(712f) Preparation of Expandable Graphite with a Taylor-Couette Flow Reactor
In this study, we used a batch Taylor-Couette reactor setup and an aqueous solution to expand natural graphite flakes and produce EG. Conventional Taylor-Couette setups consist of two coaxial cylinders with the inner cylinder rotating while the outer cylinder is still, creating Toroidal, or Taylor, vortices that enhance the mass transfer of the reaction medium. The Taylor-Couette setup used in this study included the rotation of the outer cylinder while the inner cylinder is still. Laminar Couette flow structure and high shear rates were achieved via the rotation of the outer cylinder, which dampened vortex formation due to the absence of centrifugal forces acting on the reaction medium. To study the effect of residence time on graphite expansion, different residence times were employed and investigated.
Our results reveal that expanding graphene sheets could be achieved in an aqueous solution using a dispersant and a stabilizing agent. In addition, the level of expansion using an aqueous solution and a Taylor-Couette reactor is comparable to commercial EG synthesized by intercalating sulfuric acid, as revealed by x-ray diffraction. More importantly, the resultant EG flakes were more structurally homogeneous than commercial EG, and residence time exceeding three hours resulted in structural defects on the EG flakes. The resulting solution could be used for electrode fabrication in lithium-ion battery setups and graphene fiber applications.