ACerS Robert B. Sosman Award Symposium: Bridging the Gap between Atomistic and Continuum Approaches to Interface Science: Sosman I
Sponsored by: ACerS Basic Science Division
Program Organizers: John Blendell, Purdue University
Wednesday 8:00 AM
October 20, 2021
Room: B130
Location: Greater Columbus Convention Center
Session Chair: John Blendell, Purdue University
8:00 AM Introductory Comments
8:10 AM Invited
Stressing Surfaces and Interfaces to Change Microstructure: Klaus van Benthem1; 1University of California, Davis
Exerting external electrical or chemical stress on surfaces or interfaces will change surface and interface energies, respectively, which impact microstructure. Electric field assisted sintering has demonstrated the feasibility to accelerate densification of powder compacts, lower processing temperatures, and suppress or enhance grain growth. In this presentation a series of recent bicrystal diffusion bonding experiments will be reviewed that were designed to systematically elucidate electric field effects on the atomic and electronic structures of individual grain boundaries. Electric field direction relative to the grain boundary plane will be discussed. In a separate study growth of NiO nanorods from individual Ni nanoparticles was observed during in-situ electron microscopy at high temperature and in the presence of water vapor. High-aspect ratio growth of NiO is favored for sufficiently high total surface energies. Potential growth modes are discussed. This work was financially supported by the National Science Foundation under award DMR-1836571.
8:40 AM Invited
Atomic Structure of Two Phases of a Cu Tilt Grain Boundary Resolved by Scanning Transmission Electron Microscopy: Gerhard Dehm1; Thorsten Meiners1; Jazmin Duarte1; Timofey Frolov2; Christian Liebscher1; 1MPI Eisenforschung; 2Lawrence Livermore National Laboratory
Bulk phases and their transformations play a key role in the design of materials. In nanocrystalline materials and thin films the abundance of grain boundaries opens an additional route to tailor properties via segregation and/or grain boundary phase transitions. In this presentation, we report on grain boundary segregation and grain boundary phase transformation in Cu thin films studied by aberration corrected scanning transmission electron microscopy. Atomic resolved imaging of a Sigma 19b grain boundary revealed novel grain boundary structures and unexpectedly the coexistence of two different atomic motifs indicating the coexistence of two grain boundary phases. The two grain boundary structures are separated by a line defect. The experimental observations are discussed and compared to molecular dynamic simulations.Acknowledgement: Financial support by the ERC Advanced Grant GB CORRELATE (Grant Agreement 787446 GB-CORRELATE) is gratefully acknowledged.
9:10 AM Invited
Formation/Migration of Faceted Boundaries and Grain Growth Behavior in Ni: Suk-Joong Kang1; 1KAIST
When highly pure Ni powder compacts with a size of 180 micron were annealed at 550⁰C, abnormal grains with {100} facets formed, grew, and impinged upon each other. All the boundaries were dry with no liquid film. The {100} grain boundary planes were singular with atomic steps and had a lower energy than the other planes. This result indicates that grain growth in Ni is governed by the movement of {100} singular planes with step formation and spreading. With increasing annealing temperature, the fraction of faceted boundaries decreased. For a fixed time period and increasing temperature, the grain growth behavior changed from primary stagnant to primary abnormal with well-faceted cubic grains, secondary stagnant, secondary abnormal with apparently rounded grains and quite normal. This repetitive grain growth behavior with temperature increase can be a critical support for our mixed mechanism principle of microstructural evolution, which was deduced a decade ago.
9:40 AM Invited
Charged Interfaces: Equilibrium, Phase Transitions, and Microstructural Evolution: KSN Vikrant1; Edwin Garcia1; 1Purdue University
Surfaces and interfaces in ionic ceramics play a pivotal role in defining the properties and microstructural evolution in many of the existing and emerging material applications. In this presentation, the effects of ionic species and point defects on the stability of grain boundaries in polycrystalline ceramics are discussed by using a thermodynamically consistent variational framework. The transport properties induced by the broad region of electrochemical influence in front of a grain boundary are quantified, and the effect of non-electrochemical driving forces, including stresses, misorientations, and structural disorder are considered. The theory outlines the conditions that lead to the interfacial phase transition of surfaces and interfaces. Further, the effects of electrostatic charge on grain boundary motion during grain growth are quantified as a direct extension of John Cahn’s solute drag theory. Presented applications include the microstructural mechanisms leading to the onset of flash sintering, abnormal grain growth, and ferroelectric fatigue.
10:10 AM Break
10:30 AM Invited
Microstructure Evolution in Thin Film Yttria-doped Barium Zirconate: Dylan Jennings1; Ivar Reimanis1; Sandrine Ricote1; Jose Santiso2; 1Colorado School of Mines; 2Catalan Institute of Nanoscience and Nanotechnology, ICN2
Microstructure evolution in mixed metal oxides exposed to various redox conditions is important to understand for applications such as catalysis, solid oxide fuel cells, and solar thermal water splitting. The present work examines the behaviors of thin films comprising yttria-doped barium zirconate (BZY), a classical proton conductor, under various environmental conditions. It is shown that the chemical and morphological stability of the films decreases when Ni is added; in contrast, the presence of Fe, either as an impurity or added intentionally, enhances film stability. Exsolution of metallic Ni from solution in the BZY at the film surface readily occurs under reducing conditions. The exsolved particles display a unique crystallographic relationship with the BZY, unlike Ni particles formed via dewetting experiments where several orientations were observed. The Ni/BZY interface energy was determined with a Winterbottom analysis and results are discussed in the context of microstructure evolution and stability of the films.
11:00 AM Invited
FCC Films on c-sapphire: Why Do Single Elements and High Entropy Alloys Adopt the Same Orientation Relationships?: Dominique Chatain1; 1CNRS
The physical origin of the orientation relationships (ORs) of thin film grains of an fcc phase on c-sapphire is revisited. Interestingly, they are found to be identical for different phases such as pure Ni, Cu, Al, Pt and CoCrFeNi, while their characteristic parameters (lattice constants, elastic constants, interfacial energies, etc.), which are considered to govern an OR, are different. The role of other parameters such as the interfacial steps are investigated.
11:30 AM Invited
Combining Atomistic to Thermodynamic Modeling with Machine Learning and Advanced Microscopy to Understand General Grain Boundaries and Interfaces: Jian Luo1; 1University of California, San Diego
This talk first reviews a series of our studies to compute grain boundary (GB) counterparts to bulk phase diagrams. Here, a grand challenge is to construct complexion diagrams for general GBs as function of five macroscopic (crystallographic) degrees of freedom (DOFs). A most recent collaborative study uses genetic algorithm-guided deep learning to predict GB properties in a 7-D space (5 macroscopic DOFs plus temperature and composition) [Materials Today 2020]. Furthermore, several examples of complexions formed at general GBs are discussed. Complex interfacial superstructures with gradients in the chemical, structural, and bonding characters were characterized and modeled at both general GBs [Materials Horizons 2020] and phase boundaries [Science Advances 2021]. An electrochemically induced GB transition was discovered and modeled, which can induce abnormal grain growth [arXiv: 2012.15862]. Here, thermodynamic models, DFT calculations, hybrid Monte Carlo and molecular dynamics simulations, machine learning, and advanced microscopy are combined to understand these interfaces.