“Mechanically Reconfigurable Materials and Devices based on 2D TMD layers” and “Structural Supercapacitor Electrodes Based on Reduced Functionalized Graphene Oxide”

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Thursday, November 5, 2020 -
2:00pm to 3:15pm
Emmanuel Okogbue, Graduate Student, University of Central Florida and Paraskevi Flouda, Graduate Research Assistant, Texas A&M University

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 (11/5 2-3:15PM or 11/6 3-4:15PM):  RSVP Here

Asynchronously view the presentation ONLY here:  Asynchronous Presentation (link not live yet)

 

“Mechanically Reconfigurable Materials and Devices based on 2D TMD layers”

Emmanuel Okogbue,

Graduate Student,

University of Central Florida

The recent advances in modern electronics have been geared towards the combination of miniaturized device components and their deterministic integration onto unconventional platforms. This endeavor is aimed towards achieving new generation of electronic devices with exotic functionalities, which are unachievable with traditional approaches. Among these envisioned cutting-edge technologies, electronic devices which are mechanically reconfigurable and operable under harsh operational conditions such as mechanical deformation in form of stretching, twisting and folding offer tremendous amount of unparalleled opportunities. Traditional devices rely on intrinsically rigid and bulky three-dimensional (3D) silicon (Si) wafers, which need to undergo complicated and unsustainable fabrication steps to enable mechanical deformation. This bottleneck in conventional technologies and manufacturing triggered the exploration of new electronics materials possessing superior properties even at very low dimensions. Two-dimensional (2D) transition metal dichalcogenide (TMD) layers have gained increasing attention for their unique electrical, mechanical and optical properties unattainable in conventional thin films. Moreover, their intrinsically large strain limits, small thickness and van der Waals attraction makes them uniquely suited for mechanically reconfigurable electronics. In this talk, I will give an overview of my research efforts primarily focused on mechanically reconfigurable devices based on 2D TMD layers. This study encompasses synthetic methods for achieving wafer-scale high quality 2D TMD layers, directly grown on both rigid and deformable substrates, as well as novel approaches to deterministically transfer them onto arbitrary substrates, further diversifying their applicability. Furthermore, I will present viable strategies employing strain-engineering concepts to three-dimensionally architect 2D TMD layers into tailored geometry which can ensure high mechanical stability accompanying well preserved electrical/optical integrity. Lastly, I will present applications of these mechanically reconfigurable 2D TMD layers for emerging and unconventional electronics such as smart windows and wearable e-skin sensors by exploring their strain variable and invariable exotic properties. 

Emmanuel Okogbue is a fourth-year Ph.D. student in the Electrical Engineering Department at the University of Central Florida. He earned his M.S. in electrical engineering and obtained his B.S. in electrical and electronics engineering from Federal University of Technology, Akure while completing his senior year at Florida A&M University. 

His research focus is in the area of nano-materials with a focus on mechanically reconfigurable devices using two-dimensional materials. He is an author of more than ten journal publications and has been a recipient of several awards including first prizes at the NanoFlorida International Conference in 2019 and Conference of Florida Graduate Schools, and was recently fully funded to present his research at the Materials Research Society conference in 2019. He has also carried out industrial research on nano-materials as a research intern at Honda Research Institute.   Emmanuel is also an active member of the National Society of Black Engineers and Materials Research Society. 

“Structural Supercapacitor Electrodes Based on Reduced Functionalized Graphene Oxide”

Paraskevi Flouda,

Graduate Research Assistant,

Texas A&M University

Structural energy storage devices address both energy storage and structural functionalities in a single unit leading to lighter electric vehicles and more miles between recharging. However, the key challenge is to design electrodes that can simultaneously store energy and bear mechanical loads as these properties come with an inherent trade-off. In this context, here, we demonstrate how selected materials such as reduced graphene oxide (rGO) and aramid nanofibers (ANFs) can be processed into supercapacitor electrodes with enhanced mechanical properties by engineering the interfacial interactions. Recently developed aramid nanofibers, nanoscale Kevlar® fibers, are of great interest due to their exceptional mechanical properties, such as ultimate strength and stiffness. rGO has high electrical conductivity, high surface area, high capacitance, and excellent mechanical properties. ANFs interact with rGO through hydrogen bonding and π-π stacking interactions. To enhance hydrogen bonding interactions, GO was functionalized with -NH2 groups, -COOH groups, dopamine, and tannic acid.

Furthermore, branching the ANFs was investigated. Divalent (Ca2+) and trivalent (Fe3+) ions were introduced to chelate with rGOand further improve the interfacial interactions through coordination bonding. The composite electrodes were fabricated utilizing vacuum-assisted filtration to achieve a nacre-like ‘brick-and-mortar’ structure. The effects of these modifications on the mechanical and energy storage properties are discussed to determine the approach that leads to the best multifunctional performance.

Overall, the enhanced interfacial interactions led to significant improvements in the mechanical performance (up to five-fold increase in Young’s modulus and four-fold increase in tensile strength compared to pure rGO), while maintaining good energy storage performance. This work highlights the importance of chemical interactions for realizing stronger multifunctional materials.

Evi Flouda is a Ph.D. candidate in the Department of Materials Science and Engineering at Texas A&M University working with Professor Lutkenhaus and Professor Lagoudas. In 2016, she received her diploma in materials science and engineering from the University of Ioannina, Greece.

During her undergraduate studies, she worked at the Max Planck Institute for Polymer Research in Germany on the synthesis of hybrid nanoparticles for the catalysis of organic sulfides. Currently, her research focuses on the design and development of structural electrodes for supercapacitors and batteries.

Evi has received several awards for excellence and has served as the internal outreach chair of the Texas A&M Energy Research Society, which organizes the annual TAMU Conference on Energy

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