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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mechanical Solutions Scan Report

Power lines, poles, and towers are the backbone of the United States (U.S.) electric-power grid. These transmission and distribution networks route electricity from generator to loads. The characteristics of these routes are rapidly changing -- trending towards decentralized renewable generation, electric heating, vehicle charging, and large data-center loads. Coupled with aging infrastructure and the increased frequency of extreme weather events, there is concern about the future reliability and transmission capacity of conductors and adjacent components. This scan report seeks to provide an overview of mechanical solutions to challenges caused by extreme weather events associated with components of transmission and distribution infrastructure, including conductor heat sag, ice accumulation, wind, and wildfire. Many options could increase transmission capacity or reliability, and these are at various stages of technological readiness. Some have only been lab tested, while some have been widely deployed in the U.S. or overseas for decades. The solution categories and providers featured in this report are intended to be comprehensive at the time of publication and to serve as a reference for decision-makers concerned about transmission and distribution reliability. There are two other categories of large, complex solutions, which are not covered in this report: replacing existing conductors with advanced conductors and implementing digital grid enhancing technologies. A separate scan report titled “Advanced Conductor Scan Report,” which discusses advanced carbon-core conductors, was published by the Idaho National Laboratory (INL) in 2023. Information on digital technologies, such as dynamic line ratings, power-flow controllers, and other power electronics and communications-based devices, can be found on the Grid- Enhancing Technologies landing page. Mechanical grid-enhancing technologies, or solutions covered in this report, often do not require full equipment replacement and do not rely on digital components. Mechanical technologies are overlooked because they may be older, simpler, or seemingly “more obvious” than digital or carbon-core technologies. However, it is wise to consider mechanical solutions in a thorough evaluation of grid enhancing technology solutions.

24 - POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Hard x-ray scanning imaging achieved with bonded multilayer Laue lenses

Here, we report scanning hard x-ray imaging with a monolithic focusing optic consisting of two multilayer Laue lenses (MLLs) bonded together. With optics pre-characterization and accurate control of the bonding process, we show that a common focal plane for both MLLs can be realized at 9.317 keV. Using bonded MLLs, we obtained a scanning transmission image of a star test pattern with a resolution of 50 × 50 nm 2 . By applying a ptychography algorithm, we obtained a probe size of 17 × 38 nm 2 and an object image with a resolution of 13 × 13 nm 2 . Finally, the significant reduction in alignment complexity for bonded MLLs will greatly extend the application range in both scanning and full-field x-ray microscopies.

36 MATERIALS SCIENCE↗
DOE OSTI2018

VULCON: A System for Vulnerability Prioritization, Mitigation, and Management

Vulnerability remediation is a critical task in operational software and network security management. In this paper, an effective vulnerability management strategy, called VULCON (VULnerability CONtrol), is developed and evaluated. The strategy is based on two fundamental performance metrics: i). Time-to-Vulnerability Remediation (TVR) and; ii). Total Vulnerability Exposure (TVE). VULCON takes as input real vulnerability scan reports, metadata about the discovered vulnerabilities, asset criticality, and personnel resources. VULCON uses a mixed integer multi-objective optimization algorithm to prioritize vulnerabilities for patching, such that the above performance metrics are optimized subject to the given resource constraints. VULCON has been tested on multiple months of real scan data from a Cyber-Security Operations Center (CSOC). Results indicate an overall Total Vulnerability Exposure reduction of 8.97\% when VULCON optimizes a realistic security analyst workforce's effort. Additionally, it is demonstrated that VULCON can determine monthly resources required to maintain a target TVE score. As such, VULCON provides valuable operational guidance for improving vulnerability response processes in CSOCs.

Farris, Katheryn A.↗
DOE OSTI2024

Coexistence of antiferrodistortive and polar order in a superconducting SrTi⁢O 3 film

Strontium titanate (SrTiO 3 ) can exhibit multiple orders, including superconductivity, an antiferrodistortive instability and ferroelectricity. The cooperation or competition between these orders in samples that undergo all three transitions is of great fundamental interest. Here we report scanning transmission electron microscopy imaging of the antiferrodistortive and ferroelectric structural distortions in a compressively strained SrTiO 3 film that was previously shown to become superconducting at ~ 410 mK. The experiments are complemented by first-principles simulations. Unlike the polar ferroelectric phase, which is suppressed by dopants, the antiferrodistortive order is insensitive to the presence of the free carriers. The single domain nature of the antiferrodistortive phase excludes any role of antiferrodistortive domain walls in the superconductivity. Furthermore, a previously reported low temperature resistance anomaly is associated with the ferroelectric transition, not the antiferrodistortive transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Nanoscale Observation and Control of Quasiparticle Induced Magnetic Noise in a Superconducting Resonator

Superconducting circuits are arguably taking a leading role in driving the ongoing quantum technological revolution. A detailed knowledge of the microscopic fluctuating electromagnetic properties plays an important role in advancing the circuitry design, testing, and material integration of cutting-edge superconducting quantum electronics. Here, in this work, we report scanning nitrogen-vacancy (NV) quantum sensing of local magnetic noise environment of an on-chip superconducting resonator. We find that quasiparticle-induced fluctuating magnetic fields can drive NV spin relaxation, which shows a peak value around the superconducting transition point of niobium at the thermal equilibrium state. External microwave driving at the resonator mode frequency significantly increases the quasiparticle density, leading to enhancement of magnetic noise. We further perform optically detected magnetic resonance measurements to demonstrate quasiparticle magnetic noise mediated off-resonant dipole coupling between the NV center and niobium resonator. Our Letter reports experimental observation of the Hebel-Slichter peak signature by an external sensor outside of a superconductor. The presented study also highlights the advantages of quantum sensors in investigating miniaturized superconducting devices, providing insights into their future performance improvements.

Li, Senlei [Georgia Institute of Technology]↗
DOE OSTI2022

Structural and optical properties of cubic GaN on U-grooved Si (100)

Cubic GaN epitaxy on large-area U-grooved silicon (100) dies is demonstrated by metalorganic chemical vapor deposition, and its structural and optical properties are reported. Scanning electron, atomic force, and transmission electron microscopy studies reveal that cubic GaN shows no discernible threading dislocations and a low stacking fault density of 3.27 ± 0.18 × 10 4 cm –1 . Temperature-dependent photoluminescence studies reveal as-grown cubic GaN band edge emission internal quantum efficiency as 25.6% ± 0.9%. Selective etching of the low-temperature AlN buffer layer, SiO 2 sidewalls, and hexagonal-phase GaN is demonstrated, which increases the cubic GaN band edge emission internal quantum efficiency to 31.6% ± 0.8%. This increase is attributed to the decrease in the radiative recombination lifetime via the removal of defective hexagonal-phase GaN. Altogether, cubic GaN on U-grooved silicon with high structural and optical quality is reported, promising its suitability for next-generation devices.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Heterostructures through Divergent Edge Reconstruction in Nitrogen-Doped Segmented Graphene Nanoribbons

Atomically precise engineering of defined segments within individual graphene nanoribbons (GNRs) represents a key enabling technology for the development of advanced functional device architectures. In this paper, the bottom-up synthesis of chevron GNRs decorated with reactive functional groups derived from 9-methyl-9H-carbazole is reported. Scanning tunneling and non-contact atomic force microscopy reveal that a thermal activation of GNRs induces the rearrangement of the electron-rich carbazole into an electron-deficient phenanthridine. Finally, the selective chemical edge-reconstruction of carbazole-substituted chevron GNRs represents a practical strategy for the controlled fabrication of spatially defined GNR heterostructures from a single molecular precursor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Triphenylene‐Derived Electron Acceptors and Donors on Ag(111): Formation of Intermolecular Charge‐Transfer Complexes with Common Unoccupied Molecular States

Abstract Over the past years, ultrathin films consisting of electron donating and accepting molecules have attracted increasing attention due to their potential usage in optoelectronic devices. Key parameters for understanding and tuning their performance are intermolecular and molecule–substrate interactions. Here, the formation of a monolayer thick blend of triphenylene‐based organic donor and acceptor molecules from 2,3,6,7,10,11‐hexamethoxytriphenylene (HAT) and 1,4,5,8,9,12‐hexaazatriphenylenehexacarbonitrile (HATCN), respectively, on a silver (111) surface is reported. Scanning tunneling microscopy and spectroscopy, valence and core level photoelectron spectroscopy, as well as low‐energy electron diffraction measurements are used, complemented by density functional theory calculations, to investigate both the electronic and structural properties of the homomolecular as well as the intermixed layers. The donor molecules are weakly interacting with the Ag(111) surface, while the acceptor molecules show a strong interaction with the substrate leading to charge transfer and substantial buckling of the top silver layer and of the adsorbates. Upon mixing acceptor and donor molecules, strong hybridization occurs between the two different molecules leading to the emergence of a common unoccupied molecular orbital located at both the donor and acceptor molecules. The donor acceptor blend studied here is, therefore, a compelling candidate for organic electronics based on self‐assembled charge‐transfer complexes.

Müller, Kathrin↗
DOE OSTI2016

Effect of solvent/polymer infiltration and irradiation on microstructure and tensile properties of carbon nanotube yarns

Recently carbon nanotube (CNT) yarns have been gaining importance as an approach to harvest the excellent properties of the CNTs. However, the properties of CNT yarns at this stage are well below the expected value. Investigation of the structure of CNT yarns and possible approaches to enhance the strength and modulus are reported. Scanning electron microscopy and focused ion beam imaging reveal the inherently porous structure and poor orientation, emphasizing the need to enhance packing of CNT bundles in the yarns for increased strength and modulus. Densification of CNT yarn by toluene or polystyrene increases the strength by 140 or 172 % and modulus by 79 or 218 %, respectively, as compared to that of the pristine yarn. E-beam irradiation was investigated as a means to introduce crosslinking and enhanced internanotubes bonding to increase strength and modulus. However, the irradiation resulted in generation of defects and damages to the yarn contributing to reduction in strength and modulus. Raman spectroscopy studies on the irradiated samples reveal the change in bonding characteristics resulting in poor mechanical properties. As a result, denser packing of nanotubes and increased interaction without any damage is the key to improve the properties of CNT yarns.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Property-structure-process relationships in dissimilar material repair with directed energy deposition: Repairing gray cast iron using stainless steel 316L

Directed energy deposition (DED) based remanufacturing leverages the flexibility of additive manufacturing to add value to broken or worn components. DED offers the ability to repair cast iron, a material difficult to repair with traditional welding techniques. Despite this, development of appropriate DED process conditions for bimetallic cast iron structures lags low- and medium-carbon steel repair. Thermal stresses and porosity generated by high-temperature deposition on cast iron often lower mechanical properties and hinder the qualification process. In this report scanning speed, powder mass flow rate, and stepover width are studied in multiple-track structures deposited on gray cast iron. Dilution and residual stresses are found to be highly dependent on the selected process parameters. Samples with a higher volumetric energy input, e.g., slower scanning speeds and higher powder feed rates, showed improved density and lower residual stresses but suffered lower dilution into the substrate. The presented conditions further the development of additive manufacturing technologies for automotive repair.

42 ENGINEERING↗
DOE OSTI2017

Growth of Pd Nanoclusters on Single-Layer Graphene on Cu(111)

We report scanning tunneling microscopy results on the nucleation and growth of Pd nanoclusters on a single layer of graphene on the Cu(111) surface. The shape, organization, and structural evolution of the Pd nanoclusters were investigated using two different growth methods, continuous and stepwise. The size and shape of the formed nanoclusters were found to greatly depend on the growth technique used. The size and density of spherical Pd nanoclusters increased with increasing coverage during stepwise deposition as a result of coarsening of existing clusters and continued nucleation of new clusters. In contrast, continuous deposition gave rise to well-defined triangular Pd clusters as a result of anisotropic growth on the graphene surface. Exposure to ethylene caused a decrease in the size of the Pd clusters. As a result, this is attributed to the exothermic formation of ethylidyne on the cluster surfaces and an accompanying weakening of the Pd–Pd bonding.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Visualizing discrete Fermi surfaces and possible nodal-line to Weyl state evolution in ZrSiTe

Topological nodal line semimetals (TNLSMs) represent a quantum state of topological matter. When the crystal/time-reversal symmetry is broken, a nodal line state is expected to evolve into a Dirac semimetal, a Weyl semimetal, or other topological phases according to theoretical studies. Here, we report scanning tunneling microscopy (STM) based quasiparticle interference (QPI) measurements performed on the surface of TNLSM ZrSiTe single crystal. A discrete Fermi surface with multiple electron/hole pockets and the impurity-induced inter-/intra- pockets scatterings are directly visualized from QPI patterns. Moreover, the degenerated Dirac points at X point evolve into the pairs of Weyl nodes when Fe atoms are deposited, suggesting a possible phase transition from the nodal line to the Weyl state. The calculated band structures and the Weyl points by applying Zeeman splitting energies along x-direction, further confirm the existence of Weyl points in the Fe-doped ZrSiTe induced by the broken of time-reversal symmetry.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Preliminary study of CdTe and CdTe:Cu thin films nanostructures deposited by using DC magnetron sputtering

Growth and properties of CdTe and CdTe:Cu thin films nanostrucures deposited by using dc magnetron sputtering are reported. Scanning electron microscope (SEM) was used to observe the surface morphologies of the thin films. At growth conditions of 250 °C and 14 W, CdTe films did not yet evenly deposited. However, at growth temperature and plasma power of 325 °C and 43 W, both CdTe and CdTe:Cu(2%) have deposited on the substrates. In this condition, the morphology of the films indicate that the films have a grain-like nanostructures. Grain size diameter of about 200 nm begin to appear on top of the films. Energy Dispersive X-rays spectroscopy (EDX) was used to investigate chemical elements of the Cu doped CdTe film deposited. It was found that the film deposited consist of Cd, Te and Cu elements. XRD was used to investigate the full width at half maximum (FWHM) values of the thin films deposited. The results show that CdTe:Cu(2%) thin film has better crystallographic properties than CdTe thin film. The UV-Vis spectrometer was used to investigate the optical properties of thin films deposited. The transmittance spectra showed that transmittance of CdTe:Cu(2%) film is lower than CdTe film. It was found that the bandgap energy of CdTe and CdTe:Cu(2%) thin films of about 1.48 eV.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Growth and structural studies of In/Au(111) alloys and InO x /Au(111) inverse oxide/metal model catalysts

Indium oxide has received attention as an exciting candidate for catalyzing the CO 2 hydrogenation to methanol due to its high selectivity (>80%). Compared to the extent of research on the activity of indium oxide-based powder catalysts, very little is known about the phenomena associated with the formation of surface alloys involving indium or the growth mechanism for indium oxide nanoparticles. In this report, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) were employed to elucidate the growth mode, structure, and chemical state of In/Au(111) alloys and InO x /Au(111) inverse model catalysts. Here, our study reveals distinct morphological differences between In/Au(111) and InO x /Au(111), and the InO x structure also depends strongly on the preparation conditions. In/Au surface alloy systems with extremely low coverage (0.02 ML) form islands preferentially on the elbow sites of reconstructed Au(111) herringbone, regardless of hcp and fcc stacking. At higher coverage (0.1 ML), the In islands expand over the herringbone in the <110> direction and create two dimensional domain structures over the entire surfaces. Moreover, this 2D domain structure is disturbed by temperature with high dispersion of indium atoms observed during the annealing process. Oxidation of the In/Au(111) surface alloys with O 2 at 550 K produces InO x /Au(111) systems which contain various sizes of InO x aggregates (from 0.7 to 10 nm). On the other hand, InO x /Au(111) surfaces prepared by vapor deposition of In at 550 K in an O 2 background exhibit highly dispersed and uniformly small InO x particles (~1 nm). Both InO x systems were confirmed to be partially oxidized by XPS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗