Simple Salt‐Template Assembly for Layered Heterostructures of C/Ferrite and EG/C/MFe₂O₄ (M = Fe, Co, Ni, Zn) Nanoparticle Arrays toward Superior Microwave Absorption Capabilities

Abstract

carbon, [1] expanded graphite (EG), carbon nanotubes (CNTs), and graphene), dielectric loss materials (ZnO [2] and BaTiO 3), and magnetic loss materials (MFe 2 O 4 , [3] Fe, Co, Ni, and their alloys [4,5]) are generally included. Among them, ferrite materials are widely used as EAMs because of their abundant raw materials, low cost, easy preparation, nontoxicity, and good chemical stability. [3,6] However, their low permittivity and large density render them too thick and heavy to be used in light and thin electronic devices. Besides, EG consisting of sheet-like graphite as an EAM has also attracted much attention. Its excellent properties (low cost, low density, large conductivity, large specific surface area, good antioxidation ability, and big shape anisotropy [6,7]) make it a superb host for nanoparticles. [8] Nevertheless, studies have demonstrated that EG solely used as an EAM hardly meets the high demand of broadband EAMs due to its single conductivity loss and poor impedance matching. Layered C/ferrite nanoparticle array (NPA) and expanded graphite (EG)/C/MFe 2 O 4 (M = Fe, Co, Ni, Zn) NPA heterostructures are synthesized via a simple sodium salt-template method. An array of well-distributed ferrite nanoparticles supported by layered carbon grows simultaneously on the EG surface from metal-oleate complexes. Some dynamic factors are systematically optimized to well adjust the size, content, and morphology of the heterostructures. The heterostructures show good soft magnetic nature with the M s decreasing in the following order: EG/C/γ-Fe 2 O 3 > EG/C/CoFe 2 O 4 > EG/C/NiFe 2 O 4 > EG/C/ZnFe 2 O 4. As microwave absorbers, these heterostructures of EG/C/MFe 2 O 4 NPA exhibit significantly enhanced electromagnetic-wave absorbing capabilities (EWACs) compared with pure EG, EG/γ-Fe 2 O 3 NPA heterostructure, and other C-based composites. Hereinto, EG/C/CoFe 2 O 4 NPA heterostructures exhibit the optimal EWAC with a minimal reflection loss of −49.85 dB at 13.9 GHz and a 1.3 mm coating thickness. The frequency range of 99% absorption is over 2.0-17.0 GHz and the corresponding thickness is 1.10-8.0 mm. The excellent microwave absorption relies on cooperation of double dielectric relaxations, natural resonance, eddy current loss, high attenuation, and appropriate impedance matching. Therefore, layered heterostructures of EG/C/MFe 2 O 4 NPA are promising electromagnetic wave absorbers for practical application.

Microstructure induced dielectric loss in lightweight Fe3O4 foam for electromagnetic wave absorption

“…Additionally, the small fluctuation at about 4.5 GHz originates from natural resonance, which verified by the distinct resonance peak at the same frequency in tan μ ∼ f carves ( Figure S9 F). As is well known, if eddy current loss is the leading factor of magnetic loss, the C 0 values will remain constant with the varied frequency ( Wu et al., 2020 ). As shown in Figure S10 E, the C 0 values of S0.7 and S0.9 keep unchanged in the frequency of 10-18 GHz, proving the existence of eddy current loss.…”

Broadband electromagnetic absorption of Ti3C2Tx MXene/WS2 composite via constructing two‐dimensional heterostructure

“…As mentioned above, the Ti 3 C 2 T x /WS 2 composite has abundant functional groups (-OH, -O, and -F), which can produce dipolar polarization relaxation, while the multilayer heterostructure interfaces generates a large anisotropic field to boost the interface polarization. 46 In other words, the composite exhibits synergistic effect of the 2D heterostructure interfaces and the dual dielectric components.…”

Hollow MoC/NC sphere for electromagnetic wave attenuation: direct observation of interfacial polarization on nanoscale hetero-interfaces

“…For solving the spatial electromagnetic radiation, in recent decades, scientists have developed many groups of high-efficient electromagnetic wave absorbing materials (EWAMs), including carbon-based materials 1-3 , silicon carbides 4,5 , transition metal-based carbides 6,7 , oxides 8,9 , sulfides 10,11 , nitrides 12,13 , and ferromagnetic metal-based materials [14][15][16] . In the electromagnetic wave absorbing process, the combination of permittivity and permeability directly determines the electromagnetic wave storage and attenuation capacities of the materials [17][18][19][20][21] .…”