Search NASA⌕ Search

SEARCH · Search NASA

Results for “BARIUM”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9

Accelerated Discovery of Cost-Effective Photoabsorber Materials for Near-Infrared (λ = 1600 nm) Photodetector Applications

Current infrared sensing devices are based on costly materials with relatively few viable alternatives known. To identify promising candidate materials for infrared photodetection, we have developed a high-throughput screening methodology based on high-accuracy r 2 SCAN and HSE calculations in density functional theory. Using this method, we identify ten already synthesized materials between the inverse perovskite family, the barium silver pnictide family, the alkaline pnictide family, and ZnSnAs 2 as top candidates. Among these, ZnSnAs 2 emerges as the most promising candidate due to its experimentally verified band gap of 0.74 eV at 0 K and its cost-effective synthesis through Bridgman growth. BaAgP also shows potential with an HSE-calculated band gap of 0.64 eV, although further experimental validation is required. Lastly, we discover an additional material, Ca 3 BiP, which has not been previously synthesized, but exhibits a promising optical spectra and a band gap of 0.56 eV. The method applied in this work is sufficiently general to screen wider bandgap materials in high-throughput and now extended to narrow-band gap materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability

Increasing demand for effective energy conversion materials and devices has renewed interest in semiconductors comprised of earth-abundant and biocompatible elements. Alkaline-earth sulfides doped with rare earth ions are versatile optical materials. However, relatively little is known about controlling the dimensionality, surface chemistry, and inherent optical properties of the undoped versions of alkaline-earth monoand polychalcogenides. Here, we describe the colloidal synthesis of alkaline-earth chalcogenide nanocrystals through the reaction of metal carboxylates with carbon disulfide or selenourea. Systematic exploration of the synthetic phase space allows us to tune particle sizes over a wide range using a mixture of commercially available carboxylate precursors. Solid-state NMR spectroscopy confirms the phase purity of the selenide compositions. Surface characterization reveals that bridging carboxylates and amines preferentially terminate the surface of the nanocrystals. While these materials are colloidally stable in the mother solution, the selenides are susceptible to oxidation over time, eventually degrading to selenium metal through polyselenide intermediates. As part of these investigations, we have developed the colloidal syntheses of barium di- and triselenides, two among few reported nanocrystalline alkaline-earth polychalcogenides. Electronic structure calculations reveal that both materials are indirect band gap semiconductors. The colloidal chemistry presented here may enable the synthesis of more complex, multinary chalcogenide materials containing alkaline-earth elements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Joint Experimental and Computational Characterization of Sum-Frequency Generation between a Continuous Wave Laser and an Ultrafast Frequency Comb Laser for Tunable Laser Development

Ultrafast optical frequency combs allow for both high spectral and temporal resolution in molecular spectroscopy and have become a powerful tool in many areas of chemistry and physics. Ultrafast lasers and frequency combs generated from ultrafast mode-locked lasers often need to be converted to other wavelengths. Commonly used wavelength conversions are optical parametric oscillators, which require an external optical cavity, and supercontinuum generation combined with optical parametric amplifiers. Whether commercial or home-built, these systems are complex and costly. Here, we investigate an alternative, simple, and easy-to-implement approach to tunable frequency comb ultrafast lasers enabled by new continuous-wave laser technology. Sum-frequency generation between an Nd:YAG continuous-wave laser and a Yb:fiber femtosecond frequency comb in a beta-barium borate (BBO) crystal is explored. The resulting sum-frequency beam is a pulsed frequency comb with the same repetition rate as the Yb:fiber source. SNLO simulation software is used to simulate the results and provide benchmarks for designing future systems to achieve wavelength conversion and tunability in otherwise difficult-to-reach spectral regions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Rapid Mineral Precipitation During Shear Fracturing of Carbonate-Rich Shales

Target subsurface reservoirs for emerging low-carbon energy technologies and geologic carbon sequestration typically have low permeability and thus rely heavily on fluid transport through natural and induced fracture networks. Sustainable development of these systems requires deeper understanding of how geochemically mediated deformation impacts fracture microstructure and permeability evolution, particularly with respect to geochemical reactions between pore fluids and the host rock. Here, a series of triaxial direct shear experiments was designed to evaluate how fractures generated at subsurface conditions respond to penetration of reactive fluids with a focus on the role of mineral precipitation. Calcite-rich shale cores were directly sheared under 3.5 MPa confining pressure using BaCl 2 -rich solutions as a working fluid. Experiments were conducted within an X-ray computed tomography (xCT) scanner to capture 4-D evolution of fracture geometry and precipitate growth. Three shear tests evidenced nonuniform precipitation of barium carbonates (BaCO 3 ) along through-going fractures, where the extent of precipitation increased with increasing calcite content. Precipitates were strongly localized within fracture networks due to mineral, geochemical, and structural heterogeneities and generally concentrated in smaller apertures where rock:water ratios were highest. The combination of elevated fluid saturation and reactive surface area created in freshly activated fractures drove near-immediate mineral precipitation that led to an 80% permeability reduction and significant flow obstruction in the most reactive core. While most previous studies have focused on mixing-induced precipitation, this work demonstrates that fluid–rock interactions can trigger precipitation-induced permeability alterations that can initiate or mitigate risks associated with subsurface energy systems.

58 GEOSCIENCES↗

eReaxFF force field development for BaZr 0.8 Y 0.2 O 3-δ solid oxide electrolysis cells applications

The use of solid-oxide materials in electrocatalysis applications, especially in hydrogen-evolution reactions, is promising. However, further improvements are warranted to overcome the fundamental bottlenecks to enhancing the performance of solid-oxide electrolysis cells (SOECs), which is directly linked to the more-refined fundamental understanding of complex physical and chemical phenomena and mass exchanges that take place at the surfaces and in the bulk of electrocatalysis materials. Here, we developed an eReaxFF force field for barium zirconate doped with 20 mol% of yttrium, BaZr 0.8 Y 0.2 O 3-δ (BZY20) to enable a systematic, large-length-scale, and longer-timescale atomistic simulation of solid-oxide electrocatalysis for hydrogen generation. All parameters for the eReaxFF were optimized to reproduce quantum-mechanical (QM) calculations on relevant condensed phase and cluster systems describing oxygen vacancies, vacancy migrations, electron localization, water adsorption, water splitting, and hydrogen generation on the surfaces of the BZY20 solid oxide. Using the developed force field, we performed both zero-voltage (excess electrons absent) and non-zero-voltage (excess electrons present) molecular dynamics simulations to observe water adsorption, water splitting, proton migration, oxygen-vacancy migrations, and eventual hydrogen-production reactions. Based on investigations offered in the present study, we conclude that the eReaxFF force field-based approach can enable computationally efficient simulations for electron conductivity, electron leakage, and other non-zero-voltage effects on the solid oxide materials using the explicit-electron concept. Moreover, we demonstrate how the eReaxFF force field-based atomistic-simulation approach can enhance our understanding of processes in SOEC applications and potentially other renewable-energy applications.

08 HYDROGEN↗

Immobilization of active ammonia-oxidizing archaea in hydrogel beads

Abstract Ammonia-oxidizing archaea (AOA) are major players in the nitrogen cycle but their cultivation represents a major challenge due to their slow growth rate and limited tendency to form biofilms. In this study, AOA was embedded in small (~2.5 mm) and large (~4.7 mm) poly(vinyl alcohol) (PVA)—sodium alginate (SA) hydrogel beads cross-linked with four agents (calcium, barium, light, or sulfate) to compare the differences in activity, the diffusivity of nitrogen species (NH 4 + , NO 2 − , and NO 3 − ), and polymer leakage in batch systems over time. Sulfate-bound PVA-SA beads were the most stable, releasing the lowest amount of polymer without shrinking. Diffusion coefficients were found to be 2 to 3 times higher in hydrogels than in granules, with ammonium diffusivity being ca . 35% greater than nitrite and nitrate. Despite a longer lag phase in small beads, embedded AOA sustained a high per volume rate of ammonia oxidation compatible with applications in research and wastewater treatment.

42 ENGINEERING↗

Conformally coated scaffold design using water-tolerant Pr 1.8 Ba 0.2 NiO 4.1 for protonic ceramic electrochemical cells with 5,000-h electrolysis stability

Protonic ceramic electrochemical cells (PCECs) have potential as long-duration energy storage systems. However, their operational stability is limited under industrially relevant conditions due to the intrinsic chemical instability of doped barium cerate-based electrolytes and oxygen electrodes against H 2 O, as well as the poor electrode–electrolyte interfacial contact. Here, in this study, we present a conformally coated scaffold (CCS) design to comprehensively address these issues. A porous proton-conducting scaffold is constructed and conformally coated with Pr 1.8 Ba 0.2 NiO 4.1 electrocatalyst, which has high chemical stability against H 2 O, triple conductivity and hydration capability, and protects vulnerable electrolytes from H 2 O. The CCS structure consolidates the electrode–electrolyte interfacial bonding to enable fast proton transfer in the percolated network. This design enables PCECs to reach electrolysis stability for 5,000 h at −1.5 A cm−2 and 600 °C in 40% H 2 O. This work provides a general strategy to stabilize PCECs and offers guidance for designing resilient and stable solid-state energy storage systems.

Protonic ceramic electrochemical cell↗

Atomic-scale imaging of frequency-dependent phonon anisotropy

Directly visualizing vibrational anisotropy in individual phonon modes is essential for understanding a wide range of intriguing optical, thermal and elastic phenomena in materials. Although conventional optical and diffraction techniques have been used to estimate vibrational anisotropies, they fall short in achieving the spatial and energy resolution necessary to provide detailed information. Here, we introduce a new form of momentum-selective electron energy-loss spectroscopy, which enables the element-resolved imaging of frequency- and symmetry-dependent vibrational anisotropies with atomic resolution. Vibrational anisotropies manifest in different norms of orthogonal atomic displacements, known as thermal ellipsoids. Using the centrosymmetric strontium titanate as a model system, we observed two distinct types of oxygen vibrations with contrasting anisotropies: oblate thermal ellipsoids below 60 meV and prolate ones above 60 meV. In non-centrosymmetric barium titanate, our approach can detect subtle distortions of the oxygen octahedra by observing the unexpected modulation of q-selective signals between apical and equatorial oxygen sites near 55 meV, which originates from reduced crystal symmetry and may also be linked to ferroelectric polarization. These observations are quantitatively supported by theoretical modelling, which demonstrates the reliability of our approach. The measured frequency-dependent vibrational anisotropies shed new light on the dielectric and thermal behaviours governed by acoustic and optical phonons. Furthermore, the ability to visualize phonon eigenvectors at specific crystallographic sites with unprecedented spatial and energy resolution opens new avenues for exploring dielectric, optical, thermal and superconducting properties.

Ferroelectrics and multiferroics↗

Large electromechanical strain and unconventional domain switching near phase convergence in a Pb-free ferroelectric

In many ferroelectrics, large electromechanical strains are observed near regions of composition- or temperature- driven phase coexistence. Phenomenologically, this is attributed to easy re-orientation of the polarization vector and/or phase transition, although their effects are highly convoluted and difficult to distinguish experimentally. Here, we used synchrotron X-ray scattering and digital image correlation to differentiate between the microscopic mechanisms leading to large electrostrains in an exemplary Pb-free piezoceramic Sn-doped barium calcium zirconate titanate. Large electrostrains of ~0.2% measured at room-temperature are attributed to an unconventional effect, wherein polarization switching is aided by a reversible phase transition near the tetragonal-orthorhombic phase boundary. Additionally, electrostrains of ~0.1% or more could be maintained from room temperature to 140°C due to a succession of different microscopic mechanisms. In situ X-ray diffraction elucidates that while 90° domain reorientation is pertinent below the Curie temperature ( T C ), isotropic distortion of polar clusters is the dominant mechanism above T C .

36 MATERIALS SCIENCE↗

Critical role of acceptor dopants in designing highly stable and compatible proton-conducting electrolytes for reversible solid oxide cells

Proton-conducting electrolytes are receiving increasing attention due to their high ionic conductivity at intermediate temperatures, enabling the operation of solid oxide cells with high energy efficiency at low cost. However, the effect of B-site dopants on the properties of doped barium hafnate-cerate electrolyte materials, especially in single cells under operating conditions, has not been systematically studied. Here we report our findings in the development of a series of proton-conducting electrolytes with a general formula of BaHf 0.1 Ce 0.7 R 0.2 O 3–δ (BHCR172, R = Yb, Er, Y, Gd, Sm). Here, the results reveal that electrical conductivity, ionic transference number, chemical stability against steam and CO 2 , and compatibility with NiO during sintering are all closely correlated with the dopant size. In particular, the reaction with NiO is found to strongly affect the properties of the electrolytes and hence cell performance. Among all tested compositions, BaHf 0.1 Ce 0.7 Yb 0.2 O 3–δ (BHCYb172) shows excellent chemical stability and minimal reactivity towards NiO, as predicted from density functional theory (DFT)-based calculations and confirmed by experimental results. In addition, proton-conducting reversible solid oxide cells (P-ReSOCs) based on the optimized electrolyte composition, BHCYb172, demonstrate exceptional performance and stability, achieving a remarkable peak power density of 1.74 W cm –2 (O 2 as the oxidant) at 600 °C in the fuel cell mode and a high current density of 2.0 A cm –2 at 1.3 V and 600 °C in the steam electrolysis mode while maintaining excellent durability for over 1000 h.

25 ENERGY STORAGE↗

XANES analysis of phosphate glasses melted with Tb 4 O 7 and SnO: evaluating the impact of valence states on structural, thermal, and luminescent properties

Barium phosphate glasses were prepared with 0.5 mol% Tb 4 O 7 added alongside SnO up to 5 mol% with the purpose of evaluating the resulting terbium and tin oxidation states and their impact on glass structural, thermal, and luminescent properties. In this work, following material synthesis by melt-quenching, the composition-structure–property investigation was pursued encompassing measurements by X-ray diffraction (XRD), X-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy, differential scanning calorimetry (DSC), dilatometry, and photoluminescence (PL) spectroscopy. While XRD confirmed the amorphous nature of the glasses, results from XANES indicated that terbium occurs as terbium(III) with a predisposition for tin to exist as tin(IV) which decreased at high SnO content. The structural as well as the thermal properties appeared to be mostly impacted by the presence of tin(IV). Specifically, glass depolymerization was indicated to be induced by Sn 4+ ions, and their concentration was observed to correlate with glass transition and softening temperatures. On the other hand, the tin(II) remnants were observed to exert an impact on the luminescent properties shifting light emission from the green towards the blue-green (cyan). It is indicated that Tb 4 O 7 reacting to produce Tb 2 O 3 supports the oxidation of tin(II) to tin(IV) which in turn dominates the physical properties. However, this was somewhat circumvented at the highest SnO content wherein tin(IV) appeared to be lower.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Ion-temperature determination with a baffled Langmuir probe

An electrostatic Langmuir probe for real-time measurements of parameters in magnetized plasma is tested in fully ionized, barium, Q-machine plasma. The small-diameter, long-length, tungsten wire sensor, i.e., the probe tip, oriented with its cylindrical axis perpendicular to the magnetic field (B), is partially shielded by ceramic baffles, or masks, that form sensor-access slots between the baffles. Adjusting the azimuthal orientation of the slots, by rotating the probe about its cylindrical axis, changes the fraction of proximity gyro-orbiting electrons, relative to the fraction of proximity gyro-orbiting ions, that can access the recessed sensor along the magnetic field. Thus, the ratio between the electron and ion saturation currents, $I^{sat}_e$ and $I^{sat}_i$, can be adjusted without having affected the probe bias voltage V b . When optimally shielded ($I^{sat}_e/I^{sat}_i$=1), accurate, real-time measurements of space potential Vs can be acquired. When maximally shielded ($I^{sat}_e/I^{sat}_i$ << 1), accurate, real-time measurements of ion temperature T i can be acquired. Subtracting the floating potential V f of an optimally shielded baffled probe from V f of a maximally shielded baffled probe yields T i (and its fluctuation phase) in real time.

47 OTHER INSTRUMENTATION↗

Novel design for a polarizing DUV spectrometer using a Wollaston prism and its application as a diagnostic for measuring Thomson scattering data in the presence of strong self-emission backgrounds

We present a novel design for an optical spectrometer for use in ultraviolet Thomson scattering measurements of plasma parameters in high energy density (HED) inertial confinement fusion experiments on large-scale high-energy laser facilities. In experiments investigating high-Z plasmas, the fidelity of measurements is commonly limited by signal/background ratios approaching or exceeding unity. An alpha barium borate Wollaston prism can provide both spectral dispersion and polarization channel separation, allowing simultaneous measurement of both the Thomson scattering signal and plasma self-emission along a single line of sight and in a single experiment, which should greatly improve data quality and reduce the opportunity cost of taking high quality measurements. Here, we present a basic discussion of the design and a worked example of an instrument designed to take fourth harmonic electron plasma wave measurements in HED experiments at the OMEGA laser facility.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Design of the Lanthanum hexaboride based plasma source for the large plasma device at UCLA

The Large Plasma Device (LAPD) at UCLA (University of California, Los Angeles) produces an 18 m long, magnetized, quiescent, and uniform plasma at a high repetition rate to enable studies of fundamental plasma physics. Here, we report on a major upgrade to the LAPD plasma source that allows for more robust operation and significant expansion of achievable plasma parameters. The original plasma source made use of a heated barium oxide (BaO) coated nickel sheet as an electron emitter. This source had a number of drawbacks, including a limited range of plasma density (≲4.0 × 10 12 cm −3 ), a limited discharge duration (∼10 ms), and susceptibility to poisoning following oxygen exposure. Further, the new plasma source utilizes a 38 cm diameter lanthanum hexaboride (LaB 6 ) cathode, which has a significantly higher emissivity, allowing for a much larger discharge power density, and is robust to exposure to air. Peak plasma density of up to 3.0 × 10 13 cm −33 in helium gas has been achieved. The typical operating pressure is ∼10 −5 Torr, while dynamic pressure can be achieved through the gas-puffing technique. Discharges as long as 70 ms have been produced, enabling a variety of long-time-scale studies of processes, such as turbulent particle transport. The new source has been in continuous operation for 14 months, having survived air leaks, power outages that led to rapid temperature changes on the cathode and heater, and planned machine openings. We describe the design, construction, and initial operation of this novel new large-area LaB6 plasma source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Effect of fabrication processes on BaTiO 3 capacitor properties

There is an increasing desire to utilize complex functional electronic materials such as ferroelectrics in next-generation microelectronics. As new materials are considered or introduced in this capacity, an understanding of how we can process these materials into those devices must be developed. Here, the effect of different fabrication processes on the ferroelectric and related properties of prototypical metal oxide (SrRuO 3 )/ferroelectric (BaTiO 3 )/metal oxide (SrRuO 3 ) heterostructures is explored. Two different types of etching processes are studied, namely, wet etching of the top SrRuO 3 using a NaIO 4 solution and dry etching using an Ar + -ion beam (i.e., ion milling). Polarization-electric-field hysteresis loops for capacitors produced using both methods are compared. For the ion-milling process, it is found that the Ar + beam can introduce defects into the SrRuO 3 /BaTiO 3 /SrRuO 3 devices and that the milling depth strongly influences the defect level and can induce a voltage imprint on the function. Realizing that such processing approaches may be necessary, work is performed to ameliorate the imprint of the hysteresis loops via ex situ “healing” of the process-induced defects by annealing the ferroelectric material in a barium-and-oxygen-rich environment via a chemical-vapor-deposition-style process. This work provides a pathway for the nanoscale fabrication of these candidate materials for next-generation memory and logic applications.

36 MATERIALS SCIENCE↗

Irradiation-induced gas production in REBCO-based magnet materials used for future compact fusion reactors

Nuclear fusion is an enticing alternative to current sources of energy, with multilayered Rare-Earth Barium Copper Oxide (REBCO) coated conductors deemed pivotal in the race toward fully realized, commercially viable, and magnetic confinement fusion reactors. In this study, we simulated the ion spectrum expected to evolve from REBCO's nickel-based Hastelloy C-276 substrate and copper stabilizer in an affordable robust compact-like reactor. We then emulated this gas production through helium implantation to investigate changes in materials and superconducting properties. Our results revealed that the substrate and stabilizer are capable of producing protons energetic enough to recoil throughout the tape thickness in appreciable doses, and alphas energetic enough to deposit 7.54 × 1014 ions/cm2 or 50.1 helium appm in the superconducting layer over a 30-year reactor lifetime. The superconducting layer of SuperPower® tapes exhibited at least double the swelling rate of the other major layers, and both SuperPower and Fujikura Ltd. tapes displayed microstructural changes in the REBCO layer not observed in isotropic metals. For the estimated lifetime fluence, the Fujikura tapes showed a ∼1 K reduction in critical temperature and a 32% degradation in critical current for compact reactor-relevant conditions (16 T, 20 K). Nuclear transmutation, low-temperature solder implantations, gas-ion evolution, the influence of gas production on vortex dynamics, and other related considerations are also discussed.

Reis, Chris↗

A round bobbin critical current measurement and thermal runaway simulation of REBCO coated conductors

A round bobbin test has been widely used to measure critical current Ic of practical superconductors including Nb–Ti, Nb3Sn, and Bi-2212 round strands at 4.2 K and in high magnetic fields but rarely used for rare earth-barium-copper-oxide (REBCO) coated conductor tapes. Here, we applies this method to REBCO tapes and test their Ic at 77 K, self-field, and 4.2 K with a magnetic field of 14 T applied parallel to the tape. The sample carries very high current densities; it is 1.3 m long and has a dense array of voltage taps that allows probing localized thermal runaways and correlation with Ic variations along the length. At 77 K, the Ic values of all sections were measured and found to be rather uniform. However, at 4.2 K, we found that a 3 cm section has 90% of the overall voltage drop and it went into thermal runaways upon further increasing current. Thus, at 4.2 K, we were prevented by localized thermal runaways and unable to determine Ic of most of the REBCO conductor sections; this behavior is different from Bi-2212 and Bi-2223 for which Ic of all turns of a round barrel sample can be determined. We simulate REBCO tapes during current ramping to a thermal runaway and analyze impacts of various factors including cooling, conductor n-values, and thickness of stabilizer on the thermal runaway current Iq. The combined experiments and simulations identify n-value as a crucial factor that leads to the observed differences between Bi-2212 and REBCO. Together with cooling and the standard deviation of Ic variations along the length, the n-value determines whether Iq is above or below the average Ic of a long piece of conductor and their ratio Iq/Ic,ave, greatly affecting quench detection and thermal runaway prevention strategies of Bi-2212 and REBCO magnets.

Mosat, Marek↗

A high-efficiency cryogenic neutron spin flipper for IMAGINE-X at the high flux isotope reactor

The Laue neutron macromolecular crystallography beamline, IMAGINE, at the High Flux Isotope Reactor (HFIR) is undergoing a major upgrade to incorporate the dynamic nuclear polarization (DNP) technique. Upon completion, the new IMAGINE-X instrument is expected to enhance the signal-to-noise ratio of the diffraction data by an order of magnitude. To take full advantage of the benefits of DNP, both a highly polarized neutron beam and a high-efficiency neutron spin flipper are required. We have developed a compact cryogenic spin flipper utilizing the Meissner effect in high-Tc yttrium–barium–copper–oxide superconducting films. The flipper has been successfully tested at two HFIR neutron development beamlines, Larmor and Poplar, with neutron wavelengths of 5.3 and 2.4 Å respectively. At Larmor, a flipping efficiency of 0.995 ± 0.004 was achieved for 5.3 Å neutrons, and at Poplar, efficiency of up to 0.9987 ± 0.0004 was obtained for 2.4 Å neutrons. Both tests demonstrated the flipper’s excellent performance and suitability for integration into IMAGINE-X.

Fu, Sichao [Oak Ridge National Laboratory (ORNL), ↗