Study On Microwave Absorption Properties Of Porous Carbon Fiber And Its Absorbing Mechanism

Modern warfare urgently needs radar stealth technology to meet the shelter requirements of weapons and equipment.Among lots of kinds of absorbing materials,porous carbon meet high requirements for the future absorbing material due to its developed pore structure and high conductively.Therefore,it’s significant to prepare porous carbon fibers and study their radar absorbing properties.In this paper,polyacrylonitrile(PAN)was used as carbon precursor polymer(CPP),while polymer methacrylate(PMMA)as thermally decomposed polymer(TDP).PAN/PMMA blend fibers were prepared by wet spinning and electrospinning.Secondly,Porous carbon fibers(PCF)and nano carbon fiber(n-PCF)were obtained through carbonization of the blend fibers.Pore size of PCF and n-PCF can be controlled by changing PMMA content and degree of graphitization can be controlled by carbonization temperature.Using PCF and n-PCF as absorbing agent,combined with epoxy resin to prepare microwave composite samples.The electromagnetic parameters of the absorbing composite were tested by vector network analyze and the reflection loss of the composite material to the electromagnetic wave is calculated from the electromagnetic parameters.When PCF as absorbing agent,we study the effect of pore volume,pore size,fiber diameter and carbonization temperature.On this basis,the absorption mechanism is studied.The main research is as follows:The PAN / PMMA blends are prepared by conventional wet spinning and the diameter of PCF is 10-20 μm,the pore size is 0.5 to 1.5 μm.The diameter of n-PCF is 100-200 nm and the pore of n-PCF is 10-20 nm.The pore volume of PCF and n-PCF increased with the increase of PMMA content in the original wire.The graphitization degree of PCF and n-PCF is complete with the increase of carbonization temperature,and n-PCF has a completed graphitization structure.When 4% PCF was as the absorbing agent combined with the epoxy resin to make absorbing material,ε’ and ε’’ increase with the increase of PMMA content in the original wire.The microwave absorbing properties of the absorbing material on the electromagnetic wave are calculated by simulation.The absorption performance increases with the increase of pore volume in PCF.When PCF-30 is used as the absorbing agent,the lowest reflectivity is-27.2dB,and the effective absorption bandwidth is 1.8GHz.The absorbing property of 4% n-PCF was corresponded to the other PCF,while n-PNF showed superior property(lower reflection loss).The lowest reflectivity was about-29.7dB as the carbonization temperature rises.When regarding PCF and n-PCF with different carbonization temperature as absorbing agent,the absorbing property of the composites get improved as the carbonization temperature rises.The PCF and n-PCF carbonized in 1400℃ had a better property compared with the sample of 1000℃.The porous damaged PCF revealed that the porous structure did great contribution to the absorbing property.Meanwhile the volume and the size of porous structure also had a big influence to the absorbing property.In this situation,we inferred that the distribution of pour size can be an important way to adjust the frequency of absorbing.The paper has important reference value for the development of a lightweight and efficient absorbing composite.