Synthesis And Microwave Absorbing Property Research Of Fe₃O₄@MoS₂ Composites

The stealth of weapon equipment and the prevention and control of electromagnetic pollution promote the development of absorbing material technology.The development of high-performance absorbing material has become the goal of stealth field.Along the development direction of the new type of absorbing materials,the traditional absorbing materials ferrite and the two-dimensional semiconductor materials rookie molybdenum disulfide are compounded to form the Fe₃O₄@MoS₂composite.The Fe₃O₄@MoS₂has both electrical loss and magnetic loss characteristics,at the same time,the impedance matching problem of ferrite has been improved,so that more electromagnetic waves are transmitted into the materials and lost.In this thesis,the Fe₃O₄@MoS₂composite was prepared by two-step hydrothermal method,and its microwave absorption properties have been studied.The absorption mechanism and growth process of the composite have been explored,and the absorption properties of the composite were studied by adding graphene oxide?GO?.The main work of this thesis is as follows:Firstly,Fe₃O₄/MoS₂composite was prepared by hydrothermal-precipitation method and two-step hydrothermal method,and characterized by XRD,SEM and Raman.The results show that the Fe₃O₄@MoS₂prepared by two-step hydrothermal method has better electromagnetic wave absorption?-19.84 d B,matching thickness of 2.5 mm,absorption bandwidth of 3.47 GHz?than that prepared by hydrothermal precipitation method?-5.5 d B,matching thickness of 2.5 mm?.Secondly,based on the theory of orthogonal design and hydrothermal method,the optimal process parameters are found:the mass of Fe₃O₄is 50 mg,the molar number of sulfur ion is10 mmol,the reaction time is 10 h and the reaction temperature is 200?.Through range analysis,the order of influence of these four factors on the result was obtained:sulfur ion molar number>Fe₃O₄mass>reaction temperature>reaction time.Based on the optimized process parameters,Fe₃O₄@MoS₂composite at 14.29 GHz?matching thickness of 2 mm?has a maximum reflection loss of-39.56 d B and an absorption bandwidth of 5.39 GHz.Compared with pure MoS₂?-4.8 d B,matching thickness of 5 mm?and Fe₃O₄?-17 d B,matching thickness of 2.5 mm and absorption bandwidth of 0.5 GHz?,the absorption performance is enhanced.With the increase of matching thickness,the maximum reflection loss peak gradually moves to the low frequency direction.The absorbing property of Fe₃O₄@MoS₂composite ascribe to,on the one hand,it may be due to the high specific surface area of thin layer MoS₂,which increase the conductivity loss;on the other hand,the rough porous surface of Fe₃O₄can reflect electromagnetic waves many times,increase the transmission distance of electromagnetic waves and improve the absorption efficiency of electromagnetic waves.At the same time,the existence of the heterogeneous interface in the composite will inevitably lead to the interface relaxation polarization loss.The single factor experiment of time was designed to explore the growth mechanism of the complex.Finally,in order to improve the impedance matching of Fe₃O₄@MoS₂composite and improve the wave absorption performance,GO was introduced into Fe₃O₄@MoS₂composite.The results show that the introduction of GO increases the dielectric loss of the system.It is not difficult to find that there are abundant polar oxygen-containing functional groups in the lamellar GO,and these polar functional groups may produce shift polarized relaxation loss under the action of high frequency electric field.At the same time,the multilayer GO has a good conductivity,which is easy to form a space conductive network and generate conductivity loss.In addition,there must be abundant heterogeneous interfaces in ternary composites,which will absorb electromagnetic wave through interface relaxation loss.It can be seen that the introduction of GO will enhance the microwave absorbing properties of the composite.