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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Evaluating the exfoliation of two-dimensional materials with a Green's function surface model

Previous methods for the evaluation of the exfoliation of two-dimensional (2D) layered materials have drawbacks in computational efficiency and are unable to describe cases with semi-infinite substrates. Based on a Green's function surface (GFS) model, here we develop an approach to efficiently determine the tendency of exfoliation of 2D materials from their bulk crystals or semi-infinite substrates. By constructing appropriate surface configurations, we may calculate the exfoliation energy more precisely and quickly than the traditional way with the slab model. Furthermore, the GFS approach can provide angle-resolved photoemission spectroscopy of surface systems for direct comparison with experimental data. In this work, our findings indicate that the GFS approach is powerful for studies of 2D materials and various surface problems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1995

Low temperature Zn diffusion for GaSb solar cell structures fabrication

Low temperature Zn diffusion in GaSb, where the minimum temperature was 450 C, was studied. The pseudo-closed box (PCB) method was used for Zn diffusion into GaAs, AlGaAs, InP, InGaAs and InGaAsP. The PCB method avoids the inconvenience of sealed ampoules and proved to be simple and reproducible. The special design of the boat for Zn diffusion ensured the uniformality of Zn vapor pressure across the wafer surface, and thus the uniformity of the p-GaSb layer depth. The p-GaSb layers were studied using Raman scattering spectroscopy and the x-ray rocking curve method. As for the postdiffusion processing, an anodic oxidation was used for a precise thinning of the diffused GaSb layers. The results show the applicability of the PCB method for the large-scale production of the GaSb structures for solar cells.

Sulima, Oleg V.↗
NASA NTRS1999

The Astro-E High Resolution X-Ray Spectrometer

The Astro-E High Resolution X-ray Spectrometer (XRS) was developed jointly by the NASA/Goddard Space Flight Center and the Institute of Space and Astronautical Science in Japan. The instrument is based on a new approach to spectroscopy, the X-ray microcalorimeter. This device senses the energies of individual X-ray photons as heat with extreme precision. A 32 channel array of microcalorimeters is being employed, each with an energy resolution of about 12 eV at 6 keV (the Fe-K region). This will provide spectral resolving power 10 times higher than any other non-dispersive X-ray spectrometer. The instrument incorporates a three stage cooling system capable of operating the array at 60 mK for about two years in orbit. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the X-ray mirror system combine to give high throughput over the 0.3-12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. This paper presents the basic design requirements and implementation of the XRS, and also describes the instrument parameters and performance.

Kelley, Richard L.↗
NASA NTRSDate not supplied

Quantative Measurements of Trace Elements and Three-Dimensional Atomic Scale Characterisation of Presolar O-rich Oxides and Silicates: An Atom Probe Tomography Approach

Presolar grains are recordsof a single moment in stellar evolution which have survived nebula and parent body processingwithin our Solar System. These grains condensed within a range of stellar envi-ronments including asymptotic giant branch stars, red giant branch stars, nova, supernova (SN) and hydrogen burning electron capture supernova(ECSN)[1,2]. Iso-topic and chemical compositions can be used to unravel details about environmental conditions at the time of their condensation and physical and chemical processes occurring at the time. For example,nucleosynthesis, stellar evolution, physical properties of stellar atmos-pheres, mixing from inner core to outer envelope, galac-tic chemical evolution, interstellar medium and parent body processing.NanoSIMS enables detailed characterisation of iso-topic compositions and rapid in situidentification of O-rich presolar oxides and silicates using their character-istic 17O/16O and 18O/16O isotopic ratios.Spectroscopic techniques e.g., auger spectroscopyand transmission electron microscopy, have provided additional details on major and minor chemical signatures. However, due tospatial resolution limitations,interaction volumes and interferencesfrom surrounding grains for in situtech-niques, attaining quantative characterisation of trace el-ements,hasproved challenging[1,3]. As the most sensitive geochemical tracers of envi-ronmental changes, trace elements are essential to un-ravelling the geochemical record of their parent stellar environments and evolutionary pathways[4].We car-ried out correlated in situisotopic and chemical analyses of 13 presolar grains to better understand stellar evolu-tion. In this work, we achieved this using a custom ap-proach, coordinating NanoSIMS, Scanning Electron Microscopy Energy Dispersive X-Ray Spectroscopy (SEM-EDX)and Atom Probe Tomography(APT).Our objective was to develop an approach which could ena-ble precise targeting of presolar grains for atom probe tomography and successfully execute atomic scale anal-yses of presolar oxides and silicates, to achieve quantative analysis of their trace elements for the first time.We also aimed to test the capability for Atom Probe tomography to measure isotopic compositions and stoichiometries of presolar oxide and silicate grains.

N D Nevill↗
DOE OSTI2021

Microneedle-based electrical impedance sensor to monitor plant water status in real time

A sensor uses microneedle electrodes and multi-frequency electrical impedance spectroscopy to monitor plant water status in real time. The microneedle can be between 10 and 1000 microns in length, enabling precise placement in a variety of plant tissues. The impedance behavior can distinguish electrical properties and physiological functions of different plant tissue types. Therefore, impedance measurements can be used to monitor water stress to prevent irreversible damage to a plant and to enable improvement of plant biomass or fruit yield.

Hanson, David T.↗
DOE OSTI2026

In-Band Scattering and Absorption of Infrared Blocking Foam Filters for Millimeter-wave Cameras

Expanded closed-cell polymer foams are widely used as thermal infrared (IR) blocking filters in millimeter-wave cameras, particularly for Cosmic Microwave Background observations. Precise knowledge of their millimeter-wave properties is essential for optimizing sensitivity. We present broadband (150 GHz - 2 THz) transmittance spectroscopy of Styroace-II and several Zotefoam filters, fitting their spectra with a radiative transfer model incorporating dielectric absorption and Rayleigh, Mie, and higher-order scattering. For a typical 5~cm thick filter stack at 280~GHz, Styroace-II exhibits ${\sim}10\%$ scattering with absorption estimated as ${\lesssim}5\%$ by effective-medium theory, while Zotefoam HD30 offers superior performance at ${\sim}3\%$ scattering and absorption likewise bounded to ${{\lesssim}0.3\%}$. Each model component is constrained at the ${\sim}0.1\%$ transmittance level for millimeter wavelengths. We observe batch-to-batch scattering variability of up to 2 percentage points in foams with multiple tested batches. Less commonly used Zotefoam formulations (LD15 and LD24) can further reduce in-band scattering to ${<}1\%$ while maintaining negligible in-band absorption and likely comparable IR blocking due to shared polyethylene absorption features and similar cell sizes. Based on this work, a filter constructed from the best measured LD24 batch has replaced the Styroace-II filter in a Simons Observatory 220/280 GHz Small Aperture Telescope.

Thomas, Alex [Chicago U., Astron. Astrophys. Ctr.;↗
DOE OSTI2025

LDRD conclusion poster - Synthesizing Heterometallic Uranium Single Crystals to Understand the Influence of the Secondary Metals on Uranyl Axial Bond Strength

Understanding how transition metals influenced the chemistry of lanthanide and actinide (f-element) materials is critical for advancing separation technologies, materials design, and coordination chemistry. This project examined how incorporating first-row transition metals affected the structural and spectroscopic properties of f-element coordination polymers. In uranium(VI)-based systems synthesized with 2,6-pyridinedicarboxylic acid (PDC) ligands, single-crystal X-ray diffraction and Raman spectroscopy revealed that the presence of transition metals shortened the uranyl axial bond and induced a blue shift in its symmetric stretching vibration—evidence of increased bond strength. Electronic structure analysis, including Density of States (DOS) calculations using density functional theory (DFT), revealed altered orbital overlaps and highlighted the role of transition metal d-orbitals in modulating bonding. Raman modes were modeled using truncated structural fragments in collaboration with the University of Notre Dame, and although the predicted frequencies were lower than experimental values, they remained within expected ranges. In parallel, similar experiments with cerium (Ce) in the presence of cobalt (Co) and PDC demonstrated multi-step single-crystal-to-single-crystal transformations—behavior not observed in the uranium systems. Initial products included light yellow, orange, and polycrystalline materials. Single-crystal X-ray diffraction studies, conducted in collaboration with the Colorado School of Mines, identified the yellow phase as monometallic Ce(PDC)2(H2O)2·4H2O and the orange phase as heterometallic Ce2Co(PDC)4(H2O)6. After standing in solution for one week, both phases fully transformed into a dark yellow crystalline phase, [Ce3(PDC)5(H2O)8].6(H2O). Remarkably, this transformation was reversible—disturbing the equilibrium by removing some crystals caused reversion to the initial Ce(PDC)2(H2O)2·4H2O phase, highlighting dynamic behavior. All three structures were previously unreported. Solid-state UV-visible and Raman spectroscopy further distinguished these phases, revealing ligand-to-metal charge transfer involving Ce and characteristic d–d transitions from Co(II). The precise mechanism driving these transformations remained unclear; however, pH-dependent experiments confirmed that the transformation did not occur when the pH decreased. Overall, the project demonstrated that transition metals could be employed to tune bonding interactions, structural dimensionality, and optical properties in f-element materials, establishing new pathways for designing functional heterometallic systems. The work resulted in several novel structural discoveries and fostered productive collaborations with the University of Notre Dame and the Colorado School of Mines.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2023

Precision measurement of 65 Zn electron-capture decays with the KDK coincidence setup

65 Zn is a common calibration source, moreover used as a radioactive tracer in medical and biological studies. In many cases, γ-spectroscopy is a preferred method of 65 Zn standardization, which relies directly on the branching ratio of Jπ( 65 Zn) = 5/2- → Jπ( 65 Cu) = 5/2 - via electron capture (EC*). We measure the relative intensity of this branch to that proceeding directly to the ground state (EC 0 ) using a novel coincidence technique, finding I EC 0/IEC* = 0.9684 ± 0.0018. Re-evaluating the decay scheme of 65 Zn by adopting the commonly evaluated branching ratio of I β+ = 1.4271(7)% we obtain IEC* = (50.08 ± 0.06)%, and I EC 0 = (48.50 ± 0.06)%. The associated 1115 keV gamma intensity agrees with the previously reported NNDC value, and is now accessible with a factor of ~2 increase in precision. Our re-evaluation removes reliance on the deduction of this gamma intensity from numerous measurements, some of which disagree and depend directly on total activity determination. The KDK experimental technique provides a new avenue for verification or updates to the decay scheme of 65 Zn, and is applicable to other isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Solid state reduction of nickelate thin films

The square-planar nickelates are a class of superconductors analogous to the cuprates and promise to provide insight into the pairing mechanism in high-temperature superconducting oxides. The parent phase of doped superconducting films is NdNiO 2 , which is prepared by reducing 3 + Ni in NdNiO 3 films. In this paper, we develop an ultrahigh vacuum reduction method using aluminum deposited on top of the 3 + nickelates and monitor the reduction process in real time through in situ crystal truncation rod measurements and diffraction x-ray absorption near edge spectroscopy measurements across the Ni K edge. Further, we establish a relation between Ni valence and the lattice constant of NdNiO 3-x and show that the process can precisely control the oxygen content in the films. Finally, we extend the reduction process to quintuple square-planar nickelates.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ligand effect on switching the rate-determining step of water oxidation in atomically precise metal nanoclusters

The ligand effects of atomically precise metal nanoclusters on electrocatalysis kinetics have been rarely revealed. Herein, we employ atomically precise Au 25 nanoclusters with different ligands (i.e., para-mercaptobenzoic acid, 6-mercaptohexanoic acid, and homocysteine) as paradigm electrocatalysts to demonstrate oxygen evolution reaction rate-determining step switching through ligand engineering. Au 25 nanoclusters capped by para-mercaptobenzoic acid exhibit a better performance with nearly 4 times higher than that of Au 25 NCs capped by other two ligands. We deduce that para-mercaptobenzoic acid with a stronger electron-withdrawing ability establishes more partial positive charges on Au(I) (i.e., active sites) for facilitating feasible adsorption of OH – in alkaline media. X-ray photo-electron spectroscopy and theoretical study indicate a profound electron transfer from Au(I) to para-mercaptobenzoic acid. The Tafel slope and in situ Raman spectroscopy suggest different ligands trigger different rate-determining step for these Au 25 nanoclusters. The mechanistic insights reported here can add to the acceptance of atomically precise metal nanoclusters as effective electrocatalysts.

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

Stereogenic-at-silicon hybrid conjugated polymers

Stereoregularity in carbon-based polymers impacts critical physical properties such as crystallinity, but achieving comparable precision in polysilanes remains challenging. Herein, we report the synthesis of hybrid σ,π-conjugated polysilanes with defined stereoregularity, derived from cis- and trans-cyclosilane building blocks. Using Kumada polycondensation, we accessed a series of atactic, trans-enriched, and cis-enriched polysilanes, enabling a systematic investigation of how tacticity influences thermal and optical properties. Differential scanning calorimetry revealed distinct glass transition behaviors for stereoregular polymers compared to their atactic counterpart, and UV-vis spectroscopy demonstrated enhanced spectral resolution upon annealing of stereoregular films. A linear silane-based analog further underscored the structural impact of cyclic stereogenic units. These findings highlight how stereochemical precision in silicon-containing backbones can modulate macromolecular properties, opening avenues for the rational design of stereoregular polysilanes.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Tunable far-IR laser spectroscopy of jet-cooled carbon clusters - The nu-2 bending vibration of C3

Seven rovibrational transitions of the (01/1/0)-(00/0/0) fundamental bending band of C3 have been measured with high precision with the use of a tunable far-infrared laser spectrometer. The C3 molecules were produced by laser vaporization of a graphite rod and cooled in a supersonic expansion. The astrophysically important nu-2 fundamental frequency is determined to be 63.416529(40)/cm. These measurements provide the basis for studies of C3 in the interstellar medium with far-infrared astronomy.

Schmuttenmaer, C. A.↗
DOE OSTI2026

Terahertz 2D coherent spectroscopy for probing and controlling multicorrelations in quantum matter

Terahertz 2D coherent spectroscopy (THz-2DCS) is an emerging technique that brings multidimensional resolution to the ultrafast spectral–temporal dynamics of non-equilibrium quantum phases of matter, enabling new capabilities for precise coherent control in many-body dynamics and multiorder correlations. Here, by mapping and disentangling complex excitation and detection pathways across distinct time and frequency dimensions, THz-2DCS provides a form of coherence tomography of light-induced quantum matter — revealing multiquantum coherences, separating nonlinear response functions and capturing collective modes and quantum kinetics on ultrafast THz timescales. This Perspective discusses the technical capabilities of THz-2DCS, provides a comparison to other multidimensional and coherent transient spectroscopies and looks ahead towards opportunities for advancing THz-2DCS instrumentation and experimental strategies towards new frontier discoveries.

Huang, Chuankun [Ames Laboratory (AMES), Ames, IA ↗
DOE OSTI2020

The working principle of hybrid perovskite gamma-ray photon counter

Gamma-ray spectroscopy that quantifies the gamma-ray energies is a critical technology widely needed in astrophysics, nuclear material detection and medical treatment. The key is to precisely count gamma-ray photons using sensitive detectors. In this paper, we investigate the operational principles of chlorine-doped methylammonium lead tribromide (MAPbBr 3-x Cl x ) perovskite single crystal detectors that can efficiently count gamma-ray photon events with electrical pulses. Specifically, we find the main dark current originates from the thermally activated electron injection from the impurities, and using high work function contacts can block out the dark noise thus allows for efficient pulse collection at higher electrical fields ~500 V/cm. As a result, we observe strong electrical pulses when exposing the detector under radioactive sources emitting gamma-ray photons at various energies. Our results also reveal the fundamental issues that prevent the reliable observation of photo-electric peak. This work suggest pathway towards energy resolved gamma-ray spectroscopy using perovskite crystal detectors.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Cyclotron radiation emission spectroscopy signal classification with machine learning in project 8

The Cyclotron Radiation Emission Spectroscopy (CRES) technique pioneered by Project 8 measures cyclotron radiation from individual electrons in a background magnetic field to construct a highly precise energy spectrum for beta decay studies and other applications. The detector, magnetic trap geometry, and electron dynamics give rise to a multitude of complex electron signal structures which carry information about distinguishing physical traits. Here, we develop machine learning models to classify CRES signals with high accuracy based on these traits, improve the resultant frequency spectrum, and offer the potential for a sophisticated analysis which will help Project 8 achieve tritium endpoint measurement in the future.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Instantaneous difference frequency locking observed during toroidicity-induced Alfvén eigenmode coupling in the DIII-D tokamak

In magnetic confinement fusion, toroidicity-induced Alfvén eigenmodes (TAEs) are well-studied, weakly stable solutions of the linearized ideal magnetohydrodynamic equations. Driven unstable by suprathermal populations of energetic particles, TAE pose a key vulnerability to the confinement of high-energy alpha particles generated by fusion reactions. Hence, it is paramount to understand TAE dynamics if a working reactor is to be realized. In this work, we detect and characterize signatures of nonstationary nonlinear coupling between TAE using a novel, time-resolved bispectral analysis; results are supported by analytic signal of band-passed data. Crucially, a stationary phase relationship between two TAE and a nascent low frequency fluctuation is observed precisely when the triple product of magnetic fluctuation amplitudes is enhanced. Local mode number and frequency spectrum, gleaned from beam-emission spectroscopy, corroborates simultaneous satisfaction of nonlinear matching conditions, and provides a tool to identify theorized pathways of energy transfer, e.g. TAE parametric instability.

bispectral analysis↗
DOE OSTI2021

Pulse-burst spontaneous Raman thermometry of unsteady wave phenomena in a shock tube

A high-speed temperature diagnostic based on spontaneous Raman scattering (SRS) was demonstrated using a pulse-burst laser. The technique was first benchmarked in near-adiabatic H 2 -air flames at a data-acquisition rate of 5 kHz using an integrated pulse energy of 1.0 J per realization. Both the measurement precision and accuracy in the flame were within 3% of adiabatic predictions. Furthermore, this technique was then evaluated in a challenging free-piston shock tube environment operated at a shock Mach number of 3.5. SRS thermometry resolved the temperature in post-incident and post-reflected shock flows at a repetition rate of 3 kHz and clearly showed cooling associated with driver expansion waves. Collectively, this Letter represents a major advancement for SRS in impulsive facilities, which had previously been limited to steady state regions or single-shot acquisition.

47 OTHER INSTRUMENTATION↗
NASA NTRS1981

Investigations of coherent anti-Stokes Raman spectroscopy /CARS/ for practical combustion diagnostics

Coherent anti-Stokes Raman spectroscopy (CARS) is a coherent wave-mixing process in which the signal emerges as a laser-like beam in a precise direction. The spectroscopic technique is appropriate to spatially and temporally resolved measurements of temperature and major species concentrations in combustion. It has been generated from all of the dominant constituents in air-fed, hydrogen, and hydrocarbon fueled combustion, and found applicable to practical combustion systems. High pressure effects on CARS spectra have also been examined.

Eckbreth, A. C.↗