Preparation And Properties Of Graphene Matrix Composite

Graphene is a single-atom-layer two-dimensional crystal, in which carbon atoms form hexagonal honeycomb structure. It has very excellent physical and chemical properties, such as large specific surface area, high electrical and thermal conductivity, excellent mechanical property and chemical stability.The exceptional thermal conductivity of graphene is expected to endow polymer composites with ultrahigh thermal conductivities, which can be even similar to those of some metals such as stainless steel and aluminum alloy.In this dissertation, my research mainly focuses on a facile fabrication method to get aligned grephene and epoxy composite,Additionally, we discuss the properties of the composite, and the related conclusions as follows:First,using in situ polymerization to the prepare aligned grephene and epoxy composite with high thermal conductivity: using vacuum filtration to assemble graphene into closely packed and aligned bulk, then, epoxy monomers were infiltrated into the gaps between the graphene layers in the premade, macroscopic aligned grephene bulk. After the cure cycle, we succeeded in making the grephene and epoxy composite.The ultrahigh thermal conductivity of 33.54 W/(m K) has been achieved in the aligned graphene and epoxy composite. The thermal conductivity of aligned graphene and epoxy composite exhibits a positive temperature response related to the aligned structure while increasing the temperature from 40 °C to 90 °C.The experimental results clearly demonstrate huge enhancement in thermal conductivity and the positive temperature response through the aligned graphene as the filler in aligned graphene and epoxy composite. To account for the observed behavior, we consider the effective medium theory model and thermal expansion properties. Effective medium theory has been used to model the thermal conductivities of the thermal conductive fillers and polymer composites in parallel and perpendicular directions.The evaluated values of theoretical thermal conductivities within the small θ for the aligned graphene and epoxy composite can be consistent with the expermental results in the parallel direction. Each aligned graphene layer in the composite is arranged as a parallel conduction medium and provides direct graphene-graphene conduction to form conductive chains. The aligned structures of graphene in epoxy and thermal expansion properties of the components are responsible for the anisotropic temperature response of thermal conductivity. The reason is that as the epoxy expanse, the tensile strain further improves the alignment along the parallel direction and the more impacted stacking of graphene.In the finality, the problems requiring further studies are discussed.