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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly4 increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO 2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly 4 increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO 2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

Oxidative Dehydrogenation of Propane to Propylene with Soft Oxidants via Heterogeneous Catalysis

Oxidative dehydrogenation of propane to propylene can be achieved using conventional, oxygen-assisted dehydrogenation of propane (O 2 –ODHP) or via the use of soft oxidants, such as CO 2 , N 2 O, S-containing compounds, and halogens/halides. The major roles of soft oxidants include inhibiting overoxidation and improving propylene selectivity, which are considered to be current challenges in O 2 -assisted dehydrogenation. For both CO 2 – and N 2 O–ODHP reactions, significant efforts have been devoted to developing redox-active (e.g., chromium, vanadate, iron, etc.), nonredox-type main group metal oxide (e.g., group IIIA, gallium), and other transition metal/metal oxide catalysts (e.g., molybdenum, palladium platinum, rhodium, ruthenium, etc.), as well as zeolite-based catalysts with adjustable acid–base properties, unique pore structures, and topologies. Metal sulfides have shown promising performance in DHP, whereas the development of suitable catalysts has lagged for SO 2 - or S-assisted ODHP. Recently, significant efforts have been focused on homogeneous and heterogeneous ODHP using halogens (e.g., Br 2 , I 2 , Cl 2 , etc.) and hydrogen halides (e.g., HCl and HBr) for the development of facile processes for C 3 H 6 synthesis. This work aims to provide a critical, comprehensive review of recent advances in oxidative dehydrogenation of propane with these soft oxidants, especially highlighting the current state of understanding of the following factors: (i) relationships between composition, structure, and catalytic performance, (ii) effects of the support, acidity, and promoters, (iii) reaction pathway and mechanistic insights, and (iv) the various roles of soft oxidants. Theoretical and computational insights toward understanding reaction mechanisms and catalyst design principles are also covered. Future research opportunities are discussed in terms of catalyst design and synthesis, deactivation and regeneration, reaction mechanisms, and alternative approaches.

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

Exposure of Stainless Steel 316 to Subcritical, Transition, and Near-Supercritical Water

This work investigates the oxidation of austenitic stainless steel 316 at temperatures close to the critical point of water: subcritical water at 330°C and 27 MPa, the transition between subcritical and supercritical water at 374°C and 27 MPa, and supercritical water (SCW) at 380°C and 27 MPa. The surfaces of the samples were characterized using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy before and after exposure. Magnetite (Fe3O4) was found to be present on all surfaces of all samples. The samples exposed to subcritical water also showed the presence of a nickel-iron chromium mixed spinel Ni(Fe2-xCrx)O4. The oxide morphology was observed to vary based on exposure temperature; an increased nucleation and growth rate, and an increased generation of Fe2+ was observed on samples exposed to the transition region and SCW.

Materials Science↗
DOE OSTI2026

High-throughput oxidation screening and down-selection of refractory high entropy alloys in the Al-Cr-Mo-Nb-Ta-Ti system

Rapid experimentation and characterization are ever-present needs in the discovery of high entropy alloys. High entropy alloy systems are difficult to survey with systematic composition sweeps using traditional synthesis methods. The number of distinct compositions in even a four-element system is experimentally intractable. Exploration of these, and higher-element systems, necessitates thermodynamic prediction coupled with an automated sample creation method and a rapid screening methodology to effectively down-select alloys with targeted properties. As a result, a high-throughput method for evaluating the oxidation performance of refractory high entropy alloys was developed and tested. The six-element system of aluminum, chromium, molybdenum, niobium, tantalum, and titanium was evaluated for single phase stability and short-duration oxidation resistance. Target compositions were initially determined via thermodynamic predictions of single-phase stability across a wide temperature range. A twenty-five-sample build plate was produced using directed energy deposition additive manufacturing. After fabrication, the twenty-five 1 cm 3 samples were heat treated and characterized for composition and phase identification. The build plate was exposed to a high temperature oxidizing environment at 1000 °C for three hours. After oxidation, the composition, morphology, and chemistry of the oxides formed were characterized. Of the twenty-five samples produced, nine exhibited a favorable oxidation response, from which a single-phase BCC alloy at a composition of Al 13 Cr 7 Mo 19 Nb 18 Ta 26 Ti 17 was identified as the alloy with the most protective oxidation coating with a thin, adherent oxide scale. Finally, the complete experimental down-selection—from machine setup to final alloy identification—required approximately 45 labor hours, demonstrating a rapid validation for alloy discovery.

Additive manufacturing↗
DOE OSTI2023

The Reductive Leaching of Chalcopyrite by Chromium(II) Chloride for the Rapid and Complete Extraction of Copper

A hydrometallurgical process is developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The unique feature of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite reduction by chromium(II) ion is described for the first time and superior kinetics are shown. At high concentrate loadings of 39, 78, and 117 gL –1 , chalcopyrite reacted completely within minutes at room temperature and pressure. The XRD, SEM-EDS, and XPS measurements indicate that chalcopyrite reacts to form copper(I) chloride (CuCl). After the reductive treatment, the mineral products are leached by iron(III) sulfate to demonstrate the complete extraction of copper. The chromium(II) ion may be regenerated by an electrolysis unit inspired by an iron chromium flow battery in a practical industrial process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis and Physical Properties of Manganese Chromium Nitride Thin Films Grown via Molecular Beam Epitaxy

Here, we demonstrate the ability to grow epitaxial thin films of manganese–chromium nitride (Mn x Cr 1–x N) across the entire composition range on magnesium oxide (MgO) (1 0 0) surfaces by molecular beam epitaxy. By independently controlling the ratio of the atomic fluxes of manganese and chromium, the compositional dependence of structural and electrical transport properties is determined. Soft X-ray absorption shows that the valence states of Cr( 3+ ) and Mn( 3+ ) remain identical among these MnCrN epitaxial films. The metallic transport behavior of binary manganese nitride (MnN) and chromium nitride (CrN) is suppressed in the ternary alloys. Changes in room temperature electrical resistivity of up to 100 times and 5 orders of magnitude at cryogenic temperatures are observed. This work expands the variety of nitride compounds available for epitaxial integration and could provide additional flexibility for the development of metal–semiconductor–insulator junctions for spintronic devices.

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

Carburization behavior of FeCrAl alloy APMT and the critical role of pre-oxidation

The carburization behavior of bare and pre-oxidized APMT has been assessed after long-term graphite exposure at 1000 °C. Bare coupons formed a thick scale after graphite exposure due to carbon interaction and chromium-rich carbides were detected, as predicted from thermodynamic calculations. Additionally, pre-oxidation of APMT was conducted in air, and oxidation kinetics were measured through thermogravimetry. The oxide layer formed at 800 °C failed to prevent carburization. However, increasing the pre-oxidation temperature to 1200 °C produced an oxide layer with good resistance to carbon diffusion indicating that the alpha-alumina formed at high temperatures is key in preventing carburization of the material.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electron microscopy characterization of the fuel-cladding interaction in medium burnup annular fast reactor MOX

In this work, we present electron microscopy data focused on the fuel-cladding interaction layer in annular fast reactor MOX with HT-9 cladding at medium burnup. In agreement with previous literature data, the volatile fission products Cs, Te and I have migrated radially into the extreme fuel periphery and partially interacted with the cladding. The accumulation of Cs has occurred in the outermost rim of the fuel pellet, where grain recrystallization has also been observed. Significant amounts of Pd have been found in the interaction zone, particularly in the sample taken from the upper half of the fissile column where the cladding temperatures are higher. At this axial location, Cr has been enriched at the cladding inner surface and diffused into the fuel. Furthermore, chromium remains mainly in metallic form, but locally formed oxides. The fission products Cs, Te and I are found, with variable composition, in form of nanocrystalline regions dispersed in the metallic Cr-rich layer. The morphology and chemical characteristics of the layer suggest a non-oxidative corrosion mechanism as principal cladding degradation phenomenon occurring in this sample, with local onset of Cr oxidation within the nanocrystalline precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Chromium and Vanadium Incorporation in Sulfate-Containing Sodium Aluminoborosilicate Glass

In the composition space for Hanford low-activity nuclear waste glass, the waste loading of some formulations is limited by poor incorporation of sulfate. In particular, certain elements identified in previous studies tend to raise or lower sulfate solubility in borosilicate glass. The aim of the current study is to understand how vanadium and chromium each affect a sulfate-containing sodium aluminoborosilicate glass structure. Glass transition temperature, mass density, visible absorption, and Raman scattering were measured to investigate changes in the glass structure. Both Cr6+ (CrO42-) and Cr3+ were found in the chromium-containing glasses while vanadium primarily existed in the 5+ oxidation state in the vanadium-containing glasses. Electron probe microanalysis determined elemental compositions to assess retention of components. Increasing Cr2O3 caused saturation of Cr concentration within the glass and formation of crystalline eskolaite (Cr2O3). On the other hand, all the targeted V was incorporated into the glass. A fraction of batched S was not incorporated in any glass, presumably due to volatilization during melting. Apparently, the details of incorporation of Cr, and to an extent V, are different depending on whether sulfur is added as in this study or in oversaturated conditions as described in the literature, where Cr partitions to a sulfate-containing salt phase.

Borosilicate glass, Waste Glass, vanadium chemistr↗
DOE OSTI2025

The impact of chromium coatings on Zircaloy cladding deformation behavior under reactivity-initiated accident-like mechanical loading conditions

A reactivity-initiated accident (RIA) occurs when a control rod ejection or control blade drop causes an increase in the fission rate. The injection of energy results in an increase in fuel temperature which in turn causes rapid thermal expansion of the fuel pellet. This thermal expansion may result in pellet-cladding mechanical interaction (PCMI) in which the fuel imparts a mechanical strain to the cladding. PCMI may cause the cladding to fail, and thus, the mechanical response of cladding due to PCMI must be investigated when characterizing new cladding materials. Chromium-coated Zircaloy-4 is a near-term accident-tolerant fuel cladding that exhibits improved high-temperature oxidation resistance. Modified burst testing was utilized to experimentally simulate the effects of PCMI on both uncoated and chromium-coated Zircaloy cladding samples at hot zero power conditions. Samples were coated using either cold spraying or physical vapor deposition to understand the differences in behavior that the coating application method may cause. Digital image correlation was used to analyze images of the deforming specimens to extract the in-situ strain behavior of the cladding. The uncoated specimens burst at hoop strains ranging from 8.8 % to 17.2 %. The cold-spray chromium-coated Zircaloy specimens burst at hoop strains of 7.0 % to 11.0 %. The physical vapor deposition coated tubes burst at hoop strains of 9.1 % to 11.5 %. These results indicate that the chromium coating causes a loss in the ductility of the cladding. Furthermore, the higher burst hoop strains of the physical vapor deposition-coated samples relative to the cold-spray samples indicate that the cold-spraying technique causes more of a loss in ductility than physical vapor deposition. All samples burst at higher hoop strains than those expected to occur in an RIA for fresh cladding.

Accident-tolerant fuel↗
DOE OSTI2024

Enhanced Mechanical Properties and Wear Resistance of FeCrAl Alloys at ~ 300°C and Higher Temperatures

Abstract Worldwide, light water reactors (LWRs) have been using zirconium (Zr)-based alloys for the cladding of the uranium dioxide fuel for more than 6 decades. Zr alloys oxidize rapidly in the presence of water and steam at temperatures > 450°C; therefore, they do not respond well to scenarios of loss of coolant accidents. There is a global effort by nuclear materials technologists to find more robust or stronger cladding materials for LWRs. One option is to use an iron-chromium-aluminum (FeCrAl) alloy since they have excellent resistance to high temperature oxidation and superior mechanical properties at LWR operation temperatures. Results show that (1) FeCrAl alloys have better mechanical properties than Zr alloy and are orders of magnitude more resistant to creep at temperatures higher than LWR normal operation conditions. (2) FeCrAl alloys have better resistance to fretting wear than Zr alloys at the normal operation conditions of LWRs.

Materials Science↗
DOE OSTI2025

Hydrogen and water interactions with CrMnFeCoNi alloy from density functional theory calculations

High entropy alloys (HEAs) are a promising class of materials with remarkable mechanical and catalytic properties. Among these, the quinary CrMnFeCoNi alloy (also called “Cantor alloy”) has attracted considerable attention given its thermodynamic stability and remarkable mechanical properties under different temperatures. Given that various degradation mechanisms involve multiple contaminants, such as hydrogen and water in hydrogen embrittlement and surface poisoning, respectively, understanding their interactions with the Cantor alloy is critical for its practical applications as structural, nuclear, or hydrogen storage material. In this work, we perform first-principles calculations based on Density Functional Theory (DFT) to investigate such interactions when considering various microstructures, including bulk materials and those containing certain defects, such as grain boundaries, stacking faults, and vacancies. We also employ Global Sensitivity Analysis to identify the importance of different factors in the stability of the impurities. We find that the accuracy of the H formation energy is significantly affected by spin polarization and chemical short-range order. The study also identifies a strong tendency for hydrogen interstitials to segregate to Σ5(210)/[001] symmetric tilt grain boundary, even when H concentrations are high, suggesting that a certain type of grain boundaries acts as H sinks within the alloy. Further, this result is reinforced by the low formation energy of vacancy-hydrogen complexes, which can contain multiple hydrogen atoms. Finally, the surface reactivity analysis reveals that the adsorption energy of oxygen and hydroxyl groups is highly sensitive to the specific metal atom involved in the binding, with a clear preference for chromium atoms, which could have implications for the alloy’s oxidation and corrosion behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Elucidating the impact of stress states on grain boundary passivation in Ni-5Cr using the Rhines pack method

The oxidation behavior of a Ni–5Cr (at.%) alloy was evaluated at 420 ° C using the Rhines pack method and simultaneous tensile and compressive stress states via a miniature four-point bending fixture. At this moderate temperature, grain boundaries dominate mass transport and the resulting oxidation response. Oxidation produced approximately 1μ⁢m-wide protective Cr 2 O 3 films capping some grain boundaries and penetrative, intergranular Cr-rich oxides at other grain boundaries. Externally applied tensile and compressive stress during oxidation increased the prevalence of Cr 2 O 3 cap formation compared to no applied stress, with tensile stress resulting in more Cr 2 O 3 caps than compressive stress. The observed oxide cap morphology was similar across all test conditions. Regions under compressive stress showed an order of magnitude greater Cr depletion depth along the grain boundary. Chromium nitrides (CrN), likely from N contamination of the Rhines pack cell, were observed both at the oxide–metal interface and intergranularly within the alloy. Collectively these results demonstrate that applied stress promotes localized protective oxide cap formation over grain boundaries, with compressive stress additionally promoting deeper Cr depletion. Furthermore the experimental approach helped separate out the effects of stress on local oxide formation and grain boundary passivation.

4 point bend↗
DOE OSTI2025

Supported Single‐Atom Manganese Catalysts for the Trimerization of Ethylene

Selective ethylene oligomerization via oxidative cyclization, forming metallacyclic intermediates, is typically catalyzed by molecular titanium and chromium complexes to produce butenes, hexenes, or octenes, depending on the supporting ligand framework. However, this mechanism requires significant electron density at the metal active site and is not known to be generalizable to other first-row transition metals. In this work, we computationally investigate the electronic modulation of five transition metals (Mn, Fe, Co, Ni, and Cu) supported on titania (TiO₂) through reductive lithium intercalation to promote selective oligomerization via oxidative cyclization, using density functional theory (DFT). Our findings predict that Mn/LiTiO₂ exhibits high catalytic activity due to the exergonic nature of oxidative cyclization with two ethylene molecules. Additionally, lithium titanate (LiTiO₂) supports enhance catalytic performance compared to TiO₂. Experimental validation confirms that Mn/LiTiO₂ achieves higher conversion rates and improved selectivity toward hexene (C₄:C₆ = 1:2.6). The enhanced activity is attributed to lithiation, which alters the electronic environment around Mn active sites. Mechanistic studies reveal that the formation of a seven-membered ring, a key intermediate for hexene formation, is more favorable on LiTiO₂ than TiO₂. This work provides the first evidence of Mn catalyzing selective ethylene oligomerization via oxidative cyclization in either homogeneous or heterogeneous catalysis.

Kim, Yu Lim [Argonne National Laboratory (ANL), Ar↗
DOE OSTI2021

In Situ Growth and Interlayer Modulation of Layered Double Hydroxide Thin Films from a Transparent Conducting Oxide Precursor

Layered double hydroxides (LDHs) are a class of cationic-layered solids that can be synthetically designed for a variety of advanced functions. Facile thin film growth of LDHs is an important requisite for a variety of applications including functional coatings, displays, and sensing. In this work we demonstrate, for the first time, an in-situ and patternable thin film synthesis of interconnected Zn-Cr LDH particles from a transparent conducting oxide (TCO) precursor, aluminum-doped zinc oxide (AZO), at room temperature within minutes. Synthetic parameters such as chromium (III) nitrate concentration, solvent composition, and reaction time were found to significantly affect the thickness and morphology of the resulting LDH films. These LDH thin films can undergo interlayer anion exchange, which modulates the interlayer distance of the LDH sheets and surface energy of the thin film. Replacement of the interlayer anion with perfluorooctanoate increases the interlayer sheet distance from 0.9 nm to 2.8 nm and induces a super-hydrophobic thin film that is capable of adsolubilizing and retaining organic guest molecules. The synthetic method and structural analysis of the LDH thin films introduced in this work opens new avenues of application for LDH films.

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

Optimizing chemistry for designing oxidation resistant FeCrAl alloys

Abstract Traditionally, FeCrAl alloys played an important role in high-temperature applications due to their ability to form a passive Al oxide film at temperatures above ~ 800 °C. Recently, FeCrAl alloys became of interest for the application of accident tolerant nuclear fuel cladding. This study covers work done at GE Research for better understanding the role of Al, Cr, and Mo in oxidation kinetics and thermodynamics. Several models and commercial prototype alloys have been tested in hydrothermal corrosion autoclave loops, at low temperature steam exposure (~ 400 °C), high temperature steam exposure (~ 1000 °C or higher), and high temperature air exposures. The results provide insights on how chromium and aluminum play a significant role in both high temperature and low temperature oxidation of FeCrAl. Additionally, machine learning tools are used to gain further insights on both predicting future optimized chemistries for balancing the properties of hydrothermal corrosion, low and high temperature steam oxidation, and thermal aging (which is exacerbated due to radiation in a nuclear reactor environment). GE plans to use this framework to further optimize the FeCrAl alloy system for use in nuclear reactor environments. Graphical abstract

Roy, Indranil (ORCID:0000000336124323)↗
DOE OSTI2025

Accelerated and heterogeneous corrosion of Cr-doped uranium nitride fuel pellets

The steam oxidation of Cr-doped UN fuel pellets is analyzed during sequential isothermal holds up to 720 °C. In situ neutron diffraction results show how Cr is accommodated in a secondary U 2 CrN 3 phase, leading to the formation of a duplex UN/U 2 CrN 3 microstructure. Under corrosion, the oxidation of the two phases begins at 400 °C for UN and 430 °C for U 2 CrN 3 , respectively. Because the UN phase is preferentially oxidized in the presence of U 2 CrN 3 , addition of Cr in UN based nuclear fuel is found to accelerate the corrosion rate. At 430 °C the oxidation of UN in the UN/U 2 CrN 3 microstructure is ~ 5 times faster than pure UN, increasing to ~19 times faster at 460 °C. The oxidation of U 2 CrN 3 produces UO 2 via the formation of two transient intermediate phases. In situ neutron diffraction enables oxidation processes of UN and U 2 CrN 3 components to be followed separately within the two-phase system.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗