Preparation And Microwave Absorption Properties Of One-Dimensional Chain Like MOF Derived Composites

With the rapid development of science and technology,we have already entered a time of the electronic and information.With the use of all kinds of electronic products,electromagnetic radiation pollution has become an important problem to be solved.Therefore,the design and study of high performance microwave absorption materials has become a research hotspot in recent years.One dimensional nanostructure nanomaterials such as carbon fiber have long been used in the microwave absorption field due to their advantages such as high aspect ratio,high intensity and good thermal stability.At the same time,MOFs are provided more possibilities for the researchers to design new absorbing materials with controllable structure and pore sizes.In this paper,one-dimensional chain like structure of MOF derived composites are prepared by self-assembly with one dimensional nanowires as template.The microwave absorption performance of the composites is improved with their synergistic effect,the constructing of network structure,the increasing of interfacial polarization and the lengthening of the effective transmission path of electromagnetic wave.The details are as fo llows:(1)Metal Organic Frameworks(MOF)-derived the necklace-like carbon nanofibers(CNFs)@carbonaceous Co/CoO composite is synthesized by wet chemical and pyrolysis method.The CNFs are penetrated through the derived carbonaceous Co/CoO frameworks which retain the ZIF-67's sizes.Due to their unique structure and the well controlling of experimental parameters,the optimum reflection loss value of-53.1 dB at 6.56 GHz is obtained,and the corresponding bandwidth below-10 dB(90%absorption)is up to 13.52 GHz with the thickness range of 2.0-5.0 mm.(2)One-dimensional chain-like MnO@Co/C composite is synthesized by hydrothermal and high temperature pyrolysis mehod.This structure not only solves the agglomeration problem of the single ZIF-67,but also provides more effective transmission paths for the propagation of electromagnetic wave in the material,and increases the attenuation of electromagnetic wave.After test and calculation,the minimum reflection loss of the MnO@Co/C composites can reach to-49.06 dB at 6.48 GHz.(3)CNTs@Fe/C nanocomposites with unique one-dimensional chain like structure are prepared by a facile two-step method.Firstly,CNTs are used as the templates to in-situ nucleation and growth of prussian blue crystals and then converted into CNTs@Fe/C composites by pyrolysis at high temperature.The results show that CNTs and prussian blue derivatives have higher electromagnetic wave absorption performance.And the conductive network constructed by them is conducive to electron hopping and migration and greatly enhanced microwave absorption performance.In addition to excellent microwave absorbing properties,this material also meets the practical requirements of lightweight.The minimum reflection loss can reach-44.26 dB with a thickness of 2.4 mm and the effective absorption bandwidth is 3.68 GHz.