Study On Preparation And Microwave Absorption Performance Of Metal Chalcogenide/Carbon Composites

In the information age,electromagnetic pollution and electromagnetic radiation are becoming more and more serious.The role of electromagnetic wave absorbing materials in military operations,equipment anti-interference,and human health is becoming more and more prominent.New microwave absorbing materials should meet the requirements of thin thinness,low lightweight,broad width and strong absorption.With these goals,in this thesis,we prepared several carbon fiber-based composite materials,studied their microwave absorption properties,and systematically explored the material composition and structure.The structure-effect relationship between the microwave absorbing performance and the possible microwave absorption mechanism is proposed.It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.Mo Se₂,as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/Mo Se₂ nanocomposite was fabricated by facile process and economic raw materials,and phosphoric acid was used to dope phosphorus in BC,in which Mo Se₂microspheres were irregularly dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and Mo Se₂ is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches-53.33 d B with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(-66.84 d B)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.Metal chalcogenides have been widely utilized as microwave absorbers.However,it remains a challenge for them to achieve efficient and broadband absorption performance with low filler content.Herein,a series of carbon paper@Bi₂S₃ hybrid structures are fabricated by a facile one-step solvothermal process,whose morphology and microwave absorption properties also can be easily adjusted by the dosage control of raw materials.The Bi₂S₃ clusters are grown densely on the surface of carbon paper fibers,like the rime in winter.The collocation of carbon paper and Bi₂S₃ is beneficial to impedance matching and synergistically enhances microwave absorption capability based on various attenuation mechanisms,including interfacial/dipolar polarization loss,conduction loss,and multiple reflection.At a low filler content(only 5 wt%),the optimal reflection loss among these composites is-56.63 d B at 8.84 GHz with a thickness of 3.3 mm,and the broadest efficient absorption bandwidth reaches 7.32 GHz with a thickness of 2.4 mm,covering the whole Ku band.By adjusting the thickness,the total covered frequency range is up to 13.36 GHz(83.5%of 2-18 GHz).In the range of 2-3 mm,the absorption capacity and average effective bandwidth of two composites can reach above 5.5 GHz.The as-prepared materials have unique microstructure and exhibit strong and broadband absorption performance with thin thickness and low filler content,matching the requirements of thin thinness,low lightweight,broad width and strong absorption.