Facile Synthesis and Hierarchical Assembly of Flowerlike NiO Structures with Enhanced Dielectric and Microwave Absorption Properties

Abstract

In this work, two novel flowerlike NiO hierarchical structures, rose-flower (S1) and silk-flower (S2), were synthesized by using a facial hydrothermal method, coupled with subsequent postannealing process. Structures, morphologies, and magnetic and electromagnetic properties of two NiO structures have been systematically investigated. SEM and TEM results suggested that S1 had a hierarchical rose-flower architecture with diameters in the range of 4-7 μm, whereas S2 exhibited a porous silk-flower architecture with diameters of 0.7-1.0 μm. Electromagnetic performances indicated that the NiO hierarchical structures played a crucial role in determining their dielectric behavior and impedance matching characteristic, which further influenced the microwave attenuation property of absorbers based on them. Due to its hierarchical and porous architectures, S2 had higher microwave absorption performances than S1. The maximum R value for sample S2 can reach -65.1 dB at 13.9 GHz, while an efficient bandwidth of 3 GHz was obtained. In addition, the mechanism of the improved microwave absorption were discussed in detail. It is expected that our NiO hierarchical structures synthesized in this work could be used as a reference to design novel microwave absorption materials.

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

“…Due to the laminar growth habit of Ni x S y @MoS 2 , the agglomerated nuclei tend to self-assemble into a sphere-like microstructure to reduce the interfacial energy in nanosheets [17,47,48,49,50,51]. The wrinkled nanoplates would increase the specific surface area where it is beneficial to obtain higher microwave absorption performance [17,52,53]. When the ratio of S/Mo reached up to 6 (GNPs@Ni x S y @MoS 2 -2), the as-synthesized Ni x S y @MoS 2 nanosheets increased in size to such an extent that the space was insufficient for the nanosheets to assemble into nanospheres (Figure 3e,f).…”

Metal‐Organic Framework Derived Hierarchical Co/C@V2O3 Hollow Spheres as a Thin, Lightweight, and High‐Efficiency Electromagnetic Wave Absorber

“…[1] Numerous efforts have been devoted to fulfillingt he harsh requirements of these absorbers by exploring new materials with designedc ompositions andn anostructures. [2] Transition metal oxides( TMO), such as Fe 2 O 3 , [3] Co 3 O 4 , [4] CoO, [5] NiO, [6] and TiO 2 [7] have been developed as effective EM wave absorbersd ue to their excellent chemical stability,l arge specific surface area, and abundanti ntrinsic defects, which can induce interfacial and dipole polarization for enhanced wave attenuation.V anadium oxides, at ype of earth-abundant and inexpensive TMO, have drawn great interestd ue to their exciting behavioro na ccount of their optical, [8] electrical, [9] and magnetic properties. [10] Among the various vanadium oxides, vanadium sesquioxide (V 2 O 3 )e xhibits metallicc haracteristics with relativelyh igh electrical conductivity at room temperature, since the V3de lectrons can itinerate along the V-V chains.…”

Recent Development in Fabrication of Co Nanostructures and Their Carbon Nanocomposites for Electromagnetic Wave Absorption

“…[19,20,44] On one hand, the large surface area of hierarchical structures is beneficial to generate multiple dielectric polarizations (such as interface polarizations and dipole polarizations). [45,46] On the other hand, the 3D structure could induce the production of multiple reflections and scatterings, through which the incident EM waves can be attenuated gradually. [47,48] Liu et al investigated the effect of hierarchical architecture on the microwave absorption properties of Co/paraffin wax composites.…”