Preparation And Performance Study Of One-dimensional Carbon-based Core-shell Composites

With the development of information technology,electromagnetic pollution has become an increasingly prominent problem.Currently,electromagnetic pollution has posed a serious hazard to electronic devices and health.Microwave absorption materials are the key to solve this problem.One-dimensional core-shell carbon matrix composites were prepared by compositing magnetic loss materials and carbon,which improved the impedance matching and increased the loss mechanism of carbon materials.A core-shell structure is a combination structure in which one material is orderly bonded to another material by chemical bonding or other forces.Recent studies have also shown that core-shell heterostructures play an important role in improving microwave absorption through space charge polarization and quantum confinement effects.Therefore,four one-dimensional core-shell carbon-based composites were designed and prepared in this paper.Their microscopic morphology,elemental composition and microwave absorption properties were also characterized.The main studies are as follows:（1）PBA was grown on the surface of PAN fibers by in-situ growth method,and the one-dimensional core-shell structure of Co C@Co Fe/C was formed after carbonization.Then the impedance matching performance of the microwave absorber was tuned by further compounding PPy.Finally,the optimal filling ratio of microwave absorption materials was explored by adjusting the ratio of Co C@Co Fe/C composites and paraffin wax.The Co C@Co Fe/C composite exhibited the best microwave absorption performance at 25 wt%filling.The minimum reflection loss（RLmin）of the sample is-64.32 d B at a thickness of only 1.69 mm,and the effective absorption bandwidth（EAB）of the sample is 5.38 GHz at a thickness of 1.88 mm.（2）PAN fibers containing metal ions were prepared by electrostatic spinning technology,and Mn²⁺was oxidized by KMn O4 to generate Mn O2 during the hydrothermal process.This experiment cleverly used Mn²⁺diffused from PAN as one of the reaction raw materials,so that this redox reaction occurred at the interface of PAN fibers.The Mn O2 prepared in this way can better adhere to the surface of the fiber to form PAN@Mn O2 nanofibers.After carbonization,the dielectric parameters were adjusted by PPy to prepare Fe/C@Mn O2@PPy composites with excellent matching properties.The RLmin of the composite is-68.19 d B at 20 wt%filling and 1.92 mm thickness,and the maximum EAB of the composite is 6.16 GHz at 2.17 mm thickness.（3）Cotton-derived carbon fibers were prepared from natural cotton fibers,and then the carbon fiber surface was coated with flower-like Ni（OH）2.Finally,the surface was modified with PPy to produce C@Ni（OH）2@PPy nanofibers,which has a layered core-shell structure that can reflect and absorb electromagnetic waves well.The material was also tested for microscopic morphology,structural composition and microwave absorption properties using SEM,XRD,XPS and vector network analyzer.The results show that the RLmin of the composite is-56.02 d B at a thickness of 4.97 mm,and the maximum EAB of the composite is 4.98 GHz at a thickness of 1.95 mm.（4）PAN fibers containing nickel and iron ions were prepared by electrostatic spinning method,and then MIL-88A was generated on its surface by hydrothermal method.Ni Fe/C@Fe/C nanofibers were obtained by carbonization of PAN@MIL-88A.Finally,the Ni Fe/C@Fe/C@PPy nanocomposite fibers were produced by modifying their surfaces using PPy.The materials were characterized by microscopic morphology and structural composition using SEM,XRD and XPS tests.In addition,the absorption test results show that the sample with 20 wt%filling has the best microwave absorption performance.At a thickness of 1.64 mm,the composite has a RLmin of-62.62 d B.The maximum EAB of the composite is 5.54 GHz at a thickness of 1.91 mm.