| In order to obtain a lightweight wood-based electromagnetic shielding plywood with broadband application,low reflection and high absorption,a multi-layer electromagnetic shielding plywood was prepared based on the multiple reflection absorption mechanism,using a kind of SiO2-TiO2 modified wood and BaFe11.6 Ce0.4O19/EG(Expanded Graphite)and reflective layer as the main structure.The contents and results are as follows:1.BaFe12O19 and BaFe12O19/EG were prepared by sol-gel calcinations method.Based on the analysis of saturation flux density,coercive force afid electromagnetic properties.The saturation flux density of the sample was positively correlated with the mass fraction of BaFe12O19,and the coercive force was negatively correlated with that.The saturation flux density was 26.153emu/g,the coercive force was 233.770e and the electrical resistivity was 69.033m?·cm,when the mass ratio of EG and BaFe12O19 was 1:3,The SEM and EDS analysis showed that BaFe12O19 and EG were evenly inserted.Having the layers of 3 and the single-layer thickness of 1mm and the density of 1.0g/cm3,the SE of plywood was more than 49dB in the range of 300?1500MHz,and the peak value of Shielding effectiveness was-5.12dB in the 2?18GHz range.2.When Ce doped X = 0.4,the optimum content of EG in the BaFe11.6Ce0.4O19/EG is 25%(mass fraction),the electromagnetic shielding performance is the best of all.The saturation flux density was 37.935emu/g,which was higher than BaFe12O19/EG of 11.782emu/g.the coercive force was 136.7Oe reduced 97.07Oe than that of BaFe12O19/EG,and the electrical resistivity was 13.3959m?·cm reduced more 55 m?·cm than that of BaFe12O19/EG,Having the layers of 3 and the single-layer thickness of 1mm and the density of 1.0g/cm,the plywood of SEwas more than 42dB in the range of 250?1500MHz and in the range of 650?1500MHz was more than 55dB.the SE was 63dB in 700?950MHz,enhancing SE uptake by 10 than without Ce.and the peak value of Shielding effectiveness was-5.81dB in the 2?18GHz range.3.Prepared modified wood by sol-gel method and lowry process.Compared with the unmodified wood,The electrical resistivity of the modified wood decreased significantly,the resistivity of Toona sinensis was 26166.6 m?·cm,the Cunninghamia lanceolata was 25942.1m?·cm,and the Khaya senegalensis was 24913.3 m?·cm.It can be seen that the reflectivity curve of plywood whichthe bottom of the reflective layer use the copper foil and the graphite coating has little change,the absorption peak is similar to each other.The SE of multilayer plywood has higher than single layer structure.Using the SiO2/TiO2 modified board as impedance matching Layer that the thickness of 1mm,BaFe11.6Ce0.4O19/EG as the absorption layer,BaFe11.6Ce0.4O19 and EG ratio of 3:1,the absorption layers are 3 layers,each layer thickness of 1mm;with copper foil as the reflective layer,the SE of plywood more than 60dB in the range of 300?1500MHz,in the range of 800?1500MHz more than 72dB and the absorption peak is-7.5 1dB at 10.8GHz.4.Using the method of surface pretreatment,the quantity of isocyanate adhesive is 10%that the mass of BaFe12-xCexO19/EG.The bonding strength of multilayer plywood can reach the requirements of class ? plywood. |
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