[PAST EVENT] Dilshan Premathilake, Applied Science - Ph.D. Dissertation Defense
Abstract: The development of electrical double layer capacitors using vertically oriented graphene nanosheets with fast frequency response continues. The inherent open morphology of the nanosheet films is such that it allows efficient ingress and egress of electrolyte ions, making them suitable for AC line filtering. Since the molecular surface area is only about a factor of ~320x over the geometric area, the specific capacitance available remains limited. This dissertation presents a study of the growth of vertically oriented graphene nanosheets on Ni and Al substrates and the resulting performance as electrical double layer capacitors. Additionally, the underlying architecture of VOGN on Ni is used for coating with high surface area carbon black to substantially increase the specific capacitance while still retaining the open morphology to allow good frequency response at 120 Hz. The carbon black coating was deposited on ~1.2 mm high vertically oriented graphene nanosheets providing a specific capacitance of 2.3 mF/cm2 at 120 Hz. This is the highest specific capacitance at 120 Hz for electric double layer capacitors reported to date and is now in the range to replace some electrolytic capacitors.
Bio: Dilshan Viraj Premathilake was born in Kandy, Sri Lanka on September 1983. He graduated from Trinity College-Kandy in 2002 after sitting for the island wide advanced level examination and became eligible for university studies in physical science at the University of Peradeniya. In 2004 he started his Bachelor?s degree in physics and advanced mathematics. Due to exemplary work, in 2006 he was chosen to do a special degree in physics minoring in advanced mathematics and graduated in 2008. After a year of working as a teaching assistant at the University of Peradeniya, he was selected in August 2009 for graduate studies by the Department of Physics at Old Dominion University. In 2011 he was awarded a Master of Science in Physics. In August 2012, he was accepted into the Department of Applied Science Ph.D. program at William & Mary and began his graduate studies.