Research On The Structure And Performance Of Flexible Microwave Absorbing Materials

In the era of rapid development of information technology,electromagnetic wave,as the carrier of information dissemination,has been widely used in all aspects of life,and has made great contributions to the development of material civilization and social progress.At the same time,the environmental pollution caused by electromagnetic wave and the harm to human health cannot be ignored.Therefore,the research of absorbing materials has become a hot spot.At present,the common problem of absorbing materials is that it is difficult to take into account the four requirements of"light weight,wide frequency band,thin thickness and strong absorbing ability".In order to solve these problems,Ba Fe₁₂O₁₉,graphene,PANI were selected as absorbents to prepare multi absorbent single-layer and three-layer coated fabrics by mechanical mixing method.Based on the absorbing mechanism,the absorbing property of coated fabric is optimized by adjusting the ratio of absorbent and designing the coating structure.Finally,the thin flexible absorbing material with excellent absorbing property and bearing property is prepared.Firstly,pure phase Ba Fe₁₂O₁₉ with hexagonal sheet structure was prepared by microwave hydrothermal method,and microwave absorbing coated fabric was prepared with Ba Fe₁₂O₁₉as absorbent.When the coating thickness is 1.2 mm,the minimum reflection loss RL at 13.15GHz is-17.19 d B,the effective absorption bandwidth(RL?-10)is 1.22 GHz,and the average absorption rate is 37.21%.The single loss mechanism makes its absorbing effect poor,and the composite with graphene is used to make up for the problems of single loss mechanism,high density and poor impedance matching.Ba Fe₁₂O₁₉/graphene coated fabrics with five different mass ratios were prepared by tape casting.The experimental results show that when the thickness of the coating is 1.2 mm and the ratio of Ba Fe₁₂O₁₉ to graphene is 6:1,the microwave absorption performance is the best,the minimum reflection loss RL value can reach-36.83d B,the effective absorption bandwidth can reach 4.04 GHz,and the average absorption rate is78.79%.The absorbing performance is greatly improved.In order to further optimize the absorbing properties of the fabric,Ba Fe₁₂O₁₉/graphene/PANI single-layer coated fabrics with six different absorbent ratios were prepared by tape casting.When the coating thickness of the fabric is 1.2mm,the minimum reflection loss RL at 13.76GHz can reach-37.36,and the absorption bandwidth can reach 5.40 GHz.Due to the interaction and synergistic effect of the three-phase absorbents,the microwave absorbing properties of the fabric are further improved.The coating structure was designed to prepare Ba Fe₁₂O₁₉/graphene/PANI three-layer coating fabric.Compared with the single-layer coated fabric,the absorbing frequency band of the fabric has changed.The absorption band of single-layer coated fabric is mainly 11.9-18 GHz,while that of three-layer coated fabric is between 6.57-9.99 GHz.The experimental results show that the change of coating sequence has a certain influence on the microwave absorbing property of the fabric under the premise of determining the thickness of the absorbing coating and the proportion of absorbent.The absorbing property of the coated fabric with the 1.2 mm thickness of the coating is the best when the upper layer is PNAI,the middle layer is Ba Fe₁₂O₁₉,and the bottom layer is graphene.The minimum reflection loss RL at 9.53 GHz is-25.45d B,and the average absorptivity is 86.69%.According to the experimental results,the selection of absorbing frequency band can be realized through the design of coating structure,which provides an experimental basis for the selectivity of absorbing frequency band of materials.