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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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29 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Observation of a Giant Goos-Hänchen Shift for Matter Waves

The Goos-Hänchen (GH) shift describes a phenomenon in which a specularly reflected beam is translated along the reflecting surface such that the incident and reflected rays no longer intersect at the surface. Using a neutron spin-echo technique and a specially designed magnetic multilayer mirror, we have measured the relative phase between the reflected up and down neutron spin states in total reflection. The relative GH shift calculated from this phase shows a strong resonant enhancement at a particular incident neutron wave vector, which is due to a waveguiding effect in one of the magnetic layers. Calculations based on the observed phase difference between the neutron states indicate a propagation distance along the waveguide layer of 0.65 mm for the spin-down state, which we identify with the magnitude of the giant GH shift. The existence of a physical GH shift is confirmed by the observation of neutron absorption in the waveguide layer. Here, we propose ways in which our experimental method may be exploited for neutron quantum-enhanced sensing of thin magnetic layers.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Evidence of antiferromagnetism in ultrathin metallic (111)-oriented LaNiO 3 films

Antiferromagnets with exotic spin textures promise low-power spintronic devices with extremely high operating frequencies and resistance to external perturbations. In particular, the combination of highly tunable correlated electron physics, as in complex oxides, with metallicity and antiferromagnetism is desirable but exceedingly rare. LaNiO 3 , the lone example of a perovskite nickelate which is metallic across all temperatures, has long been a promising candidate, but the antiferromagnetic metallic state has remained elusive. Here, we demonstrate the emergence of this state in ultrathin films of (111)-oriented LaNiO 3 using a combination of polarized neutron reflectometry, low-energy muon spectroscopy and anomalous Hall effect measurements, and density functional theory calculations with a Hubbard U term. Further, we find a highly strained symmetry-breaking interfacial region which may support canting of the AFM moments leading to a vanishingly small net magnetization at the film-substrate interface, providing a convenient route toward control of the Néel order. Evidence of antiferromagnetic metallic behavior in (111)LNO films highlights the role of crystal symmetry in tuning the novel quantum states in complex oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Controlling magnetism and transport at perovskite cobaltite interfaces via strain-tuned oxygen vacancy ordering

Complex oxides such as perovskite cobaltites exhibit rich phenomena at interfaces due to the complex interplay between their structural, defect, electronic, and magnetic degrees of freedom. Here, we study this interplay here in the ferromagnetic metallic cobaltite La 1−𝑥 ⁢Sr 𝑥⁢ CoO 3−𝛿 , using specific substrates to vary both the heteroepitaxial strain (compressive vs tensile) and growth orientation ((001) vs (110)). Transmission electron microscopy, electron energy-loss spectroscopy, high-resolution X-ray diffraction, magnetometry, polarized neutron reflectometry, and electronic magnetotransport measurements are applied. Lattice mismatch and growth orientation are found to enable the precise control of interfacial oxygen vacancy ordering in La 1−𝑥⁢ Sr 𝑥 ⁢CoO 3−𝛿 , thus dictating strain relaxation and oxygen vacancy depth profiles, in turn controlling thickness-dependent magnetic and electronic properties. In particular, compressive strain and (110) orientations minimize deleterious magnetic/electronic dead layer effects, leading to the optimization of interfacial magnetism and transport. Strain and orientation tuning of oxygen vacancy ordering are thus established as powerful means to control physical properties at cobaltite-based interfaces, relevant to several fields.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Advanced Characterization of Solid-State Battery Materials Using Neutron Scattering Techniques

Advanced batteries require advanced characterization techniques, and neutron scattering is one of the most powerful experimental methods available for studying next-generation battery materials. Neutron scattering offers a non-destructive method to probe the complex structural and chemical processes occurring in batteries during operation in truly in situ/in operando measurements with a high sensitivity to battery-relevant elements such as lithium. Neutrons have energies comparable to the energies of excitations in materials and wavelengths comparable to atomic distances in the solid state, thus giving access to study structural and dynamical properties of materials on an atomic scale. In this review, a broad overview of selected neutron scattering techniques is presented to illustrate how neutron scattering can be used to gain invaluable information of solid-state battery materials, with a focus on in situ/in operando methods. These techniques span multiple decades of length and time scales to uncover the complex processes taking place fundamentally on the atomic scale and to determine how these processes impact the macroscale properties and performance of functional battery systems. This review serves the solid-state battery research community by examining how the unique capabilities of neutron scattering can be applied to answer critical and unresolved questions of materials research in this field. A thorough and broad perspective is provided with numerous practical examples showing these techniques in action for battery research.

25 ENERGY STORAGE↗
DOE OSTI2024

Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?

Herein we study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF 4 - d 11 ), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS-d 7 ). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ~8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.

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

Understanding the Dissolution and Passivation of an Aluminum Electrode during Electrocoagulation of Groundwater Using Neutron and X-ray Reflectometry

An aluminum (Al)-based electrocoagulation (EC) system can effectively remove dissolved silica and hardness in groundwater. The effectiveness of Al-EC in terms of pollutant removal, Faradaic efficiency, and energy consumption depends on the interfacial electrolysis or passivation of the electrode in water. Thus, understanding the electrolysis reaction at the liquid/electrode interface during operation is important for sustainable EC deployment. Here, a continuous flow-through Al-EC system was tested with various groundwater simulants, i.e., chloride (Cl – )-based, sulfate (SO 4 2– )-based, and mixed solutions. High pollutant removal with low energy consumption was observed in Cl – -based groundwater treatment, while low pollutant removal with high energy consumption was observed in SO 4 2– -based groundwater. For example, the required energy per unit mass of Al dosing in SO 4 2– -based groundwater is three times higher than that in Cl – -based groundwater at 10 mA/cm 2 . However, increasing the Cl – concentration significantly reduces this energy demand. In SO 4 2– -based groundwater, the silicate removal efficiency drops from 85.1% to 24.0% compared to that for Cl – -based groundwater, while Mg 2+ and Ca 2+ removal efficiencies decrease to 0.6% from 15.8% and 5.7% from 44.8%, respectively. To better understand this EC performance, we used in situ neutron reflectometry (NR) to examine the interfacial dynamics of Al dissolution and passivation at a 100 nm scale occurring on the surface of the sacrificial Al electrodes during EC. Ex situ X-ray reflectometry (XRR) was also used to support the in situ NR results. Both NR and XRR results revealed that Al dissolution is influenced by the presence of Cl – in the simulants, while a passivating layer forms on the electrode in a SO 4 2– -based solution. In the Cl – -based solution, anodic Al dissolution occurred locally and inhomogeneously across the surface of the Al anode film, resulting in a localized thickness reduction over time. In the SO 4 2– -based solution, no apparent dissolution of the Al anode was identified. Instead, Al underwent oxidation, forming an amorphous Al 2 O 3 surface layer within the Al electrode film that increased in thickness over time. In the mixed solution, both anodic Al dissolution and surface Al 2 O 3 layer formation occurred, indicating that Al dissolution and surface Al 2 O 3 layer formation are attributable to the Cl – and SO 4 2– ions, respectively.

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

Role of Salt Concentration on Interphase Dynamics and Chemistry of Silicon Anodes during Electrochemical Cycling

We investigated the chemistry and structure of the solid electrolyte interphase (SEI) grown over a silicon anode as a function of the lithium salt concentration. In these experiments, in situ neutron reflectivity measurements were performed to measure the thickness and composition of the SEI formed from 1.0 and 5.5 M lithium bis(trifluoromethane)sulfonimide (LiTFSI) in standard ethylene carbonate:dimethyl carbonate electrolytes. These measurements reveal the formation of a 350+ Å thick SEI layer that is predominantly organic (∼80%) and dimensionally stable when using a 1.0 M salt solution. In contrast, increasing the salt concentration to 5.5 M resulted in an SEI that exhibited thickness changes from 100 to 375 Å and became up to 30% inorganic. In conclusion, these compositional and structural changes point to the role of salt speciation on the resulting passivation of silicon electrodes and indicate the need to form more organic-like passivation layers to promote the calendar life of silicon anodes.

Electrodes↗
DOE OSTI2026

Confined Room-Temperature Ferromagnetism in Kagome (Fe 3 Sn 2 /CoSn) Superlattices

We reveal the presence of robust ferromagnetism in topological kagome (Fe 3 Sn 2 /CoSn) ×n superlattices via polarized neutron reflectivity (PNR) and magnetization measurements. Using molecular beam epitaxy, we have synthesized superlattices of alternating ferromagnetic Fe 3 Sn 2 and paramagnetic CoSn layers, the interfacial integrity of which is confirmed using scanning transmission electron microscopy. Magnetization depth profiles, obtained by fitting the PNR data, confirm the presence of ferromagnetism in the confined Fe 3 Sn 2 layers at room temperature, with minimal thickness dependence down to 2 nm. A net magnetization is found in the near-surface region of CoSn, which we attribute to surface oxidation. Our results demonstrate that superlattice engineering is a means to confine ferromagnetism in kagome metals, enabling future studies of thickness-dependent anomalous Hall and Nernst effects as well as spin-dependent transport and tunneling in device structures.

kagome metals↗
NASA NTRS2000

BOREAS HYD-1 Volumetric Soil Moisture Data

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-1 team made measurements of volumetric soil moisture at the Southern Study Area (SSA) and Northern Study Area (NSA) tower flux sites in 1994 and at selected tower flux sites in 1995-97. Different methods were used to collect these measurements, including neutron probe and manual and automated Time Domain Reflectometry (TDR). In 1994, the measurements were made every other day at the NSA-OJP (Old Jack Pine), NSA-YJP (Young Jack Pine), NSA-OBS (Old Black Spruce), NSA-Fen, SSA-OJP, SSA-YJP, SSA-Fen, SSA-YA (Young Aspen), and SSA-OBS sites. In 1995-97, when automated equipment was deployed at NSA-OJP, NSA-YJP, NSA-OBS, SSA-OBS, and SSA-OA (Old Aspen), the measurements were made as often as every hour. The data are stored in tabular ASCII files. The volumetric soil moisture data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Cuenca, Richard H.↗
DOE OSTI2024

Effect of Biomass Water Dynamics in Cosmic-Ray Neutron Sensor Observations: A Long-Term Analysis of Maize–Soybean Rotation in Nebraska

Precise soil water content (SWC) measurement is crucial for effective water resource management. This study utilizes the Cosmic-Ray Neutron Sensor (CRNS) for area-averaged SWC measurements, emphasizing the need to consider all hydrogen sources, including time-variable plant biomass and water content. Near Mead, Nebraska, three field sites (CSP1, CSP2, and CSP3) growing a maize–soybean rotation were monitored for 5 (CSP1 and CSP2) and 13 (CSP3) years. Data collection included destructive biomass water equivalent (BWE) biweekly sampling, epithermal neutron counts, atmospheric meteorological variables, and point-scale SWC from a sparse time domain reflectometry (TDR) network (four locations and five depths). In 2023, dense gravimetric SWC surveys were collected eight (CSP1 and CSP2) and nine (CSP3) times over the growing season (April to October). The N0 parameter exhibited a linear relationship with BWE, suggesting that a straightforward vegetation correction factor may be suitable (fb). Results from the 2023 gravimetric surveys and long-term TDR data indicated a neutron count rate reduction of about 1% for every 1 kg m−2 (or mm of water) increase in BWE. This reduction factor aligns with existing shorter-term row crop studies but nearly doubles the value previously reported for forests. This long-term study contributes insights into the vegetation correction factor for CRNS, helping resolve a long-standing issue within the CRNS community.

Chemistry↗
DOE OSTI2024

Dopant, coating, and grating effects in silica optical fibers under extreme neutron irradiation

Radiation effects on fiber Bragg gratings (FBGs) have been studied but data gaps related to the effects of displacement damage resulting from high fast neutron fluence remain. In this work, Type-I and Type-II FBGs inscribed in optical fibers with various core dopants (Ge and F) and fiber coatings (acrylate, polyimide) were monitored in situ during 75 days of neutron irradiation to a peak fast (>0.1 MeV) neutron fluence of 3 X 10 21 n fast /cm 2 . Further, the reflected intensity of the Type-I FBGs inscribed in a Ge-doped core fiber decreased by > 30 dB within 7 h of irradiation (10 19 n fast /cm 2 ), whereas Type-II FBGs inscribed in a pure silica core fiber eventually approached >40 dB attenuation after accumulating a fast neutron fluence on the order of 10 20 n fast /cm 2 . Type-II FBGs inscribed in F-doped core fiber improved stability: the attenuation approached an equilibrium value in the range of 10 to 20 dB.

47 OTHER INSTRUMENTATION↗