ACerS Robert B. Sosman Award Symposium: Bridging the Gap between Atomistic and Continuum Approaches to Interface Science: Sosman II
Sponsored by: ACerS Basic Science Division
Program Organizers: John Blendell, Purdue University
Wednesday 2:00 PM
October 20, 2021
Room: B130
Location: Greater Columbus Convention Center
Session Chair: Carol Handwerker, Purdue University
2:00 PM Invited
Grain Boundaries in the Wild: Gregory Rohrer1; 1Carnegie Mellon University
Much of what we know about grain boundaries and the way they move derives from the study of bicrystals using elegant experiments and atomistic simulations. In a bicrystal, the grain boundaries are free to migrate without the constraints imposed by a grain boundary network. In a polycrystal, each boundary is connected to other boundaries at triple lines; the average boundary is connected to five triple lines and 10 other boundaries. In this talk, I will discuss the ways in which grain boundaries in the wild differ from the captive grain boundaries that are usually studied. The role of grain boundary crystallography in grain boundary motion will be discussed, with reference to data from recent high energy diffraction microscopy measurements of grain grain boundary migration velocities.
2:30 PM Invited
Stress-Induced Interface Instability in Battery Electrode Materials: Ming Tang1; 1Rice University
Stress-driven morphological instability of interfaces is a phenomenon found in many materials, such as the well-known Asaro-Tiller-Grinfeld instability during epitaxial thin film growth. Large stress often arises within rechargeable battery electrodes during charging/discharging. Its effect on the morphological evolution of moving interfaces between Li-rich and Li-poor phases is an interesting scientific question with significant technological implications. In this talk, I will present some recent studies on this topic for several electrode systems including single-crystalline and polycrystalline intercalation cathode compounds and metallic anodes. We find that stress can destabilize the reaction front via different mechanisms in battery systems, which compromise cycling performance and life and need to be mitigated.
3:00 PM Invited
Tracing Impurities at Surfaces and Interfaces of Renewable Energy Materials: Christina Scheu1; Joohyun Lim1; Se-Ho Kim1; Raquel Aymerich Armengol1; Rajib Sahu1; Olga Kasian1; Leigh T. Stephenson1; Baptiste Gault1; 1Max-Planck-Institut Fuer Eisenforschung Gmbh
Nanostructured materials, in particular nanosheets and nanowires, can be applied in renewable energy application such as (photo)electrocatalysis as they possess a large surface to volume ratio. This is beneficial as the number of sites where reactions can take place are increased. Often these materials are synthesized by wet chemical approaches. Besides using high purity reactants, impurities can be incorporated into the nanostructures either by the precursor itself or by subsequent heat treatment in various atmospheres. In our work we combine various scanning transmission electron microscopy methods including electron energy loss spectroscopy with atom probe tomography to determine the location of unintentionally added impurities or dopants, their atomic arrangement and oxidation state with ultimate spatial resolution. In the presentation, several examples will be discussed including the presence of impurities at the surface region of hollow, partially reduced titania nanowires (TiO2) and molybdenum disulfide (MoS2) nanosheets stemming from synthesis process and precursor.
3:30 PM Break
3:50 PM Invited
Surface Segregation in Multicomponent High Entropy Alloys: A Comparison between Atomistic Simulations and a Simple Analytical Model: Paul Wynblatt1; Dominique Chatain2; 1Carnegie Mellon University; 2Aix-Marseille Univ, CNRS, CINAM
We have recently published the results of atomistic simulations of grain boundary segregation in the Cantor alloy: Co20Ni20Cr20Fe20Mn20, using the LAMMPS software in conjunction with Modified Embedded Atom Method (MEAM) potentials. Those previous simulations required significant computation resources (typical simulations made use of ~100 parallel processors for about 2 to 3 hours), whereas a typical computation using our analytical model takes less than 1 minute on a laptop. Here, we compare the results obtained on surface segregation by computer simulations, in several of the binary systems that underlie the Cantor alloy, with the results of a simple nearest neighbor bond model. For maximum consistency of the comparison, the thermodynamic parameters required for the simple model have been estimated with the MEAM potentials used in the atomistic modeling. With these parameters, total adsorption is correctly estimated, although adsorbate distribution can be somewhat different, due to the different range of interactions.
4:20 PM Invited
Disconnections, Faceting, Solutes and Their Impact on Grain Boundary Migration in Ceramics: Rheinheimer Wolfgang1; Hadas Sternlicht2; 1Forschungszentrum Jülich; 2Brown University
The recent years have seen several new concepts appearing in the field of grain growth in ceramics. From a macroscopic perspective, the impact of anisotropy and space charge on grain boundary migration has moved into focus. On atomistic scale, grain boundary adsorption and complexions have been investigated in detail, and disconnections and their migration has been proposed as mechanism of grain boundary migration.Most recent work has focused on alumina and strontium titanate. From a defect-chemical perspective, these two materials are fundamentally different regarding the solubility limits of dopants. In general, alumina has a low and strontium titanate high solubility. As a result, alumina tends to from adsorption structures at the interfaces, while grain boundaries in strontium titanate are well-known for diffuse accumulation (i.e. space charge). In this light, this talk follows the concepts listed above from macroscopic down to atomistic and discusses their impact on grain boundary migration.
4:50 PM Invited
Mechanistic Insights into the Effect of Heating Rate on Sintering and Sintering Stress Evolution: Shen Dillon1; 1University of Illinois
High heating rate sintering methods have been known, for ≈4 decades, to enhance the rate of densification relative to that of coarsening. Limited experimental evidence also suggests that high heating rate sintering methods better facilitate constrained sintering than conventional sintering, presumably by mitigating sintering stresses. These effects are difficult to rationalize in context of classical sintering models from Coble, Kuczynski, and Johnson and Cutler. Prof. Kaplan has been a strong voice in the field in support of the idea that atomic scale mechanisms should be invoked more often to better inform our understanding of microstructural evolution at the continuum scale. In that vein, this talk will discuss the importance of the densification mechanism in affecting stress evolution during sintering and the sintering trajectory during high heating rate sintering. The discussion will be supported by our experimental results from microscale bicrystal sintering and Coble creep experiments.