Complex permittivity, permeability and electromagnetic wave absorption of  -Fe/C(amorphous) and Fe₂B/C(amorphous) nanocomposites

Abstract

The complex permittivity, permeability and electromagnetic (EM) wave absorption properties have been investigated for resin compacts containing 75 wt% composite powders of α-Fe/C(a) and Fe2B/C(a). The real and imaginary parts ( and εr′) of relative permittivity for the resin composites remained almost constant in the 0.05–20.05 GHz range. The imaginary part of the relative permeability (μr′) exhibited a wide peak in the 1–9 GHz range for α-Fe/C(a) and in the 2–18 GHz range for Fe2B/C(a). Both resin composites exhibited good EM wave absorption properties (RL < −20 dB) in the 4.4–8.3 GHz range with an absorber thickness of 1.9–3.4 mm, and in the 7.5–16 GHz range for an absorber thickness of 1.2–2.2 mm, respectively.

Synthesis, characterization and microwave dielectric properties of flower - like Co(OH)2/C nanocomposites

“…An EDS attached to the TEM was used to analyze the composition of the products. The Co(OH) 2 /C nanocomposite-paraffin composite was prepared by uniformly mixing Co(OH) 2 nanocomposites with paraffin and pressing them into cylinder-shaped compacts. Then the compact was cut into toroidal shape with 7.00 mm outer diameter and 3.04 mm inner diameter.…”

“…Figure 1 shows the XRD patterns of products with heating time of 6 and 10 h. In Figure 1a, the broad diffraction peak at 20-25° arises from the amorphous carbon. It is worthy noted that there are no peaks for Co(OH) 2 , indicating that the Co(OH) 2 is not crystalline at heating time of 6 h. When the heating time reaches to 10 h, main peaks of Co(OH) 2 are observed at 32.48°, 37.90°, 57.92°, 61.52° and 67.94°, corresponding to the reflections of (100), (101), (102), (111) and (200) of Co(OH) 2 , respectively. All the observed peaks can be matched with the Co(OH) 2 (JCPDS no.…”

“…34-0443). The average grain size of Co(OH) 2 is calculated to be about 30 nm from the full width at half maximum of the Co(OH) 2 Figure 2 shows different magnified SEM images of the products with heating time of 6 and 10 h, respectively. All images clearly indicate that the presence of threedimensional (3D) flower-like structures.…”

“…In recent decades, much attention has been paid to the core-shell structured nanoparticles, namely 'nanocapsules' [1][2][3][4][5] . Up to now, with the development of local electronic devices, microwave communication, and the rising pollution of electromagnetic (EM) interference, materials with EMwave absorption in a wide frequency range, with strong absorption, low density, and low cost are more and more desirable.…”

“…Among them, Co(OH) 2 is widely investigated as electrode material, catalytic material and magnetic cooling materia [13][14][15][16][17][18] . There are few reports on the EM properties of carbon-coated Co(OH) 2 nanocomposites.…”