| The rapid development of modern electronic technology and highly integrated circuits has resulted in serious electromagnetic radiation,which has caused harmful effects on highly sensitive precision electronicequipment and human living environment.Iron-based microstructures or nanostructured materials are ideal for magnetic applications due to their strong magnetic resonance properties,domain wall displacement,low cost,and non-toxicity.The important application of these materials is as an electromagnetic wave absorber to absorb radar waves in centimeter waves(2-18 GHz).Meanwhile,ferromagnetic like Fe can hardly provide strong enough magnetic polarization moments as ferromagnetic materials can,but it suffers from shortcomings such as easy oxidation,high density and magnetic aggregation which hamper their applications.In order to change these shortcomings,we have nanosized and hollowed out the magnetic material.At the same time,we use the carbon layer to protect the magnetic material from oxidation and increase the internal interface of the material,resulting in more microwave loss.Macroscopic three-dimensional(3D)graphene has received extensive attention due to its lightweight,porous structure and excellent electrical/thermal properties.However,the extremely large pores of commonly reported 3D graphene make it difficult to support high loadings.Herein,we report a novel approach for constructing 3D graphene nanostructures with polystyrene(PS)microspheres as the template via hydrothermal reaction and the followed drying process.The obtained 3D graphene shows a high electricalconductivity and an outstanding electromagnetic interference(EMI)shielding effectiveness(SE).The contents of this subject are as the following parts:(1)Buffer solution assisted synthesis of SPS@Fe(OH)3 core-shell structure:Metal oxide nano-coating formed a uniform core-shell nano structure material is well known in the challenge.By using a buffer solution as a reaction medium,the precipitate growth kinetics is controlled,so as to achieve a balance between nucleation and growth.We demonstrate the possibility to grow thin nanoshells of Fe(OH)3 on SPS,forming a uniform surface-coating layer.We have demonstrated that uniform Fe(OH)3 nanoshells can be prepared with good control over the shell thickness.We also show that the synthetic schemes can scale well to various substrates including GO and phenol resin microspheres.(2)Lightweight hollow Fe@C nanospheres towards enhancement in microwave absorption:Efficient and lightweight are key factors for microwave absorbing materials.Looking to the essential function remains a big challenge.Herein,Dual-shell Fe@C hollow nanospheres have been successfully prepared by decorating polydopamine(PDA)on the surface of SPS@Fe(OH)3 prior to annealing process,which can effectively anchor inorganic particles and help retain the spherical morphology during the annealing process.Afterward,hollow structure is formed with the decomposition of PS nanospheres and the carbonization of outer PDA layer into amorphous carbon.Meanwhile,the later can effectively reduce the formation of ferric derivatives to zero-covalent Fe via the carbon thermal reduction,giving rise to hollow Fe@C.The hollow structure effectively reduces the density of the material.It was found that when the PDA coating time was 3 h and the initial charge ratio of Fe2(SO4)3 and SPS was 0.8:1 exhibit the champion EM absorption performance,a minimum reflection loss(RLmin)of-44.44 dB,along with the corresponding bandwidth of RL less than-10 dB covering 8.1 GHz,168%and 87%higher than Hollow C prepared by only coating the carbon layer.(3)Highly Conductive Three-dimensional Graphene(RGM)with Polystyrene Microspheres as template for efficient electromagnetic interference shielding:Macroscopic three-dimensional(3D)graphene has received extensive attention due to its lightweight,porous structure and excellent electrical/thermal properties.However,the extremely large pores of commonly reported 3D graphene make it difficult to support high loadings.Herein,we report a novel approach for constructing 3D graphene nanostructures with Polystyrene(PS)microspheres as the template via hydrothermal reaction and the followed air-drying process.The obtained 3D graphene with density of 0.146 g cm-3 shows a high electrical conductivity of 343.7 S/m and an outstanding electromagnetic interference shielding effectiveness(EMI SE)of around 57.05 dB.This excellent electrical and EMI SE properties are correlated with the duplicated sphere-like structures,which provides a promising material platform for multifunctional applications. |
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