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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Architecture and Design of Molecule Logic Gates and Atom Circuits: Modeling and Simulation of Electron Transport at the Nanoscale: Illustrations in Low-Dimensional Carbon Nanostructures, Chapter 9.

This chapter showcases selected illustrations of various manifestations of nanoscale and molecular electronic effects as investigated by quantum mechanical methods. The examples include results demonstrating (1) how graphitic nanoribbons can be assembled into multiterminal networks and the influence on electron transport; (2) how the position of a single embedded molecule can be modified to change the overall conduction state of a nanowire; (3) how carbon nanotubes can be assembled into complex covalent arrays and how these can be obtained experimentally; (4) how quantum interference can be understood as emerging from the presence of multiple levels of confinements in carbon nanorings; (5) how new functionality emerges at the nanoscale due to the interplay of magnetic, electronic, and structural properties of individual graphitic nanoribbons assembled into wiggle-like structures; and (6) how quantum chemical modeling can lead to the design of electrodes with enhanced interfaces for molecular coupling.

Electronic Molecular State↗
DOE OSTI2026

Cryogenic light detectors with thermal signal amplification for 0 νββ search experiments

As a step towards the realization of cryogenic-detector experiments to search for neutrinoless double-beta decay (such as CROSS, BINGO, and CUPID), we investigated a batch of 10 Ge light detectors (LDs) assisted by Neganov-Trofimov-Luke (NTL) signal amplification. Each LD was assembled with a large cubic light-emitting crystal (45 mm side) using the recently developed CROSS mechanical structure. The detector array was operated at milli-Kelvin temperatures in a pulse-tube cryostat at the Canfranc underground laboratory in Spain. We achieved good performance with scintillating bolometers from CROSS, made of Li 2 100 MoO 4 crystals and used as reference detectors of the setup, and with all LDs tested (except for a single device that encountered an electronics issue). No leakage current was observed for 8 LDs with an electrode bias up to 100 V. Operating the LDs at an 80 V electrode bias applied in parallel, we obtained a gain of around 9 in the signal-to-noise ratio of these devices, allowing us to achieve a baseline noise RMS of O(10 eV). Thanks to the strong current polarization of the temperature sensors, the time response of the devices was reduced to around half a millisecond in rise time. The achieved performance of the LDs was extrapolated via simulations of pile-up rejection capability for several configurations of the CUPID detector structure. Despite the sub-optimal noise conditions of the LDs (particularly at high frequencies), we demonstrated that the NTL technology provides a viable solution for background reduction in CUPID.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Pt-Ni/WC Alloy Nanorods Arrays as ORR Catalyst for PEM Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) among the other types of fuel cell technology are attractive power sources, especially for electric vehicle applications. While significant progress and plausible prospects of PEMFCs have been achieved, there are still some challenges related to the performance, durability, and cost that need to be overcome to make them economically viable for widespread commercialization. Our strategy is to develop thin films of high-active and stable catalyst coated on vertically aligned nanorod arrays of conductive and stable support. In this work, we fabricated tungsten carbide (WC) nanorods as support and coated them with a platinum-nickel (Pt-Ni) alloy shell denoted as Pt-Ni/WC catalysts. The Pt- Ni/WC nanorods were deposited on glassy carbon disks as well as on silicon substrates for evaluation of their electrocatalytic oxygen reduction reaction (ORR) activity and physical properties. Cyclic voltammetry experiments using rotating disk electrode were performed in perchloric acid (0.1 M HClO4) electrolyte at room temperature to characterize the ORR activity and stability of Pt-Ni/WC nanorods catalysts. Scanning electron microscopy and X-ray diffraction techniques were utilized to study the morphology and crystallographic properties, respectively.

Begum, Mahbuba↗
DOE OSTI2026

Host-Directed, Bioelectronic Immunomodulation for Protection Against Emerging Pathogens

Acute care of patients with severe infections often relies on systemic administration of pharmaceuticals and monitoring of complex physiological symptoms to identify immune system dysfunction, which can lead to increased mortality. Furthermore, determining disease-specific treatment plans often leads to a delay in patient care. To address this, we proposed an immune modulation system that electrically detects and responds to a patient’s immune system status, creating an agnostic means of treating illness and infection. Two pieces of hardware were developed for this task: a minimally-invasive sensor and a vagus nerve stimulator. Stimulation of the vagus nerve is known to modulate the immune system. The sensor is a microfabricated, silicon-based microneedle array capable of interfacing with interstitial fluid to detect small molecules such as inflammatory proteins (cytokines) and pharmaceuticals (vancomycin). Process optimization to manufacture the needles refined the silicon etch process, creating needle patches long enough to penetrate skin and reach interstitial fluid. The needles were tested for mechanical strength and stability, and did not shatter when inserted into skin models. The needles are coated with a thin film metal, turning them into electrodes for electrochemical sensing of our target molecules. We hybridized aptamers to the surface of the electrode to act as the sensing layer and were able to detect changes in the conformation of the aptamer electrochemically in the presence of the target molecule. The stimulator was a cuff electrode that encircled the vagus nerve. Rodent studies were conducted in which rodents were exposed to an inflammatory event and vagus nerve stimulation (VNS) was applied. It was demonstrated that optimized electrical stimulation of the vagus nerve created measurably different levels of cytokines in blood samples, and certain cytokines released during the inflammatory event were either upregulated or downregulated. In sum, this project successfully developed new platforms and technologies that can, with further development, enable better temporal insight into biomarker changes in the body, letting healthcare providers know of possible immune system dysfunction before they are detected physiologically. We also demonstrated the value of VNS and its possible use in treating immune system response to inflammation and illness.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

New detection system and signal processing for the tokamak ISTTOK heavy ion beam diagnostic

The tokamak ISTTOK heavy ion beam diagnostic (HIBD) operates with a multiple cell array detector (MCAD) that allows for the plasma density and the plasma density fluctuations measurements simultaneously at different sampling volumes across the plasma. To improve the capability of the plasma density fluctuations investigations, a new detection system and new signal conditioning amplifier have been designed and tested. The improvements in MCAD design are presented which allow for nearly complete suppression of the spurious plasma background signal by applying a biasing potential onto special electrodes incorporated into MCAD. The new low cost and small size transimpedance amplifiers are described with the parameters of 400 kHz, 10{sup 7} V/A, 0.4 nA of RMS noise, adequate for the plasma density fluctuations measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Demonstration of waferscale voltage amplifier and electrostatic quadrupole focusing array for compact linear accelerators

Compact linear accelerators, with beam energies in the kiloelectron volt to megaelectron volt range, have applications in medicine, neutron/X-ray generation, surface modifications, etc. The size, weight, and power of existing accelerators preclude them from mass availability in portable formats. This paper presents a specific implementation of an ion accelerator architecture based on planar wafers with accelerating and focusing sections. Our low cost approach allows the control of the final ion beam energy with potential applications, for example, for accelerator-based ion implantation. In this paper, we demonstrate two important waferscale modules required to build a linear particle accelerator; these include (1) on-wafer voltage amplification for beam acceleration using Inductor-Capacitor (LC) resonators and (2) waferscale electrostatic quadrupole arrays (ESQA) to refocus the ion beams during transport. On-board LC resonators were developed using Printed Circuit Board fabrication processes to implement an LC element resonant at ~ 16.6 MHz with a quality factor of 25. An energy gain of ~ 250 eV was observed using a two wafer acceleration unit with an argon ion beam with 6.5 keV initial energy. A 3 × 3 ESQA was fabricated on a glass wafer with metal electrodes formed by depositing copper metal around the beam apertures. The ESQA was used to focus and defocus an argon ion beam, demonstrating a field gradient of ~ 500 V over a gap of ~ 250 μm.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Near-field radiative thermal transfer between a nanostructured periodic material and a planar substrate

This paper provides a method based on rigorous coupled wave analysis for the calculation of the radiative thermal conductance between a layer that is patterned with arbitrary, periodically repeating features and a planar substrate. This method is applied to study the transfer from an array of beams with a rectangular cross section. Herein the impact of the structure size and spacing on the thermal conductance are investigated. These calculations are compared to an effective medium theory, which becomes increasingly accurate as the structure sizes fall well below the relevant resonance wavelengths of materials and structures. Moreover, comparisons are made with a modified proximity approximation and the far-field approximation, which become valid for small and large spacings, respectively. Results show that new levels of control over the magnitude and spectral contributions to thermal conductance can be achieved with corrugated structures relative to planar ones. Specifically, we show for SiC arrays with rectangular cross sections and with the same filling fraction, that the use of a smaller periodicity leads to a lowered far-field thermal transfer and an increased near-field thermal transfer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Redox transistors for neuromorphic computing

Efficiency bottlenecks inherent to conventional computing in executing neural algorithms have spurred the development of novel devices capable of “in-memory” computing. Commonly known as “memristors,” a variety of device concepts including conducting bridge, vacancy filament, phase change, and other types have been proposed as promising elements in artificial neural networks for executing inference and learning algorithms. In this article, we review the recent advances in memristor technology for neuromorphic computing and discuss strategies for addressing the most significant performance challenges, including nonlinearity, high read/write currents, and endurance. As an alternative to two-terminal memristors, we introduce the three-terminal electrochemical memory based on the redox transistor (RT), which uses a gate to tune the redox state of the channel. Decoupling the “read” and “write” operations using a third terminal and storage of information as a charge-compensated redox reaction in the bulk of the transistor enables high-density information storage. These properties enable low-energy operation without compromising analog performance and nonvolatility. Finally, we discuss the RT operating mechanisms using organic and inorganic materials, approaches for array integration, and prospects for achieving the device density and switching speeds necessary to make electrochemical memory competitive with established digital technology.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Multiport high-pressure synchrotron x-ray microscopy cell (CRADA Final Report)

The LBNL team developed a multiport cell allowing for fluid flow, with electrical contacts for sample bias, and with reference electrodes. The cell is currently installed and operating in beam-line 11.0.2 of the ALS, the Berkeley Synchrotron. The cell is closed by a membrane consisting of several stacked layers of graphene (1 to 3). The graphene membrane is supported on a 100 nm thick Si3N4 membrane covered with a 20 nm thin gold film for improved adhesion of the graphene and to ensure electrical conductivity. The Si3N4 film is perforated with a periodic array of holes 1 to 2 micrometers diameter. The cell can withhold an internal pressure (gas or liquid) of up to 10 atmospheres for in situ/operando studies using X-ray Photoelectron emission (XPS), and X-ray Absorption Spectroscopy (XAS). It is also ideal for tip-enhanced nano-Infrared Spectroscopy studies of molecules at the interface between the graphene and the liquid or gas filling the cell. Materials studied in the LBNL laboratory are in the form of nanoparticles, or thin films (few nm) deposited on the side of the graphene membrane facing the solution or gas inside the cell.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Final Technical Report for project entitled Highly Active, Durable, and Ultra-Low PGM NSTF Thin Film ORR Catalysts and Support

In this project, the objective was to develop new oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cells (PEMFCs) which could exceed all of the Department of Energy (DOE) 2020 targets listed in DE-FOA-0001224, Subtopic 1b, Table I. The expected outcome was development of one or more electrocatalysts which are substantially improved over the current state-of-the-art in terms of overall activity, durability, and cost, and are suitable for automotive traction and stationary fuel cell applications. This report summarizes this project’s progress towards meeting the stated objectives and includes a summary of key findings and conclusions. The development activities towards new highly active and durable thin film electrocatalysts has led to the discovery of several electrocatalysts which approached or exceeded several DOE 2020 targets for activity, durability, and performance in proton exchange membrane fuel cell (membrane electrode assemblies (MEAs). In this project, electrocatalyst development focused on systematic physical and electrochemical characterization of electrocatalyst activity, durability, and performance in MEAs as a function of electrocatalyst fabrication, compositional and structural variables. The project approach was to develop relationships between the catalyst functional responses (activity, durability and performance) with catalyst physical properties and catalyst fabrication methods. Additionally, the thin film catalysts were integrated onto the unique and durable 3M Nanostructured Thin Film (NSTF) support, consisting of arrays of self-assembled organic crystalline whiskers. The catalysts were evaluated against the project targets via extensive electrochemical characterization in MEA format at 3M, advanced structural and compositional microscopy at Oak Ridge National Laboratory (ORNL), and atomic structure analysis via XAFS at Argonne National Laboratory (ANL). The extensive electrochemical and physical characterization resulted in development of several trends which correlate the catalysts’ electrochemical properties to their physical properties, including composition, structure, and method of fabrication. The development was guided by density functional theory (DFT) modeling at Purdue University and kinetic Monte Carlo (kMC) modeling at Johns Hopkins University. The catalyst simulations provided key insights into the observed experimental activity and durability trends, and additionally were utilized to assess new electrocatalyst concepts prior to or coincident with physical catalyst development. This development has led to several electrocatalyst candidates with activity and durability which approach or exceed DOE targets. One class of catalysts, based on nm-scale thin layers of Pt on Ir, met or exceeded 6 of the 6 DOE targets the project addressed.

08 HYDROGEN↗
DOE OSTI2018

The Mochi LabJet Experiment for Measurements of Canonical Helicity Injection in a Laboratory Astrophysical Jet

The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are ~10 22 m -3 , ~0.4 T, and 5–25 eV, with velocities of ~20–80 km s -1 . Finally, the combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (~10 μs, ≳5 Alfvén times) collimated magnetic jets with a ~10:1 aspect ratio and long-lived (~100 μs, ≳40 Alfvén times) flow-stabilized, collimated, magnetic jets with a ~30:1 aspect ratio.

42 ENGINEERING↗
DOE OSTI2013

Photoelectrochemistry of core–shell tandem junction n–p + -Si/n-WO 3 microwire array photoelectrodes

Tandem junction (n–p + -Si/ITO/WO 3 /liquid) core–shell microwire devices for solar-driven water splitting have been designed, fabricated and investigated photoelectrochemically. The tandem devices exhibited open-circuit potentials of E oc = –1.21 V versus E 0 '(O 2 /H 2 O), demonstrating additive voltages across the individual junctions (n–p + -Si E oc = –0.5 V versus solution; WO 3 /liquid E oc = –0.73 V versus E 0 '(O 2 /H 2 O)). Optical concentration (12×, AM1.5D) shifted the open-circuit potential to E oc = –1.27 V versus E 0 '(O 2 /H 2 O) and resulted in unassisted H 2 production during two-electrode measurements (anode: tandem device, cathode: Pt disc). Here, the solar energy-conversion efficiencies were very low, 0.0068% and 0.0019% when the cathode compartment was saturated with Ar or H 2 , respectively, due to the non-optimal photovoltage and band-gap of the WO 3 that was used in the demonstration system to obtain stability of all of the system components under common operating conditions while also insuring product separation for safety purposes.

Shaner, Matthew R.↗
DOE OSTI2022

Theoretical Modeling of Electrochemical Proton-Coupled Electron Transfer

Proton-coupled electron transfer (PCET) plays an essential role in a wide range of electrocatalytic processes. Here, a vast array of theoretical and computational methods have been developed to study electrochemical PCET. These methods can be used to calculate redox potentials and pKa values for molecular electrocatalysts, proton-coupled redox potentials and bond dissociation free energies for PCET at metal and semiconductor interfaces, and reorganization energies associated with electrochemical PCET. Periodic density functional theory can also be used to compute PCET activation energies and perform molecular dynamics simulations of electrochemical interfaces. Various approaches for maintaining a constant electrode potential in electronic structure calculations and modeling complex interactions in the electric double layer (EDL) have been developed. Theoretical formulations for both homogeneous and heterogeneous electrochemical PCET spanning the adiabatic, nonadiabatic, and solvent-controlled regimes have been developed and provide analytical expressions for the rate constants and current densities as functions of applied potential. The quantum mechanical treatment of the proton and inclusion of excited vibronic states have been shown to be critical for describing experimental data, such as Tafel slopes and potential dependent kinetic isotope effects. The calculated rate constants can be used as input to microkinetic models and voltammogram simulations to elucidate complex electrocatalytic processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Electrodeposition of InSb branched nanowires: Controlled growth with structurally tailored properties

In this article, electrodeposition method is used to demonstrate growth of InSb nanowire (NW) arrays with hierarchical branched structures and complex morphology at room temperature using an all-solution, catalyst-free technique. A gold coated, porous anodic alumina membrane provided the template for the branched NWs. The NWs have a hierarchical branched structure, with three nominal regions: a “trunk” (average diameter of 150 nm), large branches (average diameter of 100 nm), and small branches (average diameter of sub-10 nm to sub-20 nm). The structural properties of the branched NWs were studied using scanning transmission electron microscopy, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, energy dispersive x-ray spectroscopy, and Raman spectroscopy. In the as-grown state, the small branches of InSb NWs were crystalline, but the trunk regions were mostly nanocrystalline with an amorphous boundary. Post-annealing of NWs at 420 °C in argon produced single crystalline structures along 〈311〉 directions for the branches and along 〈111〉 for the trunks. Based on the high crystallinity and tailored structure in this branched NW array, the effective refractive index allows us to achieve excellent antireflection properties signifying its technological usefulness for photon management and energy harvesting.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Molecular Junctions Inspired by Nature: Electrical Conduction through Noncovalent Nanobelts

Charge transport has been famous for occuring naturally in a range of bio molecular systems, from enzymes to neurotransmitters whose structures have covalent and non covalent bonds. Understanding from these systems have yet to translate into molecular junction devices. In this work, we design junctions which have hydrogen bonds between the edges of a series of prototype noncovalent nanobelts (NCNs) and vary the number of donor acceptors to study their electrical properties. From frontier molecular orbitals (FMOs) and projected density of states (DOS) calculations, we found these NCN dimer junctions (bridging Au electrodes) to be gapless systems, with eigenvalues of occupied and unoccupied levels between -5.8 and -5.1 eV respectively, and states at the Fermi level suggesting these are metallic like systems. Their conductance properties were studied with non equilibrium Green’s functions density functional theory (NEGF-DFT) and conductance was found to decrease with cooperative H bonding, that is, the conductance decreased as the alternating donors and acceptors around the nanobelts attenuates to a uniform distribution in the H-bonding arrays. The highest conductance was 51.3 × 10 -6 S (τ=0.662 at the Fermi level), with a pair of NCN dimers having only donors on one nanobelt and acceptors on the other in the NCN junction. The Seebeck coefficient demonstrated that these are n type (-36 to 39 µV K -1 ), while the lower conductors with alternating H bonds are p type (49.7 to 204 µV K -1 ). In addition, the NCNs have appreciable binding energies (19.8 to 46.1 kcal/mol -1 ), implying that in practice, they could form self-assembled monolayer (SAM) heterojunctions, and future systems could be designed to yield a noncovalent polymeric network of nanobelts for long range charge transport.

77 NANOSCIENCE AND NANOTECHNOLOGY↗