Materials Science and Engineering Location: Zoom
Add to Calendar 2020-12-03T15:00:00 2020-12-03T15:00:00 America/New_York North American Materials Colloquium Series (NAMCS) Title: High Entropy Oxides: The Multicomponent Materials, Their Synthesis, and Properties Speaker: Ms. Brianna L. Musicó, Graduate Research Assistant, University of Tennessee, Knoxville, TN; Email address: bmusico@utk.edu Date and Time: Nov 19th (Thursday) at 3pm ET and Nov 20th (Friday) at 4pm ET. Zoom

Title: High Entropy Oxides: The Multicomponent Materials, Their Synthesis, and Properties

Speaker: Ms. Brianna L. Musicó, Graduate Research Assistant, University of Tennessee, Knoxville, TN;

Email address: bmusico@utk.edu

Date and Time: Nov 19th (Thursday) at 3pm ET and Nov 20th (Friday) at 4pm ET.

Abstract: Reports on the unique properties achieved with HEAs, including improved mechanical properties, has motivated the application of the multi-component approach to oxide materials, expanding the available compositional space and providing greater flexibility to meet the demands of today’s advanced materials. Since the first report in 2015, High Entropy Oxides (HEOs) have gained interest from a variety of fields as they provide opportunities for designing novel materials and tuning their properties. This will cover background information on the development of the material class and provide a comprehensive overview of our completed work including successful methods of synthesis, and notable properties investigated. A comparison of synthesis methods has been done for some compositions showing polymeric steric entrapment, a polymer assisted wet chemistry method, to be advantageous in HEOs when compared to the traditional solid-state method. A broad range of compositions and crystal structures, including perovskite, spinel, and Ruddleson Popper, have been successfully made. The effects of multicomponent material design on the structural, magnetic, and chemical properties are explored. In order to compare synthesis methods and gain insight in the kinetics involved, we have also employed rapid in-situ non-ambient X-ray diffraction to characterize the phase transformation and evolution of crystallinity in HEO materials.

 

Title: Strain-Induced Electrochemical Inhomogeneity in Cathode Nanoparticles Revealed at Atomic Level

Speaker: Dr. Wenxiang Chen, Postdoctoral Research Associate, University of Illinois at Urbana-Champaign, IL;

Email address: wxchen@illinois.edu

Date and Time: Nov 19th (Thursday) at 3pm ET and Nov 20th (Friday) at 4pm ET.

Abstract: Chemomechanical coupling, a concept commonly used to describe energy conversion in molecular motors, has emerged in the field of insertion electrochemistry to illustrate the interplay between electrochemical processes and mechanical deformation in energy storage materials, catalysts, and reconfigurable architectures. In rechargeable ion batteries, chronic or acute mechanical failures originate from shuffling of guest ions in and out of host structures, which impacts ion insertion pathways and undermines battery performance. Understanding chemomechanical coupling in insertion chemistry is thus critical to inform the design of electrode materials with high capacity, long life-time, and safety. In this talk, I will discuss new strategies to probe and engineer the chemomechanical coupling and electrochemical responses in cathode materials at the atomic level. Using crystalline cathode particles in Mg ion batteries as a model system, we first identify distinctive structural phase transition pathways in particles of different sizes during Mg ion intercalation as characterized by X-ray and electron microscopy. Small, nanoscopic cathode particles exhibit a solid-solution phase transition pathway while their micron-sized counterparts undergo conventional multiphase evolution. Next, we examine the chemomechanical coupling in cathode nanoparticles by integrating scanning electron nanodiffraction microscopy with collocated atomically resolved scanning transmission electron microscopy images. We map the strain and phase in a correlative manner in the intercalated nanoparticles at an unprecedented spatial resolution of 2 nm, achieving the first direct “visualization” of the chemomechanical coupling. Assisted by density functional theory, we elucidate atomic-scale strain relaxation mechanisms as the origin of the spatial heterogeneities of strains and phases in cathode materials, which impacts macroscopic cathode performance. The engineering implications could be on designing nanomaterials of high strain tolerance by tailoring the particle size as well as atomic-scale ion diffusion processes, which we envisage are applicable for various applications in insertion electrochemistry.

Additional details about the speakers can be found here:

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