Interface Control And Properties Based On Graphene Oxide Porous Composites

Porous material has been widely used in various fields attributing to its low density,large specific surface area,high specific strength,low thermal conductivity,sound absorption and excellent permeability.Excellent performance of porous materials mainly depended on its microstructure,and the relationship between material structure and performance by structural regulation was a key issue of porous material research.In recent years,in the preparation of porous materials,researchers have carried out interface control by changing the composition and concentration of the solution,the type and dosage of additives and other factors,to explore the influence of the surface tension of the solution,phase transition temperature and other physical and chemical properties changes on the microstructure of the material,and then affect the macroscopic properties of the material.In this paper,graphene oxide(GO)was obtained by the modified Hummers method,and the graphene oxide suspension was adopted as the precursor by using the ice crystal template method to affect the graphene oxide by changing the size and concentration of graphene oxide and adding surfactants.The crystallization behavior of the aqueous solution of graphene oxide display profound effect on the morphology of ice crystals,and could further control the microstructure and the related properties of graphene oxide aerogel.Based on the research on the structural morphology regulation of GO,we have successfully designed a magnetic graphene hollow microsphere with excellent electromagnetic shielding performance,which has expanded the application field of the structural regulation of GO.With the increase of GO sheet size,ice crystal size,aerogel pore size,compression strength and thermal conductivity increase.Compared with GO-1 and GO-106 aerogels,GO-38 aerogel has a complete and compact three-dimensional network structure,and its compressive strength reaches 0.0614 MPa.1.The ice-template method was used to explore the relationship between the freezing process,ice crystal morphology,aerogel microstructure and performance,as well as to achieve precise control of the GO aerogel microstructure.A series of graphene oxide suspension systems with size and mass concentration of GO was prepared,and the effect of GO aerogel precursors on the crystallization temperature of water in the GO suspension and the growth of ice crystals was studied.The relationship between the nucleation and growth of ice crystals and the microstructure of aerogels was depicted.And we also investigated the mechanical and thermal properties of GO aerogels in order to further reveal the relationship between aerogel microstructure and macroscopic properties.2.We utilized graphene oxide(GO)as the aerogel skeleton and polyvinyl alcohol(PVA)as the ice crystal growth regulator,and the relationship between the physicochemical properties of GO/PVA aerogel precursors and the nucleation and growth of ice crystals was deeply discussed by ice-templating method.On the one hand,PVA could effectively inhibit the nucleation activity of ice crystals in a certain concentration range due to the hydrogen bonds formed between PVA and water molecules,resulting in the decrease of initial crystallization temperature decreases from-12.60 ~oC(GO/PVA-0.01)to-16.21 ~oC(GO/PVA-0.1).On the other hand,strong hydrogen bond between PVA and GO could restrict the diffusion of water molecules and inhibit the growth of ice crystals.Therefore,PVA could endow the CO/PVA aerogel with a decreased pore size from 9.96±0.13 nm in GO/PVA-0.01 to 7.19±0.10nm in GO/PVA-0.3,as well as good compression strength which was increased from0.051 MPa to 0.129 MPa because PVA could inhibit the nucleation and growth of ice crystals.Moreover,the precise regulation of GO aerogel microstructure was achieved,the thermal conductivity increased from 0.003306±0.00006 W/m K(GO/PVA-0)to0.03882±0.00098 W/m K.3.Based on the interaction between GO and PVA,Ni particles were introduced through oil-in-water emulsification technology and two-step annealing process to improve the electromagnetic matching performance of the material,and the Ni/r GO-n-P composite shielding material was obtained.By analyzing the phase structure,chemical composition and microstructure of Ni/r GO-n-P composites,it was found that the Ni/r GO-n-P composites were spherical and hollow cavity structure.Controlling the preparation process can effectively control the diameter of the microspheres and the GO reduction degree,and regulate the electrical conductivity and dielectric loss of the composites.The electromagnetic parameters of Ni/r GO-n-P composite shielding materials at different temperatures were tested and characterized by vector network analyzer.When the thickness was 1.0mm,the shielding efficiency of Ni/r GO-750-P and Ni/r GO-950-P electromagnetic shielding materials was greater than30 d B across the entire X-band.The relationship between electromagnetic shielding and material structure design was studied.It was found that the hollow cavity structure can reflect multiple electromagnetic waves and increase the absorption loss of shielding materials toward electromagnetic waves.When the thickness was 1.06 mm,the shielding efficiency of Ni/r GO-950-P was 32.01 d B at 8.2 GHz,the minimum reflection loss was only 0.48 d B,indicating that the absorption loss was 98.4%.By adjusting the physical and chemical properties of the graphene oxide precursor and the calcination process of the microspheres,such design idea of magnetic graphene composites with spherical and hollow cavity structure provides a new idea for the preparation of lightweight,high absorption and loss efficient electromagnetic shielding materials.