炭素技术

先用Hummer法氧化天然鳞片石墨制得氧化石墨,在蒸馏水中利用超声分散将氧化石墨剥片,然后在肼的作用下加热回流制得石墨烯,应用扫描探针显微镜、红外光谱和热分析技术对所得产物进行分析表征。结果表明,氧化石墨在蒸馏水中可形成稳定的悬浮液,氧化石墨薄片厚度为1.0nm左右,天然石墨的粒径和灰分含量对氧化石墨的厚度及在水中的分散没有明显的影响;由石墨烯在水中的微观形貌图可证明其在不需要化学稳定剂的情况下,可以在水中稳定地分解分层,石墨烯薄片厚度为0.7nm左右,浓度高时石墨烯颗粒趋向于规则的网状排列,而稀释后可观察均匀的单层石墨烯薄片;用红外光谱分析石墨烯与石墨表面基团,结果表明基本一致;由热分析可得出,石墨烯在氮气中的热稳定性与石墨基本一致,而氧化石墨由于含氧基团增多变得不稳定,在200℃左右发生完全的热分解反应放出CO,CO2和H2O蒸汽等;由石墨与石墨烯在空气中的热分析可知,层状的石墨晶体氧化热稳定性远远高于石墨烯。

The graphite oxide(GO) was prepared by oxiding purified natural flake graphite via the Hummer method and was exfoliated in distilled water by sonication using Panda UP3200H ultrasonic bath cleaner(200 W).Hydrazine hydrate was then added and the solution was heated in an oil bath at 100 ℃ under a water-cooled condenser for 24 h, the reduced GO(graphene) was obtained.The graphene was analyzed and characterized by the scanning probe microscope(SPM), IR and thermal analysis technique.The results show that GO readily forms stable colloidal suspensions of thin sheets in water and the reduced GO sheet was well-exfoliated with uniform thickness of 1nm.The particle size and ash content of the natural graphite had no obvious effect on the reduced GO sheet thickness and the dispersion in water.The morphology of the graphene in water revealed that it can form stable suspensions and individual graphene nanosheet with 0.7 nm thickness without any chemical dispersant added;DFM images of graphene by the ultrasonic treatment at concentrations of 0.02 mg/mL in water always revealed the presence of regular crosslinked arrangement and at concentrations of 0.0008 mg/mL in water revealed the presence of individual graphene nanosheet with uniform thickness of 0.7 nm.Functional groups on the graphite and the graphene surface was almost the same by IR spectral analysis.A conclusion could be drawed by thermal analysis that the thermal stability in N2 of graphite and graphene is basically consistant, but GO is thermally unstable and starts to lose mass upon heating even below 100 ℃ , the major mass loss occurs at 200 ℃ , presumably due to the pyrolysis of the labile oxygen-containing functional groups, yielding CO, CO2, and steam.The oxidation thermo-stability of the graphite crystal with layer structure is more higher than that of the graphene.