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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Bismuth Electrocatalyst Enabling Reversible Redox Kinetics of a Chelated Chromium Flow Battery Anolyte

Metal electrocatalysts have been reported to improve the electron transfer kinetics of aqueous redox flow battery electrolytes on various types of carbon electrodes. In this work, we electrodeposited bismuth metal onto a carbon paper anode of a redox flow battery containing our previously reported polyaminocarboxylate-chelated chromium electrolyte. Depositing 0.58 mg cm –2 of bismuth metal enabled an electrochemically reversible electron transfer for the Cr(II)/Cr(III) couple, resulting in a 3.9% voltage efficiency increase over ten cycles at 100 mA cm –2 across an 80% state of charge window, while maintaining >99% current efficiency. The bismuth electrocatalyst provided other improvements, such as a 13% increase in average discharge power density when cycling at 80% energy efficiency, along with a 60% decrease in charge transfer resistance and 12% decrease in the full cell area specific resistance. A chelated bismuth complex was also utilized as a bismuth source for electrodeposition, providing an example of how polyaminocarboxylate ligands can be further implemented into efforts towards improving the energy efficiency of aqueous redox flow batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Flexible 3D printed silicones for gamma and neutron radiation shielding

Here, resin formulations for direct ink write (DIW) additive manufacturing (AM) were developed for facile customization to shield radiation signatures consisting of a range of gamma radiation and neutron energies in a variety of applications. The resin developed in this work has been formulated to accommodate very high loadings of shielding filler materials: up to 40 wt% bismuth (Bi) metal for gamma radiation shielding, and up to 60 wt% boron-10 ( 10 B) metal for neutron shielding. We report the first instance of a printable resin containing 60 wt% 10 B, which remains flexible after curing despite the high solids content. We demonstrate that these resins can not only tolerate formulation modulation for radiation profile-matched shielding, but they can also be printed in a variety of geometries such that mechanical properties of the printed shield are readily tuned to specific applications. In contrast, most existing shielding materials are rigid, bulky, and do not allow for the complex shapes and mechanical flexibility needed in high-usage applications. This work demonstrates the successful development of a tunable resin for additively manufactured, flexible radiation shielding material, containing high loadings of shielding filler, which can be utilized in harsh radiation environments associated with nuclear materials.

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1992

Search for new high temperature thermoelectric materials

Although important efforts are actually devoted to improve Si-Ge materials, their thermoelectric energy conversion efficiency remains relatively low and the nondimensional ZT value does not exceed 1. Higher values can be obtained by investigating new materials. A search for new high temperature thermoelectric materials identified a certain number of compounds between transition metals and bismuth, antimony and germanium as potential candidates. Results of the preliminary synthesis of samples by a variety of techniques (Bridgman, mechanical alloying) are presented as well as some electrical measurements. Some compounds showed interesting properties and need to be investigated in more details.

Caillat, Thierry↗
DOE OSTI2019

Bismuth as a Reactive Solvent in the Synthesis of Multicomponent Transition-Metal-Bearing Bismuthides

Employment of liquid bismuth (Bi) allows the facile single-crystal growth of compounds containing elements with high melting points, provided that these elements have reasonably high solubility in Bi. Utilization of the Bi flux approach yielded two new ternary bismuthides, SrNi 0.17(1) Bi 2 [a defect variant of the BaCuSn 2 type, space group Cmcm , α = 4.879(2) Å, b = 17.580(6) Å, and c = 4.696(2) Å] and CaTi 3 Bi 4 [NdTi 3 (Sn 0.1 Sb 0.9 ) 4 structure type, space group Fmmm , a = 5.6295(7) Å, b = 9.8389(1) Å, and c = 23.905(3) Å]. In addition, the ternary antimonide CaV3Sb4, isostructural with CaTi 3 Bi 4 , was synthesized from antimony (Sb) flux, and analyzed with the goal of validating structural assessment of the bismuthide analogue, where the X-ray crystallographic work proved to be very challenging. All synthesized compounds exhibit complex crystal structures featuring quasi-two-dimensional building blocks of different topologies. First-principle calculations reveal hypervalent bonding in the homoatomic Bi subunits. Lastly, physical property measurements indicate metallic conductivity and the absence of localized magnetism in the studied compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Connectivity-Dependent Exciton–Phonon Coupling in Cesium Bismuth Halide Quantum Dots

Metal halide octahedra form the fundamental functional building blocks of metal halide perovskites, dictating their structures, optical properties, electronic structures, and dynamics. Here, in this study, we show that the connectivity of bismuth halide octahedra in Cs 3 Bi 2 Br 9 and Cs 3 Bi 2 I 9 quantum dots (QDs) changes with different halide elements. We use first-principles calculations to reveal the key role of the connectivity of bismuth halide octahedra on the wave function symmetry, Huang-Rhys factor, and exciton-phonon interaction strength. Following QD synthesis via a ligand-mediated transport method, the effect of connectivity is verified with transient absorption spectroscopy, where we contrast Cs 3 Bi 2 Br 9 and Cs 3 Bi 2 I 9 QD exciton dynamics. In photoexcited Cs 3 Bi 2 I 9 QDs, phonons related to the vibrational motions of face-sharing [BiI 6 ] 3- bioctahedra couple strongly to the electronic state and drive rapid carrier relaxation. Equivalent signals are not observed for photoexcited Cs 3 Bi 2 Br 9 QDs, implying a lack of phonon involvement in band-edge absorption and subsequent exciton relaxation. Our findings suggest that structural engineering can effectively tune the exciton-phonon coupling and therefore influence exciton relaxation and recombination in perovskite nanomaterials.

TDDFT↗
DOE OSTI2025

Ternary Potassium‐Bismuth‐Telluride Intermetallic Support Promotes Electrochemical Stability in Potassium Metal Anodes

We employed accumulative roll bonding to fabricate self‐standing metallurgical composite of in situ formed alkaline potassium‐bismuth‐telluride intermetallic K 2 (Bi 2/6 Te 3/6 Vac 1/6 ) embedded in potassium metal. This newly discovered thermodynamically stable potassiophilic crystal, termed “KBT”, is fcc antifluorite with K 2 Te archetype. Symmetric cells achieve 880 h of cycling at 0.5 mA cm −2 and 0.5 mAh cm −2 . Potassium metal battery (KMB) with Prussian blue (PB) cathode in carbonate electrolyte retains 80% capacity after 200 cycles at 1C. In ether‐based electrolyte with organic cathode, it achieves 80% retention after 900 cycles at 2C. Combined synchrotron X‐ray nano‐tomography, cryogenic‐focused ion beam microscopy (Cryo‐FIB) and sputter‐down X‐ray photoelectron spectroscopy (XPS) demonstrate uniform electrodeposits, versus baseline of potassium filaments intermixed with pores and coarse SEI. Binary K 3 Bi‐K and K 2 Te‐K intermetallic supports also provide improved electrochemical performance, albeit to lesser extent. Multiscale simulation provides insight into role of support structure in adatom energetics, film nucleation, early‐stage SEI morphology and interfacial stability.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Niowave Flow Testing of the High Power Converter - FY 21

Design work for a 100 kW converter to produce a neutron flux via electron impact on a flowing stream of liquid metal lead-bismuth (LBE) was conducted in FY20. In FY21, the focus shifted to a 20 kW converter which was designed in collaboration with Niowave engineers. A flow visualization model is needed to validate model results for the 20 kW converter and ensure adequate coolant flow over containment structures. This work highlights the mockup that was made with quartz side plates by LANL.

42 ENGINEERING↗
DOE OSTI2021

Charge Transfer Properties of Heterostructures Formed by Bi 2 O 2 Se and Transition Metal Dichalcogenide Monolayers

Atomically thin bismuth oxyselenide (Bi 2 O 2 Se) exhibits attractive properties for electronic and optoelectronic applications, such as high charge-carrier mobility and good air stability. Recently, the development of Bi 2 O 2 Se-based heterostructures have attracted enormous interests with promising prospects for diverse device applications. Although the electrical properties of Bi 2 O 2 Se-based heterostructures have been widely studied, the interlayer charge transfer in these heterostructures remains elusive, despite its importance in harnessing their emergent functionalities. Here, a comprehensive experimental investigation on the interlayer charge transfer properties of two heterostructures formed by Bi 2 O 2 Se and representative transition metal dichalcogenides (namely, WS 2 /Bi 2 O 2 Se and MoS 2 /Bi 2 O 2 Se) is reported. In this work, Kelvin probe force microscopy is used to measure the work functions of the samples, which are further employed to establish type-II band alignment of both heterostructures. Photoluminescence quenching is observed in each heterostructure, suggesting high charge transfer efficiency. Time-resolved and layer-selective pump–probe measurements further prove the ultrafast interlayer charge transfer processes and formation of long-lived interlayer excitons. These results establish the feasibility of integrating 2D Bi 2 O 2 Se with other 2D semiconductors to fabricate heterostructures with novel charge transfer properties and provide insight for understanding the performance of optoelectronic devices based on such 2D heterostructures.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Stabilized Alkali-Metal Ultraviolet-Band-Pass Filters

Layers of bismuth 5 to 10 angstrom thick incorporated into alkali-metal ultraviolet-band-pass optical filters by use of advanced fabrication techniques. In new filters layer of bismuth helps to reduce surface migration of sodium. Sodium layer made more stable and decreased tendency to form pinholes by migration.

Mardesich, Nick↗
NASA NTRS2011

Thermoelectric Performance Enhancement by Surrounding Crystalline Semiconductors with Metallic Nanoparticles

Direct conversion of thermal energy to electricity by thermoelectric (TE) devices may play a key role in future energy production and utilization. However, relatively poor performance of current TE materials has slowed development of new energy conversion applications. Recent reports have shown that the dimensionless Figure of Merit, ZT, for TE devices can be increased beyond the state-of-the-art level by nanoscale structuring of materials to reduce their thermal conductivity. New morphologically designed TE materials have been fabricated at the NASA Langley Research Center, and their characterization is underway. These newly designed materials are based on semiconductor crystal grains whose surfaces are surrounded by metallic nanoparticles. The nanoscale particles are used to tailor the thermal and electrical conduction properties for TE applications by altering the phonon and electron transport pathways. A sample of bismuth telluride decorated with metallic nanoparticles showed less thermal conductivity and twice the electrical conductivity at room temperature as compared to pure Bi2Te3. Apparently, electrons cross easily between semiconductor crystal grains via the intervening metallic nanoparticle bridges, but phonons are scattered at the interfacing gaps. Hence, if the interfacing gap is larger than the mean free path of the phonon, thermal energy transmission from one grain to others is reduced. Here we describe the design and analysis of these new materials that offer substantial improvements in thermoelectric performance.

Kim, Hyun-Jung↗
DOE OSTI2023

Bismuth-Polyoxocation Coordination Networks: Controlling Nuclearity and Dimension-Dependent Photocatalysis

Bismuth-oxocluster nodes for metal–organic frameworks (MOFs) and coordination networks/polymers are less prolific than other families featuring zinc, zirconium, titanium, lanthanides, etc. However, Bi 3+ is non-toxic, it readily forms polyoxocations, and its oxides are exploited in photocatalysis. This family of compounds provides opportunity in medicinal and energy applications. Here, we show that Bi node nuclearity depends on solvent polarity, leading to a family of Bi x -sulfonate/carboxylate coordination networks with x = 1–38. Larger nuclearity-node networks were obtained from polar and strongly coordinating solvents, and we attribute the solvent’s ability to stabilize larger species in solution. Here, the strong role of the solvent and the lesser role of the linker in defining node topologies differ from other MOF syntheses, and this is due to the Bi 3+ intrinsic lone pair that leads to weak node–linker interactions. We describe this family by single-crystal X-ray diffraction (eleven structures), obtained in pure forms and high yields. Ditopic linkers include NDS (1,5-naphthalenedisulfonate), DDBS (2,2'-[biphenyl-4,4'-diylchethane-2,1-diyl] dibenzenesulphonate), and NH 2 -benzendicarboxylate (BDC). While the BDC and NDS linkers yield more open-framework topologies that resemble those obtained by carboxylate linkers, topologies with DDBS linkers appear to be in part driven by association between DDBS molecules. An in situ small-angle X-ray scattering study of Bi 38 -DDBS reveals stepwise formation, including Bi 38 -assembly, pre-organization in solution, followed by crystallization, confirming the less important role of the linker. We demonstrate photocatalytic hydrogen (H 2 ) generation with select members of the synthesized materials without the benefit of a co-catalyst. Band gap determination from X-ray photoelectron spectroscopy (XPS) and UV–vis data suggest the DDBS linker effectively absorbs in the visible range with ligand-to-Bi-node charge transfer. In addition, materials containing more Bi (larger Bi 38 -nodes or Bi 6 inorganic chains) exhibit strong UV absorption, also contributing to effective photocatalysis by a different mechanism. All tested materials became black with extensive UV–vis exposure, and XPS, transmission electron microscopy, and X-ray scattering of the black Bi 38 -framework suggest that Bi o is formed in situ, without phase segregation. This evolution leads to enhanced photocatalytic performance, perhaps due to increased light absorption.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Design and Analysis of a Mutual Inductance Level Sensor for Liquid Metals

Here, this article describes the design and analysis of an electromagnetic level sensor for use in high-temperature liquid metal systems. The mutual inductance level sensor (MILS) described in this work was fabricated using two single-conductor mineral insulated cables wrapped in a bifilar fashion around a stainless steel tube core and was housed in an isolating thimble that preserved the pressure boundary of the test vessel. Two sensor variations were fabricated that differ only in active length, 1016 and 1778 mm. Experimental data were collected using the 1016-mm sensor (MILS-MKII-040) that demonstrated a sensitivity of 9.2 μ V/mm in a room temperature testing stand that used solid aluminum as a surrogate for liquid metal. Experimental data were collected using the 1778-mm sensor (MILS-MKII-070) that demonstrated a sensitivity of 6.9 μ V/mm in the high-temperature (300 ° C) liquid sodium environment at the mechanisms engineering test loop (METL) of Argonne National Laboratory. The sensor performance was found to be repeatable over the course of several months, with roughly ±1% deviation from nominal output. Finite element models were developed in COMSOL Multiphysics that fully describe each test setup, and the models were validated using experimental data. The validated COMSOL models were used to perform an array of analyses that examined the performance of the sensor in differing environments. Maximizing the coil diameter inside the isolating thimble was found to maximize the signal and sensitivity of the sensor. An optimal operating frequency was found near 1000 Hz using both experimental data and COMSOL. The influence of a metallic thimble surrounding the sensor and a metallic sensor core was quantified and found to be negligible at the optimal operating frequency. The sensitivity of the sensor was quantified when monitoring the level of additional liquid metals. These include lead, lead-bismuth eutectic (LBE), sodium-potassium alloy (NaK), and lithium (in addition to sodium). The sensitivities were quantified using liquid metal properties at 350 ° C and 650 ° C. The geometry of the test stand model, all material properties used in the model, and the results are presented in a manner that allows the reader can replicate the model and perform additional analyses.

COMSOL↗
NASA NTRS2007

Bismuth Propellant Feed System Development at NASA-MSFC

NASA-MSFC has been developing liquid metal propellant feed systems capable of delivering molten bismuth at a prescribed mass flow rate to the vaporizer of an electric thruster. The first such system was delivered to NASA-JPL as part of the Very High Isp Thruster with Anode Layer (VHITAL) program. In this system, the components pictured were placed in a vacuum chamber and heated while the control electronics were located outside the chamber. The system was successfully operated at JPL in conjunction with a propellant vaporizer, and data was obtained demonstrating a new liquid bismuth flow sensing technique developed at MSFC. The present effort is aimed at producing a feed-system for use in conjunction with a bismuth-fed Hall thruster developed by Busek Co. Developing this system is more ambitious, however, in that it is designed to self-contain all the control electronics inside the same vacuum chamber as an operating bismuth-fed thruster. Consequently, the entire system, including an on-board computer, DC-output power supplies, and a gas-pressurization electro-pneumatic regulator, must be designed to survive a vacuum environment and shielded to keep bismuth plasma from intruding on the electronics and causing a shortcircuit. In addition, the hot portions of the feed system must be thermally isolated from the electronics to avoid failure due to high heat loads. This is accomplished using a thermal protection system (TPS) consisting of multiple layers of aluminum foil. The only penetrations into the vacuum chamber are an electrically isolated (floating) 48 VDC line and a fiberoptic line. The 48 VDC provides power for operation of the power supplies and electronics co-located with the system in the vacuum chamber. The fiberoptic Ethernet connection is used to communicate user-input control commands to the on-board computer and transmit real-time data back to the external computer. The partially assembled second-generation system is shown. Before testing at Busek, a more detailed flow sensor calibration will be performed to accurately quantify the flow monitoring capabilities. This effort is funded under a Technology Innovation Program (TIP) award from NASA-MSFC's Technology Transfer office and performed under SAA8-061060.

Polzin, Kurt A.↗
DOE OSTI2022

Extracting information from X-ray diffraction patterns containing Laue oscillations

The presence of Laue oscillations in a film grown on a solid surface is broadly taken as indicating a high quality, crystallographically aligned film of the targeted compound. In this paper we briefly review the origins of both Laue oscillations and Kiessig fringes and show how they can be used together to determine if extra thickness exists above or below the coherently diffracting domains. The differences between experimental and “ideal” films are discussed and the effect of structural features (roughness, different thickness coherently diffracting domains and thickness in addition to the coherently diffracting domains) are illustrated with experimental and simulated data for metal and mixed-metal chalcogenide films of titanium, bismuth, vanadium/iron, and bismuth/molybdenum. Examples are given showing how quantitative information can be extracted from experimental diffraction patterns.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗