Facile Synthesis of GNPs@NixSy@MoS2 Composites with Hierarchical Structures for Microwave Absorption

Abstract

Graphene-based powder absorbers have been used to attain excellent microwave absorption. However, it is not clear if inferior microwave absorption by pure graphene materials can be attributed to impedance mismatching or inadequate attenuation capability. In this comparative study, we focus on these aspects. Graphene nanoplatelets (GNPs) multi-component composites (GNPs@NixSy@MoS2) were prepared by hydrothermal reaction with different S and Mo molar ratios. The morphologies, phase crystals, elemental composition, and magnetic properties of the composites were also analyzed. In addition, microwave absorption of the as-prepared samples was investigated and it revealed that the impedance mismatching could be responsible for inferior microwave absorption; higher conductivity can lead to skin effect that inhibits the further incidence of microwaves into the absorbers. Furthermore, the optimum reflection loss (RL) of GNPs@NixSy@MoS2-2 can reach −43.3 dB at a thickness of 2.2 mm and the corresponding bandwidth with effective attenuation (RL < −10 dB) of up to 3.6 GHz (from 7.0 to 10.6 GHz). Compared with the GNPs, the enhanced microwave absorption can be assigned to the synergistic effects of conductive and dielectric losses.

Synthesis of Controllable Nickel Chalcogenide Nano‐Hollow Spheres and Their Tunable Absorbing Properties

“…Figure 1d is the XRD pattern of the resulting product, which clearly indicates the presence of NiS2 in the final product, as well as the phase and purity of the resulting product. [34,35] All the different peaks of the products can be exclusively indexed to a pure cubic phase of NiS2 (JCPDS card no. 89-1495).…”

Preparation and Microwave Absorption Properties of NixSy/PVDF Nanocomposites

“…The peaks at the 2q of the asterisk in the figure are 30.34 • , 34.88 • , and 46.16 • , which correspond to the standard card PDF#02-1280 of NiS (Lv et al, 2018). The peaks at the remaining 2q angles correspond exactly to the standard card PDF#11-0099 of the cubic structure of NiS 2 (Zhu et al, 2019).…”

“…The Debye relaxation process has been hidden because of the enhanced electrical conductivity. The higher conductivity can lead to skin effect that inhibits the further incidence of microwaves into the absorbers (Zhu et al, 2019), which is the reason that high filler rate will reduce the absorbing performance of the composite.…”

Superior Microwave Absorption Properties Derived from the Unique 3D Porous Heterogeneous Structure of a CoS@Fe3O4@rGO Aerogel

“…The closer the Z value is to 1, the more EMWs can be incident to the material. In Figure 10 b, the impedance matching curve of S3 is lower than S1 and S2, which may be due to the high conductivity and the influence of the skin effect [ 60 ]. The oscillating skin current enhances the reflected waves, which is not conductive to the attenuation of EMWs.…”