Preparation And Study Of SiC/BC Porous Composites On Microwave Absorption Properties

At present,absorbing materials,as the key point of material field,have attracted extensive attention from researchers all over the world.It is of great significance and valuable in reducing electromagnetic pollution,promoting electromagnetic protection,and improving the stealth performance of aircraft and weapons.In the natural world,green porous materials still retain their unique biological morphology and pore structure characteristics after high temperature carbonization,and have a certain bearing capacity.Combining with their own physical and chemical properties,a novel solution can be proposed for the design of new absorbing materials.The results are as follows:?1?In this paper,bamboo charcoal?BC?with biological porous structure was used as the template.BC can be obtained from natural bamboo,it is cracked and carbonized at high temperature.Molybdenum disilicide?MoSi₂?,an intermetallic compound,was used as the absorbent.Under the action of catalyst carbonyl iron powder?Fe?CO?₅?,we produce a type of silicon carbide whisker?SiC_W?on the BC substrate surface to improve and enhance the absorbing properties,and do further research under this technical route.First of all,we combine the BC substrate with absorbent MoSi₂ by vacuum pumping process,then imbed them in silicon powder.Under the protection of argon gas,MoSi₂/SiC/BC porous composites were obtained under sintering at a temperature of1450?.In addition,its phase composition,microstructure,dielectric properties and absorbing mechanism were studied.The results show that the pores of MoSi₂/SiC/BC porous composites are filled with a large number of SiC_W networks.It has a certain absorption effect when the dielectric sample of the MoSi₂/SiC/BC composites and epoxy resin mixed mass ratio is 1:1.In this situation,it represents the lowest reflectivity,the maximum reflection loss is-13.48dB,and the effective absorption band width is about 1.0GHz.?2?the BC piece is triturated with 200 mesh powder particles using two different technics?a heated water bath and ball mill mixing?for pretreatment of raw materials?BC powder?carbon source?and Si powder?silicon source??.In this process,the carbon source and the silicon source are mixed fully.The obtained mixed raw materials is then vacuum-impregnated,suction-filtered and vacuum-dried,and then sintered at 1450? under an argon atmosphere and kept for 1 hour to finally complete the Si/SiC/BC porous composites with a porous structure.The phase composition,microstructure,dielectric properties and its absorbing mechanism were studied.The results show that the absorbing property of the materials is excellent when the mixed raw materials are pretreated and sintered at high temperature by the water bath and heating processes.The dielectric samples have a reflection loss of less than-10 dB in the entire X-band at a thickness of 2.2-2.5mm,and the sample can absorb more than 90%of the electromagnetic waves.As stated above,after using water bath heating technic on the BC powder and mixing together Si powder during raw material for pretreatment,then adding a certain amount of catalyst Fe?CO?₅ promotes thermal reduction reaction and the formation of SiC.?3?the composite was then sintered at 1450? under an argon atmosphere to prepare Si/SiC/BC porous composites with a porous structure.we study the phase composition,microstructure,the type of functional groups,graphitization degree of carbon materials and its absorbing properties.The results show that BC granular pore structure were filled with long size and intertwined SiC_W in SiC/BC porous composites.The three-dimensional reflectance figure of SiC/BC porous composites with 2.0%catalyst content at 1-5mm thickness was simulated.The reflection loss of the entire X-band is below-10dB when the thickness of the dielectric sample is 2.5-2.8mm.At the same time,the minimum reflectance is-32.15dB,and the effective absorption band width is up to 4.2GHz.In the end,we present the prospect of BC-based porous absorbing materials in the later studies,which are the preparation of SiC nanowires,bamboo carbon fiber,and the addition of interfacial layers on BC matrix.