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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 OSTI2020

Cooperative Ru(4 d )–Ho(4 f ) magnetic ordering and phase coexistence in the 6 H perovskite multiferroic Ba 3 HoRu 2 O 9

We report cooperative magnetic orderings in a 6H-perovskite multiferroic system, Ba 3 HoRu 2 O 9 , via comprehensive neutron powder diffraction measurements. This system undergoes long-range antiferromagnetic ordering at T N1 ~ 50 K with a propagation wave vector of K 1 = (0.5 0 0), a transition temperature much higher than the previously reported one at ~10 K (T N2 ). Both Ru and Ho-moments order simultaneously below T N1 , followed by spin-reorientations at lower temperatures, demonstrating strong Ru(4d)-Ho(4f) magnetic correlation. Below T N1 another magnetic phase with a propagation wave vector K 2 = (0.25 0.25 0) emerges and coexists with the one associated with K 1 , which is rarely observed and suggests complex magnetism due to phase competition in the magnetic ground state. Here, we argue that the exchange-striction arising from the up-up-down-down spin structure associated with K 2 below T N2 may be responsible for the small ferroelectric polarization reported previously in this compound.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Structural and double magnetic transitions in the frustrated spin- 1 2 capped-kagome antiferromagnet ( RbCl ) Cu 5 P 2 O 10

The structural and magnetic properties of the geometrically frustrated spin- 1 2 capped-kagome antiferromagnet (RbCl) Cu 5 P 2 O 10 are investigated via temperature-dependent x-ray diffraction, magnetization, heat capacity, and 31 P NMR experiments on a polycrystalline sample. It undergoes a structural transition at around T t ≃ 310 K from a high-temperature trigonal (P ¯3m1) to a low-temperature monoclinic (C2/c) unit cell, where the low-temperature structure features the capped-kagome geometry of Cu 2+ ions. Interestingly, it shows the onset of two successive magnetic transitions at T N1 ≃ 20 K and T N2 ≃ 7 K. The shape of the 31 P NMR spectra unfolds the possible nature of the transitions below T N1 and T N2 to be of incommensurate and commensurate antiferromagnetic type, respectively. A large value of the Curie-Weiss temperature as compared to T N1 sets the frustration parameter f ≃ 8, ensuring strong magnetic frustration in the compound. From the 31 P NMR spin-lattice relaxation rate, the leading antiferromagnetic exchange coupling is estimated to be J/k B ≃ 117 K. Furthermore, these unusual double magnetic transitions make this compound beguiling for further investigations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Single-crystal growth and characterization of antiferromagnetically ordered EuIn 2

Here, we report the single crystal growth and characterization of EuIn 2 , a magnetic topological semimetal candidate according to our density functional theory (DFT) calculations. We present results from electrical resistance, magnetization, Mössbauer spectroscopy, and X-ray resonant magnetic scattering (XRMS) measurements. We observe three magnetic transitions at T N1 ~ 14.2 K, T N2 ~ 12.8 K and T N3 ~ 11 K, signatures of which are consistently seen in anisotropic temperature dependent magnetic susceptibility and electrical resistance data. Mössbauer spectroscopy measurements on ground crystals suggest an incommensurate sinusoidally modulated magnetic structure below the transition at T N1 ~ 14 K, followed by the appearance of higher harmonics in the modulation on further cooling roughly below T N2 ~ 13 K, before the moment distribution squaring up below the lowest transition around T N3 ~ 11 K. XRMS measurements showed the appearance of magnetic Bragg peaks below T N1 ~ 14 K, with a propagation vector of $τ$ = ($τ_h$, $\overline{τ}_h$, 0), with $τ_h$ varying with temperature, and showing a jump at T N3 ~ 11 K. The temperature dependence of $τ_h$ between ~ 11 K and 14 K shows incommensurate values consistent with the Mössbauer data. XRMS data indicate that $τ_h$ remains incommensurate at low temperatures and locks into $τ_h$ = 0.3443(1).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Successive magnetic orderings in the Ising spin chain magnet DyNi 5 Ge 3

In this report, we investigated a new rare-earth-based one-dimensional Ising spin chain magnet DyNi 5 Ge 3 by means of magnetization, specific heat, and powder neutron diffraction measurements. Due to the crystalline electrical field splitting, the magnetic Dy ions share an Ising-like ground doublet state. Owning to the local point symmetry, these Ising moments form into two canted magnetic sublattices, which were further confirmed by the angle-dependent magnetization measurement. In zero fields, two successive antiferromagnetic phase transitions were found at temperatures T N1 =6K and T N2 =5K, respectively. Only part of the moments are statically ordered in this intermediate state between T N1 and T N2 . Powder neutron diffraction experiments at different temperatures were performed as well. Further, an incommensurate magnetic propagation vector of k m =(0.5,0.4,0.5) was identified. The refined spin configurations through the irreducible representation analysis confirmed that these Ising spins are canted in the crystal ab plane.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Sawtooth lattice multiferroic BeCr 2 O 4 : Noncollinear magnetic structure and multiple magnetic transitions

Noncollinear magnetic structures and multiple magnetic phase transitions in a sawtooth lattice antiferromagnet consisting of Cr 3+ are experimentally identified in this work, thereby proposing the scenario of magnetism-driven ferroelectricity in a sawtooth lattice. The title compound, BeCr 2 O 4 , displays three magnetic phase transitions at low temperatures—at T N1 ≈ 7.5 K, at T N2 ≈ 25 K, and at T N3 ≈ 26 K—revealed through magnetic susceptibility, specific heat, and neutron diffraction in this work. These magnetic phase transitions are found to be influenced by externally applied magnetic fields. Isothermal magnetization curves at low temperatures below the magnetic transitions indicate the antiferromagnetic nature of BeCr 2 O 4 with two spin-flop-like transitions occurring at H c1 ≈ 29 kOe and H c2 ≈ 47 kOe. Our high-resolution x-ray and neutron diffraction studies, performed on single crystal and powder samples, unambiguously determined the crystal structure as orthorhombic Pbnm. By performing the magnetic superspace group analysis of the neutron diffraction data at low temperatures, the magnetic structure in the temperature range T N3,N2 < T < T N1 is determined to be the polar magnetic space group P21nm. 1' (00g) 0s0s with a cycloidal magnetic propagation vector k 1 = (0, 0, 0.090 (1)) . The magnetic structure in the newly identified phase below T N1 is determined as P21/b.1' [b] (00 g) 00s with the magnetic propagation vector k 2 = (0, 0, 0.908 (1)). Finally, the cycloidal spin structure determined in our work is usually associated with electric polarization, thereby making BeCr 2 O 4 a promising multiferroic belonging to the sparsely populated family of sawtooth lattice antiferromagnets.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Computational Study of a Cryopump Design for Fusion Exhaust Gas Purification Using Direct Simulation Monte Carlo

Cryopump-based direct internal recycling (DIR) of fusion fuel is an attractive prospect because it provides pumping of helium ash from a reactor along with separation of helium and other impurities from the fuel. Previous studies have demonstrated a continuously regenerating cryopump, referred to as the Snail pump, that separates helium ash from fusion fuel for reactor-relevant flow rates. Here, in this study, a conceptual cryopump was designed as a proof-of-principle study to target other impurities, besides helium ash, from the fusion exhaust that would complement the Snail pump. The impurity-removal cryopump consists of four sets of chevron fins, two sets operating at 80 K and the other two at 30 K. A computational study using direct simulation Monte Carlo (DSMC) was performed with a gas mixture of 96.5% D2, 2.0% He, and 0.5% each of CO2, N2, and CH4. In this configuration, 80 K chevron fin sets are capable of capturing CO2 and 30 K sets capable of capturing CO2, N2, and CH4. The computational study showed that the cryopump is capable of reducing the impurity content by more than two orders of magnitude from the flow.

Adhikari, Nirajan [Oak Ridge National Laboratory (↗
DOE OSTI2020

Effects of High Fuel Loading and CO2 Dilution on Oxy-Methane Ignition Inside a Shock Tube at High Pressure

Abstract Ignition delay times were measured for methane/O2 mixtures in a high dilution environment of either CO2 or N2 using a shock tube facility. Experiments were performed between 1044 K and 1356 K at pressures near 16 ± 2 atm. Test mixtures had an equivalence ratio of 1.0 with 16.67% CH4, 33.33% O2, and 50% diluent. Ignition delay times were measured using OH* emission and pressure time-histories. Data were compared to the predictions of two literature kinetic mechanisms (ARAMCO MECH 2.0 and GRI Mech 3.0). Most experiments showed inhomogeneous (mild) ignition which was deduced from five time-of-arrival pressure transducers placed along the driven section of the shock tube. Further analysis included determination of blast wave velocities and locations away from the end wall of initial detonations. Blast velocities were 60–80% of CJ-Detonation calculations. A narrow high temperature region within the range was identified as showing homogenous (strong) ignition which showed generally good agreement with model predictions. Model comparisons with mild ignition cases should not be used to further refine kinetic mechanisms, though at these conditions, insight was gained into various ignition behavior. To the best of our knowledge, we present first shock tube data during ignition of high fuel loading CH4/O2 mixtures diluted with CO2 and N2.

Energy & Fuels↗
DOE OSTI2023

Data for Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides . Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm3) capable of generating an electron density of greater than 1013 cm–3 was constructed to produce reactive species (N2*, N2+, O, OH, and Hα) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

Conversion↗
DOE OSTI2020

Materials Data on PtN by Materials Project

PtN is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Pt2+ is bonded to four equivalent N2- atoms to form corner-sharing PtN4 tetrahedra. All Pt–N bond lengths are 2.07 Å. N2- is bonded to four equivalent Pt2+ atoms to form corner-sharing NPt4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PtN by Materials Project

PtN is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pt2+ is bonded to six equivalent N2- atoms to form a mixture of corner and edge-sharing PtN6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Pt–N bond lengths are 2.25 Å. N2- is bonded to six equivalent Pt2+ atoms to form a mixture of corner and edge-sharing NPt6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThCN by Materials Project

NCTh crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Th4+ is bonded in a 7-coordinate geometry to three equivalent C2- and four equivalent N2- atoms. There are two shorter (2.82 Å) and one longer (2.85 Å) Th–C bond lengths. There are a spread of Th–N bond distances ranging from 2.36–2.39 Å. C2- is bonded in a rectangular see-saw-like geometry to three equivalent Th4+ and one C2- atom. The C–C bond length is 1.26 Å. N2- is bonded to four equivalent Th4+ atoms to form a mixture of edge and corner-sharing NTh4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiCN by Materials Project

SiCN is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Si4+ is bonded in a body-centered cubic geometry to four equivalent C2- and four equivalent N2- atoms. All Si–C bond lengths are 2.06 Å. All Si–N bond lengths are 2.06 Å. C2- is bonded to four equivalent Si4+ atoms to form CSi4 tetrahedra that share corners with four equivalent NSi4 tetrahedra, corners with twelve equivalent CSi4 tetrahedra, and edges with six equivalent NSi4 tetrahedra. N2- is bonded to four equivalent Si4+ atoms to form NSi4 tetrahedra that share corners with four equivalent CSi4 tetrahedra, corners with twelve equivalent NSi4 tetrahedra, and edges with six equivalent CSi4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si3N2 by Materials Project

Si3N2 is alpha Po structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one Si3N2 cluster. Si+1.33+ is bonded in a bent 120 degrees geometry to two equivalent N2- atoms. Both Si–N bond lengths are 1.76 Å. N2- is bonded in a trigonal planar geometry to three equivalent Si+1.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HgN by Materials Project

HgN is Wurtzite structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Hg2+ is bonded to four equivalent N2- atoms to form corner-sharing HgN4 tetrahedra. There are one shorter (2.20 Å) and three longer (2.27 Å) Hg–N bond lengths. N2- is bonded to four equivalent Hg2+ atoms to form corner-sharing NHg4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PdN by Materials Project

PdN is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Pd2+ is bonded to four equivalent N2- atoms to form corner-sharing PdN4 tetrahedra. All Pd–N bond lengths are 2.06 Å. N2- is bonded to four equivalent Pd2+ atoms to form corner-sharing NPd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb4NO by Materials Project

Rb4NO is Fluorite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Rb1+ is bonded to two equivalent N2- and two equivalent O2- atoms to form a mixture of corner and edge-sharing RbN2O2 tetrahedra. Both Rb–N bond lengths are 3.06 Å. Both Rb–O bond lengths are 3.02 Å. N2- is bonded in a body-centered cubic geometry to eight equivalent Rb1+ atoms. O2- is bonded in a body-centered cubic geometry to eight equivalent Rb1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PdN by Materials Project

PdN is Boron Nitride structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two PdN sheets oriented in the (0, 0, 1) direction. Pd2+ is bonded in a trigonal planar geometry to three equivalent N2- atoms. All Pd–N bond lengths are 1.95 Å. N2- is bonded in a trigonal planar geometry to three equivalent Pd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PdN by Materials Project

PdN is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pd2+ is bonded to six equivalent N2- atoms to form a mixture of face, edge, and corner-sharing PdN6 octahedra. The corner-sharing octahedral tilt angles are 46°. All Pd–N bond lengths are 2.22 Å. N2- is bonded to six equivalent Pd2+ atoms to form a mixture of distorted edge and corner-sharing NPd6 pentagonal pyramids.

36 MATERIALS SCIENCE↗