Preparation and microwave absorption properties of Gd–Co ferrite@silica@carbon multilayer core–shell structure composites

Fabrication of an Ultralight Ni-MOF-rGO Aerogel with Both Dielectric and Magnetic Performances for Enhanced Microwave Absorption: Microspheres with Hollow Structure Grow onto the GO Nanosheets

“…The degrees of graphitization of the Ni-rGO and 600Ni-rGO aerogel samples are investigated through the Raman spectra. As presented in Figure b, two peaks appear at about 1300 and 1578 cm –1 , which refer to the D band and G band, respectively . It can be seen that the value of I D / I G increases from 0.99 to 1.14 after the calcination, which indicates that the higher temperature improves the degree of crystallization of carbon .…”

“…As presented in Figure 2b, two peaks appear at about 1300 and 1578 cm −1 , which refer to the D band and G band, respectively. 50 It can be seen that the value of I D /I G increases from 0.99 to 1.14 after the calcination, which indicates that the higher temperature improves the degree of crystallization of carbon. 51 Moreover, more defects will induce more dipolar polarizations, which is a benefit for microwave absorption.…”

All-Around Electromagnetic Wave Absorber Based on Ni–Zn Ferrite

“…It is well known that dynamic magnetic loss mostly arises from domainwall resonance, magnetic hysteresis, eddy current effects, and natural and exchange resonance. 6,19 The first two contributions are less effective in this study due to the presence of a low magnetic field and high frequency. 12 For NZF samples, strong EM absorption through magnetic loss around 5.5 GHz arises as a consequence of the natural magnetic resonance (NMR) and is also related to the exchange interaction between neighboring grains.…”

“…Electromagnetic interference (EMI) arises as an inevitable offshoot from the newly emerged fifth-generation (5G) devices as well as extensively used Radar and satellite communications. , However, EMI or electromagnetic (EM) wave pollution not only adversely impacts electronic operations creating unwanted noises but is also considered as a potential environmental hazard. , Therefore, demand for an all-around efficient electromagnetic absorber (EMA) is ever-expanding to cut down the EM wave pollution. , Moreover, EMA can also shield EM waves to prevent information theft from becoming essential in defense and military fields. − In this context, ferrites with their synergistic magnetic and electrical properties are well known to be highly promising EMA components compared with other unary electrical or magnetic materials. − Proper tuning of ferrite properties such as permeability (μ) and permittivity (ε) can lead to broader bandwidth (BW) and induce better impedance matching (i.e., | Z in / Z 0 | ∼ 1), thus ensuring higher reflection loss (RL). ,, Further, a high value of ε and μ is desirable to enhance the wave attenuation and lessen the thickness ( t ) of the absorbing material . To achieve tuning, chemical doping, particle size, and morphology control, layering of EMAs are some of the popular techniques. − For instance, Gorai et al observed an optimum RL of −47.0 dB for a bilayered CoFe 2 O 4 -coated MnFe 2 O 4 nanohollow spheres increasing μ of the material closer to its ε and thus improving impedance matching in ferrites .…”

“…1,45 This can happen through either wave absorption, i.e., transforming EM wave to heat energy via losses, or transmission of EM wave. 6 Contextually, proper impedance matching ensures better propagation of EM wave through the material enhancing the chances for losses as well. 35 Frequency-dependent reflection loss (RL) curves for NZF and Mn-doped NZF cores are plotted in Figure 6(a−f) varying their thicknesses from 2 to 8 mm.…”