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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

Fabrication of thin-walled tubes from alloy 602 CA using shear assisted processing and extrusion

Thin-walled tube is usually produced seamlessly via an expensive multi-step process or via welding of thin sheets but at reduced performance. To overcome the current process and performance inefficiencies, advanced manufacturing methods need to be investigated. In this investigation, shear assisted processing and extrusion (ShAPE) was used to fabricate thin-walled Inconel 602 tube in a single-step. Tubes measuring 0.83 m length with a 12 mm outer diameter and 1 mm wall thickness were fabricated with an average surface roughness, Ra of 1.6 µm and Rz of 15 µm. Tensile testing of tubes in the as-fabricated condition showed strength increases of 4-35% over current offerings while maintaining or improving elongation. Electron microscopy analysis revealed the recrystallized microstructure with refined inter- and intra-granular carbides. Preliminary results obtained in this investigation shows the feasibility of producing thin-wall high temperature tube in single-step via ShAPE. This achievement marks a significant step towards manufacturing larger diameter nickel alloy tubes for the U.S. Department of Energy’s Waste Treatment and Immobilization Plant.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A critical analysis of U-Pu-Zr phase transitions using calorimetric, microstructural, and phase equilibria data

Metallic fuels consisting primarily of uranium, plutonium, and zirconium (U-Pu-Zr) are a leading material candidate for fast-spectrum nuclear reactors. Early demonstration programs proved the principle of safe and efficient fast reactor operation, however there is still considerable uncertainty regarding the phase equilibria and microstructural evolution across the ternary composition space. Quantitative phase formation and identification measurements are scarce and often incomplete, with studies reporting either phase transition temperatures or phase identification data, but not both from the same specimens. In this study, we critically compared experimental and calculated phase transition data and correlated with the microstructure and phase characterization data of as-cast and annealed U-Pu-Zr alloys. Differential scanning calorimetry (DSC) was used to measure phase transitions in the subsolidus regions (723−948 K) of three ternary U-Pu-Zr alloys with similar plutonium concentrations but various U/Zr ratios. Due to sluggish kinetics and narrow ranges of phase stability, complex peaks required the use of a Frazier-Suzuki peak fitting algorithm to deconvolute and calculate transition peak temperatures and enthalpies. We also identified trends of phase transition behavior by critically comparing our DSC data with previous phase transition measurements as well as historical and calculated phase equilibrium diagrams. In conclusion, this provides a critical approach for benchmarking and assessing the quality of new U-Pu-Zr phase equilibria data prior to its incorporation into nuclear material databases.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Super-resolution model for overlapping peak detection and improved spatial resolution in high-energy diffraction microscopy

Reconstruction quality in Far-field High-Energy Diffraction Microscopy (FF-HEDM) is limited by the spatial resolution of area detectors and the frequent occurrence of overlapping diffraction spots. To address these challenges, we developed a super-resolution (SR) framework using convolutional neural networks (CNNs) to recreate 2D diffraction peaks at up to ×8 resolution from raw detector data. A specialized simulation tool was created to generate synthetic training datasets with varying degrees of peak overlap. Integrated into the Microstructural Imaging using Diffraction Analysis Software (MIDAS), the SR model improves the spatial accuracy and precision of 3D grain reconstruction by an order of magnitude. This approach provides a robust solution for investigation of complex micromechanical states and material classes where the analysis is limited by the presence of overlapping peaks. Furthermore, the methodology developed here can potentially be extended to other techniques that require sub-pixel accuracy for high-fidelity data analysis.

High-energy diffraction microscopy↗
DOE OSTI2023

Effect of Re and Al additions on the microstructure and mechanical properties of Nb-18Ti-12W alloy

Microstructure and mechanical properties at 25–1200 °C of new refractory alloys, Nb-18Ti-12W (NTW), Nb-18Ti-12W-5Re (NTW-R) and Nb-18Ti-12W-5Re-1Al (NTW-RA), all compositions are in atomic percent, are reported. The alloys are developed as an alternative to a denser, more expensive and difficult-to-process refractory alloy WC-3009. After production by arc melting and hot isostatic pressing at 1400 °C, 207 MPa for 3 h, the alloys have a BCC crystal structure with the average grain size of ~150–200 μm and contain low volume fraction of (Ti,N)-rich precipitates near grain boundaries. NTW shows excellent malleability at all studied temperatures. Its yield stress at 25 °C, 1000 °C and 1200 °C is 874 MPa, 353 MPa and 202 MPa, respectively. The NTW-R and NTW-RA alloys are stronger at all the studied temperatures; however, they lack in compression ductility at 25 °C. As a result, extensive deformation twinning and formation of intergranular voids precede the fracture of these two alloys at 25 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Isolating intermediate Mg 11 Cu 6 Al 12 phase in ternary Mg-Cu-Al alloy by electrolytic dealloying

While dealloying is widely used to create nanoporous materials, it has rarely been employed to isolate difficult-to-synthesize intermediate phases. Here, in this work, we show how air-free, electrolytic dealloying at room temperature can be used to isolate the ternary intermetallic Mg 11 Cu 6 Al 12 phase. We create a ternary Mg-Cu-Al parent alloy containing the Mg 11 Cu 6 Al 12 compound and other phases, then subsequently remove these other phases via electrolytic dealloying to isolate the Mg 11 Cu 6 Al 12 phase. Isolated Mg 11 Cu 6 Al 12 phase exhibits ≈1 μm diameter rod-shaped microstructure. Phase and chemical analysis conducted using various techniques, including inductively coupled plasma and lab and synchrotron-based X-ray diffraction, show minimal impurities. This new approach to isolate the Mg 11 Cu 6 Al 12 phase can unlock its use in fundamental research and can be applied to other difficult-to-synthesize intermetallic compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A multimodal approach to revisiting oxidation defects in Cr 2 O 3

The oxidation of chromium in air at 700 °C was investigated with a focus on point defect behavior and transport during oxide layer growth. A comprehensive set of characterization techniques targeted characteristics of chromium oxide microstructure and chemical composition analysis. TEM showed that the oxide was thicker with longer oxidation times and that, for the thicker oxides, voids formed at the metal/oxide interface. PAS revealed that the longer the oxidation time, there was an overall reduction in vacancy-type defects, though chromium monovacancies were not found in either case. EIS found that the longer oxidized material was more electrochemically stable and that, while all oxides displayed p-type character, the thicker oxide had an overall lower charge carrier density. Together, the results suggest anion oxygen interstitials and chromium vacancy cluster complexes drive transport in an oxidizing environment at this temperature, providing invaluable insight into the mechanisms that regulate corrosion.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Carrier mobilities of (001) cadmium arsenide films

We investigate (001)-oriented films of the topological semimetal cadmium arsenide (Cd 3 As 2 ) grown by molecular beam epitaxy on lattice-matched III–V Al x In 1-x Sb buffer layers. Magnetotransport studies and analysis of thin film microstructures are used to determine the influence of dislocations on their carrier mobilities. We show that only a minority of the threading dislocations present in the buffer layers extend into the Cd 3 As 2 films. Threading dislocations are shown to reduce the mobilities of carriers residing in the topological surface states, while bulk transport was unaffected by a change in the dislocation density across an order of magnitude. Thick (001) Cd 3 As 2 films exhibit electron mobilities of up to 41 000 cm 2 V -1 s -1 at 2 K. The results provide insights into the influence of extended defects on the transport properties of a prototype topological semimetal.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Defect-induced phonon-resonant scattering and its influence on thermal transport of irradiated thorium-dioxide

Thermal transport in proton irradiated thorium-dioxide (ThO 2 ) is investigated. Using a combination of experiments and first-principles computational framework, the role of lattice defects on thermal conductivity is analyzed. A resonant-phonon scattering mechanism beyond the traditionally considered Rayleigh scattering is found to significantly influence low-temperature thermal transport in the presence of irradiation-induced point defects. The existence of localized phonon modes associated with irradiation-induced defects is suggested by the inability of the first-principles based thermal conductivity model—which considers only three-phonon interactions and phonon-defects scattering using the Tamura formalism—to predict the experimental results, unless a resonant scattering mechanism is included. The emergence of additional peaks in the Raman spectra in the proximity of phonon-resonant frequency provides further evidence for the existence of localized modes. Coupled with a microstructure evolution model, this analysis enables more accurate analysis for contrasting the contributions of different phonon scattering mechanisms across all irradiation doses and temperatures.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Dusty Gas Model for Solid Oxide Fuel Cell Fuel Electrode

This model applies the Dusty Gas Model simulate multi-component species transport in SOFC (solid oxide fuel cell) anodes which considers the pressure gradient across the fuel electrode. This studyhas been verified with the analytical solution for different fuel electrode thicknesses and with literature values. The model was developed using the VoronoiFVM platform in Julia which is a built in implicit and semi implicit solver that integrates electrochemical behavior, microstructural effects, and transient analysis for accurate prediction of species transport under varying conditions.

dusty gas model (DGM)↗
NASA NTRS1985

Microstructure of reaction-bonded silicon nitride consolidated by isostatic hot-pressing

A microstructural examination and chemical analysis are conducted for reaction-bonded Si3N4 specimens that were isostatically hot pressed at 1850, 1950, and 2050 C. The present observations indicate that the previously reported increase in the 1200 C bend strength of reaction-bonded Si3N4, after pressing at 2050 C exclusively, is due to the relative oxygen levels of the isostatically hot pressed specimens; calculations show that an SiO2 content of less than about 2.2 vol pct is needed to yield the 1200 C strength increase.

Mieskowski, D. M.↗
NASA NTRS1990

Heat treatment study 2

The microstructural variations in nickel based superalloys that result from modifications in processing were examined. These superalloys include MAR-M246(HF) and PWA1480. Alternate heat treatments for equiaxed as-cast specimens were studied and a sample matrix of 42 variations in the heat treatments were processed, as well as different directional solidification parameters. Variation in temperature and times for both solution and aging were performed. Photomicrographs were made of the microstructure and volume fraction analysis of primary gamma-prime and aged gamma-prime precipitates were performed. The results of the heat treatment, cooling rate, and directional solidification experiments are discussed.

Workman, Gary L.↗
NASA NTRS1990

The effect of laser pulse tailored welding of Inconel 718

Pulse tailored laser welding has been applied to wrought, wrought grain grown, and cast Inconel 718 using a CO2 laser. Prior to welding, the material was characterized metallographically and the solid state transformation regions were identified using Differential Scanning Calorimetry and high temperature x-ray diffraction. Bead on plate welds (restrained and unrestrained) were then produced using a matrix of pulse duty cycles and pulsed average power. Subsequent characterization included heat affected zone width, penetration and underbead width, the presence of cracks, microfissures and porosity, fusion zone curvature, and precipitation and liquated region width. Pedigree welding on three selected processing conditions was shown by microstructural and dye penetrant analysis to produce no microfissures, a result which strongly indicates the viability of pulse tailored welding for microfissure free IN 718.

Mccay, T. Dwayne↗
NASA NTRS2006

Multimode-Guided-Wave Ultrasonic Scanning of Materials

Two documents discuss a method of characterizing advanced composite materials by use of multimode-guided ultrasonic waves. A transmitting transducer excites modulated (e.g., pulsed) ultrasonic waves at one location on a surface of a plate specimen. The waves interact with microstructure and flaws as they propagate through the specimen to a receiving transducer at a different location. The received signal is analyzed to determine the total (multimode) ultrasonic response of the specimen and utilize this response to evaluate microstructure and flaws. The analysis is performed by software that extracts parameters of signals in the time and frequency domains. Scanning is effected by using computer-controlled motorized translation stages to position the transducers at specified pairs of locations and repeating the measurement, data-acquisition, and data-analysis processes at the successive locations. One document presents results of a scan of a specimen containing a delamination.

Roth, Don↗
NASA NTRSDate not supplied

Metal Fused Filament Fabrication of Titanium Alloy for In Space Manufacturing

NASA is developing materials and processes for the in-space manufacturing of many items for the International Space Station (ISS) and future exploration platforms. These new manufacturing processes will require the further development of current 3D printing processes to achieve high-performance metal parts within the power and space constraints of the ISS. Manufacturing Ti-6Al-4V alloy parts with 3D printing using a metal fused filament fabrication (MF3) process is an alternative process to the Direct Metal Laser Sintering (DMLS) of the metal powders additive manufacturing process. Our initial work fabricating Ti-6Al-4V parts from Ti-6Al-4V powder-binder feedstock and processed with the MF3 process has resulted in 95-97% sintered densities. The current development work of optimized sintered properties investigates the effects of variation in sintering time, temperature, and vacuum on the sintered properties of Ti-6Al-4V MF3 printed tensile bars. Sintered properties such as density, hardness, and tensile properties were characterized followed by microstructural and chemical (O/C/N) analysis to understand the role of sintering process on the ensuing material properties. Future development of the MF3 process will also involve investigation of the effects of micro-milling the Ti-64Al-4V powder to nanometer particle sizes and the investigation of laser sintering of the 3D printed devices. This new micro-milling technique will have broad application to other areas that require particle size reduction of hard metallic materials, such as Nuclear Thermal Propulsion and other NASA technologies. Laser sintering in lieu of high temperature thermal sintering should allow for significant power reduction and improved processing speeds.

sintering, alloys, 3D printing↗
DOE OSTI2022

DED Additively Manufactured HEAs Optimized via Parametric Study of Functionally Graded Materials

Complex concentrated alloys (CCAs) are a system of alloys composition of nearly equiatomic elements, creating a state of high configurational entropy in the material. These alloys are of interest for various industrial applications due to their high strength and hardness, wide operational temperature range, creep and diffusion resistance, and radiation resistance. In the current work CoCrFeNi-base CCAs are synthesize by combining three commonly industrial alloys: IN718, SS316L, and 70Co30Cr (commercially known as Stellite 21), in-situ utilizing directed energy deposition (DED) additive manufacturing (AM). One bulk specimen is fabricated with a 1:1:1 ratio of IN718, SS316L, and 70Co30Cr where IN718 is a source of nickel and chrome, SS316 is a source of iron and chrome, and 70Co30Cr is a source of cobalt and supplemental chrome. Additionally, a functionally graded material (FGM) of the identified CCA system from SS316 was fabricated with 10 layers, where the initial five layers are the base material of SS316L and graded by steps of 20% to transition to the CCA system. Overall build quality, microstructure, compositional distribution, phases analysis, and microhardness were studied by laser optical microscopy, scanning election microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and Vickers microhardness techniques. Overall build quality showed a successful bulk build with acceptable density, however unmelted particles are observed in the as-built alloy. Compositional results show that the system meets the Boltzmann’s hypothesis definition of an HEA, and that an FCC CCA was produced with increased hardness, small grain size, and superior hardness properties to the SS316L substrate. While initial XRD results show predominately FCC structure, EDS analysis of interdendritic regions show the existence of Laves phases in the material. The fabrication of an FGM CCA allowed for potential screening of additional alloy mixes which may be of interest to explore in future research, and the resulting composition is compared to predicted values. This novel method of CCA fabrication results in substantial cost savings of these CCA systems over traditional methods.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Characterization of Mechanical Performance of Composites Fabricated Using Innovative Carbon Fiber Wet Laid Process

Recent innovation in production of optimized nonwoven wet laid (WL) carbon fiber (CF) mats raised the question of optimal translation of the performance and isotropy into composites formed through these dry preforms. This work explores the mechanical behavior of composites produced from WL-CF mats in conjunction with the microstructure predicted through Object Oriented Finite Element Analysis (OOF). The mats used for the composites were prepared in two dispersion regimes using 25.4 mm long CF. The mixing regimes discussed in the author’s previous work, are identified as Method 1 for the traditional processing regime and Method 2 for the innovative regime that provided optimal nonwoven WL-CF mats. Composite panels from Method 2 mats showed a normalized tensile strength increase of 52% over those from Method 1 panels. Reproducibility analysis of composites made from Method 2 mats demonstrated a standard deviation of 2% in fiber weight content, 2% in tensile modulus and 9% in tensile strength, while composites made from Method 1 mats demonstrated a standard deviation of 5% in fiber weight content, 5% in tensile modulus and 17% in tensile strength. Systematic study of the microstructure and its analysis through OOF confirmed the isotropy translation of mats produced through method 2 to the composites. This study validated the hypothesis that optimal nonwoven mats lead to a well-balanced composite with optimal performance and that non-optimal nonwoven mats do not pack into a well-balanced composite.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Supercritical, liquid, and gas CO 2 reactive transport and carbonate formation in portland cement mortar

In this paper, we investigate carbonate formation and reactive transport rate in variably saturated portland cement mortars when high concentrations of gas, liquid, or supercritical CO 2 flow through their pore network. Xray computed tomography completed during CO 2 flow is used to quantify the microstructural evolution as the mortar carbonates. After in situ tests, higher resolution scans, thermogravimetric analysis, and desorption isotherm analysis are performed to further quantify microstructural changes. We found that at dry conditions supercritical CO 2 moves more rapidly through the pore space and precipitates more carbonates than liquid or gas CO 2 . However, at 50% degree of saturation (DOS) the CO 2 state did not affect the rate of transport in that each specimen exposed to a different CO 2 state carbonated within the first hour of CO 2 exposure. When the pore space is at 50 or 100% DOS, supercritical CO 2 did not react with hydration products more rapidly nor did it result in more carbonate formation during exposure compared to gas or liquid CO 2 . The amount of Ca(OH) 2 that contributes to CaCO 3 formation is correlated to the DOS. For the mortar composition analyzed, Ca(OH) 2 contributes to approximately 40% of the carbonates formed in the 50% DOS specimens and 15% in the 100% DOS specimens. In other words, as the amount of moisture in the pore space increases, phases other than Ca(OH) 2 contribute to more than 50% of the total CaCO 3 formed.

42 ENGINEERING↗