| These years,the new composite materials,which consist of graphene and different forms of the materials,has shown great potentials in the fields of supercapacitors,sensors and fuel cells.As we known,the properties of composites deeply depend on their composition,structure and morphology.Therefore,it is very important to design and control the microstructure of the composite to improve the performance of the material.In these study,we combine graphene with metallic copper to fabricate a variety of graphene/copper composites,and the morphology,structure and related properties of these composites were studied systematically.1.Based on the molecular-level mixing process,hydrothermal method and electrostatic self-assembly method,three different morphologies of graphene/Cu nanocomposites were fabricated,namely Cu nanoparticles-decorated two-dimensional graphene?RGO/Cu?,Cu nanoparticles-decorated three-dimensional graphene?3D-RGO/Cu?and graphene-encapsulated Cu nanoparticles?Cu@RGO?.As for RGO/Cu,it was found that the increasing reduction temperature resulted in the increase of the Cu particle size and the decrease of Cu particle loadings absorbed on the RGO,and the increasing reduction temperatures led to the decreasing concentrations of various functionalities of RGO with various degrees?especially for C=O?.As for 3D-RGO/Cu,the initial addition of copper salt will lead to the increase of copper particle loading on the surface of three-dimensional graphene and there was a limit on the amount of loading,during which the copper particles can maintain the fine structure?3-10 nm?without agglomeration.For Cu@RGO,the core-shell composite exhibited superior oxidation resistance compared to RGO/Cu and pure copper samples,and still no copper oxides and other impurities were found after standing in air for thirty days.2.The glucose detection performance of the above three composite modified electrodes was studied.The results showed that all three modified electrodes have great catalytic ability.Specifically,the detection limit of RGO/Cu electrode was 0.83?M,sensitivity was 62.5?A·mM-1·cm-2 and detection range was 2.5?M-1500?M.Moreover,the electrochemical results showed that the size and loading of copper particles played a more dominant role in the electrocatalytic process than the electron transport capacity between graphene-copper particles.In the case of the same grain size of copper,the3D-RGO/Cu modified electrode exhibited higher sensitivity than RGO/Cu(280?A·mM-1·cm-2),wider detection range?0.6?M-3.2 mM?and lower limit of detection?0.2?M?.In addition,compared with RGO/Cu and pure Cu samples,the Cu@RGO modified electrode not only has better glucose detection ability,but also retained better catalytic ability after standing for thirty days(the detection limit of Cu@RGO modified electrode was 0.34?M,sensitivity was 150?A·mM-1·cm-2 and detection range was 1?M-2 mM).In addition,the three composite modified electrodes exhibited excellent anti-interference,continuity and repeatability in alkaline environments.3.RGO/Cu,3D-RGO/Cu and Cu@RGO as conductive fillers were filled in polyethylene oxide?PEO?to obtain graphene/Cu/PEO electromagnetic shielding composites by solution blending method.The results showed that the shielding effectiveness of all three composites increased with the increase of filler loading,and increased first and then stabilized with increasing frequency?2-12 GHz?.Moreover,the absorption loss was the main shielding mechanism in all frequency ranges with certain content.The percolation threshold range of RGO/Cu/PEO was 25-30 wt.%.With the increase of conductive fillers,the electromagnetic shielding mechanism gradually changed from reflection loss to absorption loss,and the shielding effectiveness can reach as high as6.38 dB?11 GHz,35 wt.%,the same below?;The 3D-RGO/Cu/PEO percolation threshold was 25-30 wt.%,and the absorption loss was the main shielding mode under different packing loadings,up to 11.42 dB.Cu@RGO/PEO has better electromagnetic shielding effectiveness?15.97 dB?,lower percolation threshold?20-25 wt.%?than RGO/Cu/PEO and 3D-RGO/Cu/PEO.4.Graphene was deposited as a second phase in the copper matrix by electroless co-deposition to obtain a graphene reinforced copper matrix composite.The results showed that graphene oxide was successfully reduced to graphene during the co-deposition process and uniformly distributed in the copper matrix in the form of few layers.The results of nanoindentation confirmed that the addition of graphene can significantly improve the mechanical properties of composites,and within a certain range increased with the addition of GO.In addition,the addition of graphene make the composite grain refinement,micro-stress and decrease of the lattice constant in the matrix. |
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