What is the important factor affecting microwave absorption performance in corncob-derived carbon/Ni composites?

Abstract

Many factors can affect microwave absorption performance, including impedance matching, attenuation constant, electromagnetic (EM) loss capacity, multi-reflection and scattering and so on. In this work, corncob-derived carbon/Ni composites have been chosen to judge which factor has the greatest influence on the EM absorption behaviors, in which the surface area and pore size have been adjusted by the amount of chemical active additive. Closer impedance matching, larger attenuation constant and stronger EM loss capacity result in the good microwave absorbing behaviors of corncob-derived carbon/Ni composites when the mass ratio of KOH: corncob is 1.5. Minimal reflection loss values can reach −50.25 dB at 12 GHz and the effective bandwidth is 2.24 GHz and reflection loss values start be less than −10 dB at 1.2 mm. Through the analysis of morphology, microstructure, surface area and EM properties, it can be concluded that impedance matching is the most important for obtaining good microwave absorption performances, followed by EM loss ability and attenuation constant, and finally the multi-reflection and scattering by surface area.

Constructing multi-interface-structured FeNi/Fe2O3@Al2O3@C rod-like nanocomposites for superior microwave-absorption performance

“…As shown in figure 7(b), the 833 sample exhibits a thickness stability of RL m ; that is, the RL m exceeds −10 dB at 1.6-10 mm and −20 dB at 1.8-10 mm. Meanwhile, the RL m value of the 811 sample exceeds −10 dB at 1.3-10 mm, which is superior to those in previous works [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. The comparison exhibits that constructing multi-interfaces is a new strategy for obtaining microwave-absorbing materials with the merits of being strong, wide, and thin.…”

“…Therefore, hysteresis loss and domain wall resonance are excluded in GHz. If magnetic loss is only excited by eddy current loss, the µ ′′ (µ ′ ) −2 f −1 values should be constant at 2-18 GHz [8,11,14]. Obviously, the µ ′′ (µ ′ ) −2 f −1 values of the 833 sample continuously decrease with increasing f, implying that the magnetic loss is contributed to by natural/exchange resonance at 2-18 GHz.…”

“…So far, great efforts have been focused on the development of highly efficient microwave-absorbing materials, especially nanocomposites with a magnetic-dielectric interface [8][9][10]. Since 2008, our group has invested a lot of research into preparing magnetic metal/alloy core-dielectric shell-structured nanocomposites as high-performance microwave absorbers, which boost microwave-absorption properties [11][12][13][14][15]. Good microwaveabsorbing behavior is ascribed to the formation of a magneticdielectric interface, which can construct potential impedance matching through heteroatomic coupling at the interface.…”

“…Good microwaveabsorbing behavior is ascribed to the formation of a magneticdielectric interface, which can construct potential impedance matching through heteroatomic coupling at the interface. At the same time, EM loss is enhanced by interfacial polarization originating from the asymmetry of electrons at the interface [11][12][13][14][15]. However, the main disadvantages of the reported nanocomposites are strong absorption within a limited frequency range and significant changes in absorption with the thickness of the absorbing layer.…”

Recent advance in three-dimensional porous carbon materials for electromagnetic wave absorption

“…It is necessary to clarify the influence of different factors on the final EMW absorption performance, which points the direction for the follow-up design of EWAMs. Li et al [123] chose corncob-derived carbon/Ni (CDC/Ni) composites to study the influences of the graphitization degree, pore size, and surface area on the electromagnetic parameters, impedance matching, attenuation constant, and final EMW absorption performance. The authors indicated that the most important factor affecting the EMW absorption performance was the impedance matching, followed by the electromagnetic loss capability and attenuation constant, and finally the multiple reflections and scatterings of EMWs induced by the 3D structure.…”