Preparation Of Graphene/Epoxy Composites Resin And Their Dielectric Properties

Graphene and its nanocomposites have been one of the most attractive topics in the materials science.In this dissertation,multi-layered graphene was used to obtained the nanocomposies with epoxy resin.The dielectric properties of graphene/epoxy nanocomposites were investigated.A comparative study was also made between the nanocomposites with graphene and carbon black to discuss the morphological structure of nano-carbon materials on the properties.By combining graphene and barium titanate,epoxy based composites with low dielectric loss were obtained.Graphene was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The curing dynamics was investigated by differential scanning calorimetry(DSC).The mechanical properties and glass transition temperature of the nanocompositematerials were studied by dynamic mechanical analysis(DMA).The dielectric properties of the nanocomposites were studied by dielectric spectroscopy.The following results were obtained.(1)Graphene/epoxy nanocomposites showed the similar curing temperature and apparent activation energy to epoxy resin.Two kinds of nanocarbon materials,graphene and carbon black,exerted similar effects on the curing mechanism of the nanocomposites.(2)The morphological evolution of graphene dispersed in epoxy matrix,as increasing loading of graphene,was found to undergo seperated layers,locally connected layers and continuous network.Carbon black,however,was dispersed in the form of aggregates.(3)Two dimensional structure of graphene was found helpful to constrain the movement of the macromolecules,which led to the enhancedstorage modulus and the increased glass transition temperature at high loading levels of graphene.(4)A platform was found in the frequency-dependent curve of the conductivity of graphene/epoxy nanocomposite,which indicated the formation of conductive networks.Consequently,the nanocomposites showed extremely high dielectric constant and loss.Compared with graphene,carbon black can form local network at lower loading levels.(5)Combination of graphene and barium titanate was helpful to obtain the composites with high dielectric constant and low dielectric loss.In comparision with carbon black,the composites with graphene showed a 20 % higher dielectric constant and a 21 %lower dielectric loss.