Unless otherwise noted, all Seminar Series events are held at 3 p.m. in the MoSE "M" Building (Room G011). Refreshments are served in advance starting at 2:30 p.m. outside of GO11.
Ziegler Award for Best Paper
Yutong Wu (Advisor: Dr. Nian Liu)
“In Operando Visualization of the Electrochemical Formation of Liquid Polybromide Microdroplets” (accepted for publication in Angewandte Chemie International Edition)
Zn/Br flow batteries are one of the promising technologies for stationary energy storage. Bromine complexing agents have been used to form phase-separated liquid polybromide charging products. However, dynamic and microscopic understandings of the nucleation and growth of the polybromides on the electrode are limited due to the beam-sensitivity and complexity of polybromides and their surrounding electrolytes.
We report an in operando platform composed of dark-field light microscopy and a transparent planar electrochemical cell to dynamically reveal the electrochemical nucleation and formation of polybromides. Using our platform, we confirm and reveal the liquid nature, pinning effect (strong interaction with Pt), residual effect (surface residual charge products), self-discharge of the polybromide product, and overoxidation as a side reaction. We also conclude that the electrochemically formed droplets are mainly MEPBr5 rather than previously reported MEPBr3 with in situ Raman spectroscopy. These results provide mechanistic insight into the role of ionic liquid complexing agents and Zn/Br battery design. The in operando visualization platform can also be applied to study other unstable or transient products or intermediates in electrochemical reactions in a non-perturbing manner.
Ziegler Award for Best PhD Proposal
Ezgi Dogan Guner (Advisor: Dr. J. Carson Meredith)
“Incorporating Cellulose Nanocrystals into Zero-VOC Waterborne Acrylic Coatings”
Waterborne coatings are primarily produced with hard acrylic polymers that have moderate glass transition temperature (Tg-48˚C) to provide adequate hardness, adhesion strength, block resistance, and surface uniformity to the coatings. These coatings are formed by casting a stable dispersion of nano/micro scale polymer particles in water, produced by emulsion polymerization. A monomeric emulsion (monomers, water, and surfactants) is polymerized to form a polymerized emulsion, called latex. Hard acrylic latexes cannot form a continuous polymer film at ambient temperatures. Along with the aqueous phase of latex, coating formulations have significant levels of volatile organic compounds (VOCs) as a coalescing aid to ensure the film formation by temporarily plasticizing these hard polymers. The industry has been under increasing pressure to reduce VOCs to meet demanding environmental regulations. VOC reduction requires the use of low Tg polymers at higher compositions to maintain film formation at ambient temperature; however, low Tg polymers alone result in softer and tacky films. Successfully balancing hardness while reducing VOCs and ensuring proper film formation is challenging. Recent methods to lower VOCs and maintain film hardness include lowering the Tg of the dominant phase polymer and blending in small amounts of hard polymer to reinforce the soft film. These methods are not eliminating the use of coalescent. The formulation still needs VOC to achieve the required strength and hardness.
Cellulose nanocrystals (CNCs) have encouraging properties that can benefit zero-VOC waterborne acrylic coatings by improving their insufficient mechanical properties. Cellulose nanocrystals are renewable nanomaterials that possess remarkable mechanical and surface properties that can address the problems related to zero-VOC coatings. However, how CNCs will be incorporated into latexes and determining their location to polymer particles are vital questions that need to be addressed. The location and distribution of CNC in a latex system will affect the stability and rheology of latexes and final film properties. The interaction of CNCs with acrylic polymers will depend on how CNCs are located: inside, outside, core or shell of the acrylic latex particle. However, controlling this location is challenging. The proposed work described here aims to deal with the challenges in adding CNCs to acrylic latexes and evaluating the effect of the interaction between CNCs and latex particles on mechanical, thermal, and optical properties of the resultant coatings. This proposal will focus on three specific aims: (1) incorporating unmodified CNCs into the aqueous phase of the latex, (2) encapsulating surface functionalized CNCs into the acrylic polymer particles, and (3) developing a process-structure-property relationship for CNC-loaded latex coatings. Successful outcomes to these aims will enable sufficient properties in low or zero-VOC acrylic waterborne formulations, and the ability to tune the properties of latex films for an intended application.
About the Ziegler Awards:
The Waldemar T. Ziegler Awards were established by the family and friends of the late Waldemar T. Ziegler to honor his lifelong commitment to academic excellence and research.
Ziegler was on the faculty of the School of Chemical Engineering from 1946 until his retirement in 1978, when he was named Regents’ Professor emeritus. He died in 1996, leaving behind a legacy of outstanding research in the fields of cryogenics and thermodynamics. Ziegler was instrumental in establishing both the School’s and Georgia Tech’s reputations for outstanding research.
Two individual Ziegler Awards are presented annually to graduate students. The Ziegler Award for Best Paper began in 1998, and the Ziegler Award for Best Proposal began in 2005.