IMSE presents the North American Materials Colloquium Series:
Two presentations will be given in today’s seminar slot:
For the link to the synchronous presentation and live Q&A session (11/19 2-3:15PM or 11/20 3-4:15PM): RSVP Here
Asynchronously view the presentation ONLY here: Asynchronous Presentation (link not live yet)
“High Entropy Oxides: The Multicomponent Materials, Their Synthesis, and Properties”
Brianna L. Musicó,
Graduate Research Assistant,
University of Tennessee, Knoxville
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.
Brianna Musicó is a fifth-year graduate student in the Materials Science and Engineering (MSE) Department at the University of Tennessee, Knoxville (UTK) with an expected graduation spring/summer 2021. Brianna received her B.S. in August of 2016 and her M.S. in December of 2018 both in materials science and engineering from the University of Tennessee. Brianna is currently working under the direction of Veerle Keppens, Ph.D. focusing on the synthesis and characterization of high entropy oxides. Multicomponent, high entropy, systems have been investigated for their variety of physical properties achieved by forming new phases. This type of research has been done on many metallic alloy systems (HEAs) but has recently been expanded into ceramic systems by creating configurational disorder into a sublattice of a mixed oxide to form a high entropy oxide (HEO). These classes of materials are of interest as they have potential for multi-functionality. Brianna is focused predominately on spinel and perovskite type HEO systems, synthesizing single phase materials, and investigating their phase formation, structure, and magnetic properties. Her research also involves the use of resonant ultrasound spectroscopy (RUS) for elastic moduli property determination and has participated in many collaborations measuring these properties on other material systems. In 2019 she was selected as the Highlighted Graduate Student for the Center for Materials Processing, a Tennessee Higher Education Commission (THEC) supported Accomplished Center of Excellence. In the summer of 2020, she was selected as a recipient of a 12-month support package through the Center for Materials Processing Graduate Student Support Program. Brianna was the 2017-2018 vice president for the UTK chapter of the Materials Research Society, served as the 2018-2019 president, and was the recipient of the 2018 UTK MSE Graduate Student Service Award.
“Strain-Induced Electrochemical Inhomogeneity in Cathode Nanoparticles Revealed at Atomic Level”
Wenxiang Chen, Ph.D.,
Postdoctoral Research Associate,
University of Illinois at Urbana-Champaign
Chemomechanical coupling, a concept commonly used to describe energy conversionin 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 chemistryis 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.
Wenxiang has been a postdoctoral researcher with Professor Qian Chen in the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign since 2017. Prior to that, he received his Ph.D. in electrical and systems engineering at the University of Pennsylvania with Professor Cherie R. Kagan in 2017, awarded with the S. J. Stein Prize at Penn Engineering for his Ph.D. thesis. His research efforts focus on designing and understanding new generations of electrochemical and optical nanomaterials, by integrating colloidal synthesis, device fabrication, characterization, and simulation methods in both materials science and electrical engineering on length scales from atomic level all the way to meters. These approaches allow comprehending the chemomechanical coupling and engineering the strain in the electrode materials towards rationally optimizing energy technology and constructing reconfigurable, highly efficient metamaterials with unconventional optical properties