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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Theory of Spin-Excitation Anisotropy in the Nematic Phase of FeSe Obtained From RIXS Measurements

Recent resonant inelastic x-ray scattering (RIXS) experiments have detected a significant high-energy spin-excitation anisotropy in the nematic phase of the enigmatic iron-based superconductor FeSe, whose origin remains controversial. We apply an itinerant model previously used to describe the spin-excitation anisotropy as measured by neutron scattering measurements, with magnetic fluctuations included within the RPA approximation. The calculated RIXS cross section exhibits overall agreement with the RIXS data, including the high energy spin-excitation anisotropy.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method

A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials’ synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials’ placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Dynamic Properties of FeCrMnNi, a High Entropy Alloy

High entropy alloys (HEAs) represent a new class of materials that potentially possess an ideal combination of high strength and ductility and may be candidate materials that can withstand high amounts of damage before failure, especially under extreme conditions. To this end, a series of shock/spall loading experiments were conducted on an Fe/Cr/Mn/Ni HEA to assess not only its equation of state (EOS) but also its resistance to damage and failure. A single-stage light gas gun was used to conduct a series of flyer plate symmetric impact experiments coupled with recovery of the samples for post-mortem microstructural analysis to obtain fundamental understanding regarding the damage morphology. Our results show that the measured EOS for this alloy was in reasonable agreement with an estimated Hugoniot value. Additionally, the spall strength of these alloys was found to vary between 1.4 and 1.9 GPa within the same plate but was comparable to other iron-based conventional alloys. DOE/NV/03624--1059

36 MATERIALS SCIENCE↗
DOE OSTI2022

A thermochemical study of iron aluminate-based materials: a preferred class for isothermal water splitting

The use of hydrogen as a renewable fuel has been stymied by our inability to produce it cleanly and economically. The conventional solar thermochemical approach considers a two-step redox cycle with benchmark ceria or a perovskite in a temperature swing configuration, where reduction occurs at a temperature much higher than oxidation. Isothermal redox cycling is feasible and avoids the solid–solid heat recuperation and material stability challenges associated with temperature swing; yet, it has long been thought to be inefficient due to the thermodynamic unfavorability of operating the exothermic oxidation reaction at higher temperatures. Here, in this work, we show that this setback can be overcome with iron aluminate-based spinel solid solutions that preferentially exhibit large changes in oxygen content within the range of oxygen partial pressures expected in large-scale systems. We explain the experimental results with a defect model that assigns cation – not oxygen – vacancies as the predominant point defect responsible for their superior water-splitting ability. When operated isothermally at 1400 °C, the iron aluminate-based materials demonstrate a capacity for hydrogen production greater than 500 μmol g–1 and, as a result, remain viable even under high conversion conditions (i.e., pO 2 < 500 : 1 H 2 O : H 2 ), exceeding the hydrogen yields of ceria and two attractive perovskite candidates following a 400 °C (or less) temperature swing. Isothermal water splitting using iron aluminate-based materials opens the door for more simple, robust, and efficient production of renewable hydrogen.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Projector‐Based Quantum Embedding Study of Iron Complexes

Projection‐based embedding theory (PBET) is used to calculate and assess the challenging spin‐crossover energies for a selection of small Fe‐containing systems by embedding the metal center into the frozen potential of the ligands. MP2, CCSD, and CCSD(T) are embedded in potentials from the SCAN and r 2 SCAN functionals and compared with the canonical values for the constituent methods and previously reported reference values. Considering the PBET calculations as a correction for the underlying DFT, the embedding calculations are able to provided improvement for most cases. In some cases, the PBET methods are able to compensate for limitations in the wave function methods and produce results similar to more rigorous calculations from the literature. For the systems with spin‐crossover energies near zero, the current methodology fails to provide consistent improvement. In conclusion, the isolated recalculation of the electronic structure around the metal center when embedded into a DFT treatment of the ligand field shows promise as a pragmatic and lower cost treatment compared to the canonical treatment of the whole system of the difficult class of spin‐crossover complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The Beneficial Effect of Iron in Aluminum-Cerium-Based Cast Alloys

Iron (Fe) has been considered a major impurity since it is detrimental to the mechanical properties of many cast aluminum alloys due to the formation of Fe-containing brittle intermetallic phases. Fe is found naturally as an impurity in bauxite ore, resulting in Fe contamination of aluminum alloys with increasing contamination from current recycling practices. The Al–Ce–Fe system was investigated using CALPHAD (CALculation of PHAse Diagrams) modeling and experimental casting techniques. It was found that additions of Fe to the Al–Ce system are beneficial to the strength (slightly) and ductility (significantly) of the ternary alloys, which is attributed to the formation of fine metastable Al 8 CeFe 2 phase with aggregate morphology and equilibrium Al 10 CeFe 2 phase, suppressing coarse proeutectic Al 11 Ce 3 phase in near-eutectic Al–Ce alloys. Heat treatment study showed that the metastable Al 8 CeFe 2 phase transforms to predicted equilibrium Al 10 CeFe 2 phase at 500 °C, with essentially no intermetallic or grain coarsening; thus, the alloy displayed excellent property retention. The Al–Ce–Fe alloy system offers opportunities for sustainable, recyclable alloy development using low-cost Fe and low-cost cerium (a byproduct of rare-earth extraction).

42 ENGINEERING↗
DOE OSTI2020

Supplemental Microalgal Iron Helps Replete Blood Hemoglobin in Moderately Anemic Mice Fed a Rice-Based Diet

Iron deficiency anemia affects 1.2 billion people globally. Our objectives were to determine if (1) supplemental iron extracted from defatted microalgae (Nannochloropsis oceanica, DGM) and (2) a combination of minute amount of plant phytase and inulin could help replete hemoglobin in anemic mice. Mice (7 weeks old) were fed a control diet (6 mg Fe/kg). After 10 weeks, the mice were assigned to three treatments: control, control + DGM iron (Fe-DGM, 39 mg Fe/kg), or control + 1% inulin + 250 units of phytase/kg (INU–PHY, 6 mg Fe/kg). The mice had free access to diets and water for 6 weeks. The Fe-DGM group had elevated blood hemoglobin (p < 0.01) and a two-fold greater (p < 0.0001) liver non-heme iron over the control. Strikingly, the INU-PHY group had 34% greater non-heme iron than the control, despite the same concentrations of iron in their diets. Fe-DGM group had altered (p < 0.05) mRNA levels of hepcidin, divalent metal transporter 1, transferrin and transferrin receptor 1. Iron extracted from defatted microalgae seemed to be effective in alleviating moderate anemia, and INU-PHY enhanced utilization of intrinsic iron present in the rice diet. Our findings may lead to a novel formulation of these ingredients to develop safer and bioavailable iron supplements for iron-deficient populations.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Modular Iron–Bipyridine-Based Conjugated Aerogels as Catalysts for Oxygen Reduction Reaction

Aerogels have a large surface area and a porous structure, which make them an attractive catalyst support materials for fuel cells. Modifying the aerogels’ building blocks and introducing catalytic sites into their backbones allow them to function as both catalysts and supports, thereby increasing the density and distribution of catalyst active sites. In this work, we studied conjugated aerogels containing iron–bipyridine catalytic sites for the oxygen reduction reaction. To demonstrate the variation in physical and electrochemical properties of these aerogels, a series of aerogels were synthesized by a Glaser coupling reaction. Iron salt was added to the three-dimensional gel to produce iron–bipyridine complexes and obtain atomically dispersed catalytic sites. The electrocatalytic activity and electrical conductivity of the aerogels were increased after their heat treatment to yield Fe-doped carbon aerogels. The control of metal loadings was accomplished by changing the bipyridine content during the aerogel synthesis, resulting in 0.9–4.1 wt % Fe. In conclusion, the results show a correlation between Fe loading, aerogel structure, and catalytic activity, achieving high performance for the oxygen reduction reaction in both acidic and alkaline media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Selective Removal of Perfluorobutyric Acid Using an Electroactive Ion Exchanger Based on Polypyrrole@Iron Oxide on Carbon Cloth

Perfluorabutyric acid (PFBA) is one classify of perfluoroalkyl and polyfluoroalkyl substances (PFASs), which is applied to wide-spread industry compounds. The removal of PFBA has attracted considerable scientific interest in recent decades because it caused environmental pollutions and human diseases. For removing PFASs from wastewater, the adsorption method has been commonly used for the remediation of PFASs. However, it is usually limited by the inevitable “secondary waster” produced in this treatment process. In this work, PFBA can be removed effectively by synergizing the electrically switched ion exchange (ESIX) and a novel nanostructured ion exchanger. Herein, the nanostructured ion exchanger is designed by coating polypyrrole (PPy) @ Fe 2 O 3 nanoneedle on carbon cloth (PPy@Fe 2 O 3 NN-CC). Overall, results show that PPy@Fe 2 O 3 NN-CC film enhances ion exchange speed and efficiency, which endures its high-capacity adsorption ability and rapid regeneration property, thereby reducing secondary waste. Moreover, ESIX based on PPy@Fe 2 O 3 NN-CC has high selectivity for adsorption of PFBA over Cl - , SO 4 2- and NO 3 - .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Exploring the Origin of Anionic Redox Activity in Super Li-Rich Iron Oxide-Based High-Energy-Density Cathode Materials

Super alkali-rich materials (alkali:transition metal ratio of ≥2:1), such as Li 5 FeO 4 , exhibit the potential to realize anionic redox upon deep delithiation. Li 5 FeO 4 was shown to undergo reversible cycling between Li 4 FeO 3.5 and Li 3 FeO 3.5 with combined cation/anion redox, a remarkable capacity of 189 mAh/g, and no O 2 release. However, the impact of phase transformations on the reaction thermodynamics and the correlation between the structural changes and reaction reversibility remain unclear. In this study, we use first-principles calculations to examine the delithiation and (re)lithiation reactions of Li 5 FeO 4 . We show that the experimentally observed charge and discharge processes go through non-equilibrium pathways. Upon delithiation, the compound undergoes a phase transformation from Li 5 FeO 4 , with tetrahedrally coordinated (T d ) Fe ions, to a delithiated disordered rocksalt structure, with octahedral (O h ) Fe ions. Fe-ion migration has an asymmetric kinetic barrier that makes T d → O h migration facile, whereas the reverse process has a much larger barrier, explaining the difficulties in reaction reversibility. We further elucidate the transition metal and O redox sequences during the charge cycle and identify the complex electrochemistry associated with the dual participation of cationic redox (Fe 3+ /Fe 4+ ) and anionic redox (O 2– /O – /O o ). Armed with this knowledge, we conduct high-throughput screening of known alkali-rich transition metal oxides by evaluating their potential to enable reversible anionic redox, with multiple candidates proposed for further experimental trials. Furthermore, our work provides a useful guide for the further development of super alkali-rich anionic-redox-active electrodes for high-energy-density batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Mesoporous nickel-iron-manganese-alloy based metal/metal oxide composite thick film catalysts

Selective alloy corrosion is used to synthesize a robust and ultrafine mesoporous NiFeMn-based metal/metal oxide oxygen evolving catalyst with ligament and pore sizes in the range of 10 nm and a BET surface area of 43 m2/g. As an oxygen evolving catalyst, the mesoporous catalyst exhibits high stability (>264 hours) at a high current density (500 mA/cm2) with a low overpotential (360 mV) using a moderate electrolyte concentration (1 M KOH). The catalyst is made from non-precious metals and its fabrication is straight forward and directly applicable to large-scale synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Synthesis of zirconium-based metal–organic frameworks with iron( ii ) clathrochelate ligands

Zirconium-based metal organic frameworks (MOFs) are of great significance in supramolecular coordination chemistry, mainly as catalysts, due to their chemical stability and structural diversity. We report the synthesis of zirconium-clathrochelate based crystalline MOFs (Zr-GU-1to -4) made from hexanuclear zirconium inorganic nodes and iron(II) clathrochelate-based ditopic carboxylic acid ligands bearing various lateral moieties, namely, butyl, cyclohexyl, phenyl and methyl groups. Among the various iron(II) clathrochelate linkers, the one with butyl side chains, i.e., Zr-GU-1, forms stable crystalline MOFs as confirmed by single-crystal X-ray crystallography and exhibits a promising porosity with a BET surface area of ~650 m 2 g -1 after its activation with supercritical CO 2 (ScCO 2 ) from acetonitrile.

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

A Garnet-Type Solid-Electrolyte-Based Molten Lithium–Molybdenum–Iron(II) Chloride Battery with Advanced Reaction Mechanism

Solid-electrolyte-based molten-metal batteries have attracted considerable attention for grid-scale energy storage. Although ZEBRA batteries are considered one of the promising candidates, they still have the potential concern of metal particle growth and ion exchange with the β”-Al 2 O 3 electrolyte. Herein, a Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 solid-electrolyte-based molten lithium–molybdenum–iron(II) chloride battery (denoted as Li–Mo–FeCl 2 ) operated at temperature of 250 °C, comprising a mixture of Fe and LiCl cathode materials, a Li anode, a garnet-type Li-ion ceramic electrolyte, and Mo additive, is designed to overcome these obstacles. Different from conventional battery reaction mechanisms, this battery revolutionarily synchronizes the reversible Fe–Mo alloying–dealloying reactions with the delithiation–lithiation processes, meaning that the porous Mo framework derived from Fe–Mo alloy simultaneously suppresses the growth of pure Fe particles. By adopting a Li anode and a Li-ion ceramic electrolyte, the corrosion problem between the cathode and the solid electrolyte is overcome. With similar battery cost ($12 kWh –1 ), the theoretical energy density of Li–Mo–FeCl 2 battery surpasses that of a Na–FeCl 2 ZEBRA battery over 25%, to 576 Wh kg –1 and 2216 Wh L –1 , respectively. Experimental results further prove this cell has excellent cycling performance (472 mAh g LiCl –1 after 300 cycles, 50 mg active material) and strong tolerance against the overcharge–overdischarge (3–1.6 V) and freezing–thawing (25–250 °C) incidents.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Exploring the Limits of Dative Boratrane Bonding: Iron as a Strong Lewis Base in Low-Valent Non-Heme Iron-Nitrosyl Complexes

We previously reported the synthesis and preliminary characterization of a unique series of low-spin (ls) {FeNO} 8–10 complexes supported by an ambiphilic trisphosphineborane ligand, [Fe(TPB)(NO)] +/0/– . In this study, we use advanced spectroscopic techniques and density functional theory (DFT) calculations to extract detailed information as to how the bonding changes across the redox series. We find that, in spite of the highly reduced nature of these complexes, they feature an NO + ligand throughout with strong Fe–NO π-backbonding and essentially closed-shell electronic structures of their FeNO units. This is enabled by an Fe–B interaction that is present throughout the series. In particular, the most reduced [Fe(TPB)(NO)] – complex, an example of a ls-{FeNO} 10 species, features a true reverse dative Fe → B bond where the Fe center acts as a strong Lewis-base. Hence, this complex is in fact electronically similar to the ls-{FeNO} 8 system, with two additional electrons “stored” on site in an Fe–B single bond. The outlier in this series is the ls-{FeNO} 9 complex, due to spin polarization (quantified by pulse EPR spectroscopy), which weakens the Fe–NO bond. These data are further contextualized by comparison with a related N 2 complex, [Fe(TPB)(N 2 )] – , which is a key intermediate in Fe(TPB)-catalyzed N 2 fixation. Our present study finds that the Fe → B interaction is key for storing the electrons needed to achieve a highly reduced state in these systems, and highlights the pitfalls associated with using geometric parameters to try to evaluate reverse dative interactions, a finding with broader implications to the study of transition metal complexes with boratrane and related ligands.

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

Bridging the Gap in Carbon Free Iron Making: How Hydrogen Affects the Reduction of Iron Ore between 900 and 1590 °C

Hydrogen-based reduction of iron ore for iron and steel production has emerged as a promising alternative to coal and natural gas. Unlike other hydrogen-based iron ore reduction studies, this research focuses on a wide temperature range across 900–1590 °C, encompassing reduction in solid, mixed, and liquid (slag) phases. For a 20 min exposure to hydrogen, the reduction degree increased monotonically from ∼35% at 900 °C to >90% at 1550 °C, except between 1100 °C and 1400 °C, where it stagnated ∼60%. This experimental work challenges the widely accepted notion that higher temperatures enhance the reduction process. Instead, it reveals an overlooked kinetic bottleneck, suggesting complex thermodynamic and mass transfer limitations influenced by phase transformations, diffusion barriers, and microstructural changes. Density functional theory-based molecular dynamics simulations indicate that oxygen diffusivity in BCC iron is 3.88 × 10 –5 cm 2 /s which is ∼5–10 times higher than that in FCC iron. This study reports that this stagnant reduction degree in the mixed solid–liquid phase is due to competition of multiple mechanisms, such as surface- and bulk-diffusion, pore collapse mechanisms, and crystallographic transitions.

08 HYDROGEN↗
DOE OSTI2022

Iron-modified biochar-based bilayer permeable reactive barrier for Cr(VI) removal

In this study, iron (Fe)-modified biochar (FeBC) has been developed to remove hexavalent chromium (Cr(VI)) from groundwater and is suitable for use in permeable reactive barriers (PRBs). However, Cr(VI) removal behavior and chemical processes in FeBC-based PRBs are not fully understood, and the potential for Fe release has not been addressed. In this study, three FeBC-based PRBs were assessed in column experiments for 563 days with respect to their ability to remove Cr(VI). Bilayer column filled with FeBC+limestone and BC+limestone in two separate layers (FeBC_Ca_BC) showed the best performance in terms of Cr(VI) removal with a low treatment cost. The corrosion of FeBC was mainly related to pH and Cr(VI) concentration rather than flow rate. Leached Fe was attenuated by BC and limestone and reutilized in FeBC_Ca_BC. Cr(VI) was reduced to Cr(III) and then adsorbed or precipitated on the biochars. Cr and Fe formed inner-sphere complexes and then transformed from double corner sharing to edge sharing. During the reaction, Cr penetrated from the surface to the interior of the biochars and became a more stable species. This study provides evidence of the effectiveness of a new combination of biochars for Cr(VI) removal and insights into the reaction mechanisms.

42 ENGINEERING↗
DOE OSTI2020

Development of a mineralogy-based anthropogenic combustion-iron emission inventory

Atmospheric supply of iron can modulate ocean biogeochemistry, due to its key role in global nitrogen and carbon cycles. Using a detailed technology-based methodology we revise total and soluble anthropogenic iron emissions and resolve iron into its mineral components, which allows modeling mineral-specific atmospheric reactions. The inclusion of metal smelting as an iron source, increases fine iron aerosol emissions (smaller than 1 µm) compared with most previous inventories. Different assumptions about solubility lead to estimates of 40-450 Gg/year deposition of soluble anthropogenic iron. When combined with dust and wildfires, the global total anthropogenic soluble iron deposition is 1900-2300 Gg/yr, so assumptions in anthropogenic inventories can affect estimates of global soluble iron supply by about 30%. In regions where marine primary productivity is iron-limited, anthropogenic combustion-iron contributes up to half of the atmospheric soluble iron flux to North Pacific Ocean.

54 ENVIRONMENTAL SCIENCES↗