| Summary: | 碩士 === 國立臺灣師範大學 === 機電工程學系 === 105 === In this research, we represent a novel a novel and environment friendly method to produce the graphene flakes within a short time by using three separate processes of preparation. Eco-friendly and yield is the core of this research, without using any organic solvents, which could cause toxication, pollution and raise the production costs.
In this research, CO2 super critical fluid would be used to assist the process including NaHCO3 as the intercalation material. By using super critical fluid, with high temperature and high pressure, the CO2 molecule and NaHCO3 intercalate into the graphite. Because the super critical fluid is practically non-surface-tension, it could easily permeate into the porous graphite in order to shorten the processing time. When the reaction time is reached, the super critical fluid is fully intercalated and vaporized the CO2 fluid by rapid depression. The sudden pressure make the volume of CO2 expanse in the interlayer, makes the interlayer exfoliate the graphite layer for large amounts of graphene. By using thermal shock method, the CO2 exfoliated the graphene flakes again, then use ultra sonication exfoliation for further exfoliation to obtain few layer graphere.
Use centrifugation to select the solutions and test three separate processes with the samples of 3000rpm and its residuals by Raman spectra and discover the ID/IG ratio is lower than the previous process. Field emission scanning electron microscope discover that the exfoliated graphene layer is transparent and thin, smooth without winkles. The atomic force microscope detect that the first process can obtain 85% of graphene under ten layers, the second process can obtain 75% of graphene under ten layers, the third process can obtain 70% of graphene under ten layers. It determines that the supercritical fluid exfoliation can be a reliable method to obtain few layers graphene.
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