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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

System and method for parallel two-photon lithography using a metalens array

A metalens array is disclosed for controllably modifying a phase of a wavefront of an optical beam. The metalens array may have a substrate having at least first and second metalens unit cells, and forming a single integrated structure with no stitching being required of the first and second metalens unit cells. The first metalens unit cell has a first plurality of nanoscale features and is configured to modify a phase of a first portion of a wavefront of an optical signal incident thereon in accordance with a first predetermined phase pattern to create at least one first focal voxel within an image plane. The second metalens unit cell has a second plurality of nanoscale features configured to modify the phase of a second portion of the wavefront of the optical signal incident thereon, in accordance with a second predetermined phase pattern, to simultaneously create at least one second focal voxel within the image plane. Each metalens unit cell also has an overall diameter of no more than about 200 microns.

Xia, Xiaoxing↗
DOE OSTI2019

Investigation of resonant mode sensitivity in PhC based ring resonators

Quality factor and refractive index sensitivity are significant parameters in designing optical devices based on ring resonators such as filters, demultiplexers, switches in which the ring resonator is considered as an elementary componant. In this paper, we propose a photonic crystal ring resonator with super-ellipse shaped core. The proposed ring resonator placed between two parallels waveguides (bus waveguide and drop waveguide). The transmission efficiency of the proposed ring resonator at λ = 1547.3 nm is about 95% with bandwidth and quality factor values equal to 0.7 nm and 2210, respectively. Simulation results show that the resonance sensitivity upon refractive index variation of coupling, outer layer, adjacent and scattering rods are Δλ/Δn = 0.2 nm/0.01, Δλ/Δn = 0.225 nm/0.01, Δλ/Δn = 0.125 nm/0.01 and Δλ/Δn = 0.05 nm/0.01, respectively. The finite different time domain and plane wave expansion methods are used to calculate the outputs spectrum and band gap, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Common functionally important motions of the nucleotide‐binding domain of H sp70

ABSTRACT The 70 kDa heat shock proteins (Hsp70) are a family of molecular chaperones involved in protein folding, aggregate prevention, and protein disaggregation. They consist of the substrate‐binding domain (SBD) that binds client substrates, and the nucleotide‐binding domain (NBD), whose cycles of nucleotide hydrolysis and exchange underpin the activity of the chaperone. To characterize the structure–function relationships that link the binding state of the NBD to its conformational behavior, we analyzed the dynamics of the NBD of the Hsp70 chaperone from Bos taurus (PDB 3C7N:B) by all‐atom canonical molecular dynamics simulations. It was found that essential motions within the NBD fall into three major classes: the mutual class, reflecting tendencies common to all binding states, and the ADP‐ and ATP‐unique classes, which reflect conformational trends that are unique to either the ADP‐ or ATP‐bound states, respectively. “Mutual” class motions generally describe “in‐plane” and/or “out‐of‐plane” (scissor‐like) rotation of the subdomains within the NBD. This result is consistent with experimental nuclear magnetic resonance data on the NBD. The “unique” class motions target specific regions on the NBD, usually surface loops or sites involved in nucleotide binding and are, therefore, expected to be involved in allostery and signal transmission. For all classes, and especially for those of the “unique” type, regions of enhanced mobility can be identified; these are termed “hot spots,” and their locations generally parallel those found by NMR spectroscopy. The presence of magnesium and potassium cations in the nucleotide‐binding pocket was also found to influence the dynamics of the NBD significantly. Proteins 2015; 83:282–299. © 2014 Wiley Periodicals, Inc.

Gołaś, Ewa I.↗
DOE OSTI2021

Global Hybrid Simulations of Interaction Between Interplanetary Rotational Discontinuity and Bow Shock/Magnetosphere: Can Ion-Scale Magnetic Reconnection be Driven by Rotational Discontinuity Downstream of Quasi-Parallel Shock?

Ion-scale magnetic reconnection has been observed downstream of the terrestrial quasi-parallel (Q-∥) shock. Whether it is driven by interplanetary discontinuities or turbulent Q-∥ shock, however, is unclear. Using three-dimensional global hybrid simulation, we investigate the generation of magnetic reconnection downstream of the Q-∥ shock, while an interplanetary rotational discontinuity (RD) is launched to the bow shock. Cases with various solar wind Alfvén Mach numbers, M A = 3.0 to 8, and propagation directions of the RD are presented. The propagation direction n is assumed to be in the GSE xz plane and pointing earthward, with n = (-sin(θ 12 /2),0,-cos(θ 12 /2)), where θ 12 is the angle between the upstream (B1) and downstream (B2) magnetic fields across the transmitted RD. It is found that magnetic reconnection occurs inside the RD downstream of the Q-∥ shock, forming flux ropes extending along the dawn-dusk direction about tens of ion inertial lengths. Large-amplitude low-frequency waves originated from the Q-∥ shock lead to the bending and squeezing of the field lines around the RD, which play an important role in triggering reconnection inside the RD. As the RD impacts the dayside magnetopause, magnetopause reconnection takes place between the field lines behind the RD and geomagnetic field lines. Nevertheless, no reconnection is found downstream of the Q-∥ shock itself or outside the RD in the magnetosheath. The existent and structure of reconnection in the magnetosheath are found to strongly depend on the parameters M A and n. Our simulation shows that ion-scale magnetic reconnection is driven by an external driver in the form of the compression of an RD around the bow shock and in the magnetosheath, rather than caused by the turbulent Q-∥ shock alone.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO{sub 4.}6H{sub 2}O buffered with H{sub 3}BO{sub 3} and acidized by dilute H{sub 2}SO{sub 4}. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (∼ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2017

UV-activated ZnO films on a flexible substrate for room temperature O 2 and H 2 O sensing

Here, we demonstrate that UV-light activation of polycrystalline ZnO films on flexible polyimide (Kapton) substrates can be used to detect and differentiate between environmental changes in oxygen and water vapor. The in-plane resistive and impedance properties of ZnO films, fabricated from bacteria-derived ZnS nanoparticles, exhibit unique resistive and capacitive responses to changes in O 2 and H 2 O. We also propose that the distinctive responses to O 2 and H 2 O adsorption on ZnO could be utilized to statistically discriminate between the two analytes. Molecular dynamic simulations (MD) of O 2 and H 2 O adsorption energy on ZnO surfaces were performed using the large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with a reactive force-field (ReaxFF). Furthermore, these simulations suggest that the adsorption mechanisms differ for O 2 and H 2 O adsorption on ZnO, and are governed by the surface termination and the extent of surface hydroxylation. Electrical response measurements, using DC resistance, AC impedance spectroscopy, and Kelvin Probe Force Microscopy (KPFM), demonstrate differences in response to O 2 and H 2 O, confirming that different adsorption mechanisms are involved. Statistical and machine learning approaches were applied to demonstrate that by integrating the electrical and kinetic responses the flexible ZnO sensor can be used for detection and discrimination between O 2 and H 2 O at low temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Additive Manufactured Composite Phase-Change Material for Thermal Energy Storage Applications

Phase-change materials play a critical role in industrial energy storage applications to drive efficiency improvements, thermal energy management, and carbon emissions reductions. Recently, it has been shown that rapid solidification of alloys with metastable immiscibility in the liquid phase has the potential to form unique microstructures in which a low-melting phase is uniformly distributed in a high-melting matrix. This feature can be exploited using additive manufacturing to produce components with complex geometries containing such unique phase-change microstructures. Phase-field simulations utilizing high-performance computing were used to provide a detailed description of the evolution of the active phase during service in terms of their morphology and composition in different polycrystalline matrix grain morphologies that are typically produced during additive manufacturing. Phase field simulations were performed using, MEUMAPPS-SL (Microstructure Evolution Using Massively Parallel Phase-field Simulations – Solid Liquid) code that was developed in-house by the Oak Ridge National Laboratory. The simulations utilized the capabilities of the Kestrel supercomputer at the National Renewable Energy Laboratory. The simulation results were compared with experimental results generated at Siemens Energy, Inc. The results indicate that the kinetics of liquid spreading along grain boundaries is largely determined by the mobility of the triple line along the intersection of the grain boundary liquid and the grain boundary plane.

25 ENERGY STORAGE↗
DOE OSTI2022

Flow Loop Study of ECT-Based Volume Fraction Monitoring in Oil–Water Two-Phase Flows

Measurement of phase volume fractions in water-containing multiphase flows is necessary for the optimization of a host of industrial flow processes. Many water-containing multiphase flows can be classified as either water-dispersed or water-continuous mixtures. A recently developed approach based on Hanai’s mixture formula and utilizing electrical capacitance tomography (ECT) sensors have shown good potential for obtaining water volume fraction estimates in two-phase water-containing flows with different water salinity levels. However, the proposed approach was investigated via controlled experiments restricted to static configurations while, in practice, multiphase flows can be dynamic and unpredictable. In this work, we perform a flow loop study of the proposed ECT-based method for volume fraction estimation in oil–water two-phase flows. Here, we evaluate the performance of the proposed method in both water-dispersed and water-continuous flow regimes by employing different types of capacitive sensors in cylindrical arrangements and parallel-plate rectangular arrangements.

02 PETROLEUM↗
DOE OSTI2017

First-Principles Simulations of Functional Materials for Energy Conversion

Computational modeling has become a very effective approach in predicting properties of materials, and in designing functional materials with targeted structural, thermal, or optical properties. Many electronic structure methods have been developed, including density functional theory. Among them, DFT has been widely used in physics and materials science because it is computationally cheaper than other methods but still gives desired accuracy. It also provides a good starting point for higher levels of theory, such as many-body perturbation theory and quantum Monte Carlo. In parallel to these electronic structure method developments, a dramatic increase in computing capabilities over the last decade has enabled large-scale electronic structure calculations to address leading-edge materials science problems. In particular, with Theta at the Argonne Leadership Computing Facility (ALCF), our early science project investigated large-scale nanostructured materials for energy conversion and storage using two open-source electronic structure codes Qbox (http://qboxcode.org) and WEST (http://west-code.org). Qbox is an ab-initio molecular dynamics code based on plane wave DFT, and WEST is a post-DFT code for excited state calculations within many-body perturbation theory.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A generalized O-element approach for analyzing interface structures

A correct description of interfacial dislocations is critical to the understanding of physical and mechanical properties of the interfaces and their impact on phase transformation and deformation mechanisms. The O-lattice theory provides a general theoretical framework for determining interfacial dislocation structures. However, for systems having an invariant line (IL) or an invariant plane, the O-elements do not always exist in the three-dimensional (3D) space, which impedes the capability of the O-lattice theory to the interfaces in these systems. To determine the dislocation structures in interfaces for which the O-elements do not extend in the 3D space, we introduce a generalized O-element approach by employing the Moore-Penrose pseudoinverse. The generalized O-elements, as the least square solutions to the O-lattice, play a parallel role as that of the ideal O-elements and extend the candidate locations for the coherent regions between dislocations. Worked examples for dislocation structures in both homo-phase and hetero-phase systems are presented. The predicted interface structures are in good agreement with experimental observations and molecular statics (MS)/molecular dynamics (MD) simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

An optical-input Maximum Likelihood Estimation feedback system demonstrated on tokamak horizontal equilibrium control

A readily parallelized Maximum Likelihood Estimation (MLE) algorithm with linear computational complexity is demonstrated in real time using only measurements from an extreme ultraviolet (EUV) diagnostic to control the horizontal position of a tokamak plasma. A set of trial emissivity profiles are parameterized by the control quantity of interest (R m ), and the MLE is identified from the profile which minimizes the signal reconstruction residual. The algorithm depends on an empirically determined likelihood function with exponential form. EUV emission (λ ≈ 15eV-1keV) is captured in a poloidal plane by four 16-channel AXUV diodes mounted at different poloidal angles with radial and angular resolution sufficient to discern plasma equilibrium evolution in HBT-EP. Calculations of the plasma major radius by the system are consistent within diagnostic uncertainty for the majority of the discharge with those of: a weighted average of vertical soft X-ray or EUV chords, magnetic sensors, and an equilibrium reconstruction. The feedback system corrects for a horizontal displacement of the major radius equal to 20% of the plasma minor radius by adjusting the vertical field produced from 40 in-vessel control coils in real time. The MLE calculation is performed on a GPU in a 15 μs cycle, with similar performance in this application to a simple weighted average of vertical chords. Finally, results demonstrate horizontal position control using magnetic actuators and an optical observer.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Electromagnetic wave propagation based upon spectral-element methodology in dispersive and attenuating media

SUMMARY We build on mathematical equivalences between Maxwell’s wave equations for an electromagnetic medium and elastic seismic wave equations. This allows us to readily model Maxwell’s wave propagation in the spectral-element codes SPECFEM2D and SPECFEM3D, written for acoustic, viscoelastic and poroelastic seismic wave propagation, providing the ability to handle complex geometries, inherent to finite-element methods and retaining the strength of exponential convergence and accuracy due to the use of high-degree polynomials to interpolate field functions on the elements, characteristic to spectral-element methods (SEMs). Attenuation and dispersion processes related to the frequency dependence of dielectric permittivity and conductivity are also included using a Zener model, similar to shear attenuation in viscoelastic media or viscous diffusion in poroelastic media, and a Kelvin–Voigt model, respectively. Ability to account for anisotropic media is also discussed. Here, we limit ourselves to certain dielectric permittivity tensor geometries, in order to conserve a diagonal mass matrix after discretization of the system of equations. Doing so, simulation of Maxwell’s wave equations in the radar frequency range based on SEM can be solved using explicit time integration schemes well suited for parallel computation. We validate our formulation with analytical solutions. In 2-D, our implementation allows for the modelling of both a transverse magnetic (TM) mode, suitable for surface based reflection ground penetration radar type of applications, and a transverse electric (TE) mode more suitable for crosshole and vertical radar profiling setups. Two 2-D examples are designed to demonstrated the use of the TM and TE modes. A 3-D example is also presented, which allows for the full TEM solution, different antenna orientations, and out-of-plane variations in material properties.

58 GEOSCIENCES↗
DOE OSTI2016

Spall fracture in additive manufactured Ti-6Al-4V

Here, we present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on a plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Anisotropic spall failure of additively manufactured 316L stainless steel

The dynamic high strain rate tensile (spall) failure of additively manufactured (AM) materials is an area of great interest but much less understood than material failure under other loading regimes. The research presented here examines the effects of microstructure anisotropy in 316L stainless steel fabricated by laser powder bed fusion (LPBF) on its spall failure and properties. In this work, plate-on-plate impact experiments were performed using an 80-mm gas gun to investigate the spall behavior of AM fabricated sample discs with impact along the perpendicular and parallel orientations relative to build directions. Experiments were also performed on wrought 316L stainless steel as baseline material with uniform equiaxed grain microstructure for comparison with the AM material of same composition. The spall experiments involved free-surface velocity profiles measured using Photon Doppler Velocimetry (PDV) to capture the spall pull-back signals, combined with post-mortem analysis of the microstructure of soft-recovered impacted samples. In the case of AM samples, spall failure initiated preferentially at melt pool boundaries in both impact directions. The spall plane location and spall strength, however, were both heavily influenced by the orientation of the impact direction relative to the build direction in the AM samples. The spall behavior is also observed to be more complex in the samples impacted perpendicular to the build (through-thickness) direction, due in large part to the orientation of the microstructural features such as melt pool boundaries, laser scan tracks, and general grain morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Engineering the anchoring behavior of nematic liquid crystals on a solid surface by varying the density of liquid crystalline polymer brushes

Controlling the orientation of liquid crystal (LC) molecules towards contacting surfaces is a crucial requirement for the development of LC displays and passive electro-optical devices. Up to now, research has been focused on photo-responses of a LC azobenzene polymer system to obtain either planar or homeotropic orientation of LCs. It remains a challenge, however, to tune the polar angle of LC molecules on the solid surface and gain more insights about the polymer chain conformation extending in LC medium. Here, we deposit a liquid crystalline side chain polymer brush, poly(6-(4-methoxy-azobenzene-4'-oxy)hexyl methacrylate) (PMMAZO), onto the solid surface with film thickness varying between ~3 nm and 13 nm; therefore, the grafting density of the brush layer ranges from 0.0219 to 0.0924 chains per nm 2 . When LCs are confined in hybrid cells with a top surface eliciting uniform homeotropic anchoring and a bottom surface covered by the PMMAZO brush, the out-of-plane polar angle of 4-pentyl-4'-cyanobiphenyl (5CB) on the brush layer gradually changes from ~0° to ~62° by simply increasing the grafting brush density. The surface forces apparatus (SFA) measurement is used to determine 5CB as a good solvent for the PMMAZO brush and understand the relationship between the chain conformation in 5CB and the anchoring behavior of LC molecules on the polymer brush layer. Here, for high grafting density, the polymer chain in 5CB extends significantly away from the substrate, making the side chain mesogens on average almost parallel to the substrate; for the low-density case, the main chain extends in the narrow region around the surface for aligning the mesogens perpendicular to the substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2015

One-dimensional edge transport on the surface of cylindrical Bi{sub x}Te{sub 3−y}Se{sub y} nanowires in transverse magnetic fields

The geometry of topological insulators (TIs) has a major impact on the magnetoelectric band structure of their surface states. Here, we investigate the surface states of cylindrical TI bismuth telluride selenide nanowires with three different diameters, by parallel and transverse magnetoresistance (MR) measurements. In parallel configuration, we observe Aharonov-Bohm oscillations as well as weak antilocalization, indicating two-dimensional TI surface states. In transverse magnetic fields, we observed MR oscillations that are non-linear against the reciprocal of the magnetic field and thus cannot be explained by two- or three-dimensional states. Instead, our transport data analysis reveals that these MR oscillations are the consequence of one-dimensional edge channels at the nanowire surface that form due to the projection of the external magnetic field on the cylindrically curved surface plane in high magnetic fields. Our observation provides an exotic class of surface states that might be used for electronic and spintronic devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Repairable and Reconfigurable Structured Liquid Circuits

The advance of printed electronics is significantly bolstered by the development of liquid-state electronics that overcome the inherent limitations in flexibility and reconfigurability of solid-state electronics. By integrating the biocompatibility and conductivity of sulfonated polyaniline (S-PANI) and phytic acid (PA) with the reconfigurability of structured liquids, highly conductive all-liquid threads are developed. The dense packing and overlap of PA/S-PANI complexes at an oil/water interface promotes in-plane electron transport, and standard four-point probe measurements of PA/S-PANI interfacial assemblies demonstrate enhanced electrical properties. Notably, the rapid jetting of the ink phase into the matrix phase allows for liquid threads to be printed, enabling the fabrication of large-scale, conductive pathways between two electrodes and liquid circuits. Upon mechanical cleavage of the liquid wires, circuits can be broken, but will easily self-repair using an electric field, making this motif useful in the design of switches as well as restoring conductive pathways in series or in parallel. In conclusion, the demonstrated flexibility and reconfigurability these PA/S-PANI wires possess hold significant promise for their practical use in the design of flexible and adaptive bioelectronics that can be repaired on demand, signifying a transformative step in the evolution of liquid electronic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Predictive Inverse Model for Advective Heat Transfer in a Short–Circuited Fracture: Dimensional Analysis, Machine Learning, and Field Demonstration

Identifying fluid flow maldistribution in planar geometries is a well–established problem in subsurface science/engineering. Of particular importance to the thermal performance of enhanced (or “engineered”) geothermal systems is identifying the existence of nonuniform (i.e., heterogeneous) permeability and subsequently predicting advective heat transfer. Here, machine learning via a genetic algorithm (GA) identifies the spatial distribution of an unknown permeability field in a two–dimensional Hele–Shaw geometry (i.e., parallel plates). The inverse problem is solved by minimizing the L2 norm between simulated residence time distribution (RTD) and measurements of an inert tracer breakthrough curve (BTC) (C–Dot nanoparticle). Principal component analysis (PCA) of spatially correlated permeability fields enabled reduction of the parameter space by more than a factor of 10 and restricted the inverse search to reservoir–scale permeability variations. Thermal experiments and tracer tests conducted at the mesoscale Altona Field Laboratory (AFL) demonstrate that the method accurately predicts the effects of extreme flow channeling on heat transfer in a single bedding–plane rock fracture. However, this is only true when the permeability distributions provide adequate matches to both tracer RTD and frictional pressure loss. Without good agreement to frictional pressure loss, it is still possible to match a simulated RTD to measurements, but subsequent predictions of heat transfer are grossly inaccurate. Here, the results of this study suggest that it is possible to anticipate the thermal effects of flow maldistribution, but only if both simulated RTDs and frictional pressure loss between fluid inlets and outlets are in good agreement with measurements.

42 ENGINEERING↗