Date: 14th December, 2016, Wednesday
Time: 3:00 - 4:30 pm
Location: Meeting room 205 (in the former building of the School of Materials Science and Engineering)

Speaker: Dr. Gui-Ping Dai,  Department of Chemistry, North Carolina Central University

The large-area, synthetic graphene produced on copper (Cu) substrates by chemical vapor deposition (CVD) is typically poly-crystalline, consisting of a number of small single-crystalline grains separated by grain boundaries. Multiple graphene grains of different in-plane orientations are simultaneously nucleated in random and uncontrolled locations on the surface of polycrystalline copper foils. As the growth proceeds, these graphene grains coalesce and eventually form interconnected polycrystalline films. The sizes of the grains and the grain boundaries between them are predicted to strongly affect the electrical and mechanical properties of graphene films. In fact, the best carrier mobility (200000 cm2 V-1 s-1) of graphene is obtained from layers peeled from rare natural graphite, while the CVD polycrystalline graphene shows carrier mobilities of a few hundred to a few thousand cm2 V-1 s-1. Hence, the initial nucleation and growth dynamics of graphene play a critical role in determining the final quality of CVD graphene films. While it is highly desirable to synthesize large-area, high-quality single crystalline graphene films, achieving such an objective requires lower nucleation density of individual graphene grains to minimize the grain boundaries. However, merely controlling the nucleation number of graphene grains (domains) is insufficient. The shape and structure of individual graphene domains also greatly influences its properties and directly determines the grain boundary in polycrystalline graphene film. Thus, the tailoring and direct observation of the domain shape structure is very important for understanding the growth mechanism as well as to maximize single-crystalline graphene’s inherent outstanding properties for future application. I will address my recent research on the dynamics of CVD graphene growth on copper foils. This presentation also discusses the commercial application of graphene in li-ion battery.
Dr. Guiping Dai works at North Carolina Central University. Also Dr. Dai is the Chief Scientist at Chaowei Group. He leads an institute in which his team focuses on the development of next-generation motive power battery technology. He has worked extensively in graphene, carbon nanotubes and other novel nanocarbons with chemical vapour deposition, plasma torches, and chemical solutions and their applications in batteries, super-capacitors and electrochemical energy storage.