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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Long-term thermal aging behavior and strength reduction in a laser powder bed fusion 316H stainless steel

The long-term thermal stability of structural alloys is essential for ensuring the safe and reliable operation of nuclear reactors and other power plants. While extensive research has explored the effects of thermal aging on conventional stainless steels, the behavior of additively manufactured (AM) alloys remains less understood. This study examines the thermal aging response of laser powder bed fusion (LPBF) 316H stainless steel (SS) at temperatures ranging from 550 °C to 750 °C over durations of up to 10,000 h (approximately 1.14 years). Advanced characterization techniques, including electron microscopy and synchrotron X-ray diffraction, were used to investigate dislocation recovery and phase evolution. Based on these findings, a time-temperature-precipitation (TTP) diagram was developed for LPBF 316H SS, revealing a 10- to100-fold acceleration in precipitation kinetics compared to wrought 316H SS. A physics-informed model was calibrated using the short-term experimental data, enabling predictions of average precipitate sizes, volume fractions of M 23 C 6 and Laves phases, and changes in molybdenum solute concentration for aging up to 1 × 10⁶ h (114 years). These microstructural insights were further utilized to estimate yield strength and extrapolate strength reduction factors over the extended aging period. Despite the accelerated aging kinetics, LPBF 316H SS demonstrated superior yield strength retention compared to its wrought counterpart. In conclusion, this study establishes a framework for evaluating long-term performance using short-term experimental data and supports the accelerated qualification of AM materials for high-temperature structural applications.

Laser powder bed fusion↗
DOE OSTI2025

Pyrochlore NaYbO2: A Potential Quantum Spin Liquid Candidate

The search for quantum spin liquids (QSL) and chemical doping in such materials to explore superconductivity have continuously attracted intense interest. Here, we report the discovery of a potential QSL candidate, pyrochlore-lattice β-NaYbO2. Colorless and transparent NaYbO2 single crystals, layered α-NaYbO2 (∼250 μm on edge) and octahedral β-NaYbO2 (∼50 μm on edge), were grown for the first time. Synchrotron X-ray single-crystal diffraction unambiguously determined that the newfound β-NaYbO2 belongs to the three-dimensional pyrochlore structure characterized by the R3̅m space group, corroborated by synchrotron X-ray and neutron powder diffraction and pair distribution function. Magnetic measurements revealed no long-range magnetic order or spin glass behavior down to 0.4 K with a low boundary spin frustration factor of 17.5, suggesting a potential QSL ground state. Under high magnetic fields, the potential QSL state was broken and spins order. Our findings reveal that NaYbO2 is a fertile playground for studying novel quantum states.

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

Materials synthesis at terapascal static pressures

Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell, producing a rhenium–nitrogen alloy and achieving the synthesis of rhenium nitride Re 7 N 3 —which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Long-range and local crystal structures of the S r 1 - x C a x Ru O 3 perovskites

Here, the crystal structures of the Sr 1–x Ca x RuO 3 (0 ≤ x ≤ 1) perovskites are investigated using both long-range and local structural probes. High-resolution synchrotron powder x-ray-diffraction characterization at ambient temperature shows that the materials have orthorhombic long-range crystal structures to high precision, and we support previous work showing that Ca 2+ substitution for Sr 2+ primarily changes the tilting of rigid corner-sharing RuO 6 octahedra at their shared oxygen vertices. X-ray pair-distribution function analysis for SrRuO 3 , CaRuO 3 , and one intermediate composition show them to display monoclinic symmetry at the local level; when averaged over different domain orientations this yields orthorhombic symmetry in the long range, and no long-range or local phase transitions are observed between 80 and 300 K for materials with intermediate compositions. High-resolution transmission electron microscopy shows that the Sr/Ca distribution is random at the nanoscale. Lastly, we plot magnetic characteristics such as the ferromagnetic T c , Curie-Weiss theta, effective moment, and ambient temperature susceptibility vs the octahedral tilt and unit-cell volume.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

In Situ Characterization of Ferroelectric HfO 2 During Rapid Thermal Annealing

Thermal annealing is critical in governing the phase distribution, and ultimately the electrical properties, of ferroelectric hafnium oxide films. In particular, rapid thermal annealing (RTA) has been shown to favor the formation of ferroelectric crystal phases, but the dynamic behavior of the film over the course of the anneal is not well understood. Herein, synchrotron X-ray diffraction is used to characterize the phase distribution of HfO 2 films deposited by atomic layer deposition (ALD) in situ during RTA, revealing complex phase transformations occurring on the scale of seconds. All samples investigated here transform into a nonmonoclinic phase, which is required for ferroelectric films. However, this phase often converts into the more stable monoclinic phase as annealing proceeds. The kinetic barrier to the transformation to the monoclinic phase during heating is higher than 1 eV f.u. -1 In this work, the initial crystallization into the ferroelectric phase and relatively high barrier to transformation to the nonferroelectric phase suggests that careful control of the thermal annealing profile can greatly increase the ferroelectric fraction of the film. By using a fast ramp rate and a short annealing time above the ferroelectric crystallization temperature, the remanent polarization of a pure HfO 2 film can be increased more than twofold.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Boosting the Oxygen Reduction Performance via Tuning the Synergy between Metal Core and Oxide Shell of Metal−Organic Frameworks‐Derived Co@CoO x

Abstract Co core@Co oxide shell (Co@CoO x ) catalysts represent a large family with promising oxygen reduction reaction (ORR) catalytic activity. However, inadequate understanding of Co@CoO x synergy prohibits further pursuit of catalytic performance enhancement. Herein, a Co zeolitic−imidazolate framework was converted into metallic Co, followed by controlled air treatment to form Co@CoO x . The composition and structure evolution as a function of air treatment temperature were studied thoroughly through conventional and synchrotron (both ex‐situ and in‐situ) characterizations, confirming the coexistence of CoO and Co 3 O 4 in the shell. The optimal catalyst showed an ORR half‐wave potential of 0.87 V (vs. RHE) in an alkaline half‐cell and delivered high discharge capacity in an aprotic Li−O 2 battery (7,124 mAh g Cat+C −1 ) and an aqueous Zn−air battery (694 mAh g Zn −1 ) with good performance retention after durability test. Modeling simulation and density functional theory calculation confirmed the charge donation from metal core to oxide shell and shed light on new insights of how metal@metal oxide synergy impacted the ORR via tuning the charge conductivity, oxygen affinity and intermediate transfer pathway. This work opens up a venue to boost ORR catalytic activity from an interfacial synergy perspective.

Wang, Hao↗
DOE OSTI2021

Persistent Structure and Frustrated Magnetism in High Entropy Rare-Earth Zirconates

The configurational complexity and distinct local atomic environments of high entropy oxides remain largely unexplored, leaving structure-property relationships and the hypothesis that the family offers rich tunability for applications ambiguous. This work investigates the influence of cation size and materials synthesis in determining the resulting structure and magnetic properties of a family of high entropy rare-earth zirconates (HEREZs, nominal composition RE 2 Zr 2 O 7 with RE = rare-earth element combinations including Eu, Gd, Tb, Dy, Ho, La, or Sc). Here, the structural characterization of the series is examined through synchrotron X-ray diffraction and pair distribution function analysis, and electron microscopy, demonstrating average defect-fluorite structures with considerable local disorder, in all samples. The surface morphology and particle sizes are found to vary significantly with preparation method, with irregular micron-sized particles formed by high temperature sintering routes, spherical nanoparticles resulting from chemical co-precipitation methods, and porous nanoparticle agglomerates resulting from polymer steric entrapment synthesis. In agreement with the disordered cation distribution found across all samples, magnetic measurements indicate that all synthesized HEREZs show frustrated magnetic behavior, as seen in a number of single-component RE 2 Zr 2 O 7 pyrochlore oxides. These findings advance the understanding of the local structure of high entropy oxides and demonstrate strategies for designing nanostructured morphologies in the class.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Transverse impact by RCCs on S-glass and Kevlar® FRC strips

This study aims to isolate interactions between plies and tows and reveal fundamental physics involved in transverse impact on fiber-reinforced composite (FRC) structures. Composite strips were sectioned from large panels and characterized by optical photography, three-dimensional synchrotron X-ray computed tomography, and scanning electron microscopy (SEM). Each strip was impacted perpendicularly by a right circular cylinder (RCC) projectile at a velocity ranging from ~ 150 to 600 m/s. The global strip behavior, as well as localized deformation and failure of the strip near the projectile corner, were both captured by high-speed optical imaging. S-Glass FRC strips were observed to fail in tension ahead of the RCC projectiles’ flat surfaces while Kevlar® FRC strips fractured at the projectile corners. The concept of critical velocity region previously used for impact on yarns was introduced to define different failure modes of each composite strip type. The strip damage extent was found to increase with the impact velocity and reach the maximum at the upper limit of the critical velocity region. Above the critical velocity region, the damage extent decreased with impact velocity. Wave propagations and load histories in the composite strips during impact were quantified and compared with Smith’s theory. Finally, critical velocities of single fibers, yarns, and composite strips and ballistic limits of single-ply and multi-ply composite panels were compared to provide insight into the design of impact-resistant fabrics and composites.

42 ENGINEERING↗
DOE OSTI2025

Accurate and efficient predictions of keyhole dynamics in laser materials processing using machine learning-aided simulations

The keyhole phenomenon has been widely observed in laser materials processing, including laser welding, remelting, cladding, drilling, and additive manufacturing. Keyhole-induced defects, primarily pores, dramatically affect the performance of final products, impeding the broad use of these laser-based technologies. The formation of these pores is typically associated with the dynamic behavior of the keyhole. So far, the accurate characterization and prediction of keyhole features, particularly keyhole depth, as a function of time, has been a challenging task. In situ characterization of keyhole dynamic behavior using the synchrotron X-ray technique is informative but complicated and expensive. Current simulations are generally hindered by their poor accuracy and generalization abilities in predicting keyhole depths due to the lack of accurate laser absorptance data. In this study, we develop a machine learning-aided simulation method that accurately predicts keyhole dynamics, especially in keyhole depth fluctuations, over a wide range of processing parameters. In two case studies involving titanium and aluminum alloys, we achieve keyhole depth prediction with a mean absolute percentage error of 10 %, surpassing those simulated using the ray-tracing method with an error margin of 30 %, while also reducing computational time. This exceptional fidelity and efficiency empower our model to serve as a cost-effective alternative to synchrotron experiments. Our machine learning-aided simulation method is affordable and readily deployable for a large variety of materials, opening new doors to eliminate or reduce defects for a wide range of laser materials processing techniques.

Computational fluid dynamics↗
DOE OSTI2021

Investigation of breakaway corrosion observed during oxide growth in pure and low alloying element content Zr exposed in water at 360°C

The addition of small concentrations of alloying elements to pure zirconium can prevent nuclear fuel cladding material from undergoing unstable oxide growth in aqueous environments at light water reactor operating temperatures. The role of alloying elements in stabilizing the oxide growth is examined in this paper, to better understand the oxide growth stabilization mechanism. To this end, a set of initial, short-duration corrosion experiments were performed, followed by oxide layer characterization. Specifically, ten model Zr alloys were selected to test the effect of small alloying additions on the alloy corrosion rate and corrosion breakaway. Additionally, these alloys were corrosion tested in pure water in an autoclave at 360°C for up to 70 days. The alloys included crystal bar Zr, sponge Zr, and model alloys with small concentrations of Sn, Fe, and Cr. After testing, the alloys were characterized using scanning electron microscopy (SEM) and synchrotron µ-X-ray fluorescence (µXRF) to study how the structure of the oxide and alloying element distribution related to unstable oxide growth. Initial results in the 360°C water environment showed breakaway oxidation may be caused by unstable oxide growth due to heterogeneous distribution of the alloying elements. Heterogeneous distribution of alloying elements was correlated to the occurrence of unstable oxide growth (either nodule-like, grain boundary penetration, or differential grain-to-grain growth). It is possible that this heterogeneity, made possible by low alloying element content, can cause breakaway corrosion, but further study is warranted.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Global and local texture development during initial plastic deformation of cold-pilgered Zircaloy-4 tubing

In this work we present a thorough characterization of the texture development during the initial step of a cold pilgering process of a Zircaloy-4 TREX tube, on which the axial cross section is reduced by 80% over a 40cm length with an overall Q-ratio of 2.34, followed by a recrystallization thermal treatment. Texture across a tapered specimen representing this working zone was characterized by neutron diffraction and high energy synchrotron x-ray diffraction at 28 positions (4 locations along its length and 7 locations across its thickness with 0.3 mm spatial resolution), and on the deformed end after the thermal treatment. Results show that the starting material (TREX tube) presents a texture gradient through its wall thickness, with the c poles aligned to the hoop direction at the outer surface (with radial and hoop Kearns factors: f R =0.36, f H = 0.50), and gradually rotating around the axial direction to become a quasi-radial orientation (~35 o out of the radial direction) at the inner surface ( f R =0.43, f H =0.35). The overall texture becomes more radial due to the cold pilgering, but the texture gradient remains during the whole deformation process, being always more radial at the inner surface, ( f R =0.53, f H =0.37 at 80%) than at the outer surface ( f R =0.41, f H =0.50at 80%). The most remarkable changes in texture produced by the rolling process is a 30 o rotation of the grains around their c-axis, producing a marked increase of the <11 2 ¯ 0> // axial fiber texture at expenses of the original <10 1 ¯ 0> // axial fiber texture observed in the TREX tube. The observed changes in texture during deformation were correctly explained by visco-plastic self-consistent (VPSC) modelling. This was achieved after the inclusion of the basal <a> slip system, which plays a central role to explain the 30 o rotation around the c-axis during deformation. The texture evolution was correctly described after the inclusion of a drag effect to grain rotation due to the interaction with neighbouring grains. The through thickness texture differences are greatly reduced by the recrystallization thermal treatment, with similar Kearns factors at the inner surface ( f R =0.50, f H =0.28) and the outer surface ( f R =0.48, f H =0.39). The predominance of the <10 1 ¯ 0> // axial fiber texture is recovered after recrystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Elucidating the Origins of High Capacity in Iron-Based Conversion Materials: Benefit of Complementary Advanced Characterization toward Mechanistic Understanding

Lithium-ion batteries are recognized as an important electrochemical energy storage technology due to their superior volumetric and gravimetric energy densities. Graphite is widely used as the negative electrode, and its adoption enabled much of the modern portable electronics technology landscape. However, developing markets, such as electric vehicles and grid-scale storage, have increased demands, including higher energy content and a diverse materials supply chain. Alternatives that provide the opportunity to increase capacity and address supply chain concerns are of interest. Understanding the fundamental mechanisms that govern battery function is crucial to driving further improvements in the field. Advanced characterization techniques, such as those enabled by synchrotron light sources and high-resolution electron microscopes, that can uncover these mechanisms have become a necessity for elucidating structural evolution upon electrochemical conversion at the nano- to mesoscales. Performing these experiments with relevant electrochemistry using in situ and operando experiments imparts the ability to identify critical reaction pathways and capture intermediate (dis)charge products not discernible by traditional experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Conformal PEDOT Coating Enables Ultra-High-Voltage and High-Temperature Operation for Single-Crystal Ni-Rich Cathodes

Single-crystal Ni-rich Li[Ni x Mn y Co 1-x-y ]O 2 (SC-NMC) cathodes represent a promising approach to mitigate the cracking issue of conventional polycrystalline cathodes. However, many reported SC-NMC cathodes still suffer from unsatisfactory cycling stability, particularly under high charge cutoff voltage and/or elevated temperature. Herein, we report an ultraconformal and durable poly(3,4-ethylenedioxythiophene) (PEDOT) coating for SC-NMC cathodes using an oxidative chemical vapor deposition (oCVD) technique, which significantly improves their high-voltage (4.6 V) and high-temperature operation resiliency. The PEDOT coated SC LiNi 0.83 Mn 0.1 Co 0.07 O 2 (SC-NMC83) delivers an impressive capacity retention rate of 96.7% and 89.5% after 100 and 200 cycles, respectively. Significantly, even after calendar aging at 45 degrees C and 4.6 V, the coated cathode can still retain 85.3% (in comparison with 59.6% for the bare one) of the initial capacity after 100 cycles at a 0.5 C rate. Synchrotron X-ray experiments and interface characterization collectively reveal that the conformal PEDOT coating not only effectively stabilizes the crystallographic structure and maintains the integrity of the particles but also significantly suppresses the electrolyte's corrosion, resulting in improved electrochemical/thermal stability. Our findings highlight the promise of an oCVD PEDOT coating for single-crystal Ni-rich cathodes to meet the grand challenge of high-energy batteries under extreme conditions.

25 ENERGY STORAGE↗
DOE OSTI2025

Harnessing metastability for grain size control in multiprincipal element alloys during additive manufacturing

Abstract Controlling microstructure in fusion-based metal additive manufacturing (AM) remains a significant challenge due to the many parameters that directly impact solidification condition. Multiprincipal element alloys (MPEAs), also known as high entropy alloys, offer a vast compositional space to design for microstructural engineering due to their chemical complexity and exceptional properties. Here, we use the FeMnCoCr system as a model platform for exploring alloy design in MPEAs for AM. By exploiting the decreasing stability of the face-centered cubic phase with increasing Mn content, we achieve notable grain refinement and breakdown of epitaxial columnar grain growth. We employ a multifaceted approach encompassing thermodynamic modeling, operando synchrotron X-ray diffraction, multiscale microstructural characterization, and mechanical testing to gain insight into the solidification physics and its ramifications on the resulting microstructure of FeMnCoCr MPEAs. This work aims toward tailoring desirable grain sizes and morphology through targeted manipulation of phase stability, thereby advancing microstructure control in AM applications.

Wakai, Akane↗
DOE OSTI2024

Tuning collective anion motion enables superionic conductivity in solid-state halide electrolytes

Halides of the family Li 3 MX 6 (M = Y, In, Sc and so on, X = halogen) are emerging solid electrolyte materials for all-solid-state Li-ion batteries. They show greater chemical stability and wider electrochemical stability windows than existing sulfide solid electrolytes, but have lower room-temperature ionic conductivities. Here, in this work, we report the discovery that the superionic transition in Li 3 YCl 6 is triggered by the collective motion of anions, as evidenced by synchrotron X-ray and neutron scattering characterizations and ab initio molecular dynamics simulations. Based on this finding, we used a rational design strategy to lower the transition temperature and thus improve the room-temperature ionic conductivity of this family of compounds. We accordingly synthesized Li 3 YCl x Br 6-x and Li 3 GdCl 3 Br 3 and achieved very high room-temperature conductivities of 6.1 and 11 mS cm -1 for Li 3 YCl 4.5 Br 1.5 and Li 3 GdCl 3 Br 3 , respectively. These findings open new routes to the design of room-temperature superionic conductors for high-performance solid batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Microstrain screening towards defect-less layered transition metal oxide cathodes

Microstrain and the associated surface-to-bulk propagation of structural defects are known to be major roadblocks to developing high-energy and long-life batteries. However, the origin and effects of microstrain during the synthesis of battery materials remain largely unknown. Here, in this study, we perform microstrain screening during real-time and realistic synthesis of sodium layered oxide cathodes. Evidence gathered from multiscale in situ synchrotron X-ray diffraction and microscopy characterization collectively reveals that the spatial distribution of transition metals within individual precursor particles strongly governs the nanoscale phase transformation, local charge heterogeneity and accumulation of microstrain during synthesis. This unexpected dominance of transition metals results in a counterintuitive outward propagation of defect nucleation and growth. These insights direct a more rational synthesis route to reduce the microstrain and crystallographic defects within the bulk lattice, leading to significantly improved structural stability. The present work on microstrain screening represents a critical step towards synthesis-by-design of defect-less battery materials.

25 ENERGY STORAGE↗