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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Solid-state transformations during laser directed energy deposition of Ti-6Al-4V powder hydride-dehydrided from scrap metals

During laser directed energy deposition (DED-LB), thermal cycling and powder chemical composition produce distinct thermal histories, which vary mechanical properties. Using real-time X-ray diffraction, this study investigates solid-state transformations during DED-LB to understand process-structure-property relationships for angular Ti-6Al-4V powder hydride–dehydrided from scrap metals. Results showed that regions near the molten pool experienced high cooling rates, leading to martensitic transformation from the β phase and increased hardness. Regions farther from the molten pool underwent tempering without solid-state transformation and decreased hardness. These findings support alternative feedstocks for metal additive manufacturing for a circular economy and resilient supply chains.

Additive manufacturing (AM)↗
DOE OSTI2015

Understanding Low-cycle Fatigue Life Improvement Mechanisms in a Pre-twinned Magnesium Alloy

The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning process, the removal of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress-strain hysteresis loop. The pre-twinning has significant impacts on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-deformed sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in in situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Nondestructive ultrasonic characterization of a triple-weld-bead wire arc additively manufactured ER70S-6 S-curved wall

Understanding build-scale microstructural variation in wire arc additive manufacturing (WAAM) of low-carbon steels is essential for ensuring consistent structure–property relationships throughout large components. Conventional destructive characterization techniques, such as scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), are time-intensive and limited to localized regions, making comprehensive evaluation of large WAAM structures challenging. In this study, a nondestructive ultrasonic approach was employed to characterize a 252 mm tall ER70S-6 S-curved WAAM wall produced using a triple-bead deposition strategy. Optical and SEM analysis revealed a repeating dual-region microstructure consisting of uniform polygonal ferrite at melt pool centers and heterogeneous ferrite with coarse and fine grains near melt pool boundaries, attributed to cyclic thermal conditions. Longitudinal ultrasonic backscatter imaging was used to evaluate the continuity of this periodicity along the full build height. The ultrasonic response exhibited a consistent repeating pattern that correlated with the observed layer-wise microstructural variation. X-ray computed tomography confirmed the absence of detectable porosity, indicating that ultrasonic contrast is primarily governed by grain morphology. Overall, the results indicate that longitudinal backscatter ultrasound is a promising nondestructive characterization technique for validating microstructural variations along the s-curved WAAM wall, with significant potential for microstructure optimization and process control.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis, magnetic and dielectric characterization of nanocrystalline solid solutions of In{sub 2−x}Ni{sub x}O{sub 3} (x = 0.05, 0.10 and 0.15)

Graphical abstract: Monophasic and crystalline In{sub 2−x}Ni{sub x}O{sub 3} nanoparticles of size 8–15 nm have been synthesized solvothermally and showed red shift in energy band gap which decreases on increasing Ni{sup 2+} concentration in In{sub 2}O{sub 3} host lattice. - Highlights: • Monophasic Ni-doped In{sub 2}O{sub 3} nanoparticles by solvothermal method for first time. • Plausible reaction mechanism using thermogravimetric analysis. • High surface area with small particle size obtained. • Solid solutions exhibit paramagnetism with very weak antiferromagnetic interactions. - Abstract: In{sub 2−x}Ni{sub x}O{sub 3} (x = 0.05, 0.10 and 0.15) nanoparticles were successfully synthesized by solvothermal method by the thermal decomposition of oxalate precursor at 450 °C for the first time. X-ray diffraction studies showed the formation of highly crystalline and monophasic cubic structure of In{sub 2}O{sub 3} which is attributed to the formation of solid solution. These nanoparticles show good optical transmittance in the visible region. Optical measurements showed an energy band gap which decreases with increasing Ni concentration. The grain size decreases from 15 nm to 8 nm and surface area increases from 90 to 254 m{sup 2} g{sup −1} on increasing the Ni concentration. High dielectric constant and dielectric loss has been obtained which indicates the conducting nature of these solid solutions. Magnetic measurements showed that the samples are strong paramagnetic in nature with very weak antiferromagnetic interactions. No evidence of ferromagnetism is observed for these solid solutions at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Facile combustion synthesis of ZnO nanoparticles using Cajanus cajan (L.) and its multidisciplinary applications

Graphical abstract: Facile combustion synthesis of ZnO nanoparticles using Cajanuscajan (L.) and its multidisciplinary applications.Zinc oxide nanoparticles were successfully synthesized by solution combustion method (SCM) using pigeon pea as a combustible fuel for the first time. The as-prepared product shows good photocatalytic, dielectric, antibacterial, electrochemical properties. - Highlights: • ZnO Nps were synthesized via combustion method using pigeon pea as a fuel. • The structure of the product was confirmed by XRD technique. • The morphology was confirmed by SEM and TEM images. • The as-prepared product shown good photocatalytic activity, dielectric property. • It has also shown good antibacterial and electrochemical properties. - Abstract: Zinc oxide nanoparticles (ZnO Nps) were successfully synthesized by solution combustion method (SCM) using pigeon pea as a fuel for the first time. X-Ray diffraction pattern reveals that the product belongs to hexagonal system. FTIR spectrum of ZnO Nps shows the band at 420 cm{sup −1} associated with the characteristic vibration of Zn–O. TEM images show that the nanoparticles are found to be ∼40–80 nm. Furthermore, the as-prepared ZnO Nps exhibits good photocatalytic activity for the photodegradation of methylene blue (MB), indicating that they are indeed a promising photocatalytic semiconductor. The antibacterial properties of ZnO nanopowders were investigated by their bactericidal activity against four bacterial strains.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Controlling Polymer Morphology in Blade-Coated All-Polymer Solar Cells

In this report translating all-polymer solar cells from spin-coating to scalable roll-to-roll-compatible fabrication techniques is a critical step toward the application of organic photovoltaics at a scale. Techniques to control polymer crystallization and phase separation during solution printing are essential to obtain high-performance printed organic solar cells. Here, we demonstrate a novel solvent additive approach employing trace amounts of phthalates as additives to control polymer crystallinity and suppress unfavorable phase separation in a representative PTB7-Th/P(NDI2OD-2T) all-polymer solar cell. The best-performing additive increased the blade-coated device performance from 2.09 to 4.50% power conversion efficiency, an over twofold improvement, mitigating the loss in performance that is typically observed during process transfer from spin-coating to blade-coating. It is suggested that the improved device performance stems from a finer polymer phase-separation size and overall improved active layer morphology, evidenced by device characterization data and indirectly supported by grazing incidence wide-angle X-ray scattering analyses. Real-time X-ray diffraction measurements during blade-coating provide mechanistic insights and suggest that the dioctyl phthalate additive may act as a compatibilizer, reducing the demixing of the donor and acceptor polymer during film formation, enabling a smaller phase separation and improved performance. The structural diversity of the class of phthalate additives makes this simple yet effective concept promising for translating other all-polymer material systems to blade-coating and other scalable printing techniques.

14 SOLAR ENERGY↗
DOE OSTI2023

Li 2 GeS 3 : Lithium Ionic Conductor with an Unprecedented Structural Type

Lithium-ion batteries (LIBs) are widely used in electric vehicles, mobile electronic devices, and large-scale stationary energy storage systems. However, their liquid electrolytes present significant safety concerns due to their inherent flammability. To address this, the focus has shifted toward all-solid-state batteries (ASSBs) utilizing inorganic solid electrolytes that promise enhanced safety. In this work, we report the discovery of a new crystal structural type of Li-ion conductor, Li 2 GeS 3 , with a unique structure, synthesized by a solid-state reaction from Li 2 S and GeS 2 . It was first reported in 2000 with an orthorhombic unit cell, but its detailed crystal structure remains veiled. Here, we have unveiled its structure for the first time, employing an ab initio structure determination technique from powder X-ray and time-of-flight neutron diffraction data. The compound has an unprecedented crystal structural type with a hexagonal $P6_1$ symmetry and a unit cell of α = 6.79364(4) Å and c = 17.90724(14) Å. Its structure is comprised of a distorted hexagonal close-packed arrangement of sulfur anions with three asymmetric metal atoms: Li1, Li2, and Ge are in tetrahedral cavities surrounded by sulfur atoms. The ionic conductivity of Li 2 GeS 3 was measured to be 1.63 × 10 –8 S cm –1 at 303 K and 2.45 × 10 –7 S cm –1 at 383 K. Bond valence energy landscape calculations revealed three-dimensional lithium diffusion pathways within the structure. This novel crystal structure in Li 2 GeS 3 holds the potential for developing high-performance ionic conductors through suitable chemical substitution and offers valuable insights into designing new ionic conductors for ASSBs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Anomalous Nanoscale Optoacoustic Phonon Mixing in Nematic Mesogens

Recent inelastic X-ray scattering (IXS) experiments on mesogens have shown entirely new capabilities with regards to their nanoscale phonon-assisted heat management. Mesogens such as nematic liquid crystals (LCs) are appealing systems for study because their structure and morphology can easily be tuned. We report on Q-resolved ultra-high-resolution IXS, X-ray diffraction, and THz time-domain spectroscopy experiments combined with large-scale all-atom molecular dynamics simulations on the dynamic properties of 5CB LCs. For the first time, we observe a strong mixing of phonon excitations originating from independent in-phase and out-of-phase van-der-Waals-mediated displacement patterns. The coexistence of transverse acoustic and optical modes of 5CB LCs at near room temperature is revealed through the emergent transverse phonon gap and THz light–phonon coupling taking place within the same energy range. Moreover, our experimental observations are supported by analysis showing correlations of spontaneous fluctuations of LCs on picosecond time scales. These findings are significant for the design of a new generation of soft molecular vibration-sensitive nanoacoustic and optomechanical applications.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Enhanced Reactivity of Lithium and Copper at High Pressure

High pressure can profoundly affect the electronic structure and reactivity, creating compounds between elements that do not react at ambient conditions. Lithium is known to react with gold and silver; however, no copper compounds are known to date. Here, by compressing mixtures of the elements in diamond-anvil cells, compounds of lithium and copper have been synthesized and characterized by X-ray diffraction for the first time. Pressures as low as 1 GPa lead to the formation of a complex layered phase LiCu, displaying two-dimensional kagomé lattice layers of Cu atoms. With increasing pressure, the layered Cu–Cu bonding is replaced by linear chains of Cu atoms in the high-pressure phase Li 2 Cu. Here we show the powerful effects of even modest pressures on the reactivity of lithium, leading to structures of remarkable complexity and low-dimensional transition metal bonding.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Novel Ordered Rocksalt-Type Lithium-Rich Li 2 Ru 1–x Ni x O 3-δ (0.3 ≤ x ≤ 0.5) Cathode Material with Tunable Anionic Redox Potential

In this work, a series of ordered rocksalt (OR) type Li-rich Li 2 Ru 1–x Ni x O 3-δ (LRN x O, 0.3 ≤ x ≤ 0.5) are successfully synthesized and investigated for the first time. X-ray diffraction and neutron powder diffraction patterns exhibit an obvious phase transition from layered to an OR structure as the Ni content gradually increases from x = 0 to x = 0.5, which leads to different electrochemical behaviors. In the case of OR-LRN 0.4 O, an ~350 mV decrease of the oxygen oxidation potential compared with Li 2 RuO 3 (LRO) is observed from around 4.2 to 3.85 V, which is confirmed by both X-ray photelectron O 1s spectra and dQ/dV results. Additionally, the role of Ni substitution on the oxygen redox reaction is studied by first-principles calculations, and it is concluded that the formation of the OR structure caused by Ni substitution is the main reason for lowering the oxygen oxidation potential. In addition, the average discharge voltage of OR-LRN 0.4 O is also enhanced compared with LRO. This work provides a novel innovative strategy to modulate and control the oxygen anion redox reaction for high-energy-density Li-rich materials, which shed light on the fundamental understanding and optimizing of the anion redox process in Li-rich materials.

25 ENERGY STORAGE↗
DOE OSTI2019

Low-temperature microstructural studies on superconducting CaFe2As2

Abstract Undoped CaFe 2 As 2 (Ca122) can be stabilized in two slightly different non-superconducting tetragonal phases, PI and PII, through thermal treatments. Upon proper annealing, superconductivity with a T c up to 25 K emerges in the samples with an admixture of PI and PII phases. Systematic low-temperature X-ray diffraction studies were conducted on undoped Ca122 samples annealed at 350 °C over different time periods. In addition to the diffraction peaks associated with the single-phase aggregation of PI and PII, a broad intermediate peak that shifts with annealing time was observed in the superconducting samples only. Our simulation of phase distribution suggests that the extra peak is associated with the admixture of PI and PII on the nanometer scale. High-resolution transmission electron microscopy confirms the existence of these nano-scale phase admixtures in the superconducting samples. These experimental results and simulation analyses lend further support for our conclusion that interfacial inducement is the most reasonable explanation for the emergence of superconductivity in undoped Ca122 single crystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Co-existence of Gel and Fluid Lipid Domains in Single-component Phospholipid Membranes

Lateral nanostructures in membranes, so-called rafts, are believed to strongly influence membrane properties and functions. The experimental observation of rafts has proven difficult as they are thought to be dynamic structures that likely fluctuate on nano- to microsecond time scales. Using neutron diffraction we present direct experimental evidence for the co-existence of gel and fluid lipid domains in a single-component phospholipid membrane made of DPPC as it undergoes its main phase transition. The coherence length of the neutron beam sets a lower limit for the size of structures that can be observed. Neutron coherence lengths between 30 and 242A used in this study were obtained by varying the incident neutron energy and the resolution of the neutron spectrometer. We observe Bragg peaks corresponding to co-existing nanometer sized structures, both in out-of-plane and in-plane scans, by tuning the neutron coherence length. During the main phase transition, instead of a continuous transition that shows a pseudo-critical behavior, we observe the co-existence of gel and fluid domains.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Effect of high temperature deposition on CoSi{sub 2} phase formation

This paper discusses the nucleation behaviour of the CoSi to CoSi{sub 2} transformation from cobalt silicide thin films grown by deposition at elevated substrate temperatures ranging from 375 Degree-Sign C to 600 Degree-Sign C. A combination of channelling, real-time Rutherford backscattering spectrometry, real-time x-ray diffraction, and transmission electron microscopy was used to investigate the effect of the deposition temperature on the subsequent formation temperature of CoSi{sub 2}, its growth behaviour, and the epitaxial quality of the CoSi{sub 2} thus formed. The temperature at which deposition took place was observed to exert a significant and systematic influence on both the formation temperature of CoSi{sub 2} and its growth mechanism. CoSi films grown at the lowest temperatures were found to increase the CoSi{sub 2} nucleation temperature above that of CoSi{sub 2} grown by conventional solid phase reaction, whereas the higher deposition temperatures reduced the nucleation temperature significantly. In addition, a systematic change in growth mechanism of the subsequent CoSi{sub 2} growth occurs as a function of deposition temperature. First, the CoSi{sub 2} growth rate from films grown at the lower reactive deposition temperatures is substantially lower than that grown at higher reactive deposition temperatures, even though the onset of growth occurs at a higher temperature, Second, for deposition temperatures below 450 Degree-Sign C, the growth appears columnar, indicating nucleation controlled growth. Elevated deposition temperatures, on the other hand, render the CoSi{sub 2} formation process layer-by-layer which indicates enhanced nucleation of the CoSi{sub 2} and diffusion controlled growth. Our results further indicate that this observed trend is most likely related to stress and changes in microstructure introduced during reactive deposition of the CoSi film. The deposition temperature therefore provides a handle to tune the CoSi{sub 2} growth mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Microwave assisted growth of copper germanide thin films at very low temperatures

Herein the synthesis of Cu{sub 3}Ge films by exposing Cu-Ge alloy films to microwave radiation is reported. It is shown that microwave radiation led to the formation of copper germanide at temperatures ca. 80 °C. The electrical properties of the Cu{sub 3}Ge films are presented and compared for various annealing times. X-ray diffraction shows that the Cu{sub 3}Ge films formed after microwave annealing is crystalline in the orthorhombic phase. Rutherford backscattering and X-ray photoelectron spectroscopy confirms the formation of copper oxide encapsulation layer. Despite the slight oxidation of Cu during the microwave anneal the lowest resistivity of Cu{sub 3}Ge films obtained is 14 μΩ-cm.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Real time monitoring of superparamagnetic nanoparticle self-assembly on surfaces of magnetic recording media

Nanoparticle self-assembly dynamics are monitored in real-time by detecting optical diffraction from an all-nanoparticle grating as it self-assembles on a grating pattern recorded on a magnetic medium. The diffraction efficiency strongly depends on concentration, pH, and colloidal stability of nanoparticle suspensions, demonstrating the nanoparticle self-assembly process is highly tunable. This metrology could provide an alternative for detecting nanoparticle properties such as colloidal stability.

36 MATERIALS SCIENCE↗