石墨烯薄片之環保製備技術開發 Development of an eco-friendly technology for producing graphene flakes

Date
2017
Authors
葉芳均
Yeh, Fang-Chun
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Abstract
本研究提出一個新穎且綠能的方法,使用三種不同製程路徑,希望能夠縮短製程時間並量產石墨烯薄片,環保與量產是本研究的核心目標,過程中完全不使用任何的有機溶液,並且在製程之中不會衍生影響人體、環境汙染的廢液,不僅可降低石墨烯的生產成本,也可達成量產品質良好石墨烯薄片的目標。 本研究利用CO2超臨界流體處理技術來輔助生產石墨烯薄片,並加入碳酸氫鈉當作插層材料,藉由CO2超臨界流體的高溫及高壓,在反應時間超臨界流體的二氧化碳分子與酸氫鈉會插層在石墨層間,因為超臨界流體有如氣體幾乎無表面張力,故很容易滲入到多孔性材料石墨中,因此可以大幅縮短製程時間。當到達反應時間,超臨界流體已充分插層,藉由快速洩壓,使CO2流體汽化,瞬間產生的壓力讓石墨層中二氧化碳體積膨脹,將石墨層與層瞬間剝離,產生大量石墨烯薄片。以二氧化碳為流體,處理過後經釋壓成為氣體,過程中就無殘留的疑慮且它不會留在最終產物中。之後藉由熱震製程所產生的CO2再一次剝離石墨烯薄片,接下來以超音波破碎進行更進一步機械剝離處理,即獲得寡層石墨烯。 以離心篩選溶液,分別檢測三個路徑之3000 rpm樣品以及沉澱物樣品,以拉曼光譜儀檢測發現ID/IG比值越來越小,場發射穿透式電子顯發現剝離石墨烯薄片是相當透明且薄的,平滑沒有皺褶,而由原子力顯微鏡檢測,第一路徑可得70 %之10層以下石墨烯薄片,第二路徑可得75 %之10層以下石墨烯薄片,而第三路徑可得85 %之10層以下石墨烯薄片,證實CO2超臨界流體剝離方法確實具有將原始石墨剝離,並獲得寡層石墨烯之成效。
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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Keywords
寡層石墨烯, 熱震, 超音波震盪, 超臨界流體, few-layer graphene, thermal-shock, sonication, supercritical fluid
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