Dielectric Properties of Polymer Nanocomposites: Gavin Mitchell
Major: Materials Science
Engineering and Honors College
University:
WSU
Year:
Sophomore
REU Program: Materials Science
Engineering
Advisor: Associate Professor Katie
Zhong and Visiting Assistant Scientist Lili
Sun
Entering the research lab, Honors College student and WSU Regents Scholar from Spokane Gavin Mitchell begins his day by making polymer thin films. His assignment is to investigate the dielectric properties of polymer/carbon nanofiber nanocomposite materials under the tutelage of Katie Zhong, associate professor in the School of Mechanical and Materials Engineering.
The project necessitates the preparation of thin films, a process that starts by dispersing carbon nanofibers (CNFs) in a solvent or a combination of solvents, depending on the polymer that will be used, in an ultrasonic bath. Then the polymer is added and the solution is stirred constantly for 30 to 60 minutes, once again dependent on the polymer being used. The polymer/CNF solution is returned to the ultrasonic bath for a final hour to remove air bubbles that may have formed during stirring. The solution is then poured into a film mold and spread on a clean, glass sheet. Depending on the solvent(s) used, the solution can then be dried at room temperature or in an oven, and removed from the glass sheet. This is known as the “Solution-Cast” method of film preparation.
Polymer films created by Gavin Mitchell in Zhong's lab.
Part of the experiment is to test how the addition of carbon nanofibers changes the dielectric properties of polyethylene and polyethylene oxide; this allows the thin films themselves to be used without further modification. Another part is testing how the thickness of a polymer/nanofiber sample affects the dielectric properties; this requires several films to be layered together and then hot-pressed into one sample.
“The pressure applied during hot-pressing and the number of films pressed together both determine how thick the resulting sample will be,” states Mitchell.
Recently, polymer nanocomposites have attracted wide interest as a method of enhancing the properties of polymers. In polymer nanocomposities, chemically dissimilar components are combined at the nanometer scale, and strong interactions between the polymer and nanoparticles produce markedly improved materials with better electrical, mechanical, and thermal properties. Although a healthy amount of research has been directed to the study of how carbon nanotubes affect the dielectric properties of polymers, little research has been conducted on the effects of CNFs, even though CNFs are significantly cheaper to produce. This is due in part to difficulty dispersing the CNFs evenly throughout polymers. Mitchell’s research will help determine how this dispersion problem affects the dielectric properties of the nanocomposites.
The goal of this research is to develop polymeric materials with better dielectric properties.
“This basically means the ability to store a greater amount of charge than current materials with less ‘bleeding off’ of the charge over time,” explains Mitchell. The problem with most dielectric materials is that even though they can store great amounts of charge, they also lose that charge at a rapid rate.
“We want to maximize the storage component and minimize the loss component,” he says.
Mitchell enjoys making polymer films in the lab, blending the nanofibers, and using a dielectric spectrometer and a scanning electron microscope. The hardest part of the research process for him, however, is reading and understanding the scientific journals that are related to the research.
“The technical journals are a killer,” explains Mitchell. “It’s difficult to understand them when you don’t have the mathematical background for it yet.” He has just completed his first year of college.
“Mitchell has a great attitude for working and shows good practical ability in the experiments,” states Lili Sun, visiting assistant scientist in Zhong’s lab. “He is always trying to figure out the problems occurring in the experiments by himself, which is outstanding.”
Overall, Mitchell has enjoyed his undergraduate research experience at WSU and would like to participate again next summer if given the chance. He plans to work in a lab or a material science-based industry after he graduates and possibly pursue a master’s degree.
Currently, Mitchell is a member at WSU of the Honors Student Advisory Council (HSAC), the Biodiesel Club, and Engineers for a Sustainable World.
WSU Sophomore Gavin Mitchell