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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Emergence of the spin polarized domains in the kagome lattice Heisenberg antiferromagnet Zn-barlowite (Zn 0.95 Cu 0.05 )Cu 3 (OD) 6 FBr

Kagome lattice Heisenberg antiferromagnets are known to be highly sensitive to perturbations caused by the structural disorder. NMR is a local probe ideally suited for investigating such disorder-induced effects, but in practice, large distributions in the conventional one-dimensional NMR data make it difficult to distinguish the intrinsic behavior expected for pristine kagome quantum spin liquids from disorder-induced effects. Here we report the development of a two-dimensional NMR data acquisition scheme applied to Zn-barlowite (Zn 0.95 Cu 0.05 )Cu 3 (OD) 6 FBr kagome lattice, and successfully correlate the distribution of the low energy spin excitations with that of the local spin susceptibility. We present evidence for the gradual growth of domains with a local spin polarization induced by 5% Cu 2+ defect spins occupying the interlayer non-magnetic Zn 2+ sites. These spin-polarized domains account for ~60% of the sample volume at 2 K, where gapless excitations induced by interlayer defects dominate the low-energy sector of spin excitations within the kagome planes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electronic anisotropy and rotational symmetry breaking at a Weyl semimetal/spin ice interface

In magnetic pyrochlore materials, the interplay of spin-orbit coupling, electronic correlations, and geometrical frustration gives rise to exotic quantum phases, including topological semimetals and spin ice. While these phases have been observed in isolation, the interface-driven phenomena emerging from their interaction have never been realized previously. Here, we report on the discovery of interfacial electronic anisotropy and rotational symmetry breaking at a heterostructure consisting of the Weyl semimetal Eu 2 Ir 2 O 7 and spin ice Dy 2 Ti 2 O 7 . Subjected to magnetic fields, we unveil a sixfold anisotropic transport response that is theoretically accounted by a Kondo-coupled heterointerface, where the spin ice’s field-tuned magnetism induces electron scattering in the Weyl semimetal’s topological Fermi-arc states. Furthermore, at elevated magnetic fields, we reveal a twofold anisotropic response indicative of the emergence of a symmetry-broken many-body state. This discovery showcases the potential of pyrochlore frustrated magnet/topological semimetal heterostructures in search of emergent interfacial phenomena.

Science & Technology - Other Topics↗
DOE OSTI2012

Characterization and thermal behavior of PrMO{sub 3} (M = Co or Ni) ceramic materials obtained from gelatin

Graphical abstract: The micrograph in figure shows sample calcined at temperature 900 °C. The sample exhibits morphology with considerable porosity and the formation of agglomerated nanometric particles. Gelatin provides the system with a large amount of organic matter, which is then removed during calcinations, favoring the appearance of pores in the material. Highlights: ► Oxides with PrNiO{sub 3} and PrCoO{sub 3} were prepared by new method synthesis. ► The gelatin, through its carboxylate groups and amine, is an efficient director. ► The obtained materials have magnetic properties and application in catalysis. ► The decomposition kinetic study of bonding groups of gelatin with metallic ions that takes part in the synthesis of PrMO{sub 3}. -- Abstract: Metal oxides with perovskite-type structure have attracted considerable interest in recent years due to their magnetic and electrical properties, as well as their catalytic activity. In this study, oxides with PrNiO{sub 3} and PrCoO{sub 3} composition were prepared by using gelatin powder as a precursor agent for its use as a catalyst. The powders obtained were calcined at 700 °C and 900 °C and characterized using the X-ray diffraction, thermal analysis (thermogravimetry and differential thermal analysis), infrared spectroscopy, temperature programed reduction and scanning electron microscopy techniques. Thermogravimetric data using the non-isothermal kinetic models of Flynn and Wall and “Model-free Kinetics” were used to determine the activation energy to study the decomposition kinetics of the ligand groups with system's metallic ions that takes part in the synthesis of PrMO{sub 3} (M = Ni or Co).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Extraction of Rare Earth Elements from Chloride Media with Tetrabutyl Diglycolamide in 1-Octanol Modified Carbon Dioxide

Rare earth elements (REEs) are critical to our modern world. Recycling REEs from used products could help with potential supply issues. Extracting REEs from chloride media with tetrabutyl diglycolamide (TBDGA) in carbon dioxide could help recycle REEs with less waste than traditional solvents. Carbon dioxide as a solvent is inexpensive, inert, and reusable. Conditions for extraction of Eu from aqueous chloride media were optimized by varying moles percent of 1-octanol modifier, temperature, pressure, Eu concentration, TBDGA concentration, Cl– concentration, and HCl concentration. These optimized conditions were tested on a Y, Ce, Eu, Tb simulant material, REEs containing NdFeB magnets, and lighting phosphor material. The optimized conditions were found to be 23 °C, 24.1 MPa, 0.5 mol% 1-octanol, with an excess of TBDGA. At these conditions 95 ± 2% Eu was extracted from 8 M (mol/m3) HCl. Extraction from the mixed REE simulate material resulted in separation of Y, Eu, and Tb from the Ce which remained in the aqueous solution. The extraction on NdFeB magnet dissolved into 8 M HCl resulted in extraction of Pr, Nd, Dy, and Fe >97%. This ends in a separation from B, Al, and Ni. Extraction from a trichromatic lighting phosphor leachate resulted in extraction of Y and Eu >93% and no extraction of Ba, Mg, and Al.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Spiral-like multi-beam emission via transformation electromagnetics

Transformation electromagnetics offers an unconventional approach for the design of novel radiating devices. Here, we propose an electromagnetic metamaterial able to split an isotropic radiation into multiple directive beams. By applying transformations that modify distance and angles, we show how the multiple directive beams can be steered at will. We describe transformation of the metric space and the calculation of the material parameters. Different transformations are proposed for a possible physical realization through the use of engineered artificial metamaterials. Full wave simulations are performed to validate the proposed approach. The idea paves the way to interesting applications in various domains in microwave and optical regimes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Pulsed Electron Source with Grid Plasma Cathode and Longitudinal Magnetic Field for Modification of Material and Product Surfaces

The description and the main characteristics of the pulsed electron source “SOLO” developed on the basis of the plasma cathode with grid stabilization of the emission plasma boundary are presented. Тhe emission plasma is generated by a low-pressure arc discharge, and that allows to form the dense low-energy electron beam with a wide range of independently adjustable parameters of beam current pulses (pulse duration of 20–250 μs, pulse repetition rate of 1–10 s{sup –1}, amplitude of beam current pulses of 20–300 A, and energy of beam electrons of 5–25 keV). Тhe special features of generation of emission plasma by constricted low-pressure arc discharge in the grid plasma cathode partially dipped into a non-uniform magnetic field and of formation and transportation of the electron beam in a longitudinal magnetic field are considered. The application area of the electron source and technologies realized with its help are specified.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

SIGNS OF MAGNETIC ACCRETION IN THE X-RAY PULSAR BINARY GX 301-2

Observations of the cyclotron resonance scattering feature in the X-ray spectrum of GX 301-2 suggest that the surface field of the neutron star is B{sub CRSF} {approx} 4 Multiplication-Sign 10{sup 12} G. The same value has been derived in modeling the rapid spin-up episodes in terms of the Keplerian disk accretion scenario. However, the spin-down rate observed during the spin-down trends significantly exceeds the value expected in currently used spin-evolution scenarios. This indicates that either the surface field of the star exceeds 50 B{sub CRSF} or a currently used accretion scenario is incomplete. We show that the above discrepancy can be avoided if the accreting material is magnetized. The magnetic pressure in the accretion flow increases more rapidly than its ram pressure and, under certain conditions, significantly affects the accretion picture. The spin-down torque applied to the neutron star in this case is larger than that evaluated within a non-magnetized accretion scenario. We find that the observed spin evolution of the pulsar can be explained in terms of the magnetically controlled accretion flow scenario provided the surface field of the neutron star is {approx}B{sub CRSF}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Weak ferromagnetic ordering in Ca doped polycrystalline BiFeO{sub 3}

Structural and magnetic properties of polycrystalline BiFeO{sub 3}, Bi{sub 0.9}Ca{sub 0.1}FeO{sub 2.95}, Bi{sub 0.9}Ba{sub 0.05}Ca{sub 0.05}FeO{sub 2.95}, and Bi{sub 0.9}Ba{sub 0.1}FeO{sub 2.95} ceramic samples were studied to establish the effects of doping in BiFeO{sub 3} on the magnetic property. X-ray diffraction data of the undoped and doped BiFeO{sub 3} samples were refined to a rhombohedral structure with space group R3c. X-ray photoelectron spectroscopy study showed the formation of a single-phase in both the undoped and doped BiFeO{sub 3} ceramics with Fe in the 3+ valence state. Ca doped and Ba-Ca co-doped BiFeO{sub 3} ceramic samples show weak ferromagnetic ordering at room temperature. This observation makes Ca doped and Ba-Ca co-doped BiFeO{sub 3} samples an interesting material system for magnetoelectric coupling studies.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Prospects and progress of high Tc superconductivity for space applications

Current research in the area of high temperature superconductivity is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAlO3 produced far superior RF characteristics when compared to metallic films on the same substrate. The achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high-Q filters. Melt texturing and melt-quenched techniques are being used to produce bulk material with optimized magnetic properties. These yttrium-enriched materials possess enhanced flux pinning characteristics and could lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies were conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magnetoplasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar, and Mars mission applications.

Romanofsky, Robert R.↗
DOE OSTI2022

Magnetic control over the fundamental structure of atomic wires

When reducing the size of materials towards the nanoscale, magnetic properties can emerge due to structural variations. Here, we show the reverse effect, where the structure of nanomaterials is controlled by magnetic manipulations. Using the break-junction technique, we find that the interatomic distance in platinum atomic wires is shorter or longer by up to ~20%, when a magnetic field is applied parallel or perpendicular to the wires during their formation, respectively. The magnetic field direction also affects the wire length, where longer (shorter) wires are formed under a parallel (perpendicular) field. Our experimental analysis, supported by calculations, indicates that the direction of the applied magnetic field promotes the formation of suspended atomic wires with a specific magnetization orientation associated with typical orbital characteristics, interatomic distance, and stability. A similar effect is found for various metal and metal-oxide atomic wires, demonstrating that magnetic fields can control the atomistic structure of different nanomaterials when applied during their formation stage.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Heavy ion beam probe advances from the first installation of the diagnostic on an RFP (invited)

Heavy ion beam probes have been installed on a variety of toroidal devices, but the first and only application on a reversed field pinch is the diagnostic on the Madison Symmetric Torus. Simultaneous measurements of spatially localized equilibrium potential and fluctuations of density and potential, previously inaccessible in the core of the reversed field pinch (RFP), are now attainable. These measurements reflect the unique strength of the heavy ion beam probe (HIBP) diagnostic. They will help determine the characteristics and evolution of electrostatic fluctuations and their role in transport, and determine the relation of the interior electric field and flows. Many aspects of the RFP present original challenges to HIBP operation and inference of plasma quantities. The magnetic field contributes to a number of the issues: the comparable magnitudes of the toroidal and poloidal fields and edge reversal result in highly three-dimensional beam trajectories; partial generation of the magnetic field by plasma current cause it and hence the beam trajectories to vary with time; and temporal topology and amplitude changes are common. Associated complications include strong ultraviolet radiation and elevated particle losses that can alter functionality of the electrostatic systems and generate noise on the detectors. These complexities have necessitated the development of new operation and data analysis techniques: the implementation of primary and secondary beamlines, adoption of alternative beam steering methods, development of higher precision electrostatic system models, refinement of trajectory calculations and sample volume modeling, establishment of stray particle and noise reduction methods, and formulation of alternative data analysis techniques. These innovative methods and the knowledge gained with this system are likely to translate to future HIBP operation on large scale stellarators and tokamaks.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Room temperature ferromagnetic and ferroelectric properties of Bi{sub 1−x}Ca{sub x}MnO{sub 3} thin films

Bi{sub 1−x}Ca{sub x}MnO{sub 3} (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 are successfully deposited on the n-type Si (100) substrate at two different temperatures of 400 °C and 800 °C using RF magnetron sputtering. The stoichiometry of the films and oxidation state of the elements have been described by X-ray photoelectron spectroscopy analysis. Dielectric measurement depicts the insulating property of BCMO films. Magnetic and ferroelectric studies confirm the significant enhancement in spin orientation as well as electric polarization at room temperature due to incorporation of Ca{sup 2+} ions into BiMnO{sub 3} films. The BCMO (x = 0.2) film grown at 400 °C shows better magnetization (M{sub sat}) and polarization (P{sub s})with the measured values of 869 emu / cc and 6.6 μ{sub C}/ cm{sup 2} respectively than the values of the other prepared films. Thus the realization of room temperature ferromagnetic and ferroelectric ordering in Ca{sup 2+} ions substituted BMO films makes potentially interesting for spintronic device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental Study of a Vacuum Spark Discharge over a Dielectric Surface

A decrease in the amplitude of the current of a vacuum spark discharge over a dielectric surface with increasing discharge gap length is established. It is shown that, in the presence of a longitudinal magnetic field, the leading edge of the discharge voltage pulse is extended, whereas the clearly pronounced current pulse transforms into a train of alternating current oscillations. The discharge is found to decelerate when the spark is preceded by a low-current discharge.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Cation-Bonding and Protonation of the Fe[subscript 4]-Square Cluster

The synthesis and characterization of discrete, molecular iron-oxo clusters is pursued in the interest of molecular magnets, bioinspired materials and models for the geochemical aqueous-mineral interface. Iron-oxo clusters are challenging to synthesize in water, due to the extremely acidic and reactive nature of dissolved iron species, and thus require chelating ligands to passivate and neutralize the cluster surface. The 2-hydroxy-1,3-N,N,N',N'-diamino-propanetetraacetic acid (HPDTA) ligand has been used to isolate several Al and Fe cluster geometries, including the square clusters Fe{sub 4}(HPDTA){sub 2} and Al{sub 4}(HPDTA){sub 2}. While prior reports on the Fe{sub 4}(HPDTA){sub 2} cluster have focused on the magnetic properties, no solution characterization has been carried out. Using electrospray ionization mass-spectrometry (ESI-MS) we show this anionic Fe{sub 4}(HPDTA){sub 2} cluster can be dissolved intact in water, and recrystallized with virtually any metal as a countercation. The bonding of the metal cation to the square face of the cluster trends with ionic radii of the cations, as shown by structural characterization of Fe{sub 4}(HPDTA){sub 2} with Li{sup +}, Na{sup +}, Cs{sup +}, Mg{sup 2+}, Ba{sup 2+}, La{sup 3+}, Eu{sup 3+}, and Zn{sup 2+}. This trend is similar to that observed for association of cations on metal oxide surfaces in the environment. Furthermore, protonation of the bridging oxo ligands of this series of Fe{sub 4}(HPDTA){sub 2} clusters is variable (0, 1, or 2 protons), and structures as a function of protonation is discussed. This paper, largely structural in nature, sets the foundation for future aqueous phase studies of iron-oxo molecular clusters as models for the oxide-water interface in the natural aqueous environment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Hopping conduction in p-type MoS{sub 2} near the critical regime of the metal-insulator transition

We report on temperature-dependent charge and magneto transport of chemically doped MoS{sub 2}, p-type molybdenum disulfide degenerately doped with niobium (MoS{sub 2}:Nb). The temperature dependence of the electrical resistivity is characterized by a power law, ρ(T) ∼ T{sup −0.25}, which indicates that the system resides within the critical regime of the metal-insulator (M-I) transition. By applying high magnetic field (∼7 T), we observed a 20% increase in the resistivity at 2 K. The positive magnetoresistance shows that charge transport in this system is governed by the Mott-like three-dimensional variable range hopping (VRH) at low temperatures. According to relationship between magnetic-field and temperature dependencies of VRH resistivity, we extracted a characteristic localization length of 19.8 nm for MoS{sub 2}:Nb on the insulating side of the M-I transition.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Self-assembly of multiferroic core-shell particulate nanocomposites through DNA-DNA hybridization and magnetic field directed assembly of superstructures

Multiferroic composites of ferromagnetic and ferroelectric phases are of importance for studies on mechanical strain mediated coupling between the magnetic and electric subsystems. This work is on DNA-assisted self-assembly of superstructures of such composites with nanometer periodicity. The synthesis involved oligomeric DNA-functionalized ferroelectric and ferromagnetic nanoparticles, 600 nm BaTiO{sub 3} (BTO) and 200 nm NiFe{sub 2}O{sub 4} (NFO), respectively. Mixing BTO and NFO particles, possessing complementary DNA sequences, resulted in the formation of ordered core-shell heteronanocomposites held together by DNA hybridization. The composites were imaged by scanning electron microscopy and scanning microwave microscopy. The presence of heteroassemblies along with core-shell architecture is clearly observed. The reversible nature of the DNA hybridization allows for restructuring the composites into mm-long linear chains and 2D-arrays in the presence of a static magnetic field and ring-like structures in a rotating-magnetic field. Strong magneto-electric (ME) coupling in as-assembled composites is evident from static magnetic field H induced polarization and low-frequency magnetoelectric voltage coefficient measurements. Upon annealing the nanocomposites at high temperatures, evidence for the formation of bulk composites with excellent cross-coupling between the electric and magnetic subsystems is obtained by H-induced polarization and low-frequency ME voltage coefficient. The ME coupling strength in the self-assembled composites is measured to be much stronger than in bulk composites with randomly distributed NFO and BTO prepared by direct mixing and sintering.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Spin reorientation transition and near room-temperature multiferroic properties in a W-type hexaferrite SrZn{sub 1.15}Co{sub 0.85}Fe{sub 16}O{sub 27}

In this Letter, we investigate the magnetic and multiferroic properties of a W-type hexaferrite SrZn{sub 1.15}Co{sub 0.85}Fe{sub 16}O{sub 27}. Due to the strong planar contribution to the anisotropy provided by Co{sup 2+} ions, this hexaferrite shows a spin reorientation transition from easy-axis to easy-cone at 302 K, which is different from the onset temperature of ferroelectric polarization, 275 K. By applying magnetic field, a remarkable drop of polarization is observed, suggesting a large magnetoelectric effect in this multiferroics. The difference between spin reorientation and ferroelectric phase transition temperature as well as the origin of magnetoelectric effect are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Salt-Assisted Solution Combustion Synthesis of Ni and Ni/NiO Powders

In this work, Ni and Ni/NiO composite powders were synthesized by one-pot solution combustion method using different fuel to oxidant (φ) ratios (φ = 1, 1.25, 1.5, and 1.75). Phase evolution studied by X-ray diffraction (XRD) method showed that single phase Ni powders were formed at high fuel contents, while the low fuel contents led to the formation of Ni/NiO composite powders. The high combustion temperature resulted in the sintered and large Ni particles (1.1 μm). The particle size decreased up to 50 nm by adding KCl as diluent. However, the amount of NiO phase increased by addition of KCl. The saturation magnetization (Ms) of Ni powders decreased from 51 to 42 emu/g with the increase of φ values from 1.25 to 1.75. The Ms decreased up to 18.5 emu/g, due to the formation of a large amount of NiO phase by addition of KCl. The coercivity of the synthesized powders was in the range of 78 to 111 Oe, as a function of particle size.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗