Microwave Electromagnetic and Absorption Properties of N-Doped Ordered Mesoporous Carbon Decorated with Ferrite Nanoparticles

Abstract

Lightweight nitrogen-doped ordered mesoporous carbon (NOMC) with high specific surface area and pore volume have been prepared through self-assembly and subsequent heat treatment route. The spherical NOMC particles are decorated with CoFe2O4 nanoparticles via coprecipitation method to enhance their microwave absorption property. The electromagnetic parameters of the NOMC and CoFe2O4/NOMC composites are measured and the microwave reflection loss properties are evaluated in the frequency range of 0.5–18 GHz. The results show that both the real part and imaginary part of permittivity of NOMC totally decline and the real part of permeability increases with the introduction of ferrite. However, the negative values of the imaginary part of the complex permeability appear for the CoFe2O4/NOMC composites, which may be caused by enhanced eddy current effect due to the introduction of ferrite. The reflection loss results exhibit that the CoFe2O4/NOMC composites have excellent microwave absorption performances. The absorption bandwidth less than −10 dB reaches 5.0 GHz (11.9–16.9 GHz) for 40-F/NOMC composite (40 wt % ferrite) with 1.5 mm of thickness and the minimum reflection loss value is up to −38.3 dB at 3.9 GHz for 30-F/NOMC composite with 4.0 mm of thickness. The excellent absorption properties derive from the synergistic effect between dielectric loss of NOMC and magnetic loss of ferrite and better impendence matching at air and ferrite/NOMC composite interface. Thus, the lightweight ferrite/NOMC composites exhibit their great potential as microwave absorbing materials.

Structure and Microwave Absorption Properties of Polyaniline/Zn Ferrite Composites

“…Z in =Z 0 is required to equal 1.0 to meet the demands of zero re°ection at the air-absorber interface. 35 As shown in Fig. 11(c), the peak frequency of S1 at the thickness of 1.4 mm and 1.5 mm matched well with the frequency of impendence matching characteristics that were almost close to 1.0.…”

In-situ growth of Fe/Fe3O4/C hierarchical architectures with wide-band electromagnetic wave absorption

“…10d-10f, which can illustrate the complex Argand plane plot of ɛ′′ and ɛ′ (ε = ε ′ + ′′). The real (ɛ′) and imaginary (ɛ′′) part of the complex permittivity are given as [19,52] :…”

“…Pure carbon architectures, such as carbon nanotubes [12][13][14] and graphene [15,16], not only have high surface area and excellent conductivity but also exhibit intensive absorption at GHz level [17][18][19]. However, the absorption bandwidth of these carbon architectures cannot be satisfied due to the absence of magnetic loss [20].…”

Economical synthesis of composites of FeNi alloy nanoparticles evenly dispersed in two-dimensional reduced graphene oxide as thin and effective electromagnetic wave absorbers

“…[12][13][14][15] As is well known, the EM wave absorption performance of a material is determined by complex permittivity, complex permeability and impedance matching, which are affected by its components, microstructure, size and so on. 16,17 Hence, by rational cooperation of the magnetic components (Fe 3 26 carbon ber, 27 graphene, 28 porous carbon materials 29 ) within the magnetic/carbon-based hybrids, competent EM wave absorbers can be achieved.…”

“…Obviously, the uctuation trend of tan d 3 is just inverse to that of tan d m , which can be interpreted by LRC equivalent circuit model, where L, R and C are the inductance, resistance and capacitance, respectively. 16,56 Moreover, the attenuation constant (a) can be employed to further assess the integrated damping capability of the material taking into account of both dielectric loss and magnetic loss, and be calculated by the following equation:…”