Argonne National Laboratory Research Articles

ROM-Based Surrogate Systems Modeling of EBR-II

The System Analysis Module (SAM), developed and maintained by Argonne National Laboratory, is designed to provide whole-plant transient safety analysis capabilities for a number of advanced non–light water reactors, including sodium-cooled fast reactor (SFR), lead-cooled fast reactor (LFR), and molten salt reactor (MSR)/fluoride-salt-cooled high-temperature reactor (FHR) designs. SAM is primarily constructed as a systems-level analysis tool, with the potential to incorporate reduced order models from three-dimensional computational fluid dynamics (CFD) simulations to improve characterization of complex, multidimensional physics. It is recognized that the computational expense associated with CFD can be intractable for various engineering analyses, such as uncertainty quantification, inference, and design optimization. This paper explores the reducibility of a SAM model using recent advances in randomized linear algebra techniques, which attempt to find recurring patterns in the various realizations generated by a model after randomly perturbing all its input parameters. The reduction is described in terms of fewer degrees of freedom (DOFs), referred to as the active DOFs, for the model variables such as input model parameters and model responses. The results indicate that there is significant room for additional reduction that may be leveraged for additional computational gains when employing SAM for engineering-intensive analyses that require repeated model executions. Different from physics-based reduction approaches, the proposed approach allows one to estimate upper bounds on the reduction errors, which are rigorously developed in this work. Finally, different methods for surrogate model construction, such as regression and neural network–based training, are employed to correlate the input and output active DOFs, which are related back to the original variables using matrix-based linear transformations.

Using waste CO2 from corn ethanol biorefineries for additional ethanol production: life‐cycle analysis

AbstractCorn ethanol plants generate high‐purity carbon dioxide (CO2) while producing ethanol. If that CO2 could be converted into ethanol by carbon capture and utilization technologies it would be possible to increase ethanol production more than 37% without additional corn grain inputs. Gas fermentation processes use microbes to convert carbon‐containing gases into ethanol and so have the potential to be used with the CO2 from biorefineries for this purpose. However, as CO2 utilization technologies for converting thermodynamically stable CO2 are typically energy intensive, it is necessary to evaluate the related life‐cycle greenhouse gas (GHG) emissions (carbon intensities or CIs) to see whether there are actual emission reduction benefits. In this study, we evaluate the CIs of ethanol produced from high‐purity CO2 in corn ethanol plants by gas fermentation plus electrochemical reduction. Our analysis shows that the sources of electricity and hydrogen are key drivers of CO2‐based ethanol's GHG emissions. With wind electricity, the design cases show the potential of near‐zero CI ethanol (1.1 g CO2e/MJ), but that can increase to up to 331–531 g CO2e/MJ when today's U.S. Midwest electricity mix is used. To avoid the renewable electricity intermittency issue, we considered a power purchase agreement option using wind electricity 40% of the time and using the regional mix for the rest, which provides a 42% GHG emission reduction from the CI of gasoline. © 2020 The Authors and UChicago Argonne, LLC, Operator of Argonne National Laboratory. Biofuels, Bioproducts and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd.

From the pocket accelerator to major scientific facilities

The concept of “major scientific facility” was put forward by Ernest Lawrence, who invented the first cyclotron in 1929. Before Lawrence, all scientific research in the entire world can be said as “small science”, which is characterized by the research carried out by individuals or in small size of groups. Since the 1930s, due to the high financial need to build larger accelerators, Lawrence realized that a major scientific research project needs to be completed by a team with people of different expertise. His concept of teamwork has become a tradition in their laboratory at Berkeley and continues to this day. Major scientific facilities can provide ultimate research methods for exploring unknowns, which may likely lead to scientific breakthroughs. Since then, a new trend has gradually emerged in the development of science and technology, that is, every major breakthrough obtained in research, and even a significant step forward, is largely inseparable from installations of large facilities. This is precisely the impetus for countries all over the world to build major scientific facilities with huge investment. The development status of large scientific facilities determines a country’s ability to make such breakthroughs in cutting-edge research, and thus determines the country’s scientific and technological competitiveness in the world. Through the implementation of the Manhattan Project during the Second World War, the United States was directly benefited from the fact that the remaining facilities at that time all became national laboratories after the war. Following Lawrence’s original concept about the teamwork with major scientific facilities, the present article briefly reviews the history and current status of several national laboratories in the United States, and points out that the national-laboratory model can indeed form a strong scientific development impetus and play an international leading role in scientific and technological fields. I take four US national laboratories as examples: The Lawrence-Berkeley National Laboratory, the Argonne National Laboratory, the Oak Ridge National Laboratory, and the Los Alamos National Laboratory, to show that the model, centered on large-scale facilities with the management guaranteed by effective national plans and capital investment, is worthy of in-depth study for reference. In recent years, China has strongly emphasized the importance in the development of scientific research bases and has built a number of key laboratories. It is pointed out that comparing with the standard of the world-leading laboratories, China still needs to narrow the gap in management and in operation.

Balance-Of-Plant Computerized Operator Support System Implementation

A Computerized Operator Support System (COSS) is an operator assistive technology suite that aids operators in monitoring processes to detect off-normal conditions, diagnose plant faults, predict future plant states, recommend mitigation alternatives, and select appropriate mitigative actions. A COSS human-machine interface (HMI) was developed at Idaho National Laboratory (INL) in collaboration with an advanced prognostics engine called PRO-AID, developed at Argonne National Laboratory (ANL). The front-end HMI coupled with the back-end prognostics provide fault prediction to inform operators of plant faults before they occur. Historically, COSS has been focused within the control room, representing systems that are monitored and controlled solely from a centralized location. This project, however, is focused on applying the principles of previous COSS efforts to a system outside the control room, namely the boric acid concentrator and liquid radwaste (BAC/LRW) system. This effort demonstrates the applicability and usability of a COSS system in a balance-of-plant environment, and offers next steps in the development of operator support and advanced overview interfaces in existing nuclear power-generating stations, and the future advanced reactor systems.

Multi-input, Multi-output Hybrid Energy Systems

Summary Jurisdictions and industries are setting ambitious goals to decarbonize energy systems. Low-cost wind, solar, and natural gas and the resultant dynamic electric grid require energy technologies to adapt in order to meet key attributes for modern energy systems: resilience, reliability, security, affordability, flexibility, and sustainability. When considering energy sources independently and competitively, value-added synergies among energy technologies may be overlooked for meeting demanding, multidimensional requirements. This paper presents novel concepts for tightly coupled hybrid energy systems that leverage capabilities of diverse energy generators, including renewable, nuclear, and fossil with carbon capture, to provide power, heat, mobility, and other energy services. The paper also presents a framework for engineering-based modeling and analysis for complex optimization of energy generation, transmission, services, processes and products, and market interactions. New modeling capabilities are needed to adequately represent multi-input, multi-output tightly coupled hybrid energy systems that utilize multiple feedstocks to create multiple products and services in novel and synergistic ways through increased coordination of energy systems and tightly coupled hybrid system configurations.

Synthesis and ion-irradiation tolerance of the Dy2TiO5 polymorphs

In developing improvements in nuclear fuels, work has been conducted in replacing boron with lanthanides to act as neutron absorbent materials. To further this development for the first time the three major polymorphs of Dy2TiO5 have been fabricated as bulk, single-phase materials in a systematic study. Crystal structure refinement has been carried out from powder x-ray diffraction data, with further structural detail attained via electron diffraction. A cubic phase, defect-pyrochlore, Fd-3m space group, was found with cell parameter a = 10.2996 (1) Å and oxygen x48f positional parameter = 0.331 (1). Dy2TiO5 was also fabricated as a bulk, single-phase compound with hexagonal symmetry, P63/mmc space group, with cell parameters a = b = 3.6307(2), c = 11.8963(8) Å. The radiation response for each of the polymorphs has been investigated in-situ via 1 MeV Kr – ion-irradiation and transmission electron microscopy characterisation at the IVEM-TANDEM facility, Argonne National Laboratory. Critical temperatures, Tc, for maintaining crystallinity during irradiation were determined and showed Dy2TiO5 with either orthorhombic or cubic symmetry to perform the best, with the lowest Tc values of 711 and 761 K respectively when compared with the hexagonal form. These relatively low Tc values may be attributed to different characteristics for each phase; high anti-site defect formation energy for the orthorhombic symmetry, and the ability to accommodate disorder for the cubic symmetry.

Silicon Monoxide As Anode Material for Lithium Ion Batteries

Silicon monoxide (SiO) is a very promising anode material for the next generation high energy lithium ion batteries due to its high theoretical specific capacity of 1710 mAh/g and volumetric capacity of 1547 Ah/L.[1] Compared to commercially used graphite, SiO can offer 18% cell stack level improvement in volumetric energy density and 11% in gravimetric energy density (calculated based on the same cell stack model), enabling utilization of smaller and lighter batteries. It also offers more stable cycle performance compared to Si due to less volume change (134% initial volume expansion and 117% reversible volume expansion), making it a more practical choice for lithium ion batteries in the near future.SiO is composed of Si nanodomains in a SiO2 matrix. An interphase region of transitional stoichiometry (SiOx, 0 < x < 2) is also present between Si and SiO2 and takes up 20-25 at.% of the entire composition.[2] During the lithiation and delithiation, the Si nanodomains react reversibly with lithium, similar to amorphous silicon, to give the reversible capacity. The SiO2 matrix reacts irreversibly with lithium to form lithium silicates and lithium oxide. Therefore, the Si domain size and interphase suboxide between Si and SiO2 have effect on the electrochemical performance of SiO. In this study, we gradually changed the microstructure of SiO via annealing treatment and thoroughly studied the change of the SiO microstructure and its impact on the electrochemical performance of the SiO. Together with electrode formulation optimization, up to 99% capacity retention during 50 cycles was obtained in full cells when using pure SiO as anode and LiNi0.5Mn0.3Co0.2O2 as cathode. Acknowledgement We gratefully acknowledge the support from Peter Faguy at the U.S. Department of Energy’s (DOE) office of Energy Efficiency & Renewable Energy (EERE) - Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory. Argonne National Laboratory is a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357.Reference: Obrovac, M. N.; Chevrier, V. L., Alloy Negative Electrodes for Li-Ion Batteries. Chemical Reviews 2014, 114 (23), 11444-11502.Hirata, A.; Kohara, S.; Asada, T.; Arao, M.; Yogi, C.; Imai, H.; Tan, Y.; Fujita, T.; Chen, M., Atomic-scale disproportionation in amorphous silicon monoxide. Nature Communications 2016, 7, 11591.

Pre-Lithiation of Anode for Lithium Ion Batteries

Silicon monoxide (SiO), as an anode for lithium ion batteries (LIB), offers a specific capacity of 1750 mAh/g and a volumetric capacity of 1547 Wh/L,[1] which is less than Si, but still a significant improvement from the current commercial graphite anode, which has a specific capacity of 350 mAh/g and a volumetric capacity of 719 Wh/L. Compared to Si, SiO offers much more stable cycling, and is therefore the more practical material for near-future applications. The drawback of SiO is the large capacity loss observed in the initial cycles. The 1st cycle coulombic efficiency of silicon monoxide is usually lower than 70% due to the parasitic reactions between lithium and the oxide.To address the problem, prelithiation reagents can be added to either anode or cathode electrodes to compensate for the lithium loss caused by the irreversible reactions. However, dead weight left by the pre-lithiation agent adversely affects the energy density of LIB. Electrochemical pre-lithiation will only put the lithium ions into the anode and leaves no other compound behind, which is considered an ideal prelithiation method. In addition, the electrochemical pre-lithiation on the anode has the potential to be compatible with the existing roll-to-roll manufacturing line and could be immediately applicable to the current state-of-the-art LIB anodes.In this work, we conducted the electrochemical pre-lithiation of large size graphite and SiO anode electrodes in pouch cells to prove the concept. After pre-lithiation, no damage and handling issues were encountered during subsequent cleaning, drying, cell fabrication, and testing. Good electrochemical performance of the pre-lithiated graphite and SiO electrodes were obtained in both half cells and full cells. According to calculation, the pre-lithiation speed is challenging and needs to be addressed to match roll-to-roll electrode coating speed. Additionally, electrochemical pre-lithiation on graphite powder was attempted and results will be discussed. Acknowledgements: We gratefully acknowledge the support from Peter Faguy at the U.S. Department of Energy’s (DOE) office of Energy Efficiency & Renewable Energy (EERE) Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory. Argonne National Laboratory is a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357.[1] Obrovac, M. N.; Chevrier, V. L., Alloy Negative Electrodes for Li-Ion Batteries. Chemical Reviews 2014, 114 (23), 11444-11502.

Influence of Ink Formulation and Drying Conditions on Ionomer Distribution in High-Performance Roll-to-Roll-Coated Gas-Diffusion Electrodes

To enable mass production of fuel cell membrane electrode assemblies (MEAs) catalyst layers production will require continuous roll-to-roll (R2R) coating processes.1 Gas diffusion electrodes (GDEs) are advantageous for mass production because the catalyst layer can be directely coated on the microporous layer of the gas diffusion media without the need for a decal-transfer process. It is known that the water-to-alcohol ratio in the catalyst ink influences the interactions of the ionomer with the catalyst leading to different distributions of ionomer in spray-coated catalyst layers.2 It is also known that during drying of colloidal mixtures, like fuel cell inks, factors such as drying rate, particle size, and agglomeration influence how the materials distribute themselves throughout the thickness of the dired film.3,4 Thusfar there have only been limited studies to understand how process conditions such as ink formulation and drying temperature influence the distribution of ionomer and catalyst coated using scalable methods.5 This understanding is especially important for GDEs since it is known that having a sufficient amount of ionomer at the catalyst layer-membrane interface is critical for high performance.6 In this study we have focuse on determining how the ratio of water to 1-propanol in the catalyst ink ink and drying temperature influence the distribution of ionomer throughout the thickness of the catalyst layer. Using a combination of Kelvin probe and x-ray photoelectron spectroscopy we show that an ionomer-rich surface is promoted by a higher drying rate and a water-rich catalyst ink. In contrast, a 1-propanol catalyst ink leads to a lower concentration of ionomer on the top surface. Using x-ray computed tomography, we are able to characterize the ionomer distribution throughout the thickness of the layer. We find that, in addition to promoting an ionomer-rich top surface, water-rich inks lead to a more homogenous distribution of ionomer, whereas a 1-propanol-rich ink leads to a more irregular distribution. It is found that MEA performance is improved by selecting conditions and ink formulations that promote ionomer enrichment at the top surface to facilitate a good interface with the membrane. MEAs prepared with a 75 wt% water catalyst ink with a 0.9 I/C have equivalent performance to spray-coated GDEs. Critically, these R2R-coated GDEs do not need an additional ionomer overlayer like the spray-coated GDEs do, reducing the number of processing steps in a manufacturing setting. This work shows that with the appropriate selection of materials, ink formulation, and processing conditions gas-diffusion electrodes are a viable pathway for fuel cell manufacturing.This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. The submitted manuscript was created, in part, by UChicago Argonne, LLC, Operator of Argonne National Laboratory, Argonne, U.S. Department of Energy Office of Science laboratory, operated under Contract No. DE-AC02- 06CH11357. This research used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory, also under Contract No. DE-AC02-06CH11357. Funding provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and Advanced Manufacturing Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes. Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 486, 43–51 (2012).Van Cleve, T. et al. Dictating Pt-based Electrocatalyst Performance in Polymer Electrolyte Fuel Cells; from Formulation to Application. ACS Appl. Mater. Interfaces 11, 46953–46964 (2019).Makepeace, D. K. et al. Stratification in binary colloidal polymer films: experiment and simulations. Soft Matter 13, 6969–6980 (2017).Cardinal, C. M., Jung, Y. D., Ahn, K. H. & Francis, L. F. Drying regime maps for particulate coatings. AIChE J. 56, 2769–2780 (2010).Orfanidi, A., Rheinländer, P. J., Schulte, N. & Gasteiger, H. A. Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC. Journal of the Electrochemical Society 165, F1254–F1263 (2018).Mauger, S. A. et al. Fabrication of High Performance Gas-Diffusion-Electrode Based Membrane-Electrode Assemblies. J Power Sources 450, 227581 (2020).

The Effect of Dispersion-Medium Composition and Ionomer Concentration on the Microstructure and Rheology of Fe-N-C Platinum Group Metal-Free Catalyst Inks for Polymer Electrolyte Membrane Fuel Cells

The microstructure of platinum-group-metal-free (PGM-free) catalyst layers is known significantly impact mass and proton transport and is critical for optimization of PGM-free fuel cells.1 It is known that catalyst ink formulation can influence interactions between catalyst and ionomer which in turn influence the catalyst layer microstructure. In this talk, we present an investigation of catalyst inks consisting of Fe-N-C catalysts and Nafion ionomer to understand how the ratio of H2O and 1-propanol (nPA) influences ink microstructure. Steady-shear and dynamic-oscillatory-shear rheology, in combination with x-ray scattering, were used to study the interparticle interactions and the agglomerated structure of the inks. In the absence of ionomer, the inks were significantly agglomerated, approaching a gel-like microstructure. Increasing H2O% was found to increase agglomeration due to hydrophobic nature of the catalysts. Addition of ionomer was found to initially stabilize catalysts against agglomeration for all H2O%. However, at high ionomer concentrations (I/C > 0.35) interesting differences were observed based on H2O%. The nPA-rich inks were found to remain predominantly stable while ionomer appears to flocculate H2O-rich inks. Finally, the ink microstructure is compared with catalyst layer microstructure, which shows a direct correlation. This work shows that the controlling the ink microstructure is critical to designing optimized catalyst layers.This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. The submitted manuscript was created, in part, by UChicago Argonne, LLC, Operator of Argonne National Laboratory, Argonne, U.S. Department of Energy Office of Science laboratory, operated under Contract No. DE-AC02- 06CH11357. This research used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory, also under Contract No. DE-AC02-06CH11357. Funding provided as part of the Electrocatalyst Consortium (ElectroCAT), an Energy Materials Network Consortium funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.(1) Wang, G.; Osmieri, L.; Star, A. G.; Pfeilsticker, J.; Neyerlin, K. C. Elucidating the Role of Ionomer in the Performance of Platinum Group Metal-Free Catalyst Layer via in Situ Electrochemical Diagnostics. Journal of The Electrochemical Society 2020, 167 (4), 044519. https://doi.org/10.1149/1945-7111/ab7aa1.

Effect of Cobalt Content on Charge Compensation Mechanism of LiNixMnyCozO2 Cathode for Lithium Ion Battery

LiCoO2 (LCO) is commonly used as a cathode for Li-ion batteries (LiBs) owing to its excellent intercalation nature, high voltage, and cyclic performance [1, 2]. However, LCO has issues due to the potential risk of future price increases of Co [3, 4]. Many efforts have been made to reduce the amount of Co in the cathode by replacing it with Ni and/or Mn, and LiNixMnyCozO2 (NMC) has been developed. NMC622, which contains 60 mol % of Ni in the transition metal composition, is now adopted in the majority of the electric vehicle battery chemistry. Although Ni-rich NMC is a promising alternative to low-Co cathodes, it is not clear whether the amount of Co can be further reduced from the present NMC622 without degrading cyclic stability. To further reduce the amount of Co, it is necessary to clarify the role of Co in the charge compensation mechanism and replace it with alternative elements with functions similar to those of Co.In this study, we conducted XAFS, XRD and first-principles calculations for the NMC cathode with various transition metal composition ratios to clarify that the roles of Co, Ni, Mn, and O in the charge compensation mechanism. Synchrotron X-ray experiments were performed at SPring-8 and NewSUBARU synchrotron radiation facility in Japan. The first-principles calculations were carried out with Vienna Ab-initio Simulation Package (VASP) [5, 6], which uses plane-wave basis sets.Fig. 1 shows the oxygen K-edge XANES spectra collected by the partial fluorescence yield (PFY) method at different states of charge (SOCs). As for the LCO, the peak intensity around 528 eV changed along with the SOC, suggesting that oxygen contributes to the charge compensation. Similar spectral changes were also observed with NMC111, NMC622, and slightly with NMC 811. In contrast, the white line energy in the Co L3-edge absorption hardly changed at any transition metal composition. Although there are various theories about the role of Co and oxygen in the charge compensation [7], our results show that there is no obvious change in the charge state of Co and oxygen contributes the most to the charge compensation in the LCO system. Detailed analysis including first-principles calculations will be discussed at the meeting.[1] K. Mizushima et al., Mater. Res. Bull. 15, 783 (1980).[2] A. Du Pasquier et al., J. Power Sources 115, 171 (2003).[3] P.A. Nelson et al., Modeling the Performance and Cost of Lithium-Ion Batteries for Electric-Drive Vehicles, Argonne National Laboratory, 2012.[4] Elsa A. Olivetti e t al., Joule 1, 229 (2017).[5] P. E. Blöch, Phys. Rev. B 50, 17953 (1994).[6] G. Kresse et al., Phys. Rev. B 59, 1758 (1999).[7] B. Li et al., Adv. Mater. 29, 1701054 (2017) Figure 1

Operando Electrochemical Dilatometry of Si-Based Electrodes for Lithium-Ion Cells

Silicon is a promising next-generation anode material for Li-ion batteries, given its high specific capacity, abundance and low working potential. However, its application in commercial cells has been hindered by the large volumetric changes that occur during the Li (de)alloying process. While theoretical calculations predict that the full lithiation of a silicon particle would lead to ~300% expansion,1 experiments suggest that the material can undergo even larger dimensional variations due to morphological changes during repeated cycling.2 Most of the degradation mechanisms associated with Si-based electrodes, which are responsible for the poor cycling stability and rapid capacity decay, derive from the cyclic swelling/contraction effect. Understanding how the particle-level expansion projects into the electrode scale is hence a very relevant topic, specifically considering that composite electrodes are a complex combination of pores and both active and inactive materials.In this study, we use operando electrochemical dilatometry to quantify the thickness variation of Si-based electrodes during cycling. An example plot from a 70 wt% Si electrode is shown in Figure 1. The electrode expands to 300% of its initial thickness upon full lithiation. However, the swelling shows a nonlinear behavior being much slower during the initial 1000 mAh/g. At this point, the thickness change is only 17% although ~40% of the electrode capacity is utilized. During this regime, porosity and particle rearrangement within the anode may be able to partially accommodate the particles expansion. Past this stage, however, there is a steep increase in electrode dilation, which often results in coating delamination, as confirmed by post-mortem inspections.Such quantitative analyses provide important insights into the relationship between electrode capacity and expansion. More importantly, these results can be applied to inform cell design, provide guidelines for selection of cell cutoff voltages, and estimate the effect of anode utilization on cell performance. Obtaining reliable dilatometry information is challenging: hence, strategies for designing experiments that yield reproducible results will also be discussed during the presentation. REFERENCES 1. Kim et al., Journal of Physical Chemistry C, 115, 2514 (2011). 2. Wetjen et al., Journal of The Electrochemical Society, 165, A1503 (2018).Acknowledgement: We are grateful for support from B. Cunningham at the U.S. DOE Office of Vehicle Technology. This document has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. Figure 1

Correlating Calcium Electrodeposition with Solvation Structure: X-Ray Absorption Studies on Ethereal-Calcium Complexes in Solution

Ca-ion electrochemical systems have been on the forefront of multivalent energy storage due to their use of earth-abundant redox materials and their high theoretical specific capacities in relation to monovalent-charge carriers. However, significant pitfalls in cation plating and striping arise from electrolyte decomposition and can be related in-part to the coordination environment around Ca2+ with both the negatively charged anion and the organic–aprotic solvent. X-ray absorption fine structure (XAFS) studies of liquid electrolytes have been performed to identify the elemental and geometric coordination around the multivalent cation. Specifically, we can define the local geometry, coordination and electronic structure of Ca–ethereal complexes through the combined analysis of the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) to provide clear indication of the extent of Ca2+–solvent interaction. Finally, we combined these characterization results with recent progress in Ca2+ electrochemistry and suggest important structural trends for reversible plating/stripping depending on the extent of solvent chelation. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

In-situ Observations of Directed Energy Deposition Additive Manufacturing Using High-Speed X-ray Imaging

In laser-based directed energy deposition (DED) additive manufacturing, interactions among the laser beam, particle flow, and melt pool influence the properties of the solidified final part. Two separate DED systems, one with high powder flow rates to represent industrial-scale DED processing and the other with low powder flow rates for individual particle tracking, were synchronized with the high-speed imaging setup at the Advanced Photon Source in Argonne National Laboratory. In-situ x-ray imaging of the DED process using both systems highlighted the influence of powder flow rates. Increased powder flow rates resulted in less laser absorption into the melt pool, leading to a transition from a keyhole mode to a melt pool without a keyhole but with surface fluctuations due to powder flow. Increased velocities of particles during powder flow resulted in a decrease in particle melting times and a greater propensity for porosity formation. Overall, better understanding of the interactions that occur during various scales of the DED process will enable flexibility, control, and new materials development in DED-based additive manufacturing.

Effect of Anode Slippage on Cathode Cutoff Potential and Degradation Mechanisms in Ni-Rich Li-Ion Batteries

This work is supported by the Faraday Institution under grant number FIRG001. The authors are grateful to A. Jansen, S. Trask, B.J. Polzin, and A.R. Dunlop at the U.S. Department of Energy’s CAMP (Cell Analysis, Modeling, and Prototyping) Facility, Argonne National Laboratory, for producing and supplying the electrodes in this work. The authors are grateful to the Diamond Light Source for allocating beam time for the operando long-duration PXRD experiments, and to K. Kleiner, S. Day and C. Tang for their experimental support. C.X. gratefully acknowledges support from a Science and Technology Facilities Council (STFC) Experimental Design Award from the STFC Batteries Network (ST/R006873/1).

X-ray and gamma-ray tomographic imaging of fuel relocation inside sodium fast reactor test assemblies during severe accidents

The present work reports on x-ray and gamma-ray high-spatial resolution computed tomography measurements of the Pin Bundle Metallic Fuel Relocation (PBR) assemblies tested in the Metallic Uranium Safety Experiment (MUSE) facility at Argonne National Lab (ANL). The aim of the study was to characterize fuel relocation structures that develop during severe core accidents pertaining to SFR assemblies. In particular, two test assemblies (PBR-1 and PBR-2) were analyzed; the investigation includes but is not limited to advanced core disruption recreated in the PBR-1 assembly, and cladding breach recreated in the PBR-2 assembly. The x-ray tomography measurements were able to resolve small quantities of relocated fuel; with increased presence of relocated fuel, the x-ray measurements spatially mapped the material but could not resolve the inner regions of these because of the increased photon attenuation. The gamma-tomography measurements showed improved results, resolving the relocated structures in great detail. It is shown that the upper plenum of the PBR-1 assembly where the molten uranium was initially inserted presented high structural damage, reflected by the partial and complete disintegration of the central rods. Relocated fuel filled the subchannels, adhering to surviving cladding walls and the assembly casing. In the lower portion of the measured section, the tomogram degrades due to photon starvation effects hinting at the increased amount of relocated fuel potentially plugging the assembly; flow blockage in this section was difficult to determine due to the tomogram's degradation from photon starvation. Small fragments were observed further down the assembly, dislodged from the initial insertion of the molten material. This section was used as an unperturbed assembly reference, with a calculated blockage of less than 1% from the present fragments. The PBR-2 assembly was characterized by columnar relocation structures propagating through the subchannels. Three of the relocation structures were captured in the measured section, with evidence of cross migration on to adjacent subchannels. The measured section in this assembly captures the leading edge of two molten slug structures. The calculated flow blockage was estimated to be 16% in the planes where the three relocated structures are present, but this quickly decreases to approximately 5% past the leading edge of two of the molten slug structures.

Synthesis and Ion-Irradiation Tolerance of the Dy2TiO5 Polymorphs

In developing improvements in nuclear fuels, work has been conducted in replacing boron with lanthanides to act as neutron absorbent materials. To further this development for the first time the three major polymorphs of Dy2TiO5 have been fabricated as bulk, single-phase materials in a systematic study. Crystal structure refinement has been carried out from powder x-ray diffraction data, with further structural detail attained via electron diffraction. A cubic phase, defect-pyrochlore, Fd-3m space group, was found with cell parameter a = 10.2996 (1) A and oxygen x48f positional parameter = 0.331 (1) A. Dy2TiO5 was also fabricated as a bulk, single-phase compound with hexagonal symmetry, P63/mmc space group, with cell parameters a = b = 3.6307(2), c = 11.8963(8) A. The radiation response for each of the polymorphs has been investigated in-situ via 1 MeV Kr – ion-irradiation and transmission electron microscopy characterisation at the IVEM-TANDEM facility, Argonne National Laboratory. Critical temperatures, Tc, for maintaining crystallinity during irradiation were determined and showed Dy2TiO5 with either orthorhombic or cubic symmetry to perform the best, with the lowest Tc values of 711 and 761 K respectively when compared with the hexagonal form. These relatively low Tc values may be attributed to different characteristics for each phase; high anti-site defect formation energy for the orthorhombic symmetry, and the ability to accommodate disorder for the cubic symmetry.

The Structural Evolution of Dot-Core GaN Substrates with Annealing Under Growth-Like Conditions

The structural evolution before and after annealing of c-plane dot-core GaN substrates under growth-like conditions was studied using monochromatic X-ray topography. The anneal was performed at 1050 °C for 10 hours in a MOCVD growth chamber under conditions optimized for the growth of GaN drift layers but without the group-III alkyl. This replicates the thermal environment the substrates experiences during the growth of > 2 kV PN diodes. In the current literature, fundamental understanding of the defect structure of dot-core GaN substrates – and its direct impact on device performance – is limited. X-ray topography provides a nondestructive method for studying the structural nature of defects which can then be used to understand the impact of defects on device performance. The measurements were performed at the 1-BM beamline of the Advanced Photon Source, Argonne National Laboratory using an X-ray energy of 8.05 keV to measure the (1124) GaN reflection to generate single exposure images (images exposed at a specific ω angular position along the X-ray rocking curve) as well as rocked images (a composite image exposed at many positions along the rocking curve). The step size for the rocked images was 0.008°. The rocked images showed butterfly-shaped diffraction lines centered at each core – indicative of localized distortions due to a high density of defects aggregated at each core. Furthermore, the single exposure images revealed that in the regions between the cores, the lattice is less misoriented than at the cores. The defects present at the cores induce severe lattice tilt emanating radially from the cores, which suggests that these relatively high tilt regions (cores) would be detrimental to device performance. Before annealing, it was observed that adjacent low tilt regions were tilted with respect to each other. The radius of (lattice) curvature of the substrate before annealing was 17 ± 1 m, which indicates that globally throughout the entire substrate there was a high amount of lattice tilt misorientation. After annealing, the substrate flattens – the radius of curvature increased to 27 ± 2 m and an increase in diffracted area between adjacent “low tilt” areas also increased, which is evidence of both local and global structural reconfiguration of the lattice towards a smaller degree of misorientation due to the anneal. Figure 1

The performance of the commissioned Notre Dame multi-reflection time-of-flight mass spectrometer

The future N=126 factory at Argonne National Laboratory is aimed to produce neutron-rich elements around the N=126 peak of the rapid-neutron capture process using multi-nucleon transfer reactions. However, this radioactive ion beam production method will entail the delivery of contaminant ions. To remove the isobar contaminants from the beam, a multi-reflection time-of-flight mass spectrometer has been built and successfully commissioned at the University of Notre Dame, reaching a resolving power of 70,000, with an efficiency of 10%. According to stability study conducted, the resolving power is potentially limited to 83,000 by the power supply stability, however it can be mitigated by the addition of RC filtration as done for other MR-TOFs. The commissioned MR-TOF has been transported to Argonne National Laboratory to be used in the N=126 factory.

Microstructural evolution of a silicon carbide-carbon coated nanostructured ferritic alloy composite during in-situ Kr ion irradiation at 300°C 450°C

Abstarct This work focuses on irradiation behaviors of a novel silicon carbide and carbon coated nanostructured ferritic alloy (SiC-C@NFA) composite for potential applications as a cladding and structural material for next generation nuclear reactors. The SiC-C@NFA samples were irradiated with 1 MeV Kr ions up to 10 dpa at 300 and 450 °C. Microstructures and defect evolution were studied in-situ at the IVEM-Tandem facility at Argonne National Laboratory. The effects of ion irradiation on various phases such as α-ferrite matrix, (Fe,Cr)7C3, and (Ti,W)C precipitates were evaluated. The α-ferrite matrix showed a continuous increase in dislocation density along with spatial ordering of dislocation loops (or loop strings) at >5 dpa. The size of the dislocation loops at 450 °C was larger than that at 300 °C. The nucleation and growth of new (Ti,W)C precipitates in α-ferrite grains were enhanced with the ion dose at 450 °C. This study provides new insight into the irradiation resistance of the SiC-C@NFA system.