Intercalated Graphite And Few-layer Graphene:Fundamental Properties And Molecular Structure Thermodynamics

Molecular intercalated graphite and few-layer graphene is a novel twodimensional system,which connects the physical and chemical properties of intercalated molecules and graphene,providing a new research field for basic physics understanding and various practical applications.In this thesis,by selecting natural flake graphite as the graphite matrix and anhydrous ferric chloride powder as the intercalant,the stage1 ferric trichloride-graphite intercalation compounds(FeCl3-GIC)was successfully prepared using the vacuum two-zone method,and it is found that a superparamagnetic transition will occur at the temperature of 5K.Using stage 1 FeCl3GIC as the precursor material for mechanical exfoliation process,a ferric chloride based few-layer graphene intercalation compounds(FeCl3-FLGIC)can be obtained.FeCl3GIC and FeCl3-FLGIC are thermally annealed at different temperatures in different chemical environments,and Raman spectroscopy is used as a monitoring tool to monitor the corresponding molecular structural the evolution of the composite.FeCl3GIC annealing at 500℃ and 600℃ in air will cause half deintercalation of FeCl3,resulting crystal structure transformation from the stage 1 to the stage 2.When the annealing the FeCl3-GIC at 700℃,the FeCl3-GIC converted to a new unknown material as reflected by the presentation of only one pronounced Raman peak at～1300 cm-1.For unknown chemical substances,the deintercalation and the formation of unknown chemical substances start from the edge position.FeCl3-GIC annealing at 500℃ in argon will also cause the structure phase transition from stage 1 to the stage 2,but higher annealing temperature will cause graphite matrix be etched and the deintercalation of FeCl3 is aggravated,and the annealing product at 700℃ will eventually become normally doped few-layer graphene;When FeCl3-GIC is annealed in hydrogen environment,the originally intercalated FeCl3 started to reduce to the form of FeCl2,and accompanied by the deintercalation process.It is found that annealing in hydrogen environment does not cause the obvious etching of graphite,and the final annealing product will become the normally hole-carrier doped graphite.On the other hand,FeCl3-FLGIC will be severely etched when annealing at 500℃ in the air,and will be completely etched away at higher annealing temperatures.FeCl3-FLGIC will not be severely etched when annealing in argon atmosphere at the temperature not higher than 600℃,showing the similar structural evolution trend compared to the precursor FeCl3GIC,but it will be eventually severely etched when the annealing temperature goes up to 700℃.FeCl3-FLGIC annealed in hydrogen atmosphere will cause an obviously observed strong substrate-reaction effect,as reflected by the strong broad D band in Raman spectroscopy,and the effect becomes more pronounced with respect to the increase of annealing temperature.Finally,chapter 3 focuses on laser irradiation induced heating effect to the ferric chloride based two-layer graphite intercalation compounds(FeCl3-2LGIC)prepared by two methods(top-down method and bottomup method)were irradiated by laser to induce the dynamic evolution of the molecules between the interlayer space of bilayer graphene,and found that the intercalated FeCl3 is stably existed at relatively low irradiation induced joule flux,but the structural started to show obvious phase transition when the joule flux exceeds than 0.3J/μm2(laser irradiation time is 30 seconds).After the entire laser irradiation process,the top-down method prepared FeCl3-2LGIC deintercalated with introduction of obvious defect.The irradiated area of FeCl3-2LGIC prepared by the bottom-up method becomes doped bilayer graphene.