| Due to the needs of the wireless communication transmission system and control electromagnetic pollutionas well as the development of stealth technology,the research and application of electromagnetic wave absorption materials have become a hotspot.Traditional electromagnetic wave absorption materials have high density,low absorptive capacity and poor impedance matching characteristic.Therefore,the new generation of absorbing agents with "wide,thin,light and strong" has become the main research direction of wave absorbing material.Polymer derived SiCN ceramics(PDCs-SiCN)have unique amorphous structure,high thermal stability and the theory density is only about 2g·cm-3.PDCs-SiCN ceramics have special dielectric properties due to the free carbon which were generated in the process of high temperature annealing precipitate from amorphous structure.Therefore,PDCs-SiCN is considered to have certain potential in wave absorption filed.Combine the advantages of PDCs-SiCN ceramics and magnetic materials,which can be used to prepare lightweight the composite absorbing material.The advantages of two kinds of absorbing medium can adjust the electromagnetic parameters of materials and further improve absorbing performance.In this paper,PDCs-SiCN ceramics were prepared by polymer derived method with polysilazane as polymer precursor.The changes of structural composition during the crosslinking and curing were analyzed.Meanwhile,the ceramic microstructure,electrical properties,dielectric properties and microwave absorption performance of the samples after annealing process were analyzed.In addition,with acetylacetone iron,nanometer iron oxide as raw materials,the preparation of The iron PDCs-SiCN ceramics(PDCs-SiCN(Fe)ceramics)were prepared with ith acetylacetone iron and nanometer iron oxide as raw materials,and the ceramic phase,microstructure and electromagnetic performance of PDCs-SiCN(Fe)ceramics were analyzed.Through the preparation and properties research of PDCs-SiCN and PDCs-SiCN(Fe),the main conclusions were listed as following:The influences of crosslinking curing temperature(100?800 ?)and annealing temperature(900?1400 ?)on the phase,microstructure,electrical behavior and dielectric properties of PSZ precursor were studied.The results showed that amorphous SiCN network structure has basically formed when the crosslinking temperature was 600 ?.With annealing temperature increasing,PDCs-SiCN ceramic still exhibited uniform and stable amorphous structure and the free carbon precipitation amount increased.The density of PDCs-SiCN ceramic prepared at 1100 ? was only around 1.8g·cm-3.In the frequency range of 2?18 GHz,the dielectric constant of the PDCs-SiCN ceramic gradually declined with the increase of frequency.The reflectivity of PDCs-SiCN ceramic prepared at 1100 ? was below-10dB in the frequency range of 6?18 GHz,the dielectric loss tangent at 16GHz was around 0.6,which showed up excellent wave-absorbing properties.PDCs-SiCN(Fe)ceramics were successfully prepared using the acetylacetone iron and nano iron oxide as raw materials.The phase composition,microstructure,electrical conductivity and electromagnetic properties of obtained ceramics were also analyzed.The dominate phases were ?-Fe and C when the acetylacetone iron was chosen as the starting material.The electromagnetic properties of PDCs-SiCN(Fe)ceramics with magnetic phases were obviously improved,especially the a-SiCN-Fe0.26 in 16?17 GHz.Meanwhile,the ceramic dielectric loss tangent could reach about 1.8,the magnetic loss tangent could reach around 0.7,the reflectivity could reach-10dB in 7?11.5 GHz.The dominate phase remained ?-Fe and C when the nano iron oxide was originally used.The magnetic loss tangent of the b-SiCN-Fe0.23 ceramic could reach 1.4 at 14.5-15.5 GHz.At the same time,the reflectivity could reach-10dB in 4?16 GHz,showing good wave absorbing performance.The PDCs-SiCN ceramics and PDCs-SiCN(Fe)ceramics prepared in this study had uniform stability amorphous structure,low density,good electromagnetic performance and potential absorbing ability.It has significant meaning to promote the development of the electromagnetic wave absorption materials. |
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