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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Electric current paths in a Si:P delta-doped device imaged by nitrogen-vacancy diamond magnetic microscopy

The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy, a technique known as atomic precision advanced manufacturing (APAM), has allowed us to tailor electronic devices with atomic precision, and thus has emerged as a way to explore new possibilities in Si electronics. In these applications, critical questions include where current flow is actually occurring in or near APAM structures as well as whether leakage currents are present. In general, detection and mapping of current flow in APAM structures are valuable diagnostic tools to obtain reliable devices in digital-enhanced applications. In this report, we used nitrogen-vacancy (NV) centers in diamond for wide-field magnetic imaging (with a few-mm field of view and micron-scale resolution) of magnetic fields from surface currents flowing in an APAM test device made of a P delta-doped layer on a Si substrate, a standard APAM witness material. We integrated a diamond having a surface NV ensemble with the device (patterned in two parallel mm-sized ribbons), then mapped the magnetic field from the DC current injected in the APAM device in a home-built NV wide-field microscope. The 2D magnetic field maps were used to reconstruct the surface current densities, allowing us to obtain information on current paths, device failures such as choke points where current flow is impeded, and current leakages outside the APAM-defined P-doped regions. Analysis on the current density reconstructed map showed a projected sensitivity of ~0.03 A m -1 , corresponding to a smallest-detectable current in the 200 μm wide APAM ribbon of ~6 μA. These results demonstrate the failure analysis capability of NV wide-field magnetometry for APAM materials, opening the possibility to investigate other cutting-edge microelectronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Mesoscale Effects of Composition and Calendering in Lithium-Ion Battery Composite Electrodes

Macrohomogeneous battery models are widely used to predict battery performance, necessarily relying on effective electrode properties, such as specific surface area, tortuosity, and electrical conductivity. While these properties are typically estimated using ideal effective medium theories, in practice they exhibit highly non-ideal behaviors arising from their complex mesostructures. In this paper, we computationally reconstruct electrodes from X-ray computed tomography of 16 nickel–manganese–cobalt-oxide electrodes, manufactured using various material recipes and calendering pressures. Due to imaging limitations, a synthetic conductive binder domain (CBD) consisting of binder and conductive carbon is added to the reconstructions using a binder bridge algorithm. Reconstructed particle surface areas are significantly smaller than standard approximations predicted, as the majority of the particle surface area is covered by CBD, affecting electrochemical reaction availability. Finite element effective property simulations are performed on 320 large electrode subdomains to analyze trends and heterogeneity across the electrodes. Significant anisotropy of up to 27% in tortuosity and 47% in effective conductivity is observed. Electrical conductivity increases up to 7.5× with particle lithiation. We compare the results to traditional Bruggeman approximations and offer improved alternatives for use in cell-scale modeling, with Bruggeman exponents ranging from 1.62 to 1.72 rather than the theoretical value of 1.5. We also conclude that the CBD phase alone, rather than the entire solid phase, should be used to estimate effective electronic conductivity. This study provides insight into mesoscale transport phenomena and results in improved effective property approximations founded on realistic, image-based morphologies.

25 ENERGY STORAGE↗
DOE OSTI2026

Toward Fully Soft and Multifunctional Shape Sensing via Optical Waveguide Arrays

For soft bodies, surface deformation and pressure provide proprioceptive and exteroceptive information, including body configuration, body compliance, and external forces. We develop a sheet sensor with a fully soft sensing surface that provides surface shape reconstruction using optical waveguide arrays. The waveguides are fabricated to achieve a tunable linear response to bi‐directional bending curvature, and the waveguide arrays are configured to differentiate between ambiguous shapes. We characterize the waveguide performance, relating curvature sensitivity to the core's surface roughness. Synergy of waveguide responses reduces the number of sensing elements required and achieves damage resilience. Using waveguide sensitivity to pressure, we also demonstrate feasibility for exteroception. We demonstrate the multifunctional sensing capability by wrapping the sheet around an upper arm, showcasing joint motion and external force sensing. Integrated into or applied onto surfaces of robotic or living systems, this design can be implemented in applications such as virtual reality, teleoperation, physical therapy, and soft robotics.

Yu, Qifan [Department of Mechanical Engineering Ma↗
DOE OSTI2024

Improved Three-Dimensional Reconstructions in Electron Ptychography through Defocus Series Measurements

A detailed analysis of ptychography for three-dimensional (3D) phase reconstructions of thick specimens is performed. Here, we introduce multi-focus ptychography, which incorporates a 4D-STEM defocus series to enhance the quality of 3D reconstructions along the beam direction through a higher overdetermination ratio. This method is compared with established multi-slice ptychography techniques, such as conventional ptychography, regularized ptychography, and multi-mode ptychography. Additionally, we contrast multi-focus ptychography with an alternative method that uses virtual optical sectioning through a reconstructed scattering matrix (S-matrix), which offers more precise 3D structure information compared to conventional ptychography. Our findings from multiple 3D reconstructions based on simulated and experimental data demonstrate that multi-focus ptychography surpasses other techniques, particularly in accurately reconstructing the surfaces and interface regions of thick specimens.

3D reconstruction↗
DOE OSTI2024

Surface elevation, snow depth, vegetation height, and color imagery from multiple UAV surveys from 2018 to 2023 across a watershed near Teller road mile marker 27, Seward Peninsula, Alaska

Multiple photogrammetric surveys using an unoccupied aerial system (UAS) were performed across a watershed along Teller road on the Seward Peninsula (Alaska) to investigate terrain, vegetation and snowpack properties. This work was led by the environmental geophysics team from Lawrence Berkeley National Laboratory as part of the Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic). The multiple photogrammetric surveys used mostly a DJI Matrice 210 UAS with a DJI X5S camera, Ground Control Points (GCPs) surveyed with a Real Time Kinematic (RTK)-GPS, and a structure from motion (SfM) technique for photogrammetric reconstruction. Digital Surface elevation Models (DSMs) were inferred at various times of year, including near peak in plant and leaf density (July 19 2017), close to peak in snow depth (April 1 2019 and April 11 2022), and at low plant and leaf density of tall after the first bare-ground date (June 9 2019). Snow and canopy height were obtained by subtracting DSMs from a Digital Terrain Model (DTM) proxy inferred from the June 9 2019 survey. The derived products include ortho-mosaiced RGB map, DSMs, a DTM proxy, snow depth (April 2019 and 2022) and canopy height (July 2017). Unprocessed and processed data products are included in this package (processing levels 0-2). Data and metadata are provided as text (*.csv), image (*.jpg), and GeoTiff (*.tif) formats. This metadata document contains a description of the survey and processing steps and the inferred products.The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic) was a 15-year research effort (2012-2027) to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy’s Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy’s Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Stabilizing High–Nickel Cathodes with High–Voltage Electrolytes

Electrolytes connect the two electrodes in a lithium battery by providing Li + transport channels between them. Advanced electrolytes are being explored with high-nickel cathodes and the lithium-metal anode to meet the high energy density and cycle life goals, but the origin of the performance differences with different electrolytes is not fully understood. Here, the mechanisms involved in protecting the high-capacity, cobalt-free cathode LiNiO 2 with a model high-voltage electrolyte (HVE) are delineated. The kinetic barrier posed by a thick surface degradation layer with poor Li + -ion transport is found to be the major contributor to the fast capacity fade of LiNiO 2 with the conventional carbonate electrolyte. In contrast, HVE reduces the side reactions between the electrolyte and the electrodes, leading to a thinner nano-interphase layer comprised of more beneficial species. Crucially, the HVE leads to a different surface reorganization pathway involving the formation of a thinner nanoscale LiNi 2 O 4 spinel phase on the LiNiO 2 surface. Finally, with a high 3D Li + -ion and electronic conductivity, the spinel LiNi 2 O 4 reorganization nanolayer preserves fast Li + transport across the cathode–electrolyte interface, reduces reaction heterogeneity in the electrode and alleviates intergranular cracking within secondary particles, resulting in superior long-term cycle life.

25 ENERGY STORAGE↗
DOE OSTI2025

Kinetically Dormant Ni‐Rich Layered Cathode During High‐Voltage Operation

Abstract The degradation of Ni‐rich cathodes during long‐term operation at high voltage has garnered significant attention from both academia and industry. Despite many post‐mortem qualitative structural analyses, precise quantification of their individual and coupling contributions to the overall capacity degradation remains challenging. Here, by leveraging multiscale synchrotron X‐ray probes, electron microscopy, and post‐galvanostatic intermittent titration technique, the thermodynamically irreversible and kinetically reversible capacity loss is successfully deconvoluted in a polycrystalline LiNi 0.83 Mn 0.1 Co 0.07 O 2 cathode during long‐term charge/discharge cycling in full cell configuration. Contradicting the dramatic capacity loss, the layered structure remains highly alive even after 1000 cycles at 4.6 V while undergoing a three‐order of magnitude reduction in the mass transfer kinetics, leading to almost fully recoverable capacity under kinetic‐free conditions. Such kinetic dormant behavior after cycling is not simply ascribed to poor chemical diffusion by reconstructed cathode surface but highly synchronizes with the lattice strain evolution stemming from the structural heterogeneity between deeply delithiated layered and degraded rock‐salt phases at high voltage. These findings deepen the degradation mechanism of high‐voltage cathodes to achieve long‐cycling and fast‐charging performance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stabilized Co-Free Li-Rich Oxide Cathode Particles with An Artificial Surface Prereconstruction

Li-rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g –1 . However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well-known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full-cell performance degradation. In this study, an artificial surface prereconstruction (ASR) for Li 1.2 Mn 0.6 Ni 0.2 O 2 particles with a molten-molybdate leaching is conducted, which creates a crystal-dense anion-redox-free LiMn 1.5 Ni 0.5 O 4 shell that completely encloses the LXMO lattice (ASR-LXMO). Differential electrochemical mass spectroscopy and soft X-ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR-LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR-LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g –1 with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full-cell matched with a commercial graphite anode and lean (2 g A –1 h –1 ) electrolyte, ASR-LXMO shows high capacity retention of 76% after 125 cycles in full-cell cycling.

25 ENERGY STORAGE↗
DOE OSTI2023

Engineering a Self-Grown TiO 2 /Ti-MOF Heterojunction with Selectively Anchored High-Density Pt Single-Atomic Cocatalysts for Efficient Visible-Light-Driven Hydrogen Evolution

A photocatalyst TiO 2 /Ti-BPDC-Pt is developed with a self-grown TiO 2 /Ti-metal–organic framework (MOF) heterojunction, i.e., TiO 2 /Ti-BPDC, and selectively anchored high-density Pt single-atomic cocatalysts on Ti-BPDC for photocatalytic hydrogen evolution. This intimate heterojunction, growing from the surface pyrolytic reconstruction of Ti-BPDC, works in a direct Z-scheme, efficiently separating electrons and holes. Pt is selectively anchored on Ti-BPDC by ligands and is found in the form of single atoms with loading up to 1.8 wt %. The selective location of Pt is the electron-enriched domain of the heterojunction, which further enhances the utilization of the separated electrons. This tailored TiO 2 /Ti-BPDC-Pt shows a significantly enhanced activity of 12.4 mmol g -1 h -1 compared to other TiO 2 - or MOF-based catalysts. In conclusion, the structure-activity relationship further proves the balance of two simultaneously exposed domains of heterojunctions is critical to fulfilling this kind of catalyst.

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

Effects of crystallographic orientation on calcite dissolution under alkaline conditions

Here, this study investigates the dissolution of calcite’s (104) and (100) surfaces under alkaline conditions (pH 8.8–13.1) using vertical scanning interferometry under flow-through conditions. The dissolution rate of (100) surfaces decreases with increasing pH. For example, the dissolution rate at pH 8.8 is more than 20 times higher than that at pH 13.1. In contrast, the dissolution rate of (104) surfaces is far less sensitive to pH. We explain these observations as being on account of the preferential adsorption of [OH – ] on (100) surfaces, inhibiting their dissolution. Particularly, this is because Ca-surface sites on (100) surfaces are less coordinated and have a stronger tendency for [OH – ] adsorption. As a result, (100) surfaces dissolve nearly twice as fast as (104) surfaces at pH 8.8, whereas (104) surfaces dissolved ~4.5 times faster than (100) surfaces at pH 13.1; indicating an inversion in dissolution behavior. The dissolution rate of (104) surfaces at pH 13.1 is 60 % of the rate at pH 10–12 because of the formation of slow dissolving microfacets of other orientations. The rhombohedral dissolution etch-pits formed on (104) surfaces, at lower pH’s, disappeared upon exposure to solutions with pH > 12 and were replaced by protrusions. The addition of up to 4m (molality) NaCl enhances the dissolution of (104) surfaces at pH 8.8–13.1 and (100) surfaces at pH 8.8–11.0, and inhibited the dissolution of (100) surfaces at pH = 12.0–13.1. In addition, the competing adsorption between OH – and CO 3 2– species mitigates the inhibition effects of CO 3 2– on both surfaces at pH 13.1 compared to pH 11, and the dissolution of (100) surfaces is far less affected by CO 3 2– than (104) surfaces. These results provide new insights into the rates and mechanisms of how crystallographic orientations affect calcite’s dissolution at alkaline pH conditions.

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

Experimental and theoretical investigation of the crystalline surface, film, and interface properties of antiperovskite Mn 3 GaN grown by molecular beam epitaxy on MgO(001)

Here, we present a study of the epitaxial growth, characterization, and theoretical modeling of thin film antiperovskite Mn 3 GaN, an antiferromagnetic material with kagome structure which is grown on MgO (001) substrates using N-plasma-assisted molecular beam epitaxy. Reflection high energy electron diffraction is used to assess the in-plane evolution of the film structure during growth, and the surface is investigated in-situ using scanning tunneling microscopy and Auger electron spectroscopy. These results are combined with precision measurements done ex-situ determining the film lattice constants using a combination of x-ray diffraction with reciprocal space mapping and scanning transmission electron microscopy. Overall, a uniform, homogeneous film with an atomically smooth vacuum surface and atomically sharp substrate interface is found having very small in-plane tensile strain and mild out-of-plane compressive strain. First-principles theoretical calculations are applied in order to ascertain the lowest energy models for both the Mn 3 GaN surface and the Mn 3 GaN/MgO film/substrate interface. Models including MnGa versus MnN surface layers and MnGa versus MnN interfacial layers are considered as functions of both the Mn and Ga chemical potentials. The predictions are discussed in comparison to the experimental results. The overall findings suggest that Mn 3 GaN on MgO(001) is a viable epitaxial film which can be further explored in connection with antiferromagnetic spintronics.

Density functional theory↗
DOE OSTI2021

Alpha Shape Analysis (ASA) Framework for Post- Clustering Property Determination in Atom Probe Tomographic Data

While application of clustering algorithms to atom probe tomography data have enabled quantification of solute clusters in terms of number density, size, and subcomposition there exist other properties (e.g., volume, surface area, and composition) that are better determined by defining an interface between the cluster and the surrounding matrix. The limitation in composition results from an ion selection step where the expected matrix ion types are omitted from the cluster search algorithm to enhance the contrast between the matrix and cluster and to reduce the complexity of the search. Previously, composition determination within solute clusters has utilized a secondary envelopment and erosion step on top of conventional methods such as maximum separation. In this work, we present a novel stochastic method that combines the particle identification fidelity of a conventional clustering algorithm with the analytical flexibility of mesh-based approaches through the generation of alpha shapes for each identified cluster. Furthermore, the corresponding mesh accounts for concave components of the clusters and determines the volume and surface area of the clusters; additionally, the mesh boundary is utilized to update the total composition according to the internal ions.

42 ENGINEERING↗
DOE OSTI2023

Determining Catalytically Relevant Surfaces through Coverage-Dependent Lattice Gas Models: Carbon Adsorption on Fe(100)

Here, we have quantified the C–C lateral interactions on Fe(100) using a density functional theory (DFT)-parameterized lattice gas cluster expansion (LG CE) model trained using 265 unique configurations spanning a C coverage from 0 to 1 monolayer (ML). Our LG CE model shows high predictive accuracy with a leave-multiple-out cross-validation score of 10.2 and 16.6 meV/site for systems with and without the top two layers of Fe atoms fixed, respectively. Electronic ground-state structures identified from the lattice gas model (including the structures at 0 and 1 monolayers) were further used to generate ab initio phase diagrams under a range of temperatures and pressures. At low temperatures (<400 K), we found that the 1.0 monolayer structure is dominant, whereas at higher temperatures (>500 K), the 0.88 ML structure is most likely to form on the Fe surface. Interestingly, our model identified a c (2 × 2) ordered structure at 1/2 ML, which correlates well with previous DFT studies for carbon adsorption on iron surfaces and matches with the experimentally observed low-energy electron diffraction structure. Overall, the DFT-parameterized energies for the C/Fe system including effects of coverage and configurational space can further help in developing multiscale models for various heterogeneous reactions involving C–C and C–Fe interactions.

08 HYDROGEN↗
DOE OSTI2025

Robust Spin-Moiré-Superlattice-Driven Gap Opening in EuAg 4 Sb 2 under in-Plane Magnetic Field

Moiré superlattices introduce new length and energy scales, enabling discoveries, such as unconventional superconductivity, in 2D systems. This concept has recently been extended to bulk materials with multiple-q spin textures, opening exciting opportunities for spin moiré physics. A notable example is EuAg 4 S b2 , where a spin moiré superlattice (SMS), manifested as a double-q spin modulation, induces a superzone gap opening. In this work, we investigate the tunability of this gap by an in-plane magnetic field in EuAg 4 Sb 2 by using neutron scattering, magnetization, and transport measurements. We reveal a cycloidal ground state and multiple spin-reoriented phases induced by the in-plane field, highlighting the critical role of in-plane components in driving magnetic transitions. Moreover, we demonstrate that a robust gap opening persists in the double-q phase, regardless of in-plane field orientation. Model calculations attribute this robustness to the stability of the SMS under tilted fields. Here, our results establish EuAg 4 Sb 2 as a tunable platform for exploring the spin-texture-driven superzone gap opening in electronic states.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Single Iridium Atom Doped Ni 2 P Catalyst for Optimal Oxygen Evolution

Single-atom catalysts (SACs) with 100% active sites have excellent prospects for application in the oxygen evolution reaction (OER). However, further enhancement of the catalytic activity for OER is quite challenging, particularly for the development of stable SACs with overpotentials <180 mV. Here, we report an iridium single atom on Ni 2 P catalyst (Ir SA -Ni 2 P) with a record low overpotential of 149 mV at a current density of 10 mA·cm –2 in 1.0 M KOH. The Ir SA -Ni 2 P catalyst delivers a current density up to ∼28-fold higher than that of the widely used IrO 2 at 1.53 V vs RHE. Both the experimental results and computational simulations indicate that Ir single atoms preferentially occupy Ni sites on the top surface. The reconstructed Ir–O–P/Ni–O–P bonding environment plays a vital role for optimal adsorption and desorption of the OER intermediate species, which leads to marked enhancement of the OER activity. Additionally, the dynamic “top-down” evolution of the specific structure of the Ni@Ir particles is responsible for the robust single-atom structure and, thus, the stability property. In conclusion, this Ir SA -Ni 2 P catalyst offers novel prospects for simplifying decoration strategies and further enhancing OER performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Recent Weakening of the Global Radiative Feedback

Earth's climate stability, characterized by the global radiative feedback parameter (𝜆), varies decadally due to changing surface temperature patterns. Recent variations in 𝜆 are poorly understood as coordinated model simulations typically end in 2014. We apply a convolutional neural network trained on climate model simulations to observation-based surface temperature reconstructions to estimate variations in 𝜆 up to 2025. We find that 𝜆 reached a minimum (maximum stability) around the mid 1990s (𝜆 ≃ −3 Wm −2 /K), but has since weakened significantly (𝜆 ≃ −2 Wm −2 /K). We confirm these results with climate model simulations extended to 2022. The recent 𝜆 weakening is not significantly affected by El Niño Southern Oscillation or Pacific Decadal Oscillation. Attribution reveals that warming in the subtropical Northeast Pacific is an important driver of the recently weakened feedback, confirmed by targeted experiments in E3SMv2. Our approach enables near real-time monitoring of Earth's climate stability.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Changes in electric field noise due to thermal transformation of a surface ion trap

Here, we aim to illuminate how the microscopic properties of a metal surface map to its electric field noise characteristics. In our system, prolonged heat treatments of a metal film can induce a rise in the magnitude of the electric field noise generated by the surface of that film. We refer to this heat-induced rise in noise magnitude as a thermal transformation. The underlying physics of this thermal transformation process is explored through a series of heating, milling, and electron treatments performed on a single surface ion trap. Between these treatments, 40 Ca + ions trapped 70 μm above the surface of the metal are used as detectors to monitor the electric field noise at frequencies close to 1 MHz. An Auger spectrometer is used to track changes in the composition of the contaminated metal surface. With these tools we investigate contaminant deposition, chemical reactions, and atomic restructuring as possible drivers of thermal transformations.

36 MATERIALS SCIENCE↗