Microwave Absorption Properties of Fe-Doped Ordered Mesoporous Carbon (CMK-3)/Silica Matrix Nanocomposites with Magnetic Multi-Resonance Mechanisms

Abstract

Low-density Fe-doped ordered mesoporous carbon (CMK-3)-silica (SBA-15) nanocomposites with di®erent Fe contents have been prepared by a catalytic carbonization procedure followed by high-temperature calcination in N 2 . From¯eld emission-scanning electron microscope (FE-SEM) and high resolution-transmission electron microscope (HR-TEM) images, it can be concluded that CMK-3 particles are dispersed homogeneously into a silica matrix and form a novel, special and interesting composite nanostructure. The metal species ($18 nm) are dispersed on the surface of frameworks during the catalytic carbonization procedure and endow a magnetic property to the carbon-silica nanocomposites. The optimal re°ection loss (RL) calculated from the measured permittivity and permeability is À19 dB at 17.2 GHz for an absorber thickness of 2.00 mm. Moreover, the electromagnetic (EM) wave absorption less than À10 dB is found to exceed 5.76 GHz as the layer thickness is 2.37 mm. The permittivity dispersion behaviors have been explained based on the Cole-Cole model and the conductivity contribution model. A new simple empirical model was also supposed to¯nd the¯tted curves of the multi-resonance imaginary permeability spectra of the composites. The EM wave can hardly be re°ected on the absorber surface because of a better match between dielectric loss and magnetic loss, which originates from the combination of dielectric carbon-silica and magnetic Fe species.

Silica-Modified Ordered Mesoporous Carbon for Optimized Impedance-Matching Characteristic Enabling Lightweight and Effective Microwave Absorbers

“…Through previous research, it is known that Z = | Z in / Z 0 | will be close to 1 when absorber thickness satisfies eq , in which case a satisfactory MA performance will be obtained. Moreover, the representative carbon-based microwave absorbing materials and their MA performance have been listed in Table S2. − Compared with other carbon-based materials, OMC-5@SiO 2 in this work possesses a relatively low RL value (−40.8 dB) and broad effective absorption bandwidth (4.8 GHz) with thin absorber thickness. In addition, compared with other microwave-absorbing materials such as ferrite/Co/porous carbon and Fe 3 O 4 /SiO 2 /graphene composites, OMC-5@SiO 2 shows lower density and better corrosion resistance.…”