Preparation And Microwave Absorption Property Of Ti-based Hollow Multi-shelled Composites

In recent decades,with the rapid development of modern microwave communication and electronic industry technology,electromagnetic wave has brought great scientific and technological convenience to human beings,but the accompanying electromagnetic pollution is also a serious threat to human health and military defense.Therefore,it is imperative to design efficient absorbing materials to meet the needs of society and national defense.Traditional microwave absorption materials are heavy in weight and narrow in absorption band,so there are some limitations in application.At present,the research focus in the field of microwave absorption is to prepare“thin,light,wide and strong”new microwave absorbing materials.The hollow multi-shelled structure has the characteristics of low density,which is conducive to the realization of lightweight.In addition,multiple shells and cavities can also realize microwave reflection and scattering,thus increasing the transmission distance and residence time of microwave in the material,which is conducive to enhancing the attenuation ability of the material to microwave.In this paper,the microstructure of Barium titanate（BaTiO₃）and hydrogenated titanium dioxide,which have good dielectric properties,was designed,and the new microwave absorbing materials of Ho MSs-BaTiO₃ and hydrogenated Ho MSs-TiO₂,which not only contain the unique advantages of hollow multi-shelled structure（Ho MSs）,but also have good dielectric properties,were obtained.Then they are compounded with magnetic materials（Fe₃O₄）and conductive materials（polypyrrole,PPy）to improve impedance matching,thus achieving the effect of enhancing the absorption loss performance and broadening the effective absorption bandwidth.The specific contents of this article are as follows:（1）Ho MSs-BaTiO₃/Fe₃O₄ composites were synthesized by sequential template method and simple hydrothermal reaction,and their absorbing properties and mechanism were studied.The results show that the reflection loss extremum（-39.2d B）of Ho MSs-BaTiO₃（1-X）/Fe₃O₄（X）（X=0.6）composite is much lower than that of BaTiO₃ powder（1-X）/Fe₃O₄（X）（X=0.6）sample（-12.7 d B）,and has a wider effective absorption bandwidth（2.8 GHz）,indicating that the unique hollow multi-shelled structure can effectively extend the microwave propagation path and improve the microwave absorption performance of the composite.At the same time,the reflection loss extremum（-39.2 d B）of Ho MSs-BaTiO₃（1-X）/Fe₃O₄（X=0.6）is smaller than that of the physical mixture of Ho MSs-BaTiO₃（1-X）and Fe₃O₄（X=0.6）（-30.6 d B）.This may be due to the fact that Fe₃O₄ synthesized in situ provides more heterogeneous interfaces and enhances the microwave absorption performance of the composite.（2）Hydrogenated Ho MSs-TiO₂（HH-T）was prepared by sequential template method and hydrogenation treatment,and PPy nanoclusters were in-situ polymerized on its surface to obtain HH-T/PPy composites.The results show that HH-T sample can more effectively dissipate the electric field energy than Ho MSs-TiO₂（H-T）sample under the electromagnetic field.This enhancement may be attributed to the rutile/anatase interface and the crystalline/disordered interface in the HH-T sample.PPy with excellent conductivity can form 3D conductive network on the HH-T surface,which greatly enhances the conductivity loss of composite materials.With the increase of PPy content,the microwave absorption capacity of HH-T/PPy composites increased first and then decreased.HH-T/PPy-10 sample exhibited the best reflection loss extremum（-40.2 d B）and maximum effective absorption bandwidth（5.02 GHz）.Therefore,the microwave absorption capacity of the composite can be adjusted by adjusting the content of PPy in HH-T/PPy.