Preparation, Characterization And Performance Study Of Graphene-based Composite Materials

Graphene,as a rising star of materials science is attracting more and more attention from scientific community due to its unique two-dimensional(2D)structure and excellent physical and chemical properties.The fascinating properties render graphene a promising candidate in wild applications such as electronics,information,energy and materials.By functionalization methods,new graphene nanocomposites can be fabricated readily and the intrinsic properties of graphene can be preserved while some special properties can be introduced.We studied the functionalization and characterization of graphene together with the catalytic and electrortheological performance of new graphene nanocomposites.Especially,we developed a facile preparation of highly reduced graphene nanocomposites via chemical reduction of graphite oxide.The content of this thesis are outlined below:(1)Fabrication of Palladium-anchored graphene nanocompositesWe developed a one-pot method to fabricate palladium-anchored graphene nanocomposites from graphene oxide(GO)with N,N-dimethylformamide(DMF)as solvent and reductant.Pd nanoparticles were anchored and stabilized by the graphene oxide which can efficiently prevent Pd nanoparticles from further aggregation.The structure and the properties of G-Pd were characterized by FT-IR,Raman spectroscopy,XRD,SEM,TEM and TG,respectively.The observations of TEM and SEM showed that the surface of graphene are evenly anchored with palladium nanoparticles.With increasing reaction temperature,the size of Pd nanoparticles enlarged.XRD confirmed that Pd(OAc)2 were reduced to form Pd nanoparticles while GO was reduced in situ.Raman and FT-IR spectroscopy indicated that oxygen-containing groups on GO were gradually removed and the degree of reduction are correlated to reaction temperatures.The mechanism of the G-Pd composites is deduced as that Pd(OAc)2 was absorded on the surface of GO.In a solvothermal process,DMF releases dimethylamine and carbon monoxide(CO)as a reducing agent.Finally,G-Pd nanocomposites were isolated by filtration.In the process,DMF is used as both stabilizer and the reductant.(2)Pd-anchored graphene catalyzed CO-free aminocarbonylationPd-anchored graphene were evaluated in catalytic free-CO aminocarbonylation of aryl iodides or bromides in DMF.The catalyst system demonstrated excellent catalytic activity under ligand-free conditions.The influence of reaction temperature and time,substrates and catalyst loading were systematic examined.The results showed that the temperature is the key of catalytic efficiency.Iodobenzene gave the desired coupling product in higher yield than bromobenzene.Chlorobenzene is inert against the current aminocarbonylation.Yields of the catalytic reactions decreased notably as a small quantity of water added.The catalyst were recycled for 8 times without any significant loss in activity.The mechanism were proposed as four steps,including oxidative addition,CO insertion,reductive elimination step.All the steps presumably near or on the surface of Pd and the unique electronic graphene supporter are crucial for catalytic performance of the Pd-G catalyst.(3)Synthesis and characterization of three-dimensional porous graphene framework hybrid materials pilled with titanocene organometallic complexThree-dimensional porous GO frameworks hybrid material(GO-TDC)and RGO frameworks hybrid material(RGO-TDC)with titanocene organometallic complex pillaring units were prepared through an ultrasound intercalation.Porous materials were fully characterized by XRD,SEM,TEM,XPS,FT-IR,Raman spectroscopy and TG.XRD analysis indicated that exhibit periodic layered structures with expanded interlayer spacing.FT-IR spectroscopy identified the chemical functionalization of TDC.Raman spectroscopy demonstrated that the skeleton structure of graphene oxide remained after TDC treatment.Furthermore,the strong interaction between carbon layers improved thermal stability of the precursor.Nitrogen sorption analysis revealed the framework materials have porous structure and provide highly increased accessible surface area compared to GO or RGO alone,indicating the importance of pillaring unit.(4)Colloidal graphene oxide/titania composite microspheres and their electrorheological characteristics under applied electric fieldColloidal TiO2 microspheres and graphene oxide/TiO2 composite microspheres(GO/TiO2)were fabricated by a sol-gel method and steam hydrolysis method.The composition and structure of TiO2 and GO/TiO2 were characterized by FT-IR,XRD,XPS,Raman and TG-DTG.The results showed TiO2 microspheres were amorphous structure.The interaction between GO and TiO2 is chemical binding.The electrorheological properties(dynamic shear stress and static yield stress)of the suspensions of these particles in silicone oil were investigated under DC electric fields.The results showed that the GO/TiO2 composite materials have excellent electrorheological performance.