of 48% for ethylene and 40% for ethanol. This work highlights strategies for developing a scalable, stable, and highly energy-efficient eCO2R for C 2 products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Influence of electronic transport on electrochemical performance of (Cu,Mn) 3 O 4 solid oxide fuel cell cathodes

Alkaline Earth free spinel oxides provide a potential benefit over Sr-doped perovskite-based materials commonly used as electrodes in high-temperature electrochemical energy conversion devices, e.g., solid oxide fuel cells (SOFCs). Sr-segregation is a known issue leading to performance degradation. In this study, Cu x Mn 3-x O 4 (x = 1, 1.2, and 1.5) porous electrodes were examined as SOFC cathodes using electrochemical impedance spectroscopy to investigate the oxygen reduction reaction (ORR) kinetics in relation to the material's intrinsic conductivity, the extrinsic electrode structure, and the cell test design. Similar to the electronic conducting (La,Sr)MnO 3 SOFC cathodes, the ORR kinetics of Cu x Mn 3-x O 4 spinel electrodes was governed by the oxygen adsorption and diffusion at the particle surface as well as the charge transfer at the triple phase boundaries. The overall electrode polarization resistance was highly dependent on contact density with the metallic current collector, active material particle connectivity, electrode thickness, and the intrinsic electronic materials conductivity. Here, we describe the importance of effective electronic charge transport parallel to the electrode surface in maximizing the electrochemically active electrode volume and enhancing electrode performance. We discuss an approach to optimize cell and electrode design with respect to active materials properties. This aspect is critical to ensure reliable evaluation of new materials, since laboratory-scale button-cells typically exhibit a high degree of electrode microstructure (e.g. porosity, thickness) and electrical contact density variation from sample to sample.

(Cu,Mn)3O4↗
DOE OSTI2023

Electron Spin Polarization and Rectification Driven by Chiral Perylene Diimide-Based Nanodonuts

The chirality-induced spin selectivity (CISS) effect allows thin-film layers of chiral conjugated molecules to function as spin filters at ambient temperature. Through solvent-modulated dropcasting of chiral l- and d-perylene diimide (PDI) monomeric building blocks, two types of aggregate morphologies, nanofibers and nanodonuts, may be realized. Spin-diode behavior is evidenced in the nanodonut structures. Stacked PDI units, which form the conjugated core of these nanostructures, dominate the nanodonut–Au electrode contact; in contrast, the AFM tip contacts largely the high-resistance solubilizing alkyl chains of the chiral monomers that form these nanodonuts. Current–voltage responses of the nanodonuts, measured by magnetic conductive AFM (mC-AFM), demonstrate substantial spin polarizations as well as spin current rectification ratios (>10) that exceed the magnitudes of those determined to date for other chiral nanoscale systems. Furthermore, these results underscore the potential for chiral nanostructures, featuring asymmetric molecular junctions, to enable CISS-based nanoscale spin current rectifiers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Near-Busbar Degradation of Screen-Printed Metallization in Silicon Photovoltaic Modules

We study photovoltaic (PV) module degradation after extended accelerated stress testing including 2000 hours of damp heat followed by a current-injection procedure meant to stabilize defects linked to light-induced degradation. In addition to de-stabilization/recovery of light-induced defects, we observe severe series resistance due to loss of contact between the Si cell and near-busbar screen-printed metallization (i.e. grid finger delamination). Using scanning electron microscopy and energy dispersive x-ray spectroscopy on cell fragments cored from the module, we show poor contact is caused by a gap between the screen-printed Ag metallization and Si due to missing glass frit.

degradation↗
DOE OSTI2020

VTO FY20Q4 quarterly report

Project Objective.This project has three objectives: (1) tuning microstructures of 3D-printed SSE separators,(2) determining material and processing compatibilities with cathode printing,and (3)3D printing of sintering-free SSE separators.Project Impact.All-solid-state lithium batteries are difficult to process due to the brittleness of ceramic materials, poor solid-solid contact, and electrolyte-electrode stability issues. As a result, the energy and power density and also cycling stability are far from satisfying. This project will address fabrication difficulties by using state-of-the-art 3D-printing techniques that can introduce 3D interfaces and architectures to enhance solid-solid contact and reduce charge transfer resistance. Success will benefit the DOE by establishing the best manufacturing methods for ASSBsto achieve VTO goals on the performance of beyond Li-ion batteries. Approach.The project employs 3D-printing techniques to manufacture SSEs and related components for ASSBs. The team starts with direct ink writing (DIW) to develop ink recipes with desired rheological properties and explore post-sintering approaches to achieve high densification. In parallel with DIW3D printing, the team also explores other 3D printing options, such as projection microstereolithography (PuSL). Both sintering and sintering-free approaches can gain benefit from 3D printing and therefore will be investigated.Out-Year Goals.The team will determine particle sizes and morphologies as well as post-processing conditions that deliver good ionic conductivity and charge transfer properties of LLZTO separators. They will examine co-sintering of LLZTO/cathode and determine the effects of material, particle size, surface coating, and sintering conditions.Collaborations.Microstructures, ionic conductivities, and mechanical properties will be provided to the LLNL simulation team, led by PI B. Wood, for establishing and validating phase-field modeling methods.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Silicon Ingot Casting - Heat Exchanger Method (HEM). Multi-Wire Slicing - Fixed Abrasive Slicing Technique (Fast). Phase 4 Silicon Sheet Growth Development for the Large Area Sheet Task of the Low-Cost Solar Array Project

The crystallinity of large HEM silicon ingots as a function of heat flow conditions is investigated. A balanced heat flow at the bottom of the ingot restricts spurious nucleation to the edge of the melted-back seed in contact with the crucible. Homogeneous resistivity distribution over all the ingot has been achieved. The positioning of diamonds electroplated on wirepacks used to slice silicon crystals is considered. The electroplating of diamonds on only the cutting edge is described and the improved slicing performance of these wires evaluated. An economic analysis of value added costs of HEM ingot casting and band saw sectioning indicates the projected add on cost of HEM is well below the 1986 allocation.

Schmid, F.↗
NASA NTRS1982

Studies of single-mode injection lasers and of quaternary materials. Volume 1: Single-mode constricted double-heterojunction AlGaAs diode lasers

Constricted double-heterojunction (CDH) lasers are presented as the class of single-mode nonplanar-substrate devices for which the lasing cavity is on the least resistive electrical path between the contact and the substrate. Various types of CDH structures are considered under three general topics: liquid-phase epitaxy over channeled substrates, lateral mode control, and current control in nonplanar-substrate devices. Ridge-guide CDH lasers have positive-index lateral-mode confinement and provide: single-mode CW operation to 7 mW/facet at room temperature and to 3 mW/facet at 150 C; light-current characteristics with second-harmonic distortion as low as -57 dB below the fundamental level; threshold-current temperature coefficients, as high as 375 C (pulsed) and 310 C (CW); constant external differential quantum efficiency to 100 C; and lasing operation to 170 C CW and 280 C pulsed. Semileakyguide CDH lasers have an asymmetric leaky cavity for lateral-mode confinement and provide single-mode operation to 15 to 20 mW/facet CW and to 50 mW/facet at 50% duty cycle. Modulation characteristics and preliminary reliability data are discussed.

Botez, D.↗