The Outside-In Approach To Construct Fe₃O₄ Nanocrystals/Mesoporous Carbon Hollow Spheres Core–Shell Hybrids toward Microwave Absorption

Abstract

It is widely accepted that building a core−shell structure is an effective way to modify impedance matching behavior and induce interfacial polarization relaxtion. In this work, we adopted a novel impregnation process and subsequent calcination treatment to construct Fe 3 O 4 nanocrystals/mesoporous carbon hollow spheres (MCHS) core− shell hybrids. From the perspective of microwave absorption, MCHS possess favorable dielectric loss ability and lightweight features. Fe 3 O 4 could produce magnetic loss and regulate impedance matching characteristics. Besides, hollow voids and mesopores facilitate microwave absorption, while multiple interfacial polarization induced between Fe 3 O 4 nanocrystals and MCHS contributes to microwave attenuation. Combining these advantages, a maximum reflection loss value of −60.2 dB at 15.5 GHz and a broad effective bandwidth of 5.7 GHz can be achieved for the as-prepared sample at a thickness of 2.3 mm. Furthermore, the excellent microwave absorption properties with a ultrawide bandwidth of 8.0 GHz (10.0−18.0 GHz) at 2.6 mm of thickness was achieved. Therefore, the as-prepared hybrids can act as a lightweight and broadband microwave absorber; moreover, the corresponding method could be a sustainable and low-cost route for designing multicore−shell hybrids.

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption

“…Among these models, the MG theory has been widely applied in diverse porous materials, and it can be expressed as Eq. 1 [42,43]:…”

Preparation and electromagnetic properties characterization of reduced graphene oxide/strontium hexaferrite nanocomposites

“…Figure 4 shows the electromagnetic parameters of SrFe 12 O 19 nanoparticles and RGO/SrFe 12 O 19 nanocomposites. The real part (ε ′ ) and imaginary part (ε ′′ ) of the complex permittivity represent the storage and consumption capacity of electric energy, and the real part (µ ′ ) and imaginary part (µ ′′ ) of the complex permeability represent the storage of magnetic energy and consumption [26]. The ε ′ and ε ′′ are shown in Figure 4.…”

“…The results indicate that SrFe 12 O 19 has a poor dielectric loss ability, but the dielectric loss performance is greatly improved in the presence of RGO. From the formula ε ′′ ≈ 1/2πε 0 ρf , it can be known that due to the addition of RGO, the electrical conductivity of the composite material increases, so that the resistivity of the material decreases and the dielectric loss increases [27]. As the XRD results show, the GO is reduced to RGO during the preparation process, and the conductivity increases, which enhancing its space charge polarization.…”

Fabrication of NiFe2O4@carbon fiber coated with phytic acid-doped polyaniline composite and its application as an electromagnetic wave absorber

“…Aer stirring for about 6 hours, the CF@NiFe 2 O 4 @p-PANI hybrid was separated from the liquid by 10 000 rpm centrifugation and washed with deionized water and ethanol several times. [35][36][37][38]…”