Construction And Microwave Absorption Properties Of Polyaniline Aligned On Magnetic Functionalized Biomass Carbon

Biomass carbon,exhibiting the characteristics of carbon materials,low price,renewability,wide variety of sources and simple fabrication process,have been attracted the attention in various fields.In recent years,biomass carbon as a dielectric microwave absorbing material have gradually become a research hotspot in the field of microwave absorbing materials.Unfortunately,the good conductivity,high dielectric and nonmagnetic loss characteristic of biomass carbon materials will result in impedance mismatching,which seriously hinders their practical application as high performance of microwave absorbing materials.To solve these problems,a series of biomass carbon-based composite absorbing materials were prepared by component functionalization and microstructure design and regulation,making the material have the multiple loss mechanisms such as dielectric loss,magnetic loss and geometric effect loss?multiple reflection?,which may improve the impedance matching and microwave absorption properties.The specific contents of the study are as follows:?1?The aligned polyaniline/porous Biomass carbon?A-PANI/PBC?microwave absorbing composites,combining porous biomass carbon prepared by carbonization process with loofah as carbon source?PBC?and polyaniline?PANI?,were synthesized by in-situ polymerization.The morphology and structure of the composites were characterized by scanning electron microcopy,transmission electron microscopy,Fourier transform infrared spectra,X-ray diffraction,Raman spectroscopy and X-ray photoelectron spectra.The effects of the morphology,structure and aniline content on the microwave absorbing properties of composites were investigated.The results indicated that the A-PANI/PBC composite has the excellent microwave absorbing performance when the concentration of aniline is 0.6 mmol.The minimum reflection loss?RL?value of A-PANI/PBC composite is up to-44.8 dB at 10.02 GHz and the effective absorption frequency width?RL<-10 dB?is in the 2.5 GHz with a thickness of 2 mm.?2?In view of the single loss mechanism and poor impedance matching of biomass carbon materials,introducing the effective magnetic components in this chapter for preparation of biomass carbon-based microwave absorbing composites may to achieve multiple loss mechanism,improve the impedance matching and furtherly enhance the absorption performance.Herein,Fe₃O₄/porous biomass carbon?Fe₃O₄/PBC?microwave absorbing composites with dielectric loss and magnetic loss characteristics were obtained by hydrothermal one-step method using FeCl₃ as raw material.The effects of preparation process on the morphology and structure of the composites were investigated.The properties of Fe₃O₄/PBC composites were analyzed by vibration sample magnetometer,which demonstrate that the magnetic saturation strength of Fe₃O₄/PBC composites enhances with the increase of FeCl₃ content.The effects of the morphology,structure and Fe₃O₄content on the microwave absorbing properties of composites were investigated by vector network analyzer.The results showed that the Fe₃O₄/PBC composite?30 wt%of absorbent in paraffin wax?have the excellent microwave absorbing performance in the range of 2-18 GHz when the concentration of FeCl₃ is 4 mmol.The minimum reflection loss can be up to-42.2 dB at 11.42GHz,and the effective bandwidth is 3.14 GHz with a thickness of 2 mm?reflection loss is less than-10 dB?.?3?Based on the above research,constructing ternary composite microwave absorbing system with multi-level structure?zero-dimensional Fe₃O₄ magnetic particles,one-dimensional oriented polyaniline and three-dimensional porous biomass carbon?in this chapter may achieve multiple loss characteristics,improve impedance matching,and ultimately enhance the microwave absorbing properties.The aligned polyaniline/Fe₃O₄/porous biomass carbon?A-PANI/Fe₃O₄/PBC?composite absorbing materials were successfully prepared by hydrothermal synthesis and in situ polymerization.The effects of preparation process on the composition,structure,and microwave absorbing properties of the composites were studied and analyzed.The results demonstrated that the composition and morphology of A-PANI/Fe₃O₄/PBC composites have obvious effects on their microwave absorbing properties.And the minimum reflection loss of the A-PANI/Fe₃O₄/PBC can be up to-44.9 dB at 10.67 GHz,the effective absorbing bandwidth?RL<-10 dB?reaches 4.69 GHz with a thickness of 2.7 mm.In summary,the multi-component and multi-structure A-PANI/Fe₃O₄/PBC composite was constructed by coupling Fe₃O₄ magnetic functional nanoparticles?zero-dimensional?and polyaniline aligned nanostructures?one-dimensional?with the three-dimensional porous biomass carbon matrix,which have excellent electromagnetic absorbing performance.The reasons are as following:On the one hand,the porous carbon matrix of PANI/Fe₃O₄/PBC composites provides dielectric loss and conductivity loss,and the magnetic component?Fe₃O₄?provides magnetic loss.On the other hand,the aligned polyaniline formed by structural recombination plays a role of"wedge",which provides enhanced multiple reflection loss and improves impedance matching performance.Therefore,the research in our work provides a scientific and theoretical basis for further promoting the development of new high-performance microwave absorbing composites.