Preparation And Wave Absorption Properties Of Bamboo-like Silicon Carbide Nanowires And Its Composites

With the increasing demand for wave-absorbing materials in military and civil applications,the search for lightweight,broad-band absorbing and multifunctional integrated electromagnetic wave absorbing materials is imminent.Compared with other structural Si C materials,bamboo-like Si C nanowires（Si C NWs）have low density,a large number of internal stacking layer dislocations and defects,and high aspect ratio,which make their research and application in the field of wave absorption attract much attention.The low-cost and high-efficiency preparation of bamboo-like Si C NWs is currently an industrial difficulty,and the impedance matching and loss capability of a single Si C materials are difficult to meet the high-power requirements of wave absorbing materials,which limits their practical applications.In order to prepare high-purity,morphologically homogeneous bamboo nodular Si C NWs and enhance the wave absorption performance of bamboo nodular Si C NWs materials,this paper adopts electrostatic spinning combined with carbon thermal reduction process to prepare Si C NWs,and through the design of composite morphology and components,different material systems are constructed to obtain high-efficiency electromagnetic wave absorbing materials with excellent performance.In this paper,the dielectric and wave absorption properties of the composites were systematically analyzed and their electromagnetic wave absorption mechanism was elucidated,and the main research contents of this paper are as follows:When the filling amount of Si C NWs in the paraffin-transparent matrix is only 10wt%,the lowest reflection loss(RL_min)can reach-16.95 d B at the absorber thickness of3.5 mm,and the effective absorption bandwidth（EAB）of the sample was 4.34 GHz wide at a thickness of 2.2 mm.During the nanowire growth process,the carbon spheres react with traces of oxygen,which affects the partial pressure of the gas in the system causing a periodic change in the diameter of Si C NWs.The three-dimensional（3D）conducting network constructed by interweaving the obtained bamboo-like Si C NWs increases the possibility of multiple scattering and reflection of electromagnetic waves;its internal defects enhance the dipole polarization,and the oxide layer on the nanowire surface brings a large number of heterogeneous interfaces to promote interfacial polarization.To solve the problem of single loss mechanism and poor attenuation ability of bamboo-like Si C NWs,flower-like Cu S/Si C NWs@polyaniline（PANI）composites were prepared by hydrothermal method and in situ polymerization.When the filling amount of Cu S/Si C NWs@PANI is 25 wt%,the RLmin is-31.6 d B at a thickness of 2.1 mm and the EAB can reach 4.5 GHz;when the filling amount is increased to 35 wt%,the RL_min is as low as-41.38 d B at a thickness of 2.3 mm.the Cu S particles have a multilayer asymmetric flower-like structure,which promotes the reflection of electromagnetic waves;The heterogeneous interface between the encapsulated conductive polymer PANI and Cu S and Si C NWs constitutes a heterogeneous interface that enhances the conductivity loss.The synergistic effect between the ternary composite systems effectively enhances the electromagnetic wave absorption performance.To address the poor impedance matching characteristics of Si C NWs,the flower-like Ni/Si C NWs composites were prepared by solvent thermal method by compounding them with magnetic metal Ni.When the filling amount of Ni/Si C NWs composite is 50 wt%,the RL_min can reach-49.26 d B and EAB of 4.25 GHz at the thickness of 1.9 mm;when the filling amount is 60 wt%,the EAB width is 5.0 GHz at the thickness of 1.8 mm（12.5～17.5 GHz）.When electrons leap between the laminar petals of Ni particles,a coupling circuit is generated to convert the incident electromagnetic energy into thermal energy dissipation,which enhances the conductivity loss capability;the magnetic metal Ni brings to the material the magnetic loss dominated by eddy current loss and natural resonance,which enhances the loss mechanism and improves the impedance matching performance of Si C NWs.