FUTURE Publications

FUTURE Only

Publications for which the FUTURE EFRC was the only source of funding.

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A multimodal approach to revisiting oxidation defects in Cr2O3

R. Auguste, H. L. Chan, E. Romanovskaia, J. Qiu, R. Schoell, M. O. Liedke, M. Butterling, E. Hirschmann, A. G. Attallah, A. Wagner, F. A. Selim, D. Kaoumi, B. P. Uberuaga, P. Hosemann, and J. R. Scully
NPJ Materials Degradation (2022). DOI: 10.1038/s41529-022-00269-7

The mechanism behind the high radiation tolerance of Fe-Cr alloys

S. Agrawal, M. Butterling, M. Liedke, K. Yano, D. Schreiber, A. Jones, B. Uberuaga, Y.Q. Wang, M. Chancey, H. Kim, B. Derby, N. Li, D.J. Edwards, P. Hosemann, D. Kaoumi, E. Hirschmann, A. Wagner, F. Selim
Journal of Applied Physics (2022). DOI:10.1063/5.0085086

Insights on the corrosion thermodynamics of chromium in molten LiF-NaF-KF salts

H. Chan, E. Romanovskaia, J. Qiu, P. Hosemann, J. Scully
NPJ Materials Degradation (2022). DOI: 10.1038/s41529-022-00267-9

Microstructural dependence of defect formation in iron-oxide thin films

B. Derby, S. Mills, S. Agrawal, J. Valdez, J. Baldwin, M. Schneider, A. Minor, B. Uberuaga, F. Selim, N. Li
Applied Surface Science (2022). DOI:10.1016/j.apsusc.2022.152844

Adatom-driven oxygen intermixing during the deposition of oxide thin films by molecular beam epitaxy

T. Kaspar, P. Hatton, K. Yano, S. Taylor, S. Spurgeon, B. Uberuaga, D. Schreiber
Nano Letters (2022). DOI: 10.1021/acs.nanolett.2c01678

Constant-Potential Molecular Dynamics Simulations of Molten-Salt Double Layers for FLiBe and FLiNaK

L. Langford, N. Winner, A. Hwang, et al.
The Journal of Chemical Physics (2022). DOI: 10.1063/5.0097697

Surprisingly high irradiation-induced defect mobility in Fe3O4 as revealed through in situ Transmission Electron Microscopy

M. Owusu-Mensah, J. Cooper, A. Morales, K. Yano, S. Taylor, D. Schreiber, B. Uberuaga, D. Kaoumi
Materials Characterization (2022). DOI: 10.1016/j.matchar.2022.111863

FUTURE Primary

Publications for which the FUTURE EFRC was the primary source of funding.

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Development of a pulsed, variable-energy postiron beam for atomic scale defect studies

A. C. L. Jones, R. G. Greaves, C. L. Codding, F. A. Selim
Review of Scientific Instruments (2022). DOI:10.1063/5.0077750

The effect of Cr alloying on defect migration at grain boundaries

B. P. Uberuaga, P. Simonnin, K. M. Rosso, D. K. Schreiber, M. Asta
Journal of Material Science (2022). DOI: 10.1007/s10853-021-06590-x

FUTURE Secondary

Publications for which the FUTURE EFRC was a secondary source of funding.

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Investigation of the Fatigue Crack Behavior of 304 Stainless Steels using Synchrotron X-ray Tomography and Diffraction: Influence of the Martensite Fraction and Role of Inclusions

R. Schoell, L. Xi, H. West, P. Hosemann, J.S. Park, P. Kenesei, J. Almer, Z. Shayer, D. Kaoumi
Materials Characterization (2022). DOI: 10.1016/j.matchar.2022.111903

FUTURE Only

Publications for which the FUTURE EFRC was the sole source of funding.

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Helium Bubble Nucleation and Growth in Alloy HT9 through the use of In Situ TEM: Sequential He-Implantation and Heavy-Ion Irradiation versus Dual-Beam Irradiation

K. Duemmler, C. Zheng, C. Baumier, A. Gentils, D. Kaoumi
Journal of Nuclear Materials 545, 152641 (2021).
DOI: 10.1016/j.jnucmat.2020.152641

• What we did: For the first time, we used in-situ dual ion beam irradiation in a TEM to investigate the formation of He bubbles in Ferritic/Martensitic steel HT9 using concomitant He implantation and heavy ion irradiation.
• What we learned: We found that the larger the helium/dpa ratio, the larger the bubble density and the smaller the size of the bubbles. Further, the role of He as a nucleant depends on whether ion irradiation was done in parallel or sequentially.
• Why it matters: This work emphasizes the need to examine synergistic effects in extreme environments.

Distinguishing interfacial double layer and oxide-based capacitance using gold and pre-oxidized Fe and Fe-Cr in 1-ethyl-3-methylimidazolium methanesulfonate room temperature ionic liquid aqueous mixture

J. Han, H. L. Chan, M. G. Wartenberg, H. H. Heinrich, J. R. Scully
Electrochemistry Communication 122 106900 (2021).
DOI: 10.1016/j.elecom.2020.106900

• What we did: The objective of this work is to verify an experimental protocol to successfully determine the oxide capacitance and double layer capacitance in a non-aqueous environment. Several electrochemical methodologies to distinguish these two have been proposed; however, it has not been demonstrated in non-aqueous cases, such as room temperature ionic liquid.
• What we learned: We have verified that EIS using a power-law model can be used to determine the oxide capacitance. The measured oxide capacitance was used to calculate the oxide thickness assuming a dielectric layer, then verified with ex-situ TEM analysis. The double layer capacitance also could be obtained from the same EIS spectra at low-frequency domain.
• Why it matters: Determining and measuring the capacitance is relatively well understood in aqueous media. However, in non-aqueous cases such as ionic liquids and molten salts, it was not certain whether a direct comparison using the same methodology as in aqueous solution was possible. We have demonstrated that the EIS analysis may be applied to distinguish the capacitance values in a representative room temperature ionic liquid.

Electrochemical stability, physical and electronical properties of thermally pre-formed oxide compared to artificially sputtered oxide on Fe thin films in aqueous chloride

J. Han, M. G. Wartenberg, H. L. Chan, B. K. Derby, N. Li, J. R. Scully
Corrosion Science, 109456 (2021). DOI: 10.1016/j.corsci.2021.109456

• What we did: In this paper, we compared the stability of oxide that is thermally oxidized and iron oxide sputtered deposited on a pure Fe substrate.
• What we learned: We found that the sputtered iron oxide exhibits superior resistance to pitting and oxide dissolution in the presence of chloride at both low and high pH when compared to the thermal oxides.
• Why it matters: Understanding exposure aging and chemical stability of these oxide films is of great interest for long term utilization of reactor components. This project allows us to understand if synetic oxides can be good surrogates for thermal oxides in harsh environments.

Neutron irradiation induced defects in oxides and their impact on the oxide properties

M. Haseman, C. B. Somodi, P. Stepanov, D. E. Wall, L. A. Boatner, P. Hosemann, Y. Q. Wang, B. P. Uberuaga, F. A. Selim
Journal of Applied Physics, 215901 (2021). DOI: 10.1063/5.0046292

Bulk and short-circuit anion diffusion in epitaxial Fe2O3 films quantified using buried isotopic tracer layers

T. C. Kaspar, S. D. Taylor, K. H. Yano, T. G. Lach, Y. Zhou, Z. Zhu, A. A. Kohnert, E. K. Still, P. Hosemann, S. R. Spurgeon, D. K. Schreiber
Applied Materials Interfaces, 2001768 (2021). DOI: 10.1002/admi.202001768

• What we did: We synthesized Fe2O3 films with an isotopic tracer layer enriched in 18O, and characterized in 3D the redistribution of this tracer in the lattice and along defects with atom probe tomography (APT).
• What we learned: We made the first semi-quantitative measurement of oxygen diffusion along a structural defect in Fe2O3, and found that it exhibits 104 times higher anion diffusivity than through the pristine lattice.
• Why it matters: 3D visualization of isotopic tracer transport is a cutting-edge methodology we have developed to quantify diffusion and transport in solids. Our study uses precisely synthesized model systems to reveal new details of thermal diffusion pathways. This methodology and the results we obtained will underpin future studies of transport occurring during corrosion and irradiation.

Electrochemical study of the dissolution of oxide films grown on Type 316L stainless steel in molten fluoride salt

J. Qiu, D. D. Macdonald, R. Schoell, J. Han, S. Mastromarino, J. Scully, D. Kaoumi, P. Hosemann
Corrosion Science, 109457 (2021). DOI: 10.1016/j.corsci.2021.109457

• What we did: We employed electrochemical methods to investigate the corrosion behavior of oxide films grown on Type 316L stainless steel in molten FLiNaK salt. The oxide dissolution rate and process in high temperature molten fluoride salt was discussed.
• What we learned: The oxide film formed on Type 316L SS is unstable and can only temporarily protect materials from corrosion in molten FLiNaK salt. The oxide dissolution rate is approximately 0.0017 μm/h at 700 oC in molten FLiNaK salt according to the EIS. After the oxide film dissolved, the Cr and Fe were selective dealloying from the steel and lead to intergranular corrosion of Type 316L SS in molten fluoride salt.
• Why it matters: In most high temperature corrosive environments, such as high temperature aqueous, supercritical water, liquid metal etc., alloys derive their corrosion resistance from the formation of a continuous and compact protective oxide film on the surface of the materials. However, the protective oxide films are inherently thermodynamic unstable in molten fluoride salts. Using EIS to study the electronic properties of the oxide films that form on Type 316L SS is of fundamental interest in determining the dissolution rate and ensuring the safe application of Type 316L SS in molten fluoride salts.

Continuous Monitoring of Pure Fe Corrosion in Lead-Bismuth Eutectic Under Irradiation with Proton-Induced X-ray Emission Spectroscopy

F. Schmidt, M. Chancey, H. Kim, Y. Q. Wang, P. Hosemann
JOM (2021). DOI: 10.1007/s11837-021-04954-x

Effects of Radiation-Induced Defects on Corrosion

F. Schmidt, P. Hosemann, R.O. Scarlat, D.K. Schreiber, J.R. Scully, B.P. Uberuaga
Annual Review of Materials 51 (2020). DOI: 10.1146/annurev-matsci-080819-123403

• What we did: We reviewed simultaneous irradiation-corrosion studies on steels and Zircaloy in three different corrosive environments (water, lead-bismuth eutectic, and molten fluorides) that focus on how radiation-induced defects impact the corrosion process.
• What we learned: Effects of radiation-induced point defects on corrosion have been observed, but are difficult to separate from other environmental effects, and so mechanistic explanations for these processes are often incomplete.
• Why it matters: No similar review combining and comparing information about these three environments previously existed in the literature. This review identifies key gaps in our knowledge regarding the synergies between irradiation and corrosion.

Positron annihilation spectroscopy of defects in nuclear and irradiated materials - a review

F. A. Selim
Materials Characterization 174 110952 (2021).
DOI: 10.1016/j.matchar.2021.110952

• What we did: We described the fundamentals of positron annihilation spectroscopy (PAS), reviewed PAS studies of nuclear and irradiated materials, and discussed how to advance PAS techniques to reach their full capability in radiation damage studies.
• What we learned: Through the last decades PAS has been very effective in revealing important mechanisms in defect kinetics and radiation damage. Significant attention is currently directed to facilitate the quantitative analysis of atomic scale defects by PAS.
• Why it matters: The review provides to the nuclear materials and radiation damage communities a guide to facilitate applications of PAS in novel material systems and materials under extreme environments.

Alpha Shape Analysis (ASA) Framework for Post Clustering Property Determination in Atom Probe Tomographic Data

E. Still, D. K. Schreiber, J. Wang, P. Hosemann
Microscopy and Microanalysis (2021). DOI: 10.1017/S1431927620024939

• What we did: We designed a post-clustering analysis method to determine the volume, surface areas, and composition of concave features observed in APT data.
• What we learned: Point based meshing techniques can be used to classify features within APT data as concave or convex while generating additional useful statistics to describe local ionic enrichment.
• Why it matters: The proposed framework leverages point based meshing to combine the spatial fidelity of cluster searches when searching for features on the order of the APT voxel size with diagnostics that are not directly accessible by conventional search methods.

Ab-Initio Simulation Studies of Cr Solvation in Fluoride Molten Salts

N. Winner, H. Williams, R. Scarlat, M. Asta
Journal of Molecular Liquids 335 116351 (2021). DOI: /10.1016/j.molliq.2021.116351

Radiation Enhanced Anion Diffusion in Chromia

K. H. Yano, A. A. Kohnert, T. C. Kaspar, S. D. Taylor, S. R. Spurgeon, H. Kim, Y. Wang, B. P. Uberuaga, D. K. Schreiber
Journal of Physical Chemistry (2021). DOI: 10.1021/acs.jpcc.1c08705

FUTURE Primary

Publications for which the FUTURE EFRC was the primary source of funding.

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Interplay between defect transport and cation spin frustration in corundum-structured oxides

A. Banerjee, A. A. Kohnert, E. F. Holby, B. P. Uberuaga
Physical Review Materials 5, 033410 (2021).
DOI: 10.1103/PhysRevMaterials.5.034410

• What we did: Using density functional theory, we examine the migration of cation interstitials in corundum-structures oxides, including Cr2O3 and Fe2O3.
• What we learned: The migration of cation interstitials is sensitive to the chemistry, with much faster migration in Fe2O3 and Al2O3 than Cr2O3. Further, it is very anisotropic, with fast migration along the c axis of the crystal. Most importantly, we find that the interstitial leaves behind magnetic spin defects as it migrates, which in turn impacts the energy landscape for migration.
• Why it matters: Understanding cation transport in these oxides is absolutely critical for developing predictive models of oxidation growth and radiation damage evolution under reactor conditions.

Defect Characterization Using Positron Annihilation Spectroscopy on Laser-Ablated Surfaces

P. Hosemann, R. Auguste, S. Lam, M. Butterling, M. O. Liedke, A. G. Attallah, E. Hirschmann, A. Wagner, C. P. Grigoropoulos, F. A. Selim, B. P. Uberuaga
JOM (2021). DOI: 10.1007/s11837-021-04965-8

Correlative STEM-APT characterization of radiation-induced segregation and precipitation of in-service BWR 304 stainless steel

T. G. Lach, M. J. Olszta, S. D. Taylor, K. H. Yano, D. J. Edwards, T. S. Byun, P. H. Chou, D. K. Schreiber
Journal of Nuclear Materials 549, 152894 (2021).
DOI: 10.1016/j.jnucmat.2021.152894

• What we did: Directly correlated STEM and APT analyses were used to describe the radiation-induced segregation (RIS) and precipitation (RIP) behavior in a 304 stainless steel that was removed from service in a BWR reactor.
• What we learned: Direct quantitative comparison of RIS between STEM EDS and APT show that STEM EDS can potentially misrepresent the true RIS concentration and segregation profile at the grain boundary. This was ascribed to beam broadening effects, the magnitude of which changes with sample thickness.
• Why it matters: RIS and RIP are important microstructural changes that accompany radiation in many structural alloys. In the context of intergranular stress corrosion cracking, RIS of specific detrimental species (e.g., Si) is believed to enhance SCC susceptibility, but tremendous scatter exists in the literature for the magnitude of RIS. By directly comparing STEM EDS and APT measurements, we show that the apparent magnitude and profile shape of the effect can be quantitatively different, and care must be taken to consider artifacts introduced by sample geometry and analysis method.

Light driven permanent transition from insulator to conductor

D. Rana, S. Agarwal, M. Islam, A. Banerjee, B. P. Uberuaga, P. Saadatkia, P. Dulal, N. Adhikari, M. Butterling, M. O. Liedke, A. Wagner, F. A. Selim
Physical Review B 104 245208 (2021).
DOI: 10.1103/PhysRevB.104.245208

Radiation-Enhanced Anion Transport in Hematite

K. H. Yano, A. A. Kohnert, A. Banerjee, D. J. Edwards, E. F. Holby, T. C. Kaspar, H. Kim, T. G. Lach, S. D. Taylor, Y. Q. Wang, B. P. Uberuaga, D. K. Schreiber
Chemistry of Materials (2021). DOI: 10.1021/acs.chemmater.0c04235

• What we did: Using atom probe tomography and chemical rate theory models informed by density functional calculations, we probe radiation-enhanced diffusion of oxygen in hematite and compare it to a thermal case in the absence of radiation.
• What we learned: Radiation enhances the diffusion of oxygen by at least a few orders of magnitude. Even more important, we find a likely transition from a vacancy-mediated to an interstitial-mediated mechanism at temperatures at the end of the experimental ranges, providing new insight into the transport properties of this important material.
• Why it matters: Transport, either thermally or under irradiation, is the critical property that drives corrosion. Further, evolution under radiation is dictated by defect migration. This work provides a new perspective on transport in hematite that helps reconcile past experimental studies and inform future models of radiation damage evolution and corrosion.

FUTURE Secondary

Publications for which the FUTURE EFRC was a secondary source of funding.

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Thermal Energy Transport in Oxide Nuclear Fuel

F. Hurley, A. El-Azab, M. Bryan, M. Cooper, C. Dennett, K. Gofryk, L. He, M. Khafizov, G. Lander, M. Manley, J. Mann, C. Marianetti, K. Rickert, F. Selim, M. Tonks, J. Wharry
Chemical Reviews (2021). DOI: 10.1021/acs.chemrev.1c00262

FUTURE Only

Publications for which the FUTURE EFRC was the sole source of funding.

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A New Mechanism for Void-Cascade Interaction from Non-destructive Depth-resolved Atomic-scale Measurements of Ion Irradiation-induced Defects in Fe

S. Agarwal, M. O. Liedke, A. C. L. Jones, E. M. Reed, A. A. Kohnert, B. P. Uberuaga, Y. Q. Wang, J. Cooper, D. Kaoumi, N. Li, R. Auguste, P. Hosemann, L. Capolungo, D. J. Edwards, M. Butterling, E. Hirschmann, A. Wagner, F. A. Selim
Science Advances 6, eaba8437 (2020). DOI: 10.1126/sciadv.aba8437

• What we did: We used both positron annihilation spectroscopy and transmission electron microscopy to characterize the defects in porous Fe films irradiated to low doses.
• What we learned: The initial pores interact with the collision cascades, causing them to shrink but facilitating the formation of small vacancy clusters.
• Why it matters: This work provides new insight into how pre-existing damage and microstructure modify damage production mechanisms during irradiation.

Measurement and simulation of vacancy formation in 2 MeV self-irradiated pure Fe

R. Auguste, M. O. Liedke, F. A. Selim, B. P. Uberuaga, A. Wagner, P. Hosemann
Journal of Materials 72, 2436 (2020). DOI: 10.1007/s11837-020-04116-5

• What we did: We simulated the potential for in situ positron studies to reveal unique insight into the defect structure of ion-irradiated Fe.
• What we learned: We found that the most mobile defects that are swept away before ex situ measurements can capture them would be detectable by positrons during in situ irradiations, paving the way for new understanding of the defect content of irradiated materials.
• Why it matters: In many cases, irradiation occurs concurrently with other extreme environments and the in situ defect content is what will drive synergistic evolution. By being able to measure that in situ defect content, we will be better able to understand the synergies between e.g., irradiation and corrosion.

Chemical manipulation of hydrogen induced high p-type and n-type conductivity in Ga2O3

M. M. Islam, M. O. Liedke, D. Winarski, M. Butterling, A. Wagner, P. Hosemann, Y. Wang, B. P. Uberuaga, F. A. Selim.
Scientific Reports 10, 6134 (2020). DOI: 10.1038/s41598-020-62948-2

• What we did: Using a combination of positron annihilation spectroscopy and density functional theory calculations, we examined the changes in conductivity induced in a wide band gap material, Ga2O3, as a function of the hydrogen content in the material.
• What we learned: The conductivity of Ga2O3 changes by many orders of magnitude and from p-type to n-type as the hydrogen content changes, providing one possible route to tune the conductivity of materials for advanced applications.
• Why it matters: Understanding how the fundamental properties of materials changes with dopant content is critical for developing models of defect evolution. This work demonstrates how a combination of positron annihilation spectroscopy and computational modeling can be used to provide new insight into that defect structure.

An electrochemical impedance spectroscopic study of oxide films in liquid metal

J. Qiu, D. D. Macdonald, N. Li, R. Schoell, D. Kaoumi, P. Hosemann
Journal of Materials 72, 2082 (2020). DOI: 10.1007/s11837-020-04120-9

• What we did: We measured the impedance properties of three kinds of oxide films (anodic titanium oxide films, deposited Fe2O3 films and thermally oxidized Fe) in liquid metal.
• What we learned: Electrochemical impedance spectroscopy (EIS), a standard method for probing the properties of corrosive scales, is related to the oxide film thickness in liquid metal. To effectively use EIS methods in liquid metals, the oxide film should be thicker than 200nm without cracks.
• Why it matters: This work tells us that EIS could be used in liquid metal systems as an insitu method to monitor the electrochemical behavior of oxide film, and provides necessary background to use it as an in situ diagnostic tool.

Electrical Properties of thick Oxide scales on pure iron in liquid lead-bismuth eutectic

J. Qiu, J. Han, R. Schoell, M. Popovic, E. Ghanbari, D. Kaoumi, J. R. Scully, D. D. Macdonald, P. Hosemann
Corrosion Science 176, 109052 (2020). DOI: 10.1016/j.corsci.2020.109052

• What we did: We measured the impedance properties of thermally-oxidized Fe in liquid
  lead-bismuth eutectic (LBE), and discussed the effect of oxide scale structure on the
  impedance behavior of the oxide in liquid metal.
• What we learned: The impedance response of oxidized iron in liquid metal is sensitive to the integrity, thickness and defect density of the oxide scales. The resistance increases with increasing the oxidation temperature or time, due to the formation of a thicker scale
  and fewer defects.
• Why it matters: This study shows both the opportunities and challenges of using EIS to
  understand the properties of oxide scales in liquid metal environments and establishes a
  baseline for interpreting future EIS measurements.

FUTURE Primary

Publications for which the FUTURE EFRC was the primary source of funding.

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Critical Assessment of the Thermodynamics of Vacancy Formation in Fe2O3 Using Hybrid Density Functional Theory

A. Banerjee, A. A. Kohnert, E. F. Holby, B. P. Uberuaga
The Journal of Physical Chemistry C 124, 23988 (2020).
DOI: 10.1021/acs.jpcc.0c07522

• What we did: We examined the behavior of both Fe and O vacancies in Fe2O3 as a function of the exchange correlation functional in density functional theory.
• What we learned: The HSE06 hybrid functional predicts significantly different behavior for the properties of vacancies in hematite compared to GGA and GGA+U methods and provides an overall better description of the material.
• Why it matters: Knowing the properties of defects is fundamental to understandingradiation damage and corrosion and these results highlight the need for accurate theoretical treatments for reliable predictions.

A Pathway to Synthesizing Single-crystal Fe and FeCr Films

B. Derby, J. Cooper, T. Lach, E. Martinez, H. Kim, J.K. Baldwin, D. Kaoumi, D.J. Edwards, D.K. Schreiber, B.P. Uberuaga, N. Li
Surface and Coatings Technology 403, 126346 (2020).
DOI: 10.1016/j.surfcoat.2020.126346

• What we did: We used physical vapor deposition, transmission electron microscopy, and accelerated molecular dynamics simulations to synthesize and understand the growth of single crystal Fe and FeCr films.
• What we learned: The growth of epitaxial Fe films depends on the substrate temperatureand bias during deposition and, when the Fe films are alloyed with Cr, higher substrate temperatures and bias are needed due to lower adatom mobility.
• Why it matters: This work allows for the control over the structure and morphology of Fe and Fe-alloyed films, which are model systems for nuclear steels, used to understand fundamental mechanisms of irradiation and corrosion.

Cryogenic Stress-Driven Grain Growth Observed via Microcompression with in situ
Electron Backscatter Diffraction

D. Frazer, J. L. Bair, E. R. Homer, P. Hosemann
Journal of Materials 72, 2051 (2020). DOI: 10.1007/s11837-020-04075-x

• What we did: We developed an in situ microcompression testing capability and applied it to the deformation of Cu.
• What we learned: By keeping samples at in-situ conditions, stress-driven grain growth, consistent with previous predictions, was observed, as opposed to different mechanisms of deformation when ex situ measurements are performed.
• Why it matters: Measurements in-situ, or under the conditions of interest, are critical for revealing key mechanisms of irradiation, corrosion, and/or deformation. This work highlights the need for in situ capabilities, such as those being developed by FUTURE.

Computational Thermodynamics: Application to Nuclear Materials

C. Gueneau, B. Sundman, M. Asta
Comprehensive Nuclear Materials (Second Edition) 1, 814 (2020).
DOI: 10.1016/B978-0-12-803581-8.12054-5

• What we did: We provide an overview of how computational thermodynamics methods are applied to the study of nuclear materials, reviewing approaches to understand phase equilibria and atomic scale methods to inform those models.
• What we learned: While computational thermodynamics approaches are critical for understanding the complex materials systems in reactors, they depend on accurate thermodynamic quantities. While atomistic approaches can provide some of those values, it is critical to expand experimental capabilities to both validate models and provide data that is challenging to obtain by other methods.
• Why it matters: Understanding the phase structure in the complex materials comprising nuclear reactor systems is critical for predicting performance and ensuring safety. This review highlights computational approaches to understanding that phase structure.

Kinetics of Crystallization and Orientational Ordering in Dipolar Particle Systems

X.-Q. Xu, B. B. Laird, J. J. Hoyt, M. Asta, Y. Yang
American Chemical Society (2020).
DOI: 10.1021/acs.cgd.0c01152

FUTURE Secondary

Publications for which the FUTURE EFRC was a secondary source of funding.

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Corrosion characteristics of typical Ni-Cr alloys and Ni-Cr-Mo alloys in supercritical water: A review

S. Guo, D. Xu, Y. Liang, Y. Li, J. Yang, G. Chen, D. Macdonald
Industrial & Engineering Chemistry Research 59, 18727 (2020).
DOI: 10.1021/acs.iecr.0c04292

• What we did: In this work, the corrosion characteristics and mechanisms of Ni-based, corrosion-resistant alloys in sub- and super-critical water are reviewed and analyzed systematically.  
• What we learned: Cr is the most important element in improving the general corrosion resistance of Ni-based alloys, but Mo can strongly improve the pitting corrosion and crevice corrosion resistances of Ni-based alloys.
• Why it matters: This information is valuable for theoretically guiding material selection and design and operating parameter optimization of key equipment in the supercritical water technologies.
• What was FUTURE’s role: FUTURE helped review the literature and interpret the results.

Kinetic study of hydrogen transport in graphite under molten fluoride salt environment

J. Qiu, A. Wu, J. Yao, Y. Xu, Y. Li, R. Scarlat, D. D. Macdonald  
Electrochimica Acta 352, 136459 (2020). DOI: 10.1016/j.electacta.2020.136459

• What we did: In this work, a kinetic model, which describes the reactions occurring during the hydrogen charging process on a graphite surface in molten fluoride salts, was optimized against electrochemical impedance spectroscopy to study the entry of hydrogen (tritium) into graphite in high temperature molten salt environments.
• What we learned: The surface coverage of absorbed hydrogen increases with decreasing charging potential and increasing moisture content in molten fluoride salts.  The adsorption efficiency (the fraction of hydrogen that absorbs into the graphite lattice) of hydrogen increases with increasing charging potential and decreases with increasing moisture content of the melts.
• Why it matters: This work establishes electrochemical impedance spectroscopy as a useful approach for understanding tritium transport in graphite under molten salt conditions and thus expands our capability for understanding these extreme environments.
• What was FUTURE’s role: FUTURE helped develop the kinetic model and interpret the results.

Point and extended defects in heteroepitaxial 𝞫-Ga2O3 films

P. Saadatkia, S. Agarwal, A. Hernandez, E. Reed, I. D. Brackenbury, C. L. Codding, M. O. Liedke, M. Butterling, A. Wagner, F. A. Selim
Physical Review Materials 4, 104602 (2020).
DOI: 10.1103/PhysRevMaterials.4.104602

• What we did: We performed the first positron lifetime measurements of Ga2O3 films and combined PAS with thermally stimulated emission to identify the nature of point defects and measure their transition levels.
• What we learned: We evaluated the depth distribution of point defects in oxides from depth resolved PAS measurements.  Nonuniform spatial distribution of defects and unexpected large vacancy clusters were revealed in the films despite their high structural quality. These defects are shown to have enormous effects on the oxide properties.
• Why it matters: The work established the use and analysis of depth resolved positron lifetime measurements in characterizing point and extended defects in oxide films in general and revealed the role of point defects in controlling Ga2O3 properties, which is emerging as an important material in many fields.
• What was FUTURE’s role: FUTURE helped in the analysis of positron annihilation spectroscopy data.

Proton Irradiation-Decelerated Intergranular Corrosion of Ni-Cr Alloys in Molten Salt

W. Zhou, Y. Yang, G. Zheng, K. B. Woller, P. W. Stahle, A. M. Minor, M. P. Short
Nature Communications 11, 3430 (2020). DOI: 10.1038/s41467-020-17244-y

• What we did: We designed a unique experimental setup enabling simultaneous corrosion in molten salt and proton irradiation on the same Ni-Cr sample. We used advanced electron microscopy and machine-learning based image analysis to provide a statistically meaningful result.
• What we learned: Proton irradiation will decelerate intergranular corrosion of Ni-Cr in molten salt environments due to radiation enhanced diffusion.
• Why it matters: Our results show that in industrially-relevant scenarios irradiation can have a positive impact challenging the previous view that radiation damage always results in negative effects on corrosion.
• What was FUTURE’s role: FUTURE members performed advanced transmission electron microscopy characterizations and machine-learning based large dataset analysis, providing strong evidence for the mechanism of proton irradiation slowing down intergranular corrosion in molten salt environments.

FUTURE Only

Publications for which the FUTURE EFRC was the sole source of funding.

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Study of trap levels in β-Ga₂O₃ by thermoluminescence spectroscopy

M. M. Islam, D. Rana, A. Hernandez, M. Haseman, F. A. Selim  
Journal of Applied Physics 125, 55701 (2019). DOI: 10.1063/1.5066424

• What we did: We developed thermoluminescence (TL) spectroscopy as a method to measure the transition levels of defects in the band gap of bulk oxides.
• What we learned: TL is very effective in detecting and characterizing small levels of defects in oxides. Point defects and their transition levels in the band gap significantly impact the electronic properties of oxides.
• Why it matters: The measurement method and analysis presented in this work can be applied to a wide range of oxides to reveal their defect content and characteristics, providing new insight into their properties and explaining interesting phenomena.

FUTURE Secondary

Publications for which the FUTURE EFRC was a secondary source of funding.

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In situ small-scale mechanical testing under extreme environments

A. Barnoush, P. Hosemann, J. Molina-Aldareguia, J. M. Wheeler
MRS Bulletin 44, 471 (2019). DOI: 10.1557/mrs.2019.126

• What we did: We reviewed small scale mechanical testing studies in extreme conditions such as radiation, temperature and hydrogen exposure. This paper summarizes recent and new exciting trends in the area and was an invited feature paper by the journal.
• What we learned: We describe the challenges with high temperature, hydrogen content, high strain rate and irradiation small scale mechanical testing and that it is the combination of environments that make the materials property evaluation difficult.
• Why it matters: Small scale mechanical testing has become an integral part of the material science toolbox and it is important to understand current trends and physical limitations.

Correlating high temperature mechanical and tribological properties of CrAlN and CrAlSiN hard coatings

A. Drnovšek, M. Rebelo de Figueiredo, H. Vo, A. Xia, S. J. Vachhani, S. Kolozsvári, P. Hosemann, R. Franz
Surface and Coatings Technology 372, 361 (2019).
DOI: 10.1016/j.surfcoat.2019.05.044

• What we did: We grew CrAlN and CrAlSiN as coatings and evaluated the mechanical performance of these coatings at potential service temperatures.
• What we learned: We learned that CrAlSiN performs better under these conditions than CrAlN and correlates nicely with wear properties. The hardness/elastic modulus ratio appears to be a good measure for the materials performance and can be used as a material design parameter.
• Why it matters: Coatings are widely used to protect a material from its environment or enhance a materials wear in tooling, nuclear applications or any extreme environment. Developing a thorough understanding and design parameters to develop better performing coatings is key for designing coatings for nuclear applications.

Sink strength and dislocation bias of three dimensional microstructures

A. A. Kohnert, L. Capolungo
Physical Review Materials 3, 53608 (2019).
DOI: 10.1103/PhysRevMaterials.3.053608

• What we did:  We created a three dimensional point defect transport model which includes absorption at sinks and energetic interactions between defects and elastic strain fields
• What we learned: We learned that the configuration of the microstructure in a system changes the internal stress distribution. This in turn changes the transport of point defects, and the rates of defect absorption at different sinks.
• Why it matters:  This work reveals the interactive effect between point defects produced by irradiation and the stress field in a material.  This allows us to investigate one of FUTURE’s key hypotheses: that the simultaneous action of extreme conditions changes material response from any one of the conditions applied individually.

Influence of nanochannel structure on helium-vacancy cluster evolution and helium retention

W. Qin, S. Jin, X. Cao, Y. Wang, P. Peres,  S. Choi, C. Jiang, F. Ren
Journal of Nuclear Materials 527, 151822 (2019).
DOI: 10.1016/j.jnucmat.2019.151822

• What we did: We examined He retention and release in nanostructured tungsten through multiple characterization tools. 
• What we learned: The presence of a nanochannel structure within the material accelerates the release of He from the film even at low irradiation fluences, and the release of He is significantly enhanced at higher fluences, thus inhibiting or delaying the formation of large He-vacancy clusters in the nanochannel W film.
• Why it matters: The ability to mitigate He accumulation in materials via nanostructuring provides new routes to design materials that can withstand the extreme environments encountered in nuclear reactors.

Point Defect Model for the Corrosion of Steels in Supercritical Water: Part I, Film Growth Kinetics

Y. Li, D. D. Macdonald, J. Yang, J. Qiu, S. Wang
Corrosion Science 163, 108280 (2019). DOI: 10.1016/j.corsci.2019.108280

• What we did: A Point Defect Model (SCW-PDM) has been developed to describe theoretically the corrosion of metals and alloys in supercritical aqueous systems.  The growth kinetics of the barrier layer of oxide scales, their total scale thickness, and the oft-reported growth of the barrier layer in supercritical water environments were explained using this SCW-PDM.
• What we learned: Based on the SCW-PDM, the kinetic equation for each interfacial reaction and its related parameters are defined; solving these equations, the barrier layer is revealed to grow into the metal via the production of oxygen vacancies at the metal/barrier layer interface and their annihilation at the barrier layer/outer layer interface. The microscopic kinetic information on the corrosion and macroscopic kinetic parameters of several steels can be described successfully by SCW-PDM.
• Why it matters: A model that simultaneously considers the predominant microscale reactions in low/high density SCWs, the effect of oxygen content, and finally completely describing the fundamental atomic-level growth of oxide scales on structural materials in supercritical aqueous systems is significant for the development of supercritical reactors.

Passivity of Titanium: Part II, The Defect Structure of the Anodic Oxide Film

B. Roh, D. D. Macdonald          
Journal of Solid State Electrochemistry 23, 1967 (2019).
DOI: 10.1007/s10008-019-04254-0

• What we did: The kinetic parameters for the formation of the anodic titanium oxide film on Ti in 0.5 M H₂SO₄ have been determined using potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and the Mott-Schottky analysis (MSA), and the data are interpreted in terms of the point defect model (PDM).
• What we learned: The barrier layer of the passive film on titanium is n-type in electronic character with the oxygen vacancy being found to be the dominant point defect (over metal interstitials) in 0.5 M H₂SO₄ solution, and the oxygen vacancy concentration is found to exponentially decrease as the film formation voltage was increased.
• Why it matters: Crystallographic point defects (metal and oxygen vacancies and metal interstitials) play a critical role in defining the properties of anodic oxide passive films that form on metal surfaces. It is important for titanium whose oxide is used extensively in many applications, such as heterogeneous catalysis, photoelectrolysis, and biomaterials.

The Passivity of Titanium–Part III: Characterization of the Anodic Oxide Film          

B. Roh, D. D. Macdonald
Journal of Solid State Electrochemistry 23, 2001 (2019).
DOI: 10.1007/s10008-019-04255-z

• What we did: The passive state and passive film thickness on titanium in 0.5 M H₂SO₄ at ambient temperature (22 °C) has been explored using a combination of ellipsometry, Mott-Schottky analysis, and electrochemical impedance spectroscopy.
• What we learned: The thickness of the single (barrier) layer increases linearly with increasing formation voltage. The passive current density is found to be independent of film formation voltage, indicating an n-type film.
• Why it matters: Investigating the properties (the structure, defect type, and thickness of the anodic oxide film grown on titanium over a wide potential) of anodic oxide passive films that form on titanium surfaces is important for the application of titanium for a number of applications.

Passivity of Titanium, Part IV: Reversible Oxygen Vacancy Generation/Annihilation

B. Roh, D. D. Macdonald          
Journal of Solid State Electrochemistry 23, 2863 (2019).
DOI: 10.1007/s10008-019-04363-w

• What we did: A simplified Point Defect Model incorporating reversible oxygen vacancy generation/annihilation at the metal/film interface has been used to investigate the impedance of anodized titanium in 0.5M H₂SO₄, the oxygen vacancy profile in the anodic titanium oxide film, and the surface oxygen vacancy concentration.
• What we learned: A thin region of non-uniform oxygen vacancy concentration forms adjacent to the film/solution interface, which has an exponentially decreasing dopant concentration. The normalized surface oxygen vacancy concentration by the bulk oxygen vacancy concentration is essentially independent of potential.
• Why it matters: This work provides for identifying which effect is the major cause for changing the kinetics of the OER on the passive surface of titanium in 0.5M H₂SO₄.

Ab initio based examination of the kinetics and thermodynamics of oxygen in Fe-Cr alloys

A. J. Samin, D. A. Andersson, E. F. Holby, B. P. Uberuaga         
Physical Review B 99, 174202 (2019).
DOI: 10.1103/PhysRevB.99.174202

• What we did: We created a cluster expansion model, based on DFT calculations, for oxygen in Fe-Cr alloys and used it to study oxygen kinetics as a function of alloy composition.
• What we learned: Increasing Cr content initially leads to a decrease in oxygen mobility, which then rises again as more Cr content is added until decreasing again for pure Cr.
• Why it matters: These results provide insight into how Cr impacts the mobility of oxygen that is relevant for the altered layer that occurs during corrosion.

First-principles localized cluster expansion study of the kinetics of hydrogen diffusion in homogeneous and heterogeneous Fe-Cr alloys

A. J. Samin, D. A. Andersson, E. F. Holby, B. P. Uberuaga
Physical Review B 99, 14110 (2019). DOI: 10.1103/PhysRevB.99.014110

• What we did: We created a cluster expansion model, based on DFT calculations, for hydrogen in Fe-Cr alloys and used it to study hydrogen kinetics as a function of alloy composition.
• What we learned: Cr tends to decrease hydrogen mobility until a 50/50 Fe-Cr composition is reached, at which point it increases again; however, the distribution of Cr also matters.
• Why it matters: Understanding hydrogen transport and solubility in metals is critical for developing hydrogen storage materials and uptake of hydrogen in nuclear environments.