| Carbonyl iron powder(CIP)is a commonly used microwave absorber because it has good dielectric properties and magnetic properties.In the military,research on this absorber was mostly focused on anti-radar technology.With the development of mobile Internet,GPS,assisted driving radar,the use of the millimeter-wave frequency band in civilian equipment such as drones and driverless cars has increased.Therefore,many electromagnetic interference and electromagnetic pollution problems are generated in the scenario.The absorbing material in the civil field has wide application prospects.The aim of this research is to prepare a carbonyl iron powder/resin composite material which is suitable for industrial production.And we expect this material composite have the characteristics of “high frequency resist and low frequency pass”.It means this material has excellent absorbing properties in the strong interference band of the radar(around 24 GHz)and good wave-transmission properties in the frequency band of the network(1-5 GHz).In this paper,carbonyl iron powder was selected as filler,meanwhile,polypropylene(PP)and ABS was chosen as matrix resin.First,CIP/PP and CIP/ABS were prepared by melt blending method.In this process,the influence of processing technology on the properties of masterbatch was discussed.The effect of carbonyl iron powder content on the microstructure,processability,mechanical properties,thermal stability and electromagnetic properties of composite material was studied.After that,we prepared CIP/ABS parts by fused deposition modeling(FDM).The effect of FDM processing technology on the formability of the parts was researched in this process.Finally,the influence of carbonyl iron powder content and different array pore structures on the microwave absorbing properties of composite materials was investigated.The main conclusions are summarized as follows:(1)Considering the processability and absorbing properties of the material,the content of carbonyl iron powder in the CIP/resin prepared by melt blending is up to 70wt%.The crystallization temperature and decomposition temperature increase and the melting temperature decrease with the increase of CIP content.(2)CIP content decrease of parts in the injection molding process,and the adjustment of the molding process cannot solve the problem very effectively.FDM is a better molding method,which does not cause CIP content decrease in the parts.And this flexible molding method is beneficial to further study about the influence of the pore structure on the microwave absorbing properties of the material.(3)The addition of CIP has little effect on the microstructure and thermal stability of CIP/ABS,but has important influence on the fluidity of CIP/ABS.the fluidity of CIP/ABS greatly decrease with CIP content increase.(4)The microwave absorbing properties of the material at 2-18 GHz frequency band is conditional on CIP content and the pore area.The higher the content of CIP and the smaller the pore area,the better the microwave absorbing properties of the material.The shape of pore has little effect on it.The reflection loss of all the samples in the frequency band below 5 GHz is less than-1 d B,it means that samples have good microwave transmission properties in this frequency.In the 18-26 GHz band,the carbonyl iron powder content and the pore area still have impacts on the microwave absorbing properties.The pore shape has a more important influence on the microwave absorbing properties of the material.The samples with the same pore area has a narrow hole shape(rectangular slit)with better absorbing properties.It even has better microwave absorbing properties than the sample without pore structure in the high frequency band(21.5-26GHz).The reflection loss is less than-10 d B at 23.5-26 GHz,and the minimum is-11.3d B(absorption efficiency is 92%). |
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