Title of Paper:Exfoliation of graphite in CO2 expanded organic solvents combined with low speed shear mixing

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Date of Publication:2018-08-01

Journal:CARBON

Included Journals:SCIE

Volume:135

Page Number:180-186

ISSN No.:0008-6223

Key Words:FEW-LAYER GRAPHENE; LIQUID-PHASE EXFOLIATION; SUPERCRITICAL CO2; RAMAN-SPECTROSCOPY; NANOSHEETS; SYSTEMS; OXIDE

Abstract:A simple and effectivemethod of producing pristine graphene sheets was investigated in this study. Natural graphite flakes were exfoliated in CO2 expanded N-methylpyrrolidone with a low speed agitation of 1000 rpm followed by 30min sonication. Few-layer graphene were obtained with the concentration of 0.0576 mg/mL after centrifugation at 4000 rpm for 30min. More than 90% of the product were two or three-layer graphene and 12-38% were even monolayer. In addition, ethylene glycol and ethanol were also proved to be effective solvents with the assistance of CO2 intercalation, but they were not good solvents for the exfoliation in the subsequent sonication process. Finally, Agitation time, the system pressure and temperature were systemically investigated to find out more appropriate parameters for the production. (C) 2018 Elsevier Ltd. All rights reserved.