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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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193 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Magnetoelectric Composites: Applications, Coupling Mechanisms, and Future Directions

Multiferroic (MF)-magnetoelectric (ME) composites, which integrate magnetic and ferroelectric materials, exhibit a higher operational temperature (above room temperature) and superior (several orders of magnitude) ME coupling when compared to single-phase multiferroic materials. Room temperature control and the switching of magnetic properties via an electric field and electrical properties by a magnetic field has motivated research towards the goal of realizing ultralow power and multifunctional nano (micro) electronic devices. Here, some of the leading applications for magnetoelectric composites are reviewed, and the mechanisms and nature of ME coupling in artificial composite systems are discussed. Ways to enhance the ME coupling and other physical properties are also demonstrated. Finally, emphasis is given to the important open questions and future directions in this field, where new breakthroughs could have a significant impact in transforming scientific discoveries to practical device applications, which can be well-controlled both magnetically and electrically.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Combinatorial Cu-Ni Alloy Thin-Film Catalysts for Layer Number Control in Chemical Vapor-Deposited Graphene

We synthesized a combinatorial library of CuxNi1−x alloy thin films via co-sputtering from Cu and Ni targets to catalyze graphene chemical vapor deposition. The alloy morphology, composition, and microstructure were characterized via scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD), respectively. Subsequently, the CuxNi1−x alloy thin films were used to grow graphene in a CH4-Ar-H2 ambient at atmospheric pressure. The underlying rationale is to adjust the CuxNi1−x composition to control the graphene. Energy dispersive x-ray spectroscopy (EDS) analysis revealed that a continuous gradient of CuxNi1−x (25 at. % < x < 83 at.%) was initially achieved across the 100 mm diameter substrate (~0.9%/mm composition gradient). The XRD spectra confirmed a solid solution was realized and the face-centered cubic lattice parameter varied from ~3.52 to 3.58 A˙, consistent with the measured composition gradient, assuming Vegard’s law. Optical microscopy and Raman analysis of the graphene layers suggest single layer growth occurs with x > 69 at.%, bilayer growth dominates from 48 at.% < x < 69 at.%, and multilayer (≥3) growth occurs for x < 48 at.%, where x is the Cu concentration. Finally, a large area of bi-layer graphene was grown via a CuxNi1−x catalyst with optimized catalyst composition and growth temperature.

2D materials↗
DOE OSTI2023

Selected Area Deposition of High Purity Gold for Functional 3D Architectures

Selected area deposition of high purity gold films onto nanoscale 3D architectures is highly desirable as gold is conductive, inert, plasmonically active, and can be functionalized with thiol chemistries, which are useful in many biological applications. Here, we show that high-purity gold coatings can be selectively grown with the Me 2 Au (acac) precursor onto nanoscale 3D architectures via a pulsed laser pyrolytic chemical vapor deposition process. The selected area of deposition is achieved due to the high thermal resistance of the nanoscale geometries. Focused electron beam induced deposits (FEBID) and carbon nanofibers are functionalized with gold coatings, and we demonstrate the effects that laser irradiance, pulse width, and precursor pressure have on the growth rate. Furthermore, we demonstrate selected area deposition with a feature-targeting resolutions of ~100 and 5 µm, using diode lasers coupled to a multimode (915 nm) and single mode (785 nm) fiber optic, respectively. The experimental results are rationalized via finite element thermal modeling.

3-dimensional nanostructures↗
DOE OSTI2025

Electrical Behavior of Combinatorial Thin-Film Zr x Ta 1−x O y

Combinatorial magnetron sputtering and electrical characterization were used to systematically study the impact of compositional changes in the resistive switching of transition metal oxides, specifically the Zr x Ta 1−x O y system. Current-voltage behavior across a range of temperatures provided insights into the mechanisms that contribute to differences in the electrical conductivity of the pristine Ta 2 O 5 and ZrO 2 , and mixed Zr x Ta 1−x O y devices. The underlying conductive mechanism was found to be a mixture of charge trapping and ionic motion, where charge trapping/emission dictated the short-term cycling behavior while ion motion contributed to changes in the conduction with increased cycling number. ToF-SIMS was used to identify the origin of the “wake-up” behavior of the devices, revealing an ionic motion contribution. This understanding of how cation concentration affects conduction in mixed valence systems helps provide a foundation for a new approach toward manipulating resistive switching in these active layer materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Reactive Oxygen Ion Beam-Induced Deposition for Concurrent Purification of Platinum Nanostructures

Oxygen-focused ion beam induced deposition (O-FIBID) enables the direct-write fabrication of Pt nanostructures while simultaneously enhancing purity concurrently through reactive oxygen–deposit interactions. By systematically varying the dwell time, accelerating voltage, and precursor pressure, the Pt content and conductivity can be controlled. Under optimum conditions, the Pt content reached 63 at.%. Across the dwell-time range used for resistivity measurements, the Pt content increased from 20 to 33 at.%, while the resistivity decreased from 2.9 × 10 4 μΩ·cm to 1.2 × 10 3 μΩ·cm, which is consistent with enhanced percolation through Pt grains and the lower intrinsic resistivity of the purer Pt deposit. The simulation results support a purification mechanism driven by the beam-induced activation of implanted oxygen balanced against the preferential sputtering of Pt. These results demonstrate O-FIBID as a viable method for the nanoscale direct write of conductive Pt without post-processing, and some deviations from conventional FIBID wisdom are observed. These results serve as a foundation for exploring nascent, reactive focused ion beam-induced deposition processes.

deposit purification↗
DOE OSTI2020

PV Storm Hardening Costs

While solar arrays often survive severe weather events, systems are occasionally compromised and left unable to provide power. For PV systems to act as resilient power providers, they must remain operational. Building a system that is more likely to survive a storm comes at a cost, though. Previous efforts have identified various system measures and practices that can increase the likelihood of a PV system surviving a severe weather event. But what is the cost premium for a storm hardened PV system? This report provides initial estimates for the up-front cost premiums for various methods of storm hardening PV systems.

14 SOLAR ENERGY↗
DOE OSTI2020

PV High Wind User Test Facility

The creation of a PV high wind test facility at the NREL Flatirons Campus that will enable private and public research efforts aimed at storm hardening PV systems. The facility will be instrumented to monitor effects of high wind conditions on modules and other array components. These in-field tests will coordinate with flow models, wind tunnel testing, validation of PV aeroelastic design codes, and post-testing module and system component analysis.

14 SOLAR ENERGY↗
DOE OSTI2020

Helium Ion Microscopy

Nanotechnology research led to the development of various instruments to be used for imaging or fabrication. The helium ion microscope (HIM) became available in 2006 but quickly gained popularity. Its unique gas field ion source enables high-resolution imaging, nanofabrication, direct write, and the recent combination with a secondary ion mass spectrometer offers chemical imaging with ~15 nm resolution. Particularly attractive are the small interaction volume of He and Ne (the two gases offered), small beam spot size, and a moderate sputtering rate. Additionally, the HIM is an excellent imaging tool for insulating samples in soft, polymeric, and biological materials. It can be expected that helium ion microscopy will continue to have a strong influence on broad range of scientific disciplines, including chemistry, materials science, and biology.This chapter aims at providing an overview of the current status of HIM for imaging, analysis, and nanofabrication. It introduces the reader to key components of the instrument, theoretical background, and latest results in the areas of imaging, material fabrication, and chemical analysis capabilities of helium ion microscopy.

Belianinov, Alex↗