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

Low-density Fe-doped ordered mesoporous carbon (CMK-3)-silica (SBA-15) nanocomposites with different Fe contents have been prepared by a catalytic carbonization procedure followed by high-temperature calcination in N₂. From field 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 (â14 18nm) are dispersed on the surface of frameworks during the catalytic carbonization procedure and endow a magnetic property to the carbon-silica nanocomposites. The optimal reflection loss (RL) calculated from the measured permittivity and permeability is-19dB at 17.2GHz for an absorber thickness of 2.00mm. Moreover, the electromagnetic (EM) wave absorption less than-10dB is found to exceed 5.76GHz 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 find the fitted curves of the multi-resonance imaginary permeability spectra of the composites. The EM wave can hardly be reflected 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.