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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Nucleation kinetics model for primary crystallization in Al–Y–Fe metallic glass

The high density of aluminum nanocrystals (>10 21 m -3 ) that develop during the primary crystallization in Al-based metallic glasses indicates a high nucleation rate (~10 18 m -3 s -1 ). Several studies have been advanced to account for the primary crystallization behavior, but none have been developed to completely describe the reaction kinetics. Recently, structural analysis by fluctuation electron microscopy has demonstrated the presence of the Al-like medium range order (MRO) regions as a spatial heterogeneity in as-spun Al 88 Y 7 Fe 5 metallic glass that is representative for the class of Al-based amorphous alloys that develop Al nanocrystals during primary crystallization. From the structural characterization, an MRO seeded nucleation configuration is established, whereby the Al nanocrystals are catalyzed by the MRO core to decrease the nucleation barrier. The MRO seeded nucleation model and the kinetic data from the delay time (τ) measurement provide a full accounting of the evolution of the Al nanocrystal density (N v ) during the primary crystallization under isothermal annealing treatments. Moreover, the calculated values of the steady state nucleation rates (J ss ) predicted by the nucleation model agree with the experimental results. Moreover, the model satisfies constraints on the structural, thermodynamic, and kinetic parameters, such as the critical nucleus size, the interface energy, and the volume-free energy driving force that are essential for a fully self-consistent nucleation kinetics analysis. In conclusion, the nucleation kinetics model can be applied more broadly to materials that are characterized by the presence of spatial heterogeneities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Lasing characteristics of ZrO{sub 2} − Y{sub 2}O{sub 3} − Ho{sub 2}O{sub 3} crystals pumped by a Tm : LiYF{sub 4} laser

Two-micron lasing is obtained on the {sup 5}I{sub 7} → {sup 5}I{sub 8} transition of Ho{sup 3+} ions in ZrO{sub 2} − Y{sub 2}O{sub 3} −Ho{sub 2}O{sub 3} crystals upon resonance pumping into the {sup 5}I{sub 7} level of these ions by a pulsed laser based on a Tm : LiYF{sub 4} crystal. The efficiency of conversion of pump radiation incident on the crystal to laser radiation and the slope lasing efficiency at a pulse duration of 8 ms and a pulse repetition rate of 10 Hz were 25% and 28%, respectively. (paper)

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dual wavelength operation of the GaSb-based Y-branch distributed Bragg reflector lasers near 2.1 μ m

The GaSb-based diode lasers operating simultaneously at two wavelengths near 2.1 μm have been designed and fabricated. The Y-branch devices used the 6th order distributed Bragg reflectors (DBR) to provide spectrally selective feedback. The laser active region contained two asymmetric quantum wells with allowed optical transitions between two lowest electron (e1 and e2) and top hole (hh1) subbands. The laser emission lines loosely matched the e1-hh1 and e2-hh1 optical transitions with separation corresponding to ~3.1 THz. Finally, the 10 μm wide deeply etched straight ridge DBR lasers demonstrated stable single mode operation with more than 50 mW of output power.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Electron correlations in the ${H_{c2}}$ of FeySe$_{1-x}$Sx (0.10 $\leqslant x\leqslant$ 0.24, $y\geqslant$ 0.9)

In this work, we report on the evolution of the electronic correlation strength across the nematic critical point in FeySe$_{1-x}$Sx ($0.10\leqslant x \leqslant0.24; y \geqslant0.9$), inferred from the measurements of the slope of the upper critical field $H_{c2}$. Superconducting transition T c and quasiparticle mass $m^*$ exhibit similar reduction with sulfur content x. Our results indicate that electronic correlations from all Fermi surface pockets show strong interconnection with pairing strength and are not governed by the change of nematic fluctuations. The upper critical field anisotropy γH = $H_{c2}^{ab}$/$H_{c2}^c$ exhibits a minimum in the critical region and stronger temperature dependence away from it.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Identifying Spectral Descriptors for Protonation in BaZr 0.8 Y 0.2 O 3-x with Electron Energy Loss Spectroscopy

Hydrogen economy is of paramount importance in the global transition to a sustainable, clean energy source that contributes to decarbonization efforts. In particular, the proton conducting proton ceramic fuel cells (PCFCs) play a crucial role in promoting hydrogen energy technology [1-5]. In a PCFC, the electrolyte is typically a solid oxide material that enables proton transport and can operate at temperatures lower than those of traditional oxygen ion conducting fuel cells [6]. The reduced operating temperature of PCFCs contributes to their durability, scalability, and efficiency [7,8]. BaZr 0.8 Y 0.2 O 3-x (BZY) is a promising proton conducting solid oxide electrolyte [9,10]. The emphasis on proton conductivity entails the importance of understanding proton content in the system. However, previous studies have largely relied on bulk techniques such as electrochemical impedance spectroscopy [7,11], Karl-Fischer titration [12,13], and thermogravimetric analysis [14] to obtain proton concentration. This is due to the small atomic size and light mass of hydrogen species making direct detection challenging. Bulk methods may be useful in estimating the proton content; however, it overlooks possible proton concentration gradient or segregation that may occur across or within a nanoparticle, especially when proton incorporation occurs nonuniformly through steam exposure on powder samples. In this paper, BZY is protonated at an estimated 0.15 mol of protons via steam exposure. Electron energy loss spectroscopy (EELS) with nanoscale spatial resolution is explored to identify proxy signals for proton detection using a JEOL ARM300 microscope operated at 300 kV with a Gatan GIF Continuum detector.

08 HYDROGEN↗
DOE OSTI2025

Bats flying through a Y-maze are visually attracted to wind turbine surfaces

Wind energy’s rapid expansion has led to unintended consequences for wildlife, with migratory bats among the species most at risk. The behavioural mechanisms underlying collisions remain poorly understood, but one hypothesis is that bats are attracted to wind turbine structures. Vision is important to bat orientation and obstacle avoidance, yet it has been relatively understudied in the context of bat–turbine interactions. We hypothesize that light reflected off turbine surfaces could attract bats, acting as a sensory pollutant that may increase collision risk. To test whether reflective turbine surfaces elicit attraction, we flew 242 Lasiurus cinereus and 154 Lasionycteris noctivagans through Y-maze assays. Bats were at least twice as likely to fly towards white turbine blade sections compared to less reflective black ones. This attraction intensified when the alternative exit was a dark, empty flyway, with 74% of L. cinereus and 97% of L. noctivagans flying towards the white turbine blade. These findings provide evidence that visual sensory pollutants could underlie bat–turbine interactions, and if so, wind turbines could be ecological traps.

17 WIND ENERGY↗
DOE OSTI2026

Magnon-magnon coupling in an all-oxide insulator garnet Y 3 ⁢Fe 5 ⁢O 12 /Tm 3 ⁢Fe 5⁢ O 12 heterostructure

Hybrid magnonic systems have recently attracted significant attention due to their intriguing physics and potential applications in coherent information processing. In this regard, we have investigated magnon-magnon coupling in the all-oxide insulator garnet Y 3⁢ Fe 5⁢ O 12 (YIG)/Tm 3 ⁢Fe 5 ⁢O 12 (TmIG) heterostructure. The presence of an avoided mode crossing region between the ferromagnetic resonance modes of YIG and TmIG indicates interfacial exchange coupling. This all-insulator system enables interfacial coupling via magnon-magnon interactions. The mode crossing occurs at 𝑓 𝑐 = 6.88 GHz, corresponding to the minimal resonance separation between the two hybrid modes. The coupling strength is determined to be 78 MHz (or 2.8 mT), providing clear evidence of magnon-magnon coupling between the two Kittel modes in the YIG/TmIG insulator system at 200 K. As a result, these findings pave the way for engineering magnonic band structures, tunable coherent magnonic interactions, and nonreciprocal spin transport, which are crucial for advancing ultralow-power magnonic devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Tunable Magnetically Induced Transparency Spectra in Magnon-Magnon Coupled Y 3 Fe 5 O 12 / Permalloy Bilayers

Hybrid magnonic systems host a variety of characteristic phenomena such as the magnetically induced transparency (MIT) and Purcell effect, which are considered useful for future coherent quantuminformation processing. In this work, we experimentally demonstrate a tunable MIT effect in the Y 3 Fe 5 O 12 (YIG)/Permalloy(Py) magnon-magnon coupled system via changing the magnetic field orientations. By probing the magneto-optic effects of Py and YIG thin films, we identify clear features of MIT spectra induced by the mode hybridization between the uniform mode of Py and the perpendicular standing spin-wave modes of YIG. By changing the external magnetic field orientations, we observe a tunable coupling strength between the YIG's spin-wave modes and the Py's uniform mode, upon the application of an out-of-plane magnetic field. This observation is theoretically interpreted by a geometrical consideration of the Py and YIG magnetization under the oblique magnetic field even at a constant interfacial exchange coupling. Finally, our findings show high promise for investigating tunable coherent phenomena with hybrid magnonic platforms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Nature of the magnetic stripes in fully oxygenated La 2 CuO 4+y

We present triple-axis neutron scattering studies of static and dynamic magnetic stripes in an optimally oxygen-doped cuprate superconductor, La 2 CuO 4+y , which exhibits a clean superconducting transition at T c = 42 K. Polarization analysis reveals that the magnetic stripe structure is equally represented along both of the tetragonal crystal axes and that the fluctuating stripes display significant weight for in-plane as well as out-of-plane spin components. Both static magnetic order as well as low-energy fluctuations are fully developed in zero applied magnetic field and the low-energy spin fluctuations at ℏω = 0.3 – 10 meV intensify on cooling. We interpret this as an indication that superconductivity and low-energy spin fluctuations coexist microscopically in spatial regions which are separated from domains with static magnetic order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Suppressed incommensurate order in swedenborgite Ca 0.5 Y 0.5 BaCo 4 O 7

Swedenborgite Ca 0.5 Y 0.5 BaCo 4 O 7 (CYBCO) with geometrically frustrated kagome and triangular lattices exhibits a disordered ground state in spite of strong antiferromagnetic couplings between the Co spins. The character of the disordered state has been debated due to ambiguous Co states in the triangular layers. Here, we perform single-crystal diffuse neutron scattering experiments to fully characterize the short-range spin correlations in CYBCO. Through reverse Monte Carlo and self-consistent Gaussian approximation analyses, we confirm that the Co ions in both the kagome and triangular layers are magnetic, and the interlayer couplings, together with the lattice distortion, promote an incommensurate magnetic order that is suppressed possibly by exchange disorder. Our work clarifies the short-range spin correlations in CYBCO and establishes a general correspondence between unequal interactions and incommensurate spin correlations on the swedenborgite lattice.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

X Y Z spectroscopy at electron-hadron facilities. III. Semi-inclusive processes with vector exchange

Inclusive production processes will be important for the first observations of X Y Z states at new generation electron-hadron colliders, as they generally benefit from larger cross sections than their exclusive counterparts. We make predictions of semi-inclusive photoproduction of the χ c 1 ( 1 P ) and X ( 3872 ) , whose peripheral production is assumed to be dominated by vector exchanges. We validate the applicability of vector meson dominance in the axial-vector charmonium sector and calculate production rates at center-of-mass energies relevant for future experimental facilities. We find the semi-inclusive cross sections near the threshold to be enhanced by a factor of ∼ 2 – 3 compared to the exclusive reaction and well-suited for a first observation in photoproduction. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Magnetic phase transitions in Eu(Co 1-x Nix) 2-y As 2 single crystals

The effects of Ni doping in Eu(Co 1-x Ni x ) 2-y As 2 single crystals with x = 0 to 1 grown out of self flux are investigated via crystallographic, electronic transport, magnetic, and thermal measurements. All compositions adopt the body-centered-tetragonal ThCr 2 Si 2 structure with space group I 4= mmm . Here, we also find 3-4% of randomly-distributed vacancies on the Co/Ni site. Anisotropic magnetic susceptibility $\chi$α (α = ab; c) data versus temperature T show clear signatures of an antiferromagnetic (AFM) c-axis helix structure associated with the Eu +2 spins-7/2 for x = 0 and x = 1 as previously reported. The $\chi$α (T) data for x = 0.03 and 0.10 suggest an anomalous 2 q magnetic structure containing two helix axes along the c axis and in the ab plane, respectively, whereas for x = 0.75, 0.82, and 1 a c-axis helix is inferred as previously found for x = 1. At intermediate compositions x = 0:2, 0.32, 0.42, 0.54, and 0.65 a magnetic structure with a large ferromagnetic (FM) c-axis component is found from magnetization versus fi eld isotherms, suggested to be an incommensurate FM cone structure associated with the Eu spins, which consists of both AFM and FM components. In addition, the $\chi$ (T) and heat capacity C p (T) data for x = 0.2-0.65 indicate the occurrence of itinerant FM order associated with the Co/Ni atoms with Curie temperatures from 60 K to 25 K, respectively. Electrical resistivity ρ(T) measurements indicate metallic character for all compositions with abrupt increases in slope on cooling below the Eu AFM transition temperatures. In addition to this panoply of magnetic transitions, 151 Eu Mössbauer measurements indicate that ordering of the Eu moments proceeds via an incommensurate sine amplitude-modulated structure with additional transition temperatures associated with this effect.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Widely spaced planes of magnetic dimers in the Ba 6 Y 2 Rh 2 Ti 2 O 17-δ hexagonal perovskite

In this work, we report the synthesis and initial characterization of Ba 6 Y 2 Rh 2 Ti 2 O 17-δ , a previously unreported material, to the best of our knowledge, with a hexagonal symmetry structure. Face-sharing RhO 6 octahedra form triangular planes of Rh 2 O 9 dimers that are widely separated in the perpendicular direction. The material displays a small effective magnetic moment, due to the Rh ions present, and a negative Curie-Weiss temperature. The charge transport and optical band gaps are very similar, near 0.16 eV. A large upturn in the heat capacity at temperatures below 1 K, suppressed by applied magnetic fields larger than μ 0 H = 2T, is observed. A large T-linear term in the specific heat (γ = 166 mJ/mol f.u-K 2 ) is seen, although the material is insulating at low temperatures. These results suggest the possibility of a spin liquid ground state in this material.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Random singlet-like state in the dimer-based triangular antiferromagnet Ba 6 Y 2 Rh 2 Ti 2 O 17 − δ

We present the magnetic, thermodynamic, and muon spin relaxation ( μ SR ) results of the dimer-based triangular antiferromagnet Ba 6 Y 2 Rh 2 Ti 2 O 17 − δ . The magnetic susceptibility data show the sub-Curie-Weiss behavior χ ( T ) ∝ T − α χ below 100 K, suggesting random magnetism. The isothermal magnetization results reveal the presence of weakly interacting structural orphan spins about 6.1 % at 2 K, arising from the oxygen deficiency. The comprehensive μ SR experiments exhibit the coexisting relaxing and nonrelaxing components along with the thermally activated behavior in the muon spin relaxation rate, reflecting the fluctuating orphan spins in the dimer singlet background. In addition, we observe the scaling behavior of M ( H , T ) in H / T and P z ( t ) in t / H LF with the scaling exponents α χ = α M = 0.75 and α μ = 0.72 , respectively, but not for the magnetic specific heat data. The failure of the scaling relation in C m ( H , T ) / T implies low-energy excitations dressed by the conventional orphan spins. Based on these observations, we find that the magnetic ground state resembles random singlets and discuss the possible configurations of the spin dimer unit Rh 2 O 9 . Our results shed light on the role of quenched disorder in the dimer-based frustrated magnets. Published by the American Physical Society 2024

Lee, Wonjun (ORCID:000000034848852X)↗
DOE OSTI2022

Improving Structural Integrity of Direct Laser-Deposited Ni – Co – Cr – Al – Y Superalloys by Alloy Modification

Abstract Ni- and Co-based M–Cr–Al–Y (M = Ni and/or Co), dual phase β and γ/γ′, β—Ni–Al, γ—Ni(Co, Cr), and γ′—Ni3–Al superalloys exhibit several beneficial high-temperature (>1000 °C) (2012 °F) strength and corrosion resistance properties. Our study investigates the feasibility of fabricating a commercially available Ni–Co–Cr–AlY alloy (tradename “Amdry 386”) using laser directed energy deposition (laser-DED). A significant challenge for laser fabrication of bulk Amdry 386 (A386) structures stems from the presence of relatively higher amounts of the β phase than γ/γ′ phases. While prior studies report laser fabrication of these materials in coating and cladding configurations, bulk structures have not been realized. To investigate these challenges, this study was developed to systematically evaluate the effects of modifying the A386 alloy by adding 10, 20, and 30% by weight of a Ni–20%Cr (Ni–Cr) alloy (mainly γ/γ′). Laser-DED-fabricated A386 coupons exhibited a metastable, rapidly solidified β-rich microstructure typical to laser processes. The A386 + Ni–Cr mixtures were processed using laser-DED, and small coupons from each composition were evaluated using SEM, XRD, and microhardness to characterize the as-processed microstructure. Thermodynamic modeling was performed to determine the phase evolution as a function of the alloy composition. The dominating phase switches from β to γ/γ’ between the A386 and A386 + 10% Ni–Cr mixtures, but the increase in structural integrity is not observed until the Ni–Cr additions reach a minimum of 20%. Our results show that the alloy chemistry can be successfully modified to improve the structural integrity of laser-processed structures.

Engineering↗
DOE OSTI2023

Near-complete genome sequence of Lipomyces tetrasporous NRRL Y-64009, an oleaginous yeast capable of growing on lignocellulosic hydrolysates

ABSTRACT Lipomyces tetrasporous is an oleaginous yeast that can utilize a variety of plant-based sugars. It accumulates lipids during growth on lignocellulosic biomass hydrolysates. We present the annotated genome sequence of L. tetrasporous NRRL Y-64009 to aid in its development as a platform organism for producing lipids and lipid-based bioproducts.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Understanding Chemo-Mechanical Stability of Protonic Ceramic Cells Through Electronic Conduction in the BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ Electrolyte

BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ (BCZYYb) is a promising ceramic electrolyte for reversible protonic ceramic cells. It is reported that BCZYYb-based cells show excellent long-term durability, particularly in the electrolysis mode, in contrast to the cells based on the conventional electrolyte yttria-stabilized zirconia. In this study, we investigate the chemo-mechanical stability behavior (a low tendency of delamination) of the BCZYYb-based protonic ceramic cells in terms of local electronic conduction in the electrolyte. The local electronic conductivity of the BCZYYb electrolyte is determined using Pt-probe-embedded cells near each electrode interface. The BCZYYb electrolyte exhibits sufficient p-type conductivity (∼10 −3 S cm −1 ) near the oxygen electrode (corresponding p O 2 : 5.27–21 × 10 −2 atm) and n-type conductivity (∼10 −4 S cm −1 ) near the hydrogen electrode (corresponding p O 2 : 0.99–1.30 × 10 −24 atm) at 600 °C. A standard cell is prepared and tested over long-term in the fuel cell (at positive and negative voltages) and electrolysis modes. The cell exhibits stable performance without delamination or cracks in both operating modes, owing to local electronic conduction.

Electrochemistry↗