Research On Surface Electromagnetic Functionalization Of Basalt Fibers And Their Electromagnetic Wave Absorption Properties

As an inorganic high-performance green fiber,basalt fiber（BF）has unique advantages in mechanical strength,corrosion resistance and electromagnetic properties.Electromagnetic functionalization modification of BF can realize the integration of electromagnetic and enhancement functions.However,the research of BF in the field of electromagnetic wave（EMW）absorption is less,and most surface electromagnetic functional modification is performed on BF using single-function component.Therefore,this thesis takes BF as the research object,from the morphological level of fiber powder,short-cut fiber to fiber fabrics,and prepared carbon black/flower-like nickel（CB/Ni）electromagnetic functionalized BF,Fe₃O₄/carbon nanotubes（Fe₃O₄/CNTs）electromagnetic functionalized BF,double-layered BF composites and BF-based absorbing fabrics,respectively.Finally,we analyze the influence of surface morphology,chemical composition and electromagnetic parameters on the absorption properties of the composites,and reveal the electromagnetic loss mechanism of the composites.Taking BF powder as the research object,improving the surface roughness of BF with polydopamine coating,then electromagnetic functionalized of BF with electric and magnetic absorbents.Two different BF-based electromagnetic functionalized composites were obtained by adhering the absorbent on the surface of BF by dip-coating adsorption method.Modification of BF powder with carbon black and flower-like nickel and measurement of their electromagnetic parameters.Calculated by transmission line theory,the results show that when the mass ratio of carbon black and flower-like Ni is 1:8,reflection loss（RL）value of BF-CB/Ni8 can reach-35.29 d B with an effective absorption bandwidth（EAB）of 3.25 GHz for 1.5 mm thickness.Assembling three-dimensional structures with Fe₃O₄ and carbon nanotubes on the surface of BF can effectively enhance the absorption ability of BF,and when the thickness of BF-Fe₃O₄/7C is 1.5 mm,the modified BF has a minimum RL value of-40.57 d B and EAB is 3.42 GHz.Therefore,carbon/magnetic dual loss component cladding allows fiber composites to achieve excellent absorption properties at thin thicknesses.By exploring different approaches with different absorbents for the electromagnetic functionalization of BF,a synergistic electromagnetic loss model among magnetic loss,dielectric loss,and polarization loss between heterogeneous interfaces is proposed to effectively enhance the absorption performance of fiber composites.This provides a theoretical basis for the use of BF powder as a wave-absorbing filler.For the short-cut BF,single-layered BF/CB/epoxy and BF/Fe₃O₄/epoxy absorbing composites were prepared by using carbon black and nano-Fe₃O₄ as absorbents and epoxy resin as infiltrator and binder.Based on the principle of impedance gradient,a double-layered BF-based composite combining matching layer and absorbing layer was designed for X-band absorption,which can realize the electromagnetic functionalization modification of short-cut BF and meet the demand of quantifiable production.The results show that increase the content of absorbent can effectively improve the electromagnetic parameters of single-layered composites.The absorbent coated on the surface of BF can form resonant cavity,which prolongs the propagation path of EMW through refraction and reflection.On this basis,the composition and thickness of the double-layered composites were optimized by combination of experiments and calculations.When the thickness of the matching layer（BF/Fe₃O₄10）and absorbing layer（BF/CB7.5）were 0.3 mm and 2.7 mm,the RL value of-43.97 d B and full X band effective absorption can be achieved.In order to realize the electromagnetic functionalization of BF fabrics,lightweight and environmentally adaptable flexible absorbing materials were prepared which based on the interwoven structural characteristics and excellent mechanical flexibility of BF fabrics.The uniformly dispersed carbon black/graphene aqueous absorbing functional resin slurry was prepared by ball milling method in the experiment and using the scraping coating process to obtain a continuous light and thin electromagnetic functional layer on the surface of fiber fabrics.The electromagnetic properties of the composite fabric were optimized by regulating the content of carbon materials in the coating.The measurement and analysis show that the increase of carbon material content on the surface of BF fabrics gradually forms a dense carbon black/graphene functional layer,and the complex permittivity increases subsequently.The EAB of CB/GSs20-BF was 3.53 GHz in the X-band frequency range,and CB/GSs35-BF was3.36 GHz in the Ku-band.The prepared BF absorbing fabrics have properties of strong bonding of functional layers to fibers,hydrophobicity and durability.In this paper,the EMW absorption properties of BF composites are endowed by compositing electric and magnetic absorbents with BF at different structural levels.The intrinsic relationship between the structure and performance of electromagnetic functional BF was investigated,which provides the theoretical basis and experimental foundation for the application of BF in the field of EMW absorption.