The reduced graphene oxide (RGO)/Fe 3 O 4 composites with an obviously enhanced microwave absorption property had been successfully fabricated by rational one-pot simplified co-precipitation route, which avoided the usage of inert gas and any additional chemical agents (such as surfactants and stabilizer).Given these advantages, the strategy described in this study can be developed as a simple and large-scale yield route to RGO/Fe 3 O 4 composites. The morphology, structure, thermal stability, magnetic and microwave electromagnetic properties of as-prepared composites were characterized by XRD, XPS, TEM, FT-IR, Raman, TG and VSM. Those composites exhibit excellent microwave absorption properties, which are attributed to effective complementarities between the dielectric loss and the magnetic loss. The microwave absorption mechanism of the RGO/Fe 3 O 4 composites was studied in detail. For RGO/Fe 3 O 4 -3 composite, the maximum R L reaches -44.6 dB at 6.6 GHz with a thickness of 3.9 mm, and the bandwidth of RL less than -10 dB can reach up to 4.3 GHz (from 12.2 to 16.5 GHz) with a thickness of 2.0 mm. Moreover, the microwave absorption property can be tuned easily by varying the (RGO)/(Fe 3 O 4 ) ratio and layer thickness of the samples. It is believed that such composites will find their wide applications in microwave absorbing area.-2 -expanded EM interference problems. 3-5 They can absorb microwaves effectively and convert EM energy into thermal energy or make microwaves dissipated by interference. The microwave absorbing materials are now requested to have strong absorption characteristics, wide absorption frequency, lightweight and antioxidation. 4 There are a number of microwave absorbing materials such as ferrites, carbonyl iron, conducting polymers and carbon-based materials etc. 6-9 However, the traditional microwave absorbing materials can not meet all of the requirements such as strong, wide, lightweight and thin at the same time.Hence, extensive studies have been made to develop novel microwave absorping materials with high absorption and wide absorption frequency.Graphene, a novel carbon nanomaterial consisting of one-atom-thick, hexagonally arranged carbon atoms, has attracted extensive attention owing to its superior electronic, thermal and mechanical properties as well as its chemical stability. 10,11 Due to its special surface properties and layered structure, graphene becomes potential nanoscale building blocks for new hybrid materials. 12 Recent research shows that inorganic nanoparticles, such as Au, Ag, Fe 3 O 4 and Co 3 O 4 , etc., could be attached to graphene or graphene oxide (GO) to form hybrid materials, which have potential applications in surface enhanced Raman scattering (SERS), lithium ion batteries, hydrogen storage, microwave absorption and magnetic resonance imaging (MRI) contrast agent, etc.. [13][14][15][16] As a class of promising microwave absorping materials, carbon-based materials exhibited several exceptional properties including lightweight, wide absorption frequency, high...

Hierarchical structures of graphene@Fe3O4@SiO2@NiO nanosheets were prepared by combining the versatile sol-gel process with a hydrothermal reaction. Graphene@Fe3O4 composites were first synthesized by the reduction reaction between FeCl3 and diethylene glycol (DEG) in the presence of GO. Then, graphene@Fe3O4 was coated with SiO2 to obtain graphene@Fe3O4@SiO2. Finally, NiO nanosheets were grown perpendicularly on the surface of graphene@Fe3O4@SiO2 and graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures were formed. Moreover, the microwave absorption properties of both graphene@Fe3O4 and graphene@Fe3O4@SiO2@NiO nanosheets were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrate that graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4, which probably originate from the unique hierarchical structure with a large surface area and high porosity.

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