Fabrication And Microwave Absorption Performances Of Electromagnetic Composites Based On Xylem Fiber

Xylem fiber is a new type of biomass energy material,which own extensive sources,abundant reserves and environmental friendliness,and it can form the three-dimensional network structure.There are many hydroxyl groups on the surface of xylem fiber,which make it easily react with other substances through active sites and control the morphology.They can be used as matrix of composite materials due to their dimensional stability and thermal stability.Fe₃O₄ is a traditional microwave absorbing material,which possesses excellent magnetic anisotropy and high coercivity.The Fe₃O₄ nanoparticles have nanometer effect,such as quantum size effect,surface effect and macroscopic quantum tunneling effect.Due to the characteristic of strong absorption property,Fe₃O₄,which lose the electromagnetic wave by dielectric loss and magnetic loss.However,the disadvantages of Fe₃O₄ absorbing material are low density and narrow absorption band.As a conductive polymer,PANI has many advantages,such as high conductivity,small density,low synthesis cost and controllable conductivity.So PANI has been widely used in the field of microwave absorption.The main problem is how to maximize the microwave absorption properties as microwave absorbing material.In order to obtain microwave absorbing materials with excellent comprehensive properties,composite and nanocrystallization become the research trend.To obtain a new type of excellent electromagnetic wave absorbing material,this paper combined the advantages and disadvantages of the above materials by the experimental study and theoretical analysis.In the experimental stage,ethylene glycol was used as solvent and the pretreatment xylem fiber was used as matrix.Under the certain reaction conditions,the xylem fiber/Fe₃O₄ composite material was synthesized by solvothermal method,and its structure and microwave absorbing properties were studied and characterized.On the basis of xylem fiber/Fe₃O₄composites,the xylem fiber/Fe₃O₄@PANI three component composite microwave absorbing material has been also prepared by in-situ polymerization method.The biggest difference is that the dielectric properties of xylem fiber/Fe₃O₄@PANI microwave absorbption material by comparing with the xylem fiber/Fe₃O₄composites.The detail process and conclusions are as follows:?1?Under the condition of high temperature and pressure,the xylem fiber/Fe₃O₄magnetic composites were synthesized in the high-pressure reaction kettle.After the xylem fiber/Fe₃O₄ composites synthesized,the amount of xylem fiber was studied for the effect on the absorbing property of composites.The morphologies,structure and properties of xylem fiber/Fe₃O₄ composites were measured.When the addition amount of xylem fiber is 0.40 g,RL_min of-37.64 d B has been obtained at 17.28 GHz with the thickness of 5.0 mm,and the width of 3.52 GHz?3.84-7.36 GHz?has also been obtained blow-10 d B.Besides,it also appears double peaks in this thickness of xylem fiber/Fe₃O₄ composites.The xylem fiber/Fe₃O₄ composite materials own potential application in the field of electromagnetic absorption.?2?On the basis of nascent research,the xylem fiber/Fe₃O₄ composites were coated with polyaniline and doped with different concentrations of hydrochloric acid according to a certain proportion.The results show that hydrochloric acid concentration plays a significant role in the formation of xylem fiber/Fe₃O₄@PANI composites.It is found that the value of minimum reflection loss(RL_min)of the xylem fiber/Fe₃O₄@PANI composites are-24.4 d B,-35 d B,-39.9 d B and-43.6 d B corresponding to the concentration of hydrochloric acid is 0.125 M,0.25 M,0.5 M and 1.0 M,respectively.When the concentration of hydrochloric acid is 0.5 M,the absorption bandwidth below-10 d B is 5.52 GHz?10.32-15.84 GHz?with the matching thickness of 2.5 mm,which show excellent absorbing properties in X and Ku bands.In addition,the microwave absorption mechanism of the composites is attributed to natural resonance,eddy current loss and destructive interference.So the xylem fiber/Fe₃O₄@PANI composites have potential application prospect in the field of electromagnetic absorption.