Research Of Exfoliation Of Graphite To Graphene

Graphene is a two-dimensional material with unique structure and excellent properties.Since it was successfully prepared for the first time in 2004,Graphene has become a hot point of many fields such as materials,chemistry,physics and engineering.Presently,several methods of graphene preparation have been reported,including chemical oxidation-reduction,chemical vapor deposition(CVD)and liquid-phase exfoliation(LPE),etc.Among them,LPE is an important way to realize industrialization.In this paper,we predominantly explored the LEP process.On the one hand,we use the ultrasonic tip as our exfoliation to explore our exfoliation process.Firstly,we use liquid carbon dioxide and supercritical carbon dioxide as our exfoliation reagent.At the same time,we explore other exfoliation reagents,such as dimethylformamide and ethanol system,N-methyl-2-pyrrolidone and ethanol system,surfactant and ionic liquid etc.the topography and nanostructure of graphene are characterized by AFM,TEM and Raman spectra.Furthermore,we have exfoliated graphite to single layer graphene after 24 hour reaction,but the dispersion only contained afew number of single layer graphene,and most thickness is around 3 nm.Finally,we also explore other raw materials for our experiment,such as expansible graphite,expanded graphite,intercalated graphite and weakly oxydic graphite,but the result is not excellent.On the other hand,we use the ultrasonic bath as our exfoliation power to explore two binary solvent systems,i.e.dimethylformamide/n-butylalcohol system and dimethylformamide/ethanol system,which are mixed with guarantee reagent.As a result,all those two systems facilitate higher concentration production of graphene and improve the stability of the dispersion.And then we introduce hydrogen bond to explain exfoliation mechanism and stability mechanism.At the same time,we find that Hansen solubility theory is not suitable for our systems.Furthermore,the topography and nanostructure of graphene are characterized by AFM,TEM and Raman spectra.And then we get the absorbance coefficient of our dispersion using UV–Vis spectra.We get a dispersion that predominantly contained single-layer graphene after 6000 r/min centrifugation.Meanwhile,we compare the absorbance of graphene dispersions exfoliated at different ultrasonic conditions.We conclude that ultrasonic bath is the better way to do our experiment.Finally,we discuss the influence of raw material concentration and ultrasonic.