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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Laser diagnostics to characterize the in-flame growth of platinum nanoparticles manufactured by the reactive spray deposition technology

Reactive Spray Deposition Technology (RSDT) is an atmospheric pressure, flame-based advanced manufacturing method used to fabricate Membrane Electrode Assemblies (MEAs) for proton exchange fuel cells and water electrolyzers. RSDT combines the flame synthesis of catalyst nanoparticles and their deposition onto the membrane in one step. The properties of the synthesized nanoparticles, such as their Size Distribution Function (SDF), determine the manufactured electrodes’ performance, which can be evaluated when the deposition is complete via ex-situ characterization of the products. Efforts to improve RSDT for manufacturing state-of-the-art MEAs can be significantly enhanced with integrated laser diagnostics that enable in situ measurement of the synthesized catalyst nanoparticles. This paper reports the implementation of laser diagnostics in an RSDT facility and evaluates their potential to assist the manufacturing process. Laser Light Scattering (LS) and Laser-Induced Incandescence (LII) measurements are performed in the oxygen-rich zone of the flame at various distances from the flame fuel jet nozzle downstream of its luminous region. The measurements quantitatively track the evolution in size and volume fraction of platinum-based nanoparticles in two flames that yield different catalytic properties in the manufactured electrodes. The profiles of the measured nanoparticles’ volume fraction along the flame axis can be estimated a priori so that the average nanoparticle sizes can be measured in quasi-real time via LS. Nanoparticles experience an extremely slow growth rate while being convected at distances from 150 nm to 300 nm from the fuel nozzle. Complementary characterizations of the synthesized nanoparticles are performed ex-situ via High-Angle Annular Darkfield Scanning Transmission Electron Microscopy (HAADF-STEM) image analyses of samples collected on grids at a fixed distance from the fuel jet nozzle. Comparing the results from laser and microscopy techniques not only cross-validates the findings but also provides the parameters to infer the bimodal SDF in-situ and yields evidence that the coagulation efficiency of the synthesized nanoparticles has extremely low values in the investigated zone of the flames.

Rayleigh Light Scattering (LS)↗
DOE OSTI2021

CO 2 electro-reduction on Cu 3 P: Role of Cu(I) oxidation state and surface facet structure in C 1 -formate production and H 2 selectivity

We report the catalytic activity and mechanism of copper(I) phosphide, Cu 3 P, with predominant [00Ι] facet exposure for the electrochemical reduction of CO 2 (CO 2 RR) to formic acid. Crystalline nanosheets of this compound that show a preferential [00Ι] facet orientation exhibit undiminished CO 2 RR activity after 16 hours with full retention of crystal structure and surface chemical speciation and no detectable corrosion. In contrast to the range of products formed on Cu metal, CuO, and Cu 2 O, the CO 2 RR on Cu 3 P [00Ι] produces mainly hydrogen and formate as the sole carbon product in KHCO 3 electrolyte. Analysis of the Cu 3 P [00Ι] facet by HAADF-STEM was used to determine the surface lattice structure, while both XPS and Auger spectroscopies were used to determine the surface chemical speciation from the kinetic energies of ionized electrons. The presented analysis identifies isolated trigonal CuP 3 sites on the Cu 3 P[00Ι]-Cu 3 P 3 terminated surface and the Cu(I) oxidation state as precursor to the active catalyst. The CO 2 RR selectivity to formate and the higher turnover rate for H 2 production on the [00Ι] facet allows a structure-activity analysis and chemical mechanism to be proposed. Formation of a surface hydride at isolated *H-CuP 3 sites is proposed as the catalytic site in forming both H 2 and formate, while the long Cu—Cu separation retards forming C-C coupling products. In conclusion, these results disprove previously published claims of Cu(I) oxidation state as a sufficient criterion to promote CO 2 RR to C 2+ products, show that stronger bonded hydrides, *H-CuP 3 on Cu 3 P, favor production of the C1 product formate over all other carbon products, and predict that stronger formate binding (bidentate) is needed for CO 2 RR currents to compete with H 2 production.

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

The Instability of Monolayer-Thick PbSe on VSe 2

Two-dimensional monolayers derived from 3D bulk structures remain a relatively unexplored class of materials because of the challenge of stabilizing non-epitaxial interfaces. Here, we report an unusual reconstruction during the deposition of precursors when targeting the synthesis of heterostructures with an odd number of PbSe monolayers. Multilayer elemental precursors of Pb|Se + V|Se were deposited to have correct number of atoms to form [(PbSe) 1+δ ] q (VSe 2 ) 1 where q is the number of PbSe monolayers in the heterostructure. Structural analysis of the self-assembled precursor via xray reflectivity, x-ray diffraction, and HAADF-STEM suggests three different behaviors upon deposition. Precursors with q 7 and even values of q have the targeted nanoarchitectures after deposition which are maintained as the products are selfassembled through a near diffusionless process. Significant lateral surface diffusion occurred during deposition of precursors with q = 1, 3, and 5 resulting in the precursor having a different nanoarchitecture than targeted. Additional perpendicular long range diffusion occurs during self-assembly of these precursors resulting in different final products than targeted. DFT calculations of PbSe blocks show that the odd numbered layers are less stable than even numbered layers, which suggests an energetic driving force for the observed rearrangement. This work highlights the importance of understanding the reaction mechanism when attempting to prepare 2D layers of constituents with bulk 3D structures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Synthesis and Electrical Properties of a New Compound (BiSe) 0.97 (Bi 2 Se 3 ) 1.26 (BiSe) 0.97 (MoSe 2 ) Containing Metallic 1T-MoSe 2

The synthesis and electrical properties of a new misfit compound containing BiSe, Bi 2 Se 3 , and MoSe 2 constituent layers are reported. The reaction pathway involves competition between the formation of (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) and [(Bi 2 Se 3 ) 1+y ] 2 (MoSe 2 ). Excess Bi and Se are required in the precursor to synthesize (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ). High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) confirm the stacking sequence of the heterostructure. Small grains of both 2H- and 1T-MoSe 2 are observed in the MoSe 2 layers. X-ray photoelectron spectroscopy (XPS) indicates that there is a significantly higher percentage of 1T-MoSe 2 in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) than in (BiSe) 0.97 (MoSe 2 ), suggesting that more charge transfer to MoSe 2 occurs due to the additional BiSe layer. The additional charge transfer results in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) having a low resistivity (14–19 μΩ m) with metallic temperature dependence. Furthermore, the heterogeneous mix of MoSe 2 polytypes observed in the XPS complicates the interpretation of the Hall data as two bands contribute to the electrical continuity.

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

Delineating the Roles of Mn, Al, and Co by Comparing Three Layered Oxide Cathodes with the Same Nickel Content of 70% for Lithium-Ion Batteries

High-nickel layered oxides continue to prevail in the energy storage market as the frontmost cathode candidates for next-generation lithium-ion batteries. Demand and development of LiNi 1–x–y Mn x Co y O 2 (NMC) and LiNi 1–x–y Co x Al y O 2 (NCA) cathodes are rampantly increasing, particularly for the electric vehicle (EV) industry. However, the continued presence of cobalt in NMC and NCA cathodes raises global concerns due to geopolitical and ethical issues attributed to Co sourcing. We herein introduce a novel cobalt-free, high-nickel cathode LiNi 0.7 Mn 0.25 Al 0.05 O 2 (NMA70) and benchmark it against Co-containing LiNi 0.7 Mn 0.15 Co 0.15 O 2 (NMC70) as well as Co- and Al-free LiNi 0.7 Mn 0.3 O 2 (NM70) cathodes with equivalent 70% Ni contents that are all synthesized in-house. NMA70 displays a high initial C/10 capacity of 210 mA h g –1 , matching that of NMC70 in half cells with a cutoff voltage of 4.5 V. NMA70 also exhibits an impressive high-voltage full cell cycling performance with a cutoff voltage of 4.4 V with a nearly identical capacity retention of 83% compared to that of 82% for NMC70 after 300 cycles. Postmortem X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and electron energy loss spectroscopy (EELS) analyses indicate a thinner cathode–electrolyte interface (CEI) developed in NMA70 compared to that in NM70 and unveil a more robust solid-electrolyte interface (SEI) passivation on the graphite anode among all samples. The benefits of Al doping are additionally highlighted with enhanced high-voltage CEI and thermal stabilities in NMA70. Furthermore, this work assesses the roles of Mn, Al, and Co to demonstrate both the practicality and feasibility of synthesizing cobalt-free, high-nickel cathodes that are promising alternatives to current NMC- and NCA-based cathodes.

25 ENERGY STORAGE↗
DOE OSTI2022

The Diffusion Mechanism of Ge During Oxidation of Si/SiGe Nanofins

A recently discovered, enhanced Ge diffusion mechanism along the oxidizing interface of Si/SiGe nanostructures has enabled the formation of single-crystal Si nanowires and quantum dots embedded in a defect-free, single-crystal SiGe matrix. Here, we report oxidation studies of Si/SiGe nanofins aimed at gaining a better understanding of this novel diffusion mechanism. Here, a superlattice of alternating Si/Si 0.7 Ge 0.3 layers was grown and patterned into fins. After oxidation of the fins, the rate of Ge diffusion down the Si/SiO 2 interface was measured through the analysis of HAADF-STEM images. The activation energy for the diffusion of Ge down the sidewall was found to be 1.1 eV, which is less than one-quarter of the activation energy previously reported for Ge diffusion in bulk Si. Through a combination of experiments and DFT calculations, we propose that the redistribution of Ge occurs by diffusion along the Si/SiO 2 interface followed by a reintroduction into substitutional positions in the crystalline Si.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Highly Selective Oxygen Reduction to Hydrogen Peroxide on a Carbon-Supported Single-Atom Pd Electrocatalyst

Selective electrochemical two-electron oxygen reduction is a promising route for renewable and on-site H 2 O 2 generation as an alternative to the anthraquinone process. In this study, we report a high-performance nitrogen-coordinated single-atom Pd electrocatalyst, which is derived from Pd-doped zeolitic imidazolate frameworks (ZIFs) through one-step thermolysis. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with X-ray absorption spectroscopy verifies atomically dispersed Pd atoms on nitrogen-doped carbon (Pd-NC). The single-atom Pd-NC catalyst exhibits excellent electrocatalytic performance for two-electron oxygen reduction to H 2 O 2 , which shows ~95% selectivity toward H 2 O 2 and an unprecedented onset potential of ~0.8 V versus revisable hydrogen electrode (RHE) in 0.1 M KOH. Density functional theory (DFT) calculations demonstrate that the Pd-N 4 catalytic sites thermodynamically prefer *–O bond breaking to O–O bond breaking, corresponding to a high selectivity for H 2 O 2 production. This work provides a deep insight into the understanding of the catalytic process and design of high-performance 2e– ORR catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High-Temperature Pretreatment Effect on Co/SiO 2 Active Sites and Ethane Dehydrogenation

Here, we report the synthesis, optimization, and characterization of Co/SiO 2 for ethane nonoxidative dehydrogenation. Co/SiO 2 is synthesized via strong electrostatic adsorption using the widely available Co(NO 3 ) 2 as the precursor. We demonstrate that high-temperature pretreatment (900 °C) in an inert atmosphere can significantly enhance the initial activity of the Co/SiO 2 catalyst. X-ray absorption near-edge spectroscopy (XANES), temperature-programmed reduction (TPR), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) suggest that highly dispersed Co(II) clusters are more active than Co 0 or CoO x nanoparticles. Fourier transform infrared (FTIR) and isopropanol (IPA) temperature-programmed desorption and density functional theory (DFT) calculations suggest that high-temperature treatment significantly increases the density of active Lewis acid sites, possibly via surface dehydroxylation of the catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Atom Efficiency of Pd Sites for Methane Combustion: Single Atom Catalysts Versus Nanocatalysts

Methane combustion is an important reaction for energy production and methane removal from the atmosphere. This reaction highly relies on the use of noble metal Pd-based catalysts, which therefore drives the pursuit of catalysts with high atomic dispersion and activity. In this work, Pd/ceria catalysts dominated with Pd single atoms or nanosized Pd clusters (∼1 nm) are prepared and characterized by combining high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), and Raman and X-ray absorption spectroscopy (XAS) techniques. By comparing the turnover frequencies (TOF; per every Pd atom) of Pd/ceria single atom catalysts and nanocatalysts, it is found that the atom efficiency of Pd is increased by 10 ∼30 times from single atom catalysts to nanocatalysts. For Pd single atom catalysts, although their activity can be tuned by changing the local structures, the intrinsic activity and number of active sites need to be further improved by engineering the surfaces of supports. For nanosized Pd species, despite the high TOF, the Pd atoms in the bulk structure are not directly participating in the catalytic reaction. Furthermore, this work highlights the importance of increasing the intrinsic activity of individual noble atoms, as well as the homogeneity of their local structures. For Pd/ceria systems reported in this work, our results indicate that from the application point of view, at the current stage, it is not practical to replace Pd nanocatalysts with single atom catalysts for methane combustion.

Pd↗
DOE OSTI2025

Strain-driven oxygen vacancy ordering in LaNiO 3 thin films revealed by integrated differential phase contrast imaging in scanning transmission electron microscopy

Rare-earth nickelates, such as LaNiO 3 (LNO), exhibit complex electronic properties, with ordered oxygen vacancies (OOV) influencing conductivity and magnetic behavior. We investigate the structural stability of strain-induced OOV phases in LNO thin films grown on SrTiO 3 substrates and the impact of Ruddlesden–Popper (RP) faults. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and integrated differential phase contrast (iDPC) STEM imaging, we conducted atomic-scale structural and compositional analyses of OOV. Geometric phase analysis (GPA) was employed to measure the strain in fault-free and RP fault regions, while density functional theory (DFT) calculations explored different OOV arrangements in the LNO phase. Simulated iDPC-STEM imaging of energy-stabilized structures was performed to correlate with experimental results. Here, our findings reveal superstructure modulation in the chemical composition and atomic-scale lattice structure in LNO, primarily due to the formation of the OOV in Ni–O layers of the LaNiO 2.5 phase. The out-of-plane compressive strain of about 2% stabilizes this phase, reducing the strain, diminishing OOV, and transforming them into LNO.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Chemical order-disorder nanodomains in Fe 3 Pt bulk alloy

Chemical ordering is a common phenomenon and highly correlated with the properties of solid materials. By means of the redistribution of atoms and chemical bonds, it invokes an effective lattice adjustment and tailors corresponding physical properties. To date, however, directly probing the 3D interfacial interactions of chemical ordering remains a big challenge. In this work, we deciphered the interlaced distribution of nanosized domains with chemical order/disorder in Fe 3 Pt bulk alloy. HAADF-STEM images evidence the existence of such nanodomains. The reverse Monte Carlo method with the X-ray pair distribution function data reveal the 3D distribution of local structures and the tensile effect in the disordered domains at the single-atomic level. The chemical bonding around the domain boundary changes the bonding feature in the disordered side and reduces the local magnetic moment of Fe atoms. This results in a suppressed negative thermal expansion and extended temperature range in Fe 3 Pt bulk alloy with nanodomains. Our study demonstrates a local revelation for the chemical order/disorder nanodomains in bulk alloy. The understanding gained from atomic short-range interactions within the domain boundaries provides useful insights with regard to designing new functional compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Antiferromagnetic Fe Te 2 1 T - phase formation at the Sb 2 Te 3 / Ni 80 Fe 20 interface

Bilayer topological insulator/ferromagnet (TI/FM) heterostructures are promising for spintronic applications due to their low switching energy and therefore power efficiency. Until recently, the reactivity of TI with FM films was overlooked in the spin orbit-torque literature, even though there are reports that it is energetically favorable for TIs to react with transition metals and form interfacial layers. Here, in this study we fabricated a TI/FM heterostructure comprised of molecular beam epitaxy grown Sb 2 Te 3 and DC sputtered Ni 80 Fe 20 . Broadband ferromagnetic resonance revealed spin-pumping evident by the significant enhancement in Gilbert damping, which is likely a signature of the topological surface states or the presence of large spin-orbit-coupling in the adjacent Sb 2 Te 3 . With low-temperature magnetometry, an exchange bias is observed which indicates an exchange interaction between an antiferromagnet (AFM) and an adjacent FM. Cross-section high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) characterization of the Sb 2 Te 3 - Ni 80 Fe 20 bilayer revealed a complex interface showing diffusion of Fe and Ni into the Sb 2 Te 3 film yielding the formation of a FeTe 2 1T-type structural phase. Furthermore, density functional theory calculations revealed that the FeTe 2 1T-phase has an AFM ground state. Due to experimental limitations in the electron energy loss spectroscopy measurements precise chemistry of the interfacial phase could not be determined, therefore it is possible that the FeTe 2 1T and/or an intermixed (Fe 1-x Ni x )Te 2 1T is the AFM interfacial phase contributing to exchange bias in the system. This work emphasizes the chemical complexity of TI/FM interfaces that host novel, metastable magnetic topological phases and require more in-depth studies of other similar interfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Single Atomic Iron Site Catalysts via Benign Aqueous Synthesis for Durability Improvement in Proton Exchange Membrane Fuel Cells

Atomically-dispersed iron-nitrogen-carbon (Fe–N–C) catalysts have arisen as promising candidates for replacing the costly precious metal catalysts in fuel cells but still face some grand challenges, such as insufficient site density and durability. Herein, we report a self-assembly method in an aqueous solution to develop an atomically-dispersed iron catalyst with high oxygen reduction reaction (ORR) activity and stability in acidic electrolytes. As determined by high-resolution transmission electron microscopy (HR-TEM), X-ray absorption spectroscopy (XAS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), this benign aqueous synthesis strategy facilitates the formation of homogeneous atomic nitrogen-coordinated iron sites embedded in a popcorn-like porous graphitic carbon matrix. These catalyst properties contribute to the improved ORR kinetic current density and mass transport. By controlling synthesis chemistry, the correlation between structure and property is systematically investigated. In this work, the iron content is the most critical material property and can regulate site density and graphitic carbon structures in the catalyst, impacting catalytic activity and stability. The enhanced performance and durability were examined in both acidic aqueous electrolytes and membrane electrode assemblies.

25 ENERGY STORAGE↗
DOE OSTI2024

Plasmon assisted synthesis of TiN-supported single-atom nickel catalysts

We report the deposition of single atom nickel catalyst on refractory plasmonic titanium nitride (TiN) nanomaterials supports using the wet synthesis method under visible light irradiation. TiN nanoparticles efficiently absorb visible light to generate photoexcited electrons and holes. Photoexcited electrons reduce nickel precursor to deposit Ni atoms on TiN nanoparticles’ surface. The generated hot holes are scavenged by the methanol. We studied the Ni deposition on TiN nanoparticles by varying light intensity, light exposure time, and metal precursor concentration. These studies confirmed the photodeposition method is driven by hot electrons and helped us to find optimum synthesis conditions for single atoms deposition. We characterized the nanocatalysts using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We used density functional theory (DFT) calculations to predict favorable deposition sites and aggregation energy of Ni atoms on TiN. Surface defect sites of TiN are most favorable for single nickel atoms depositions. Interestingly, the oxygen sites on native surface oxide layer of TiN also exhibit strong binding with the single Ni atoms. Plasmon enhanced synthesis method can facilitate photodeposition of single atom catalysts on a wide class of metallic supports with plasmonic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Raw electron microscopy images for "The Importance of Nano-edges in Atomic Stencilling and Chiroptically Active Assembly of Patchy Gold Tetrahedra"

This dataset contains the raw transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images used in the main figures of the paper “The Importance of Nano-edges in Atomic Stencilling and Chiroptically Active Assembly of Patchy Gold Tetrahedra (2026).” All the images were acquired at the Materials Research Laboratory, University of Illinois at Urbana-Champaign, by Qian Chen group. 1. We provide five subfolders, each named according to the corresponding figure numbers in the paper. 2. All files in the subfolders for Figures 1–3 and 5 are named as "Panel [letter]_*", where [letter] (e.g., a, b, c) represents the raw images used for the corresponding panels. 3. All files in the subfolder for Figure 4 correspond to panel f and show the configurations of patchy tetrahedra synthesized at varying concentrations of iodide and 2-naphthalenethiol. They are named "Experiment_[number]", where [number] represents the corresponding data points in the phase diagram. 4. In TEM images, the bright and dark regions indicate the polymer patches and nanoparticle cores, respectively. 5. In SEM images, the bright and dark regions indicate the nanoparticle cores and polymer patches, respectively. 6. Abbreviations in file names: HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy), PINEM (photon-induced near-field electron microscopy), and RCP/LCP (left-/right-handed circularly polarized).

chirality↗
DOE OSTI2025

Oxygen Reduction on Platinum-Nickel and Platinum-Cobalt Alloy Based Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

Catalyst layers, with commercial PtNi/TKK (TECNiE52; platinum 46.5 wt%), PtCo/TKK (TEC36E52; platinum 45.8 wt%) catalysts, and an in-house catalyst PtNi-NC (platinum 38.4 wt%), synthesised using acoustic mixer and a tube furnace, are prepared using three different ionomers: 20 wt% Nafion®, 60 wt% polytetrafluoroethylene (PTFE), and an in-house 5 wt% ionomer (‘Ionomer X’). These inks are bar-coated onto carbon paper gas diffusion layers (GDLs), which are cut into 3 cm × 5 cm pieces. The coated layers are tested for oxygen reduction in a commercial gas diffusion electrode (GDE) test cell, FlexCell® (Gaskatel GmbH, Germany), using 85 wt% phosphoric acid at both room temperature and at 155°C. This study evaluates the polynorbornene (PNB)-based in-house ionomer performance as binder and in-house catalyst oxygen reduction reaction (ORR) activity in comparison to commercial products. The catalyst layers are characterised using X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Among the catalyst layers prepared with PTFE ionomer and tested at 155°C, the in-house catalyst demonstrates the highest ORR activity. Ionomer X proves to be a good candidate to be used as a per- and polyfluoroalkyl-free binder for high-temperature (HT) proton exchange membrane fuel cell (PEMFC) applications.

85 wt% phosphoric acid↗
DOE OSTI2024

Microstructural evaluation of the creep behavior in L-PBF Ni-based superalloys

This presentation at ICAM 2024 Conference focuses on the commonalities and differences in the creep rupture behavior and creep mechanisms for three distinct classes of laser powder-bed fusion (L-PBF) Ni-based superalloys (γ’-precipitate strengthened Haynes® 282®, γ’/γ”/δ-precipitate strengthened Alloy 718, and solid-solution strengthened Alloy 625) as compared to conventionally processed counterparts. A comparison of Larson-Miller parameter plots establishes that these alloys perform statistically within the bounds established for the wrought product, despite having dissimilar microstructural features and other artefacts associated with PBF-LB manufacturing and post-processing heat treatment. To understand the failure and the impact of composition, minor phases, and deformation defects on creep behavior, the fractography has been performed and microstructures have been evaluated in detail with SEM-EDS, EBSD, and HAADF-STEM. The underlying diffusional and dislocation creep mechanisms associated with this microstructural evaluation is discussed. This work is supported by NETL-FWP-1022408 Advanced Turbines.

Sudbrack, Chantal↗