Los Alamos National LaboratoryFUTURE: Fundamental Understanding of Transport Under Reactor Extremes
An Energy Frontier Research Center funded by the Department of Energy, Office of Basic Energy Sciences

FUTURE Publications

View the publications generated by the scientists of FUTURE.
2020

FUTURE Led


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.

 

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 understanding radiation 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. Baldwin, J. Cooper, T. Lach, D. Edwards, D. Schreiber, D. Kaoumi, 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 temperature and 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. Guneau, 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.

 

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 in-situ 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 Contributed


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.

 

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.
  • What was FUTURE’s role:  FUTURE suggested multiple approaches including PAS and SIMS to investigate ion irradiation damage phenomenon and gained first hand knowledge of ex situ PAS application in the area.

 

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.
2019

FUTURE Led


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 Contributed


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.
  • What was FUTURE’s role: FUTURE allowed for the comprehensive collaboration between different authors who all work on the synergies between environment, mechanical properties and applications. FUTURE brought together authors of different fields in a comprehensive review.

 

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.
  • What was FUTURE’s role: FUTURE allowed finalization of the defect – elastic field interaction capability and enabled completion of a large set of simulations, spanning a wide range of material conditions.  The material selected for these simulations was Fe, one of the target materials for the FUTURE experimental campaign 

 

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.
  • What was FUTURE’s role: FUTURE aims to understand the synergistic effects of environment, radiation, stress, etc. on materials. In many engineering applications these multidimensional problems are addressed by coatings. This work investigates aspects of a coating system that addresses corrosion and wear.

 

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.
  • What was FUTURE’s role: FUTURE helped develop the kinetic model and interpret the results.

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.
  • What was FUTURE’s role: FUTURE helped to interpret the experimental data using the point defect model.

The Passivity of TitaniumPart 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.
  • What was FUTURE’s role: FUTURE helped to interpret the experimental data and write a paper.

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.
  • What was FUTURE’s role: FUTURE helped to develop the simplified point defect model and interpret the results.

 

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.
  • What was FUTURE’s role: FUTURE helped plan the study and interpret the results.

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.
  • What was FUTURE’s role: FUTURE helped plan the study and interpret the results.