Facile synthesis and excellent microwave absorption properties of FeCo-C core–shell nanoparticles

Abstract

FeCo-C core-shell nanoparticles (NPs) with diameters of 10-50 nm have been fabricated on a large scale by one-step metal-organic chemical vapor deposition using the mixture of cobalt acetylacetonate and iron acetylacetonate as the precursor. The Fe/Co molar ratio of the alloy nanocores and graphitization degree of C shells, and thus the magnetic and electric properties of the core-shell NPs, can be tuned by the deposition temperature ranging from 700 °C to 900 °C. Comparative tests reveal that a relatively high Fe/Co molar ratio and low graphitization degree benefit the microwave absorption (MA) performance of the core-shell NPs. The composite with 20 wt% core-shell NP obtained at 800 °C and 80 wt% paraffin exhibits an optimal reflection loss [Formula: see text] of -60.4 dB at 7.5 GHz with a thickness of 3.3 mm, and an effective absorption bandwidth (frequency range for RL ≤10 dB) of 9.2 GHz (8.8-18.0 GHz) under an absorber thickness of 2.5 mm. Our study provides a facile route for the fabrication of alloy-C core-shell nanostructures with high MA performance.

Trimetallic FeCoNi@C Nanocomposite Hollow Spheres Derived from Metal–Organic Frameworks with Superior Electromagnetic Wave Absorption Ability

“…A distinguishing feature is that, when the calcination temperature reaches 900 °C, all of the Co will melt and merge into the FeCoNi ternary alloy, and the M s value of the MOF-900 with high Co contents will be reduced significantly, which is in good consistence with the results reported in previous literature . In addition, the increase of calcination temperature is accompanied by the grain growth process, which will also affect the magnetic properties of the samples …”

“…27 In addition, the increase of calcination temperature is accompanied by the grain growth process, which will also affect the magnetic properties of the samples. 38 In light of the principle of electromagnetic energy conversion, 9,39 the quality of the electromagnetic wave absorbers is largely determined by the relative complex permeability (μ r = μ′ − jμ″), relative complex permittivity (ε r = ε′ − jε″), and the matching degree of these two parameters. The real parts of the electromagnetic parameters (ε′, μ′) stand for the stored electrical and magnetic energy within the medium, while the imaginary parts (ε″, μ″) are related to the electromagnetic loss capacity, respectively.…”

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

“…The G-band is attributed to the stretching of sp 2 -bonded C-C pairs [44]. A broad peak from 2467.5 to 2928.1 cm -1 can be assigned to the 2D-band that indicates the number of multiple layers structure of carbon according to its relative intensity with respect to the G band and its position [45,46]. The intensity ratio value of D band to G band (I D /I G )…”

Facile synthesis of porous Fe3O4@C core/shell nanorod/graphene for improving microwave absorption properties

“…The complex permittivity and complex permeability of the samples was characterized by a HP8722ES vector network analyzer in the frequency range 1–18 GHz. The reflection loss ( R L ) is calculated according to the following equations: 32 where Z in is the input impedance, ε r and μ r are the relative complex permittivity and permeability respectively, f is the frequency of the microwaves, d is the layer thickness and c is the velocity of microwaves in free space.…”