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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Thermal evolution of spin excitations in honeycomb Ising antiferromagnetic FePSe 3

We use elastic and inelastic neutron scattering (INS) to study the antiferromagnetic (AF) phase transitions and spin excitations in the two-dimensional (2D) zig-zag antiferromagnet FePSe 3 . By determining the magnetic order parameter across the AF phase transition, we conclude that the AF phase transition in FePSe 3 is first-order in nature. In addition, our INS measurements reveal that the spin waves in the AF ordered state have a large easy-axis magnetic anisotropy gap, consistent with an Ising Hamiltonian, and possible biquadratic magnetic exchange interactions. On warming across T N , we find that dispersive spin excitations associated with three-fold rotational symmetric AF fluctuations change into FM spin fluctuations above T N . These results suggest that the first-order AF phase transition in FePSe 3 may arise from the competition between C 3 symmetric AF and C 1 symmetric FM spin fluctuations around T N , in place of a conventional second-order AF phase transition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface plasmon driven near- and midinfrared photoconductivity in ligand-free ITO nanocrystal films

Semiconductor nanocrystals (NCs) offer exciting opportunities to deploy infrared optoelectronic technology in a variety of applications that are off-limits to conventional single-crystalline materials. However, the performance and stability of state-of-the-art NC-based devices strongly depend on the details of the NC surface and its passivating ligands. Here, the authors use indium tin oxide NC films stripped of organic ligands and conformally coated with Al 2 O 3 to show that absorption enabled by infrared localized surface plasmon resonances permit infrared photoconduction. For Au electrodes, these metallic NC films exhibit stable photoconductive performance over months in ambient and under electrical stress.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

Abstract Primordial black holes (PBHs) could explain some fraction of dark matter and shed light on many areas of early-Universe physics. Despite over half a century of research interest, a PBH population has so far eluded detection. The most competitive constraints on the fraction of dark matter comprised of PBHs ( f DM ) in the (10 −9 –10) M ⊙ mass ranges come from photometric microlensing and bound f DM ≲ 10 −2 –10 −1 . With the advent of the Roman Space Telescope with its submilliarcsecond astrometric capabilities and its planned Galactic Bulge Time Domain Survey (GBTDS), detecting astrometric microlensing signatures will become routine. Compared with photometric microlensing, astrometric microlensing signals are sensitive to different lens masses–distance configurations and contain different information, making it a complimentary lensing probe. At submilliarcsecond astrometric precision, astrometric microlensing signals are typically detectable at larger lens–source separations than photometric signals, suggesting a microlensing detection channel of pure astrometric events. We use a Galactic simulation to predict the number of detectable microlensing events during the GBTDS via this pure astrometric microlensing channel. Assuming an absolute astrometric precision floor for bright stars of 0.1 mas for the GBTDS, we find that the number of detectable events peaks at ≈10 3 f DM for a population of 1 M ⊙ PBHs and tapers to ≈10 f DM and ≈100 f DM at 10 −4 M ⊙ and 10 3 M ⊙ , respectively. Accounting for the distinguishability of PBHs from stellar lenses, we conclude the GBTDS will be sensitive to a PBH population at f DM down to ≈10 −1 –10 −3 for (10 −1 –10 2 ) M ⊙ likely yielding novel PBH constraints.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1981

Aircraft NO/x/ emissions and stratospheric ozone reductions - Another look

New estimates for stratospheric ozone perturbations attributable to supersonic transport (SST) emissions are presented. First, a review is given of recent data pointing to lower OH concentrations below 30 km, as compared to the values predicted by photochemical models. The evidence for lower OH comes from a wide range of laboratory and atmospheric studies. The sensitivity of theoretical estimates of ozone change to OH abundances, and the coupling mechanisms between the O(x)-NO(x)-HO(x)-Cl(x) families which are responsible for the sensitivity, are discussed. Updated calculations for SST-induced ozone alterations are compared with older predictions. For example, assuming continuous aircraft injection of NO2 at 20 km at a rate of 1 x 10 to the 9th kg per year (globally), a 4% ozone decrease, is now calculated where earlier a 3% ozone increase was found. This large variance from previous forecasts suggests that new assessments of certain other polluting agents, particularly nitrogen fertilizers, are needed.

Turco, R. P.↗
NASA NTRS2011

Howardite Noble Gases as Indicators of Asteroid Surface Processing

The HED (Howardite, Eucrite and Diogenite) group meteorites likely or iginate from the Asteroid 4 Vesta - one of two asteroid targets of NA SA's Dawn mission. Whilst Howardites are polymict breccias of eucriti c and diogenitic material that often contain "regolithic" petrologica l features, neither their exact regolithic nature nor their formation processes are well defined. As the Solar Wind (SW) noble gas compon ent is implanted onto surfaces of solar system bodies, noble gas anal yses of Howardites provides a key indicator of regolithic origin. In addition to SW, previous work by suggested that restricted Ni (300-12 00 micro g/g) and Al2O3 (8-9 wt%) contents may indicate an ancient we ll-mixed regolith. Our research combines petrological, compositional and noble gas analyses to help improve understanding of asteroid reg olith formation processes, which will play an intergral part in the i nterpretation of Dawn mission data. Following compositional and petrological analyses, we developed a regolith grading scheme for our sampl e set of 30 Howardites and polymict Eucrites. In order to test the r egolith indicators suggested by, our 8 selected samples exhibited a r ange of Ni, Al2O3 contents and regolithic grades. Noble gas analyses were performed using furnace stepheating on our MAP 215-50 noble gas mass spectrometer. Of our 8 howardites, only 3 showed evidence of SW noble gases (e.g approaching Ne-20/Ne-22 approximately equals 13.75, Ne-21/Ne-22 approximately equals 0.033). As these samples display low regolithic grades and a range of Ni and Al2O3 contents, so far we are unable to find any correlation between these indicators and "regolit hic" origin. These results have a number of implications for both Ho wardite and Vesta formation, and may suggest complex surface stratigr aphies and surface-gardening processes.

Cartwright, J. A.↗
NASA NTRS1990

Dynamic fracture responses of alumina and two ceramic composites

A hybrid experimental-numerical procedure was used to characterize the dynamic fracture response of Al2O3 and TiB2-particulate/SiC-matrix and SiC-whisker/Al2O3-matrix composites. Unlike metals and polymers, dynamic arrest stress intensity factors (SIFs) did not exist in the monolithic ceramics and the two ceramic composites considered. Thus a running crack in these materials cannot be arrested by lowering the driving force, i.e., the dynamic SIF. Fractography study of the alumina specimens showed that the area of transgranular failure varied from about 3 percent to about 16 percent for rapid crack extensions in statically and impact loaded specimens, respectively. The influence of kinematic constraints which enforces transgranular flat crack extension, despite the higher fracture energy of transgranular fracture, is discussed.

Yang, Kwan-Ho↗
DOE OSTI2020

Materials Data on HoMg(BO2)5 by Materials Project

MgHo(BO2)5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.37 Å. Ho3+ is bonded in a 9-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.98 Å. There are five inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.49 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.38 Å) B–O bond length. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.51 Å. In the fifth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Mg2+, one Ho3+, and one B3+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2ReB6 by Materials Project

Ho2ReB6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 4-coordinate geometry to fourteen B2- atoms. There are a spread of Ho–B bond distances ranging from 2.74–2.83 Å. In the second Ho3+ site, Ho3+ is bonded to twelve B2- atoms to form a mixture of edge and face-sharing HoB12 cuboctahedra. There are a spread of Ho–B bond distances ranging from 2.59–2.62 Å. Re6+ is bonded in a 10-coordinate geometry to ten B2- atoms. There are a spread of Re–B bond distances ranging from 2.36–2.41 Å. There are six inequivalent B2- sites. In the first B2- site, B2- is bonded in a 9-coordinate geometry to six Ho3+ and three B2- atoms. There are a spread of B–B bond distances ranging from 1.84–1.95 Å. In the second B2- site, B2- is bonded in a 3-coordinate geometry to four equivalent Ho3+, two equivalent Re6+, and three B2- atoms. There are a spread of B–B bond distances ranging from 1.80–1.83 Å. In the third B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.81 Å. In the fourth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. There is one shorter (1.74 Å) and one longer (1.85 Å) B–B bond length. In the fifth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.80 Å. In the sixth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Complex-coordinate calculation of 1D(e) resonances using Hylleraas functions

The lowest 1D(e) resonances below the n = 2 and n = 3 thresholds are calculated using a method of complex-coordinate rotation. The results, obtained with the use of Hylleraas functions, are believed to be of high accuracy. This work should serve as a useful reference for other investigations.

Bhatia, A. K.↗
NASA NTRS1991

Composite load spectra for select space propulsion structural components

This report summarizes the development for: (1) correlation fields; (2) applications to liquid oxygen post; (3) models for pressure fluctuatios and vibration loads fluctuations; (4) additions to expert systems; and (5) scaling criteria. Implementation to computer code is also described. Demonstration sample cases are included with additional applications to engine duct and pipe bend.

Newell, James F.↗
NASA NTRS2019

Evidence for Late-stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-lined Ic Supernova: Pre-explosion Emission and a Rapidly Rising Luminous Transient

We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag/hr) and luminous (M(g,peak) = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L(bol) ≳ 3 x 10^(44) erg/s), the short rise time (t = 3 days rise in g band), and the blue colors at peak (g–r ~ -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T(eff) ≳ 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (M(g) ~ M(r) ≈ -14 mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E(γ,iso) < 4.9 x 10^(48) erg, a limit on X-ray emission L(X) < 10^(40) erg/s, and a limit on radio emission vL(v) ≲ 10^(37) erg/s. Taken together, we find that the early (<10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 Mꙩ) at large radii (3 x 10^(14) cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (>10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.

Anna Y. Q. Ho↗
DOE OSTI2020

Materials Data on Na2HoPCO7 by Materials Project

Na2HoCPO7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.23–2.69 Å. Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.23–2.35 Å. C4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of C–O bond distances ranging from 1.26–1.33 Å. P5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of P–O bond distances ranging from 1.55–1.58 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Na1+ and one C4+ atom. In the second O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one C4+ atom to form distorted ONa2HoC trigonal pyramids that share corners with three equivalent ONa2HoP tetrahedra and edges with two equivalent ONa2HoC trigonal pyramids. In the third O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one C4+ atom to form distorted ONa2HoC trigonal pyramids that share corners with three equivalent ONa2HoP tetrahedra and edges with two equivalent ONa2HoC trigonal pyramids. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ho3+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Ho3+, and one P5+ atom. In the sixth O2- site, O2- is bonded to two equivalent Na1+, one Ho3+, and one P5+ atom to form distorted corner-sharing ONa2HoP tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Kinetics and Mechanism of the Singlet Oxygen Atom Reaction with Dimethyl Ether

Here, we combine in situ laser spectroscopy, quantum chemistry, and kinetic calculations to study the reaction of a singlet oxygen atom with dimethyl ether. Infrared laser absorption spectroscopy and Faraday rotation spectroscopy are used for the detection and quantification of the reaction products OH, H 2 O, HO 2 , and CH 2 O on submillisecond time scales. Fitting temporal profiles of products with simulations using an in-house reaction mechanism allows product branching to be quantified at 30, 60, and 150 Torr. The experimentally determined product branching agrees well with master equation calculations based on electronic structure data and transition state theory. The calculations demonstrate that the dimethyl peroxide (CH 3 OOCH 3 ) generated via O-insertion into the C–O bond undergoes subsequent dissociation to CH 3 O + CH 3 O through energetically favored reactions without an intrinsic barrier. This O-insertion mechanism can be important for understanding the fate of biofuels leaking into the atmosphere and for plasma-based biofuel processing technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2019

Machine Learning, Markov Chain Monte Carlo, and Optimal Algorithms to Characterize the AdvACT Kilopixel Transition-Edge Sensor Arrays

Next-generation focal planes comprising dozens of kilopixel transition-edge sensor (TES) arrays require new methods to rapidly screen candidate arrays, evaluate array non-idealities in the field, identify outlier devices for removal, and optimize the array performance in the field. We demonstrate robust methods to estimate TES parameters (critical temperatures and thermal conductivity parameters) and their uncertainties using a custom Markov Chain Monte Carlo (MCMC) algorithm. We also constrain systematic effects in estimating the TES parameters from non-isothermal current-voltage curves (IVs) at approximately a ~3% level. Additionally, for the first time, we have applied Machine Learning (ML) algorithms to tune detector arrays and optimize their performance.

Maria Salatino↗
DOE OSTI2025

Extraction and Separation of Rare-Earth Elements from Coal Fly Ash and Leachate using a Recyclable Ionic Liquid

Coal fly ash (CFA) can be a promising source for recovering rare-earth elements (REEs), as it contains a broad range of REEs with average concentrations frequently exceeding those in traditional rare earth mines. Recent research from our group has demonstrated that REEs can be preferentially extracted from CFA solids using a recyclable ionic liquid (IL), betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). When CFA was heated with the mixture of IL and an aqueous solution above 65°C, most leached REEs partitioned into the IL phase and were separated from the bulk elements. Subsequent acid stripping of the REE-loaded IL removed the REEs and regenerated the IL for reuse in multiple extraction cycles. This IL-based REE-CFA recovery method has been applied to ten CFA samples derived from different coal sources, including ash recovered from disposal ponds. Analysis of 34 elements confirmed the process consistently achieved high REE recovery efficiency, with strong selectivity over bulk and trace elements across diverse CFA types. In addition to the IL-solid extraction, the performance of [Hbet][Tf2N] in extracting REEs from fly-ash leachates have been evaluated by four commonly used leaching reagents, including HCl, HNO3, H2SO4, and citrate. During the IL-leachate extraction, [Hbet][Tf2N] was mixed and heated with a Class C fly ash leachate generated from each leaching reagent, followed by an acid stripping. It was observed that the partitioning and recovery of REEs increased as the leachate pH increased from 3 to 11. Among the investigated leachates, HCl and citrate proved to be the most compatible with IL extraction, exhibiting a slightly higher REE recovery and a lower non-REE co-extraction compared to the IL-solid extraction. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently showed a high recovery rate from both CFA solids and leachates. Notably, Pr, Tb, and Ho, which were not previously leached from the CFA solids, were partially recovered from the leachates. Overall, our studies revealed the strong potential of [Hbet][Tf2N] for effectively recovering REEs from leachates, highlighting its applicability as a sustainable strategy for other aqueous REE feedstocks. Furthermore, a techno-economic analysis will be performed to quantify the economic viability of the IL-based REE recovery method and guide future process improvement.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on Na2HoNb5O15 by Materials Project

Na2HoNb5O15 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.69 Å) and four longer (2.93 Å) Na–O bond lengths. Ho3+ is bonded to twelve O2- atoms to form HoO12 cuboctahedra that share faces with two equivalent HoO12 cuboctahedra and faces with eight equivalent NbO6 octahedra. There are four shorter (2.58 Å) and eight longer (2.66 Å) Ho–O bond lengths. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 0–33°. There is two shorter (1.97 Å) and four longer (2.01 Å) Nb–O bond length. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra and faces with two equivalent HoO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 13–43°. There are a spread of Nb–O bond distances ranging from 1.92–2.08 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Na1+ and two Nb5+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+ and two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Nb5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two equivalent Nb5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Inverse-Designed Photonics for Semiconductor Foundries

Silicon photonics is becoming a leading technology in photonics, displacing traditional fiber optic transceivers and enabling new applications. Further improving the density and performance of silicon photonics, however, has been challenging due to the large size and limited performance of traditional semianalytically designed components. Automated optimization of photonic devices using inverse design is a promising path forward but has, until now, faced difficulties in producing designs that can be fabricated reliably at scale. In this paper we experimentally demonstrate four inverse-designed devices made successfully in a commercial silicon photonics foundry: a spatial mode multiplexer, wavelength demultiplexer, 50–50 directional coupler, and 3-way power splitter. These devices are efficient, robust to fabrication variability, and compact, with footprints only a few micrometers across. They pave the way forward for the widespread practical use of inverse design.

36 MATERIALS SCIENCE↗