| With the development of various electronic and electrical equipment to the miniaturization of the structure,the integration of the modules,the diversification of the function of the process,scientific research workers must face the problem of electromagnetic compatibility and cooling.On the one hand,electromagnetic radiation and interference problems restrict people's production and life,leading to human living space the electromagnetic environment deteriorating;the other hand,the problem of heat dissipation of electronic products must be resolved.Barium ferrite/ graphene composite act out excellent thermal conductivity and magnetic properties of graphene material.The heat generated by the work of electronic products can is emitted out,and have good electromagnetic compatibility effect.Composite was prepared with graphene and barium ferrite prepared by using sol-gel method.It's electromagnetic properties and its absorbing properties are studied.The main work is as follows:(1)The M-type barium ferrite powders were prepared by using sol-gel method.Powder samples were prepared by different holding times at 800?.The powder samples on the phase,size and magnetic properties were characterized by using XRD,SEM and network analyzer.The electromagnetic parameters of barium ferrite prepared under different conditions were measured by vector network analyzer.The corresponding reflection loss was simulated by MATLAB software.The results showed that the calcination temperature was 800? and the holding time was 3h.Barium ferrite has the best electromagnetic performance.(2)After analyzing the property of graphene we know: the dielectric constant of the graphene electromagnetic parameters is relatively large,the permeability is relatively small,which belongs to the electric loss type absorbing material.Meanwhile the graphene has excellent absorbing performance.The absorption performance is better where graphene thickness is 2mm and 5mm.The absorption peak is-15.6 dB when the graphene thickness is 2mm,and bandwidth that is less than-10 dB is 2.3GHz.The thermal diffusivity of the enamel material was measured and the thermal conductivity at 50? was 4.53 W/(K·m),which was 24 times silicone rubber while the silicone rubber is as the matrix of graphite.(3)The dielectric constant is also increasing and moving to the low frequency direction with the increase of graphene content.The reduction of the real part and the imaginary part is due to the increase of the graphene electric loss type absorbing material and the graphene,which enhances the polarization degree of the barium ferrite/graphene composite material under the electric field and makes the dielectric constant increase.(4)The influence of different graphene content and different thickness on the screen effect and heat dissipation of barium ferrite/graphene composites shows that the absorbing property of the composite material is better when the mass ratio of barium ferrite to graphene is 3:1 and the thickness is 2mm and 3mm.The composite material with thickness of 2mm,3mm and 4mm shows excellent absorbing performance when the mass ratio of barium ferrite to graphene is 2: 1.The peak reflectivity of composite material is-26 dB when thickness is 2mm.The bandwidth is 0.9GHz(11.9-12.8GHz).The heat transfer rate is 9.5W.However,the heat dissipation is weakened with the increase of the thickness.The composite materials with thickness of 3mm and 4mm show good absorbing performance and heat dissipation performance when the mass ratio of barium ferrite to graphene is 1: 1.In conclusion,the barium ferrite with excellent properties was prepared by using sol-gel method.The barium ferrite/graphene thermally conductive and microwave absorbing composites were prepared with barium ferrite and graphene.It provides theoretical and technical support for the application of thermally conductive absorbing materials in different absorbing bands,thickness,heat dissipation,and application conditions. |
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