Synthesis Of Graphene-based Hybrid Materials With Electromagnetic Wave Absorption Properties

Graphene,as one of typical two-dimensional carbon nanomaterials,consists of a single layer of carbon atoms in a densely packed honeycomb lattice structure,which exhibits good electrical properties,mechanical properties and excellent thermal stability.Graphene can exhibit a quantum Hall effect at room temperature,and the electron mobility remains almost unchanged with temperature variation.The electron mobility of graphene monolayer can be maintained at about15000 cm/(V·s)between 50 K and 500 K.Therefore,it can be used as a new and effective microwave absorption and electromagnetic shielding material.In this thesis,graphene/ferrite nanocomposites were prepared by hydrothermal method and radiation reduction method,respectively.The main research work carried out is as follows:1.Preparation of graphene-ferroferric oxide nanocomposite by hydrothermal method and its microwave absorbing propertiesThe nanocomposite material named graphene-ferric oxide(r GO-Fe₃O₄)was prepared by hydrothermal method.During the entire preparation process,graphene oxide(GO)is reduced to graphene(r GO),and the prepared nanoparticles Fe₃O₄ are uniformly loaded on the r GO nanosheets.When the thickness of the resultant r GO-Fe₃O₄ nanocomposite is 1.6 mm,the best reflection loss(RL)reaches-34.4 d B,and the effective absorption bandwidth(RL?-10 d B)is as high as 3.8GHz.In addition,when the sample thickness is 6.5 mm,the minimum RL value is-37.5 d B,and the effective absorption bandwidth is 1.9 GHz.The main mechanisms include conductivity loss,polarization loss,eddy current loss and natural resonance.Therefore,r GO-Fe₃O₄ nanocomposite material can be used as an efficient electromagnetic wave absorbing material.2.Annealing treatment of r GO-Fe₃O₄ nanocomposite and its microwave absorbing propertiesThe prepared r GO-Fe₃O₄ nanocomposite material was annealed at 1000°C for 2 h.The maximum reflection loss of the resultant r GO-Fe₃O₄-3 sample at 12.0 GHz is as high as-41.2 d B when the material thickness is 7.7 mm,and the effective absorption the bandwidth(RL?-10 d B)is 2.2 GHz.The experimental results show that the r GO-Fe₃O₄-3 sample has excellent electromagnetic wave absorption performance.3.Research on the preparation of graphene-ferrite nanocomposites by radiation and their microwave absorbing propertiesThe r GO nanocomposite material(r GO-Fe_nO_m)uniformly supported by Fe_nO_m(Fe₂O₃ and Fe₃O₄)nanoparticles was synthesized by?-ray irradiation.When the material thickness is 8.1 mm,the minimum RL value at 17.0 GHz is up to-42.7 d B,the effective absorption bandwidth(RL?-10 d B)is as high as 5.7 GHz,and the range is 12.3-18 GHz.Conductivity loss,polarization loss,eddy current loss and natural resonance are the main factors of electromagnetic wave attenuation.Thus,the prepared r GO-Fe_nO_m nanocomposite turns out to be a good absorbing material.