Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “wire”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

EPR of Photoexcited Triplet-State Acceptor Porphyrins

The photoexcited triplet states of porphyrin architectures are of significant interest in a wide range of fields including molecular wires, nonlinear optics, and molecular spintronics. Electron paramagnetic resonance (EPR) is a key spectroscopic tool in the characterization of these transient paramagnetic states singularly well suited to quantify spin delocalization. Previous work proposed a means of extracting the absolute signs of the zero-field splitting (ZFS) parameters, D and E, and triplet sublevel populations by transient continuous wave, hyperfine measurements, and magnetophotoselection. Here, we present challenges of this methodology for a series of mesoperfluoroalkyl-substituted zinc porphyrin monomers with orthorhombic symmetries, where interpretation of experimental data must proceed with caution and the validity of the assumptions used in the analysis must be scrutinized. The EPR data are discussed alongside quantum chemical calculations, employing both DFT and CASSCF methodologies. Despite some success of the latter in quantifying the magnitude of the ZFS interaction, the results clearly provide motivation to develop improved methods for ZFS calculations of highly delocalized organic triplet states.

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

Mechanism of Stoichiometrically Governed Titanium Oxide Brownian Tree Formation on Stepped Au(111)

Previously observed formation of substoichiometric titanium oxide dendritic structures across terraces of Au(111) is computationally studied and shown to follow the classical fractal formation mechanism of diffusion-limited aggregation (DLA). Globally optimized gas-phase oxide cluster structures are sampled in a variety of landing formations on gold surfaces and shown to favor isomers driving polymerization to Brownian tree fractal structures. Mobility of Ti 3 O 5 monomers is shown to be extremely high, with diffusion barriers of 0.21 eV or less. Through bonding stabilization, polymerization of these monomers is energetically favorable and irreversible on the 111 terrace but geometrically impossible to propagate along the step edge. Simulated scanning tunneling microscopy (STM) images show strong similarity to experiment. By contrast, observation of Ti 3 O 6 aggregating as wires along step edges is explained by the affinity of oxygen to step edges and statistical arguments for aggregation entropy at the step, in addition to low barriers for monomer diffusion and polymerization.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Targeted Writing and Deleting of Magnetic Skyrmions in Two-Terminal Nanowire Devices

Controllable writing and deleting of nanoscale magnetic skyrmions are key requirements for their use as information carriers for next-generation memory and computing technologies. While several schemes have been proposed, they require complex fabrication techniques or precisely tailored electrical inputs, which limits their long-term scalability. In this work, we demonstrate an alternative approach for writing and deleting skyrmions using conventional electrical pulses within a simple, two-terminal wire geometry. X-ray microscopy experiments and micromagnetic simulations establish the observed skyrmion creation and annihilation as arising from Joule heating and Oersted field effects of the current pulses, respectively. The unique characteristics of these writing and deleting schemes, such as spatial and temporal selectivity, together with the simplicity of the two-terminal device architecture, provide a flexible and scalable route to the viable applications of skyrmions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Spin Transport in Ferromagnet-InSb Nanowire Quantum Devices

Signatures of Majorana zero modes (MZMs), which are the building blocks for fault-tolerant topological quantum computing, have been observed in semiconductor nanowires (NW) with strong spin-orbital-interaction (SOI), such as InSb and InAs NWs with proximity-induced superconductivity. Realizing topological superconductivity and MZMs in this most widely-studied platform also requires eliminating spin degeneracy, which is realized by applying a magnetic field to induce a helical gap. Yet, the applied field can adversely impact the induced superconducting state in the NWs and also places geometric restrictions on the device, which can affect scaling of future MZM-based quantum registers. These challenges could be circumvented by integrating magnetic elements with the NWs. With this motivation, in this work we report the first experimental investigation of spin transport across InSb NWs, which are enabled by devices with ferromagnetic (FM) contacts. We determine signatures of spin polarization and spin-dependent transport in the quasi-one-dimensional ballistic regime. Moreover, we show that electrostatic gating tunes the observed magnetic signal and also reveals a transport regime where the device acts as a spin filter. These results open an avenue towards developing MZM devices in which spin degeneracy is lifted locally, without the need of an applied magnetic field. They further provide a path for realizing spin-based devices that leverage spin-orbital states in quantum wires.

1D ballistic spin transport↗
DOE OSTI2020

In Situ Structural and Electrical Conductivity Characterization of Sr2MMoO6-δ Double Perovskite Solid Oxide Fuel Cell Anode Materials

In this study, a series of Sr 2 MMoO 6-δ double perovskite solid oxide fuel cell (SOFC) anode materials (where 0 <= δ <= 0.041 and M = Fe, Co, or Ni) were synthesized, and the changes in their morphologies under relevant SOFC operating conditions were explored. Ultra-small-angle X-ray scattering (USAXS), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS) were used to determine changes in the microstructures and phase compositions of the anode materials at high temperatures and under a reducing atmosphere. The stability of the double perovskite structure was found to be highly dependent on the identity of the cation M, such that when M = Fe, the material remained stable over the course of the experiments. However, when M = Co or Ni, significant changes in the microstructure and phase composition were observed. An in situ study of the M = Co sample, in which electrical conductivity and USAXS/SAXS/WAXS measurements were conducted simultaneously, revealed the structural degradation mechanisms and electrical conductivity changes over a range of temperatures. To conduct these measurements, a cell was developed that allowed for a sample mounted on Pt wires to be placed in the X-ray beam and heated under gas flow comprising 4% mass H 2 and 96% mass N 2 . The resulting measurements allowed for the direct comparison of the electrical and morphological changes occurring in the material under operating conditions, such that increases in conductivity could be attributed to the growth of new phases.

25 ENERGY STORAGE↗
DOE OSTI2025

Unraveling Impurity-Dependent Morphological and Chemical Evolution of Ni–20Cr Alloy in Eutectic LiCl–KCl Molten Salt

Understanding the interfacial evolution of alloys in molten salt with different amounts of water (H 2 O) and oxygen (O 2 ) impurities is significant for applications in many fields, including concentrated solar power, molten salt reactors, and applications in pyrochemical reprocessing and electrorefining. Additionally, the impurity-driven corrosion mechanisms that lead to various morphological and chemical evolution characteristics at the interfaces of structural alloys and molten salts are not fully understood. In the present work, the three-dimensional (3D) morphological evolution of Ni-20Cr microwires in LiCl-KCl was studied at 500 °C under different moisture and oxygen conditions using in situ synchrotron transmission X-ray microscopy (TXM) and scanning transmission electron microscopy (STEM) techniques. No significant morphological changes were observed in Ni-20Cr microwires under vacuum conditions. However, the wires exhibited distinct morphological evolutions when exposed to molten salt containing H 2 O alone, as well as when both H 2 O and O 2 were present. Furthermore, Cr 2 O 3 precipitates were observed in the molten salt during corrosion with only H 2 O present, while Cr 6+ species were identified in the salt when O 2 was added. Further, these findings are crucial for understanding the corrosion mechanisms of molten salt with different amounts of H 2 O and O 2 contamination, providing insights for developing corrosion mitigation methods and improving the stability of containment alloys in molten salt applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

AC Magnetometry Using Nano-ferrofluid Cladded Multimode Interferometric Fiber Optic Sensors for Power Grid Monitoring Applications

The AC magnetic field response of the superparamagnetic nano-ferrofluid is an interplay between the Neel and Brownian relaxation processes and is generally quantified via the susceptibility measurements at high frequencies. The high frequency limit is dictated by these relaxation times which need to be shorter than the time scale of the time varying magnetic field for the nano-ferrofluid to be considered in an equilibrium state at each time instant. Even though the high frequency response of ferrofluid has been extensively investigated for frequencies up to GHz range by non-optical methods, harnessing dynamic response by optical means for AC magnetic field sensing in fiber-optic-based sensors-field remains unexplored. Instead, the incorporation of nano-ferrofluid as sensing materials has been only limited to DC magnetic field sensing, often citing their long response time as a limiting factor to AC field sensing. This work reports the finding of high frequency (up to 15 kHz) AC magnetic field sensing capability of nanomagnetic fluid as the cladding material of a fiber-optic multimode interferometry (MMI) structure optimized for the fourth self-imaging spectral response. The key parameter enabling high frequency response is the short response time (<1 ms) achieved by optimizing both the sensing structure and nano-ferrofluid solution. Focus has been imparted on 60 Hz line-frequency profiles of various current/magnetic fields to test the efficacy of these sensors in metering and monitoring current and current-induced magnetic fields in the electrical power grid systems. The magnetic field sensitivity of 240 mV/Gauss per dBm of transmitted power was achieved for 60 Hz field applied via Helmholtz coil, whereas the 60 Hz AC current sensitivity of 2.83 mV/A was measured due to magnetic field induced by current in a straight conducting wire.

42 ENGINEERING↗
DOE OSTI2025

Multilayered Cu-Carbon Nanotube Composites for Advanced Conductors

Improving the efficiency of electrical components is critical in reducing energy consumption for various industrial and residential applications, ranging from rotating machinery to all electric devices and electric vehicle (EV) components to power grid systems. Substituting Cu wires with reduced resistance conductors that incorporate carbon nanotubes (CNTs) into Cu─ultraconductive Cu (UCC) composites─has recently been considered a promising strategy to improve energy efficiency, power density, and/or performance across various applications. Here, in this study, we created stable material formulations [CNT-containing polyvinylpyrrolidone (PVP) in dimethylformamide (DMF) solution] and utilized commercially viable fabrication approaches (electrospinning and magnetron sputtering) that produced high-performance multilayered tape-based UCC composite architectures. Increasing the CNT volume fraction by sequential layering of the structure with additional Cu-CNT layers showed a nearly stepwise improved performance in electrical and mechanical properties. This study also provides valuable insight into the effectiveness of nitrogen doping in modifying the conductivity of the CNT matrix. Fabricated prototypes demonstrated a >10% increase in current carrying capacity and >10% improvement in mechanical strength compared to those obtained on pure Cu. We believe that the properties demonstrated here, combined with the scalable manufacturing pathway of our approach, pave the way in designing future advanced conductors for diverse energy efficient and high-performance electrical systems and applications.

Carbon nanotubes↗
DOE OSTI2024

Catalytic Reduction of Carbon Monoxide to Liquid Fuels with Recyclable Hydride Donors

Solar light absorption and catalysis are physically separated processes in natural photosynthesis. Natural cofactors, such as nicotinamide adenine dinucleotides (NADH), transport electrons and hydrogen to regulate and activate enzymes at remote locations. The physical separation of light absorption from catalysis provides some inspiration for artificial photosynthesis. One rather extreme implementation is to use copper wires to transport carriers from photovoltaic cells to dark electrodes, where catalysis occurs. Indeed, with a futuristic electrical grid powered solely by photovoltaics, solar capture could be separated from catalysis by hundreds of miles. An alternative approach, that bares more similarity to natural photosynthesis, employs mobile NADH/NAD + -like species that shuttle between the light absorber and a proximate, yet unilluminated, location where catalysis occurs. Additionally, such a remote approach to solar photocatalysis was recently proposed for the reduction of carbon oxides, CO 2 and CO, to methanol by cascade catalysis. This developing artificial photosynthetic approach offers the promise of catalytic generation of methanol and oxygen gas with sunlight as the sole energy source and CO 2 and water as the only chemical feedstocks. This Viewpoint evaluates the strengths and weaknesses of this approach with an emphasis on CO reduction catalysis with photorecyclable hydride donors while looking forward to what might reasonably be achieved with continued research.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Pyrolyzed Parylene-N for in Vivo Electrochemical Detection of Neurotransmitters

Carbon electrodes are typically used for in vivo dopamine detection, and new types of electrodes and customized fabrication methods will facilitate new applications. Parylene is an insulator that can be deposited in a thin layer on a substrate and then pyrolyzed to carbon to enable its use as an electrode. However, pyrolyzed parylene has not been used for the real-time detection of neurochemicals by fast-scan cyclic voltammetry. In this work, we deposited thin layers of parylene-N (PN) on metal wires and then pyrolyzed them to carbon with high temperatures in a rapid thermal processor (RTP). Different masses of PN, 1, 6, and 12 g, were deposited to vary the thickness. RTP-PN (6 g) produced a 194 nm layer carbon thickness and had optimal electrochemical stability. Pyrolyzed parylene-N modified electrodes (PPNMEs) were characterized for electrochemical detection of dopamine, serotonin, and adenosine. Background-normalized currents at PPNMEs were about 2 times larger than those of carbon-fiber microelectrodes (CFMEs). Rich defect sites and oxygen functional groups promoted the neurochemical adsorption of cationic neurotransmitters. PPNMEs resisted fouling from serotonin polymer formation. PPNMEs were used in vivo to detect stimulated dopamine release and monitor spontaneous adenosine release. Pyrolyzed parylene is a sensitive and fouling-resistant thin-film carbon electrode that could be used in the future for making customized electrodes and devices.

25 ENERGY STORAGE↗
DOE OSTI2023

All-Perovskite Tandem Photoelectrodes for Unassisted Solar Hydrogen Production

Unassisted solar water splitting by multi-junction tandem photoelectrodes is a sustainable approach to generating green hydrogen fuels. Here, we report on the fabrication of monolithically integrated all-perovskite tandem photocathodes for efficient unassisted solar water splitting. All-perovskite tandem photocathodes wired to an iridium oxide anode deliver a high photovoltage of more than 2 V with an operating photocurrent density of 12.5 mA cm -2 at zero applied bias under simulated AM1.5G one sun illumination, yielding a solar-to-hydrogen (STH) conversion efficiency of 15%. The tandem photoelectrode demonstrates continuous operation for more than 120 hours in water under simulated one-sun illumination with less than 5% efficiency loss. A technoeconomic analysis shows the projected production cost of all-perovskite tandem photoelectrodes is $\$30$ m -2 , promising a levelized cost of hydrogen of less than $\$1$/kg if sufficient device longevity is realized. Finally, this work provides a path toward achieving cost-effective unassisted solar hydrogen fuel production.

08 HYDROGEN↗
DOE OSTI2026

Simply Fabricatable Reference Electrode for Studying Li Metal Interfaces Operando

Reference electrodes are essential for studying Li metal interfaces, yet their integration into coin cells remains challenging due to geometric constraints and assembly complexity. Here, we present a simple three-electrode coin cell design in which a thin Cu film is evaporated directly onto a trilayer PP/PE/PP separator, forming a conductive and flexible in situ current collector. The microporous Cu preserves separator porosity and pressure uniformity, avoiding artifacts introduced by wire- or mesh-type references. It is easily activated by Li plating and provides stable potentials for over 10 days in ether-based electrolytes without affecting Coulombic efficiency (>99%) or Li deposition morphology. Operando measurements using this design reveal electrode-specific impedance evolution and voltage responses otherwise obscured in two-electrode setups, uncovering a correlation between the SEI resistance and electrolyte ionic conductivity. This microporous Cu reference electrode offers a robust and accessible platform for characterizing reactive interfaces under realistic cycling conditions.

Sacci, Robert [ORNL] (ORCID:0000000200735221)↗
DOE OSTI2021

The Steady March Toward Biomimetic Nanoelectronics

Abstract. Steady progress in unveiling nature’s long-range charge transport mechanisms in redox proteins, and in the development of versatile self-assembling scaffolds and de novo proteins by design are separate fields that soon may intersect to yield the first artificial bioelectronic wires. Here we summarize compelling developments in these areas that put a spotlight on the prospect of their convergence, featuring in particular recent work by Dai et al. that clearly illustrates success in intentional design with nuanced control, binding multiple c-type hemes into a specific ordered array bearing the essential hallmarks of heme chains in bacterial multiheme cytochromes.

Rosso, Kevin M.↗
DOE OSTI2022

Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects

Individual single-walled carbon nanotubes with covalent sidewall defects have emerged as a class of photon sources whose photoluminescence spectra can be tailored by the carbon nanotube chirality and the attached functional group/molecule. Here we present electroluminescence spectroscopy data from single-tube devices based on (7, 5) carbon nanotubes, functionalized with dichlorobenzene molecules, and wired to graphene electrodes. We observe electrically generated, defect-induced emissions that are controllable by electrostatic gating and strongly red-shifted compared to emissions from pristine nanotubes. The defect-induced emissions are assigned to excitonic and trionic recombination processes by correlating electroluminescence excitation maps with electrical transport and photoluminescence data. At cryogenic conditions, additional gate-dependent emission lines appear, which are assigned to phonon-assisted hot-exciton electroluminescence from quasi-levels. Similar results were obtained with functionalized (6, 5) nanotubes. We also compare functionalized (7, 5) electroluminescence data with photoluminescence of pristine and functionalized (7, 5) nanotubes redox-doped using gold(III) chloride solution. This work shows that electroluminescence excitation is selective toward neutral defect-state configurations with the lowest transition energy, which in combination with gate-control over neutral versus charged defect-state emission leads to high spectral purity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

MPCVD-Grown Nanodiamond Microelectrodes with Oxygen Plasma Activation for Neurochemical Applications

Nanodiamonds (NDs) are a carbon nanomaterial that has a diamond core with heteroatoms and defects at the surface. The large surface area, defect sites, and functional groups on NDs make them a promising material for electrochemical sensing. Previously, we dip-coated ND onto carbon-fiber microelectrodes (CFMEs) and found increases in sensitivity, but the coating was sparse. Here, for this work, we directly grew thin films of ND on niobium wires using microwave plasma chemical vapor deposition (MP-CVD) to provide full surface coverage. ND microelectrodes show a reliable performance in neurotransmitter detection with good antifouling properties. To improve sensitivity, we oxygen plasma etched ND films to activate the surface and intentionally add defects and oxygen surface functional groups. For fast-scan cyclic voltammetry detection of dopamine, oxygen plasma-etching increases the sensitivity from 21 nA/μM to 90 nA/μM after treatment. Fouling was tested by repeated injections of serotonin or tyramine, and both ND and plasma oxidized nanodiamond (NDO) microelectrodes maintain their currents better compared to CFMEs and therefore are more antifouling. Furthermore, a biofouling test in brain slices shows that ND microelectrodes barely have any current drop, while the more hydrophilic NDO microelectrodes decrease more, but still not as much as CFMEs. Overall, grown ND microelectrodes are promising in neurotransmitter detection with excellent fouling resistance, whereas oxygen plasma etching slightly lowers the fouling resistance but dramatically increases sensitivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Role of Intact Hydrogen-Bond Networks in Multiproton-Coupled Electron Transfer

The essential role of a well-defined hydrogen-bond network in achieving chemically reversible multiproton translocations triggered by one-electron electrochemical oxidation/reduction is investigated by using pyridylbenzimidazole–phenol models. The two molecular architectures designed for these studies differ with respect to the position of the N atom on the pyridyl ring. In one of the structures, a hydrogen-bond network extends uninterrupted across the molecule from the phenol to the pyridyl group. Experimental and theoretical evidence indicates that an overall chemically reversible two-protoncoupled electron-transfer process (E2PT) takes place upon electrochemical oxidation of the phenol. This E2PT process yields the pyridinium cation and is observed regardless of the cyclic voltammogram scan rate. In contrast, when the hydrogen-bond network is disrupted, as seen in the isomer, at high scan rates (~1000 mV s –1 ) a chemically reversible process is observed with an E 1/2 characteristic of a one-proton-coupled electron-transfer process (E1PT). At slow cyclic voltammetric scan rates (<1000 mV s –1 ) oxidation of the phenol results in an overall chemically irreversible two-proton-coupled electron-transfer process in which the second proton-transfer step yields the pyridinium cation detected by infrared spectroelectrochemistry. In this case, we postulate an initial intramolecular proton-coupled electron-transfer step yielding the E1PT product followed by a slow, likely intermolecular chemical step involving a second proton transfer to give the E2PT product. Insights into the electrochemical behavior of these systems are provided by theoretical calculations of the electrostatic potentials and electric fields at the site of the transferring protons for the forward and reverse processes. Furthermore, this work addresses a fundamental design principle for constructing molecular wires where protons are translocated over varied distances by a Grotthuss-type mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Single-Molecule Charge Transport through Positively Charged Electrostatic Anchors

The charge transport in single-molecule junctions depends critically on the chemical identity of the anchor groups that are used to connect the molecular wires to the electrodes. In this research, we report a new anchoring strategy — called the electrostatic anchor here — formed through the efficient Coulombic interaction between the gold electrodes and the positively charged pyridinium terminal groups. Our results show that these pyridinium groups serve as efficient electrostatic anchors forming robust gold–molecule–gold junctions. Here, we have also observed binary switching in dicationic viologen molecular junctions, demonstrating an electron injection-induced redox switching in single-molecule junctions. We attribute the difference in low- and high conductance states to a dicationic ground state and a radical cationic metastable state, respectively. Overall, this anchoring strategy and redox switching mechanism could constitute the basis for a new class of redox-activated single-molecule switches.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗