Fe‐, Co‐, and Ni‐Loaded Porous Activated Carbon Balls as Lightweight Microwave Absorbents

Abstract

Porous activated carbon ball (PACB) composites impregnated with iron, cobalt, nickel and/or their oxides were synthesized through a wet chemistry method involving PACBs as the carrier to load Fe(3+), Co(2+), and Ni(2+) ions and a subsequent carbothermal reduction at different annealing temperatures. The results show that the pyrolysis products of nitrates and/or the products from the carbothermal reduction are embedded in the pores of the PACBs, with different distributions, resulting in different crystalline phases. The as-prepared PACB composites possessed high specific surface areas of 791.2-901.5 m(2) g(-1) and low densities of 1.1-1.3 g cm(-3). Minimum reflection loss (RL) values of -50.1, -20.6, and -20.4 dB were achieved for Fe-PACB (annealed at 500 °C), Co-PACB (annealed at 800 °C), and Ni-PACB (annealed at 800 °C) composites, respectively. Moreover, the influence of the amount of the magnetic components in the PACB composites on the microwave-absorbing performances was investigated, further confirming that the dielectric loss was the primary contributor to microwave absorption.

Two‐step preparation of fly ash‐based composites for microwave absorption

“…75-2078). 8 Because the characteristic peak of carbon in the XRD patterns overlaps with that of SiO 2 at 2θ =26.5°, this would be further confirmed by the Raman spectrum characterization. As shown in Figure 1B, it is found that the I D /I G values of CoFA300, CoFA400, CoFA500, CoFA600, and CoFA700 composites are 0.23, 0.31, 0.41, 0.50, and 0.55, respectively.…”

In Situ Reduced Multi-Core Yolk–Shell Co@C Nanospheres for Broadband Microwave Absorption

“…Therefore, the main mechanisms in the GHz frequency band are natural resonance and eddy current loss. The eddy current loss can be expressed by the following formula [ 56 ]: where σ is the electrical conductivity and μ 0 is the permeability in vacuum. The formula can be converted to , which means that C 0 will remain constant if the magnetic loss of the material is caused solely by eddy current loss.…”

Nanostructured carbon–metal hybrid aerogels from bacterial cellulose

“…38 This combination of electric conductivity and magnetic permeability can be useful for the production of electromagnetic interference shields. 13 Moreover, preliminary tests have shown that the generation of the porous, graphitic ber network can result in very low total reectance in the visible light range, which is interesting for efficient light absorption in solar energy applications.…”

“…2 Specically, carbon-nickel nanostructured materials, oen prepared by carbothermal reduction, 9,10 nd widespread use as energy materials and optical materials. 4,6,7,[11][12][13] Herein, specially biomass like lignocellulosics, nanocellulose, or bacterial cellulose are multifarious carbon sources due to their structural pre-organization displaying porosity, brous morphology, or three-dimensional (3D) networks, respectively, which can be translated into nanostructured carbon during their carbonization. [14][15][16] Thus, careful choice of the pyrolysis conditions not only reduces the metal precursor to metal nanoparticles but concomitantly can also produce carbon nanobers, 17 carbon aerogels, 18 or graphene, 19 which integrate the functional metal nanoparticles.…”