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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Skeletal Ni electrode-catalyzed C-O cleavage of diaryl ethers entails direct elimination via benzyne intermediates

Diaryl ethers undergo electrocatalytic hydrogenolysis (ECH) over skeletal Ni cathodes in a mild, aqueous process that achieves direct C-O cleavage without initial benzene ring saturation. Mechanistic studies find that aryl phenyl ethers with a single para or meta functional group (methyl, methoxy, or hydroxy) are selectively cleaved to the substituted benzene and phenol, in contrast to recently reported homogeneous catalytic cleavage processes. Ortho positioning of substituents reverses this C-O bond selectivity, except for the 2-phenoxyphenol case. Together with isotope labeling and co-solvent studies, these results point to two distinct cleavage mechanisms: (a) dual-ring coordination and C-H activation, leading to vicinal elimination to form phenol and a surface-bound aryne intermediate which is then hydrogenated and released as the arene; and (b) surface binding in keto form by the phenolic ring of the hydroxy-substituted substrates, followed by direct displacement of the departing phenol. Notably, acetone inhibits the well-known reduction of phenol to cyclohexanol, affording control of product ring saturation. A byproduct of this work is the discovery that the ECH treatment completely defluorinates substrates bearing aromatic C-F and C-CF 3 groupings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

A deep neural network regressor for phase constitution estimation in the high entropy alloy system Al-Co-Cr-Fe-Mn-Nb-Ni

High Entropy Alloys (HEAs) are composed of more than one principal element and constitute a major paradigm in metals research. The HEA space is vast and an exhaustive exploration is improbable. Therefore, a thorough estimation of the phases present in the HEA is of paramount importance for alloy design. Machine Learning presents a feasible and non-expensive method for predicting possible new HEAs on-the-fly. A deep neural network (DNN) model for the elemental system of: Mn, Ni, Fe, Al, Cr, Nb, and Co is developed using a dataset generated by high-throughput computational thermodynamic calculations using Thermo-Calc. The features list used for the neural network is developed based on literature and freely available databases. A feature significance analysis matches the reported HEAs phase constitution trends on elemental properties and further expands it by providing so far-overlooked features. The final regressor has a coefficient of determination ( r 2 ) greater than 0.96 for identifying the most recurrent phases and the functionality is tested by running optimization tasks that simulate those required in alloy design. The DNN developed constitutes an example of an emulator that can be used in fast, real-time materials discovery/design tasks.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reactive boride infusion stabilizes Ni-rich cathodes for lithium-ion batteries

Engineered polycrystalline electrodes are critical to the cycling stability and safety of lithium-ion batteries, yet it is challenging to construct high-quality coatings at both the primary- and secondary-particle levels. Here, we present a room-temperature synthesis route to achieve full surface coverage of secondary particles and facile infusion into grain boundaries, thus offering a complete “coating-plus-infusion” strategy. Cobalt boride metallic glass is successfully applied to Ni-rich layered cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 . Here, it dramatically improves the rate capability and cycling stability, including under high-discharge-rate and elevated-temperature conditions and in pouch full cells. The superior performance originates from simultaneous suppression of microstructural degradation of intergranular cracking and side reactions with electrolyte. Atomistic simulations identified the critical role of strong selective interfacial bonding, which offers not only a large chemical driving force to ensure uniform reactive wetting and facile infusion but also lowered the surface/interface oxygen activity, contributing to the exceptional mechanical and electrochemical stabilities of the infused electrode.

25 ENERGY STORAGE↗
DOE OSTI2022

Strain-retardant coherent perovskite phase stabilized Ni-rich cathode

The use of state-of-the-art Ni-rich layered oxides (LiNi x Co y Mn 1-x-y O 2 , x > 0.5) as the cathode material for lithium-ion batteries can push the energy and power density to a higher level than is currently available. However, volume variation associated with anisotropic lattice strain and stress that is being developed during lithium (de) intercalation induces severe structural instability and electrochemical decay of the cathode materials, which is amplified further when the battery is operating at a high voltage (above 4.5 V), which is essential for unlocking its high energy. Even after much effort by the research community, an intrinsic strain-retardant method for directly alleviating the continuous accumulation of lattice strain remains elusive. By introducing a coherent perovskite phase into the layered structure functioning as a ‘rivet’, we significantly mitigate the pernicious structural evolutions by a pinning effect. The lattice strain evolution in every single cycle is markedly reduced by nearly 70% when compared with conventional materials, which significantly enhances morphological integrity leading to a notable improvement in battery cyclability. This strain-retardant approach broadens the perspective for lattice engineering to release the strain raised from lithium (de)intercalation and paves the way for the development of high-energy-density cathodes with long durability.

25 ENERGY STORAGE↗
DOE OSTI2024

Superconductivity in pressurized trilayer La 4 Ni 3 O 10-$δ$ single crystals

In this study, the pursuit of discovering new high-temperature superconductors that diverge from the copper-based model has profound implications for explaining mechanisms behind superconductivity and may also enable new applications. Here our investigation shows that the application of pressure effectively suppresses the spin–charge order in trilayer nickelate La 4 Ni 3 O 10-δ single crystals, leading to the emergence of superconductivity with a maximum critical temperature (T c ) of around 30 K at 69.0 GPa. The d.c. susceptibility measurements confirm a substantial diamagnetic response below T c , indicating the presence of bulk superconductivity with a volume fraction exceeding 80%. In the normal state, we observe a strange metal behaviour, characterized by a linear temperature-dependent resistance extending up to 300 K. Furthermore, the layer-dependent superconductivity observed hints at a unique interlayer coupling mechanism specific to nickelates, setting them apart from cuprates in this regard. Our findings provide crucial insights into the fundamental mechanisms underpinning superconductivity, while also introducing a new material platform to explore the intricate interplay between the spin–charge order, flat band structures, interlayer coupling, strange metal behaviour and high-temperature superconductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2019

High-throughput investigation of crystal-to-glass transformation of Ti–Ni–Cu ternary alloy

A high-throughput investigation of metallic glass formation via solid-state reaction was reported in this paper. Combinatorial multilayered thin-film chips covering the entire Ti-Ni-Cu ternary system were prepared using ion beam sputtering technique. Microbeam synchrotron X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements were conducted, with 1,325 data points collected from each chip, to map out the composition and the phase constitution before and after annealing at 373 K for 110 hours. The composition dependence of the crystal-to-glass transition by solid-state reaction was surveyed using this approach. The resulting composition-phase map is consistent with previously reported results. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was performed on the representative compositions to determine the inter-diffusion between layers, the result shows that the diffusion of Ti is the key factor for the crystal-to-glass transition. In addition, both layer thickness and layer sequence play important roles as well. This work demonstrates that combinatorial chip technique is an efficient way for systematic and rapid study of crystal-to-glass transition for multi-component alloy systems.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Evolution of micro-pores in Ni–Cr alloys via molten salt dealloying

Porous materials with high specific surface area, high porosity, and high electrical conductivity are promising materials for functional applications, including catalysis, sensing, and energy storage. Molten salt dealloying was recently demonstrated in microwires as an alternative method to fabricate porous structures. The method takes advantage of the selective dissolution process introduced by impurities often observed in molten salt corrosion. This work further investigates molten salt dealloying in bulk Ni–20Cr alloy in both KCl–MgCl 2 and KCl–NaCl salts at 700 °C, using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction (XRD), as well as synchrotron X-ray nano-tomography. Micro-sized pores with irregular shapes and sizes ranging from sub-micron to several microns and ligaments formed during the process, while the molten salt dealloying was found to progress several microns into the bulk materials within 1–16 h, a relatively short reaction time, enhancing the practicality of using the method for synthesis. The ligament size increased from ~ 0.7 μm to ~ 1.3 μm in KCl–MgCl 2 from 1 to 16 h due to coarsening, while remaining ~ 0.4 μm in KCl–NaCl during 16 h of exposure. The XRD analysis shows that the corrosion occurred primarily near the surface of the bulk sample, and Cr 2 O 3 was identified as a corrosion product when the reaction was conducted in an air environment (controlled amount sealed in capillaries); thus surface oxides are likely to slow the morphological coarsening rate by hindering the surface diffusion in the dealloyed structure. 3D-connected pores and grain boundary corrosion were visualized by synchrotron X-ray nano-tomography. This study provides insights into the morphological and chemical evolution of molten salt dealloying in bulk materials, with a connection to molten salt corrosion concerns in the design of next-generation nuclear and solar energy power plants.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Gas-phase fragmentation of single heteroatom-incorporated Co 5 MS 8 (PEt 3 ) 6 + (M = Mn, Fe, Co, Ni) nanoclusters

Functionalization of metal-chalcogenide clusters by either replacing core atoms or by tuning the ligand is a powerful technique to tailor their properties. Central to this approach is understanding the competition between the strength of the metal-ligand and metal-metal interactions. Here, using collision-induced dissociation of atomically precise metal sulfide nanoclusters, Co 5 MS 8 L 6 + (L = PEt 3 , M = Mn, Fe, Co, Ni) and Co 5-x Fe x S 8 L 6 + (x = 1–3), we study the effect of a heteroatom incorporation on the core-ligand interactions and relative stability towards fragmentation. Sequential ligand loss is the dominant dissociation pathway that competes with ligand sulfide (LS) loss. Because the ligands are attached to metal atoms, LS loss is an unusual dissociation pathway, indicating significant rearrangement of the core prior to fragmentation. Both experiments and theoretical calculations indicate the reduced stability of Co 5 MnS 8 L 6 + and Co 5 FeS 8 L 6 + towards the first ligand loss in comparison with their Co 6 S 8 L 6 + and Co 5 NiS 8 L 6 + counterparts and provide insights into the core-ligand interaction.

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

Crack mitigation in additively manufactured AlCrFe 2 Ni 2 high-entropy alloys through engineering phase transformation pathway

The far-from-equilibrium solidification during additive manufacturing often creates large residual stresses that induce solid-state cracking. Here we present a strategy to suppress solid-state cracking in an additively manufactured AlCrFe 2 Ni 2 high-entropy alloy via engineering phase transformation pathway. We investigate the solidification microstructures formed during laser powder-bed fusion and directed energy deposition, encompassing a broad range of cooling rates. At high cooling rates (10 4 –10 6 K/s), we observe a single-phase BCC/B2 microstructure that is susceptible to solid-state cracking. At low cooling rates (10 2 –10 4 K/s), FCC phase precipitates out from the BCC/B2 matrix, resulting in enhanced ductility (~10 %) and resistance to solid-state cracking. Site-specific residual stress/strain analysis reveals that the ductile FCC phase can largely accommodate residual stresses, a feature which helps relieve residual strains within the BCC/B2 phase to prevent cracking. Our work underscores the value of exploiting the toolbox of phase transformation pathway engineering for material design during additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Stress-dependent χ phase transformation in a Ni-based superalloy

The ongoing push to elevate operating temperatures in aerospace gas turbine engines – driven by goals of enhanced fuel efficiency and reduced CO 2 emissions – mandates advancements in the creep resistance of Ni- and Co-based superalloys, which are integral for critical engine components. This study elucidates the role of stress assisted localized phase transformations in the creep properties of these alloys. By leveraging chemo-mechanical coupling, self-healing γ′ precipitates are designed to immobilize planar defects, thereby increasing creep resistance. Employing advanced characterization techniques such as high-resolution Scanning Transmission Electron Microscopy (HR-STEM), in conjunction with atomistic simulations and thermodynamic calculations, novel deformation pathways facilitated by χ local phase transformation (LPT) strengthening have been uncovered; notably, the formation of χ nano-laths through microtwinning and superlattice intrinsic stacking fault (SISF) shearing. This study highlights critical insights into the compositional boundaries necessary for optimizing LPT strengthening while avoiding deleterious bulk formation of η/χ phases. These advancements will guide the design of new alloys maximizing high-temperature creep strength for advanced aerospace applications.

Egan, Ashton J. [Friedrich-Alexander University Er↗
DOE OSTI2020

Impact of surface coating on electrochemical and thermal behaviors of a Li-rich Li 1.2 Ni 0.16 Mn 0.56 Co 0.08 O 2 cathode

Lithium-rich layered oxide materials are considered as potential cathode materials for future high-performance lithium-ion batteries (LIBs) owing to their high operating voltage and relatively high specific capacity. However, perceptible issues such as poor rate performance, poor capacity retention, and voltage degradation during cycling need to be improved before the successful commercialization of the material. In this report, zirconia coated Li 1.2 Ni 0.16 Mn 0.56 Co 0.08 O 2 2 = 1.0, 1.5 and 2.0 wt%) materials are synthesized using a sol–gel assisted ball milling approach. A comparison of structural, morphological and electrochemical properties is examined to elucidate the promising role of ZrO 2 coating on the performance of the NMC cathode. A uniform and homogeneous ZrO 2 coating is observed on the surface of NMC particles as evident by TEM elemental mapping images. The ZrO 2 coated NMCs exhibit significantly improved electrochemical performance at a higher C-rate as compared to pristine material. 1.5% ZrO 2 coated NMC demonstrates better cycling stability (95% capacity retention) than pristine NMC (77% capacity retention) after 50 cycles. All ZrO 2 coated NMC materials demonstrated improved thermal stability compared to pristine material. The difference in onset temperature of 2 wt% ZrO 2 coated and pristine NMC is 20 °C. The improved electrochemical performance of ZrO 2 coated NMC can be attributed to the stabilization of its surface structure due to the presence of ZrO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

The NO reduction by CO over NiO x /CeO 2 catalysts with a fixed Ni surface density: pretreatment effects on the catalyst structure and catalytic activity

NiO x /CeO 2 catalysts have shown promising results in various catalytic reactions, including the NO reduction by CO. Here, in this study, we investigated the effect of oxidation and reduction treatments on the NO reduction by CO over pretreated NiO x /CeO 2 catalysts. A series of oxidized and reduced supported NiO x catalysts were synthesized in two steps: (1) the pretreatment of CeO 2 supports at different temperatures (400, 500, and 700 °C) under oxidizing and reducing conditions and (2) the synthesis of NiO x /CeO 2 catalysts by an incipient wetness impregnation method (IWI) with a fixed surface density of 5.3 Ni per nm 2 under specific conditions (oxidation/reduction) applied during the CeO 2 treatment. The prepared catalysts were characterized via BET, ICP/OES, Raman, XPS, and XRD to understand their physicochemical properties. The results showed that as the pretreatment temperature increased, the physicochemical properties of NiO x /CeO 2 catalysts were changed: a decreased specific surface area (SSA), decreased oxygen vacancy/defect sites, and an increased crystallite size. The oxidized NiO x /CeO 2 catalyst at a lower pretreatment temperature displayed a better catalytic activity, indicating that the physicochemical properties of the catalysts were key factors in enhancing the catalytic activity. To understand the intermediate species and reaction mechanism during the NO reduction by CO, an in situ DRIFTS study was performed and a possible reaction mechanism was also discussed.

36 MATERIALS SCIENCE↗