Preparation Of Element-doped LAS/rGO Composites And Study On Its Absorbing Properties

Glass-ceramic is a kind of materials obtained by controlling the precipitation of crystallite in the glass phase.It has low dielectric constant,low dielectric loss and good wave-transmitting properties.By controlling the chemical composition of the glass and the preparation process,glass-ceramics with different structures and degrees of crystallization can be obtained.Graphene is a two-dimensional carbon material composed of carbon atoms with sp² hybrid orbitals.It has excellent optical,mechanical and electrical properties and is widely used in the field of wave absorbing materials.Another kind of carbon material--organic pyrolysis carbon,due to its loose structure,when interacting with electromagnetic waves,its wave absorption mechanism is different with graphene.In this paper,different kinds of glass ceramics such as Li₂O-Al₂O₃-SiO₂(LAS)were prepared by sol-gel method,polystyrene(PS)microspheres were prepared by microemulsion method,and then solvothermal method and high temperature calcination method were used to combine different kinds of glass-ceramics with reduced graphene oxide(rGO)and PS microsphere pyrolytic carbon,and finally get XAS/rGO composites and C@LAS/rGO composites,and test the absorbing performance of the composites.Compared with XAS/rGO composites,C@LAS/rGO composites have the advantages of low filling and light weight due to the introduction of lower density polymer pyrolytic carbon.The main research contents are as follows:(1)By changing the lithium ion content in the LAS and the duration of heat preservation in the LAS preparation process,the structure and degree of crystallization of the LAS particles are changed,which affects the absorbing performance of the LAS/rGO composites.Among them,when lithium:aluminum=4:1,LAS appears as a layered structure with quartz and spodumene microcrystalline phases,the crystallinity is 60.1%,and the composites have a minimum reflection loss of 69.2 dB at a 23wt%filling amount,when lithium:aluminum=1:1,LAS is amorphous particles,and the composite has a maximum effective absorption bandwidth of 5.6 GHz at a 30wt%filling amount.When the heat preservation time of the composites is increased from 2 h to 4 h,the maximum effective absorption bandwidth of the material is reduced,and when the heat preservation time is increased to 8h,the wave absorption performance of the material is greatly reduced.(2)LAS glass-ceramic was replaced with KAS,NAS,MAS,and LKNAS glass,XAS/rGO composite was prepared and the effect of XAS composition on material structure,morphology and absorbing properties was investigated.Under the sintering parameters of 700?and 2 h,KAS,NAS,MAS,LKNAS,etc.are all amorphous glass,and the morphology varies greatly.KAS/rGO composites have the best absorption performance in the C-band,with a minimum reflection loss of-55.1dB.NAS/rGO and MAS/rGO have the best absorption performance in the X-band,with a minimum reflection loss of-43.4 dB and-43 dB,LKNAS/rGO has the best absorption performance in Ku band,and the minimum reflection loss is-41.7 dB.And through the analysis of the dielectric constant,impedance matching coefficient and Cole-Cole semicircle of the composites,the absorbing performance of the material is explained.(3)In order to further reduce the filling amount of materials,other carbon materials are introduced.The diameter of the prepared PS microspheres was between 100-300 nm.Spherical pyrolytic carbon is formed by stacking the residual carbon of PS microspheres in an irregular polygonal shape with a size of a few microns.There is flaky carbon between the surface and different particles.In C@LAS/rGO composites,C@LAS structure is evenly dispersed on the flake rGO.The mass ratio of PS@LAS and rGO in the C@LAS/rGO composites was changed to study its effect on the microwave absorption performance of the composites.When the mass ratio of PS@LAS and rGO is 3:1,the microwave absorption performance of the material reaches the best,when the filling amount is 5wt%,it reaches a minimum reflection loss of-61.39 dB at a frequency of 16.8 GHz,1.9 mm,and a maximum absorption bandwidth of 6.4 GHz.