Core–Shell Nanomaterials for Microwave Absorption and Electromagnetic Interference Shielding: A Review

Abstract

Core–shell nanoparticles are a unique class of nanostructured materials, which received significant attention in the last two decades owing to their exciting properties and a wide variety of applications. By judiciously tuning the “core” as well as the “shell”, an assortment of “core–shell” nanostructures can be obtained with tailorable properties which can play pivotal roles in designing materials for electromagnetic interference (EMI) shielding and microwave absorption. In recent times when the use of high-end electronics has been on the rise, electromagnetic pollution is inevitable and it affects every walk of life. Among numerous e-pollutions, a recently highlighted domain that has far-reaching consequences is electromagnetic interference. EMI is the disturbance created during an electronic device’s operation when it is in the vicinity of an electromagnetic field caused by another electronic or electric device. Since EMI decreases the lifetime and degrades the performance of the electronic instruments and even affects human health, it is crucial to protect sophisticated instruments and components from EM interference. High-performance EMI shields capable of attenuating microwave propagation efficiently have been developed in the past decade. Herein, in this review, we attempted to provide a logical guide to various “core–shell” nanostructures (≤500 nm) that have been synthesized in the past decade for the application in microwave absorption and EMI shielding. The prime focus of this review article is to highlight the fundamental concept of EMI shielding and microwave absorption that have been reported for various systems in the literature along with various synthetic and fabrication strategies in designing suitable broadband EM absorbers/screeners. Finally, we also made an effort to provide a holistic outlook and perspective in which upcoming research will continue to flourish.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities

“…The yolk-shell structure, a special type of core-shell structure, features interstitial void space, modifiable inner cores, high specific surface area, as well as low density, owing to its distinct core@void@shell configuration. [106] In 2015, Che et al systematically compared the response mechanism of CoNi@ SiO 2 @TiO 2 core-shell and CoNi@air@TiO 2 yolk-shell microspheres, and demonstrated that yolk-shell structure helped to minimize the impedance gap to ensure the penetration of incident microwave. [6a] Wang et al employed an in situ reduction approach to construct Fe 3 O 4 @C yolk-shell nanocomposites.…”

Dielectric Loss Mechanism in Electromagnetic Wave Absorbing Materials

“…Though plentiful excellent reviews have been reported to introduce the advances of EM wave absorbing materials, [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ] they mainly focus on introducing EM wave loss materials on basis of material categories, such as carbon materials, [ 43 , 44 , 45 , 46 , 47 , 48 ] MOFs deprived materials, [ 49 , 50 , 51 ] boron nitride, [ 52 ] conducting polymers, [ 53 , 54 ] ferrites, [ 55 , 56 , 57 ] sulfides, [ 58 ] and MXene [ 59 , 60 , 61 ] or design of peculiar micro/nanostructure. [ 62 ] As far as we know, the topic that lies on EM wave loss mechanisms and models has been rarely reported. Herein, this review provides a comprehensive summary on dielectric mechanism study in EM wave absorption field for the purpose of supplying guidance for novel EM wave absorbers design through mechanism perspective.…”

“…Though plentiful excellent reviews have been reported to introduce the advances of EM wave absorbing materials, [ 43–66 ] they mainly focus on introducing EM wave loss materials on basis of material categories, such as carbon materials, [ 43–48 ] MOFs deprived materials, [ 49–51 ] boron nitride, [ 52 ] conducting polymers, [ 53,54 ] ferrites, [ 55–57 ] sulfides, [ 58 ] and MXene [ 59–61 ] or design of peculiar micro/nanostructure. [ 62 ] As far as we know, the topic that lies on EM wave loss mechanisms and models has been rarely reported.…”

In Situ Reduced Multi-Core Yolk–Shell Co@C Nanospheres for Broadband Microwave Absorption

“…Yolk–shell structure is a special kind of core–shell structure and the structure can also be called a core@void@shell structure, which means that there is not direct contact between the core and the shell. The existence of void provides unique advantages such as low density and large surface area [ 17 , 18 , 19 ]. Furthermore, the outside dielectric shell (SnO 2 [ 20 ], MnO 2 [ 21 ], carbon [ 22 ]) cannot only effectively protect naked magnetic core from oxidation, but also provide dielectric loss capacity.…”