Interface Engineering in Honeybee-leg-like TiO2@NiCo2O4 Nanocomposites: A Novel Platform for High-Performance Microwave Absorbers
Interface Engineering in Honeybee-leg-like TiO2@NiCo2O4 Nanocomposites: A Novel Platform for High-Performance Microwave Absorbers
Introduction
The extensive usage of electronic devices in modern society has intensified concerns regarding electromagnetic pollution, which poses potential threats to both human health and the sensitive functionality of electronic equipment [1,2]. Simultaneously, electromagnetic waves (EMWs) are essential in various advanced applications, especially in defense fields such as mapping, surveillance, and radar systems [3]. In particular, research interest has increased in the radar area to manufacture materials that ensure the invisibility of vehicles to radar. Therefore, this dual context emphasizes an urgent and critical need for advanced materials capable of effectively absorbing microwave energy. Consequently, microwave absorbing materials (MAMs) have garnered substantial attention from researchers for their promising potential in a wide array of civilian and defense applications, with the primary research goal being the development of lightweight, highly efficient, and broadband absorbers [4,5].
To address the ongoing challenges in efficient microwave absorption, researchers have explored a wide range of material systems, including magnetic, dielectric, and conductive components [[6], [7], [8]]. In recent years, there has been a clear shift toward multi-component structures, as the deliberate combination of different materials and the design of tailored morphologies have been shown to synergistically improve absorption performance [9,10]. In this context, one-dimensional (1D) nanostructures have gathered significant interest due to their high surface area, directional charge transport characteristics, and their ability to form complex heterogeneous networks [11,12]. While carbon nanofibers are extensively used in this field owing to their excellent microwave absorption performance, alternative 1D materials have also been investigated for similar applications [[13], [14], [15], [16], [17]]. Among these, titanium dioxide (TiO2), a non-toxic semiconductor, stands out as a promising candidate due to easy preparation, low cost and thermal stability [18,19]. Although bare TiO2 exhibits poor microwave absorption, its performance can be further increased via doping, hydrogenating and hybridization with other functional components [[20], [21], [22]]. In particular, combining TiO2 with magnetic materials can be a promising strategy to overcome its inherent limitations and improve overall absorption performance [23,24].
Complementing this, NiCo2O4, a p-type spinel transition metal oxide, is well-known for its dual-loss mechanism, electrical conductivity, and its ability to form a wide range of nanostructured morphologies making it highly suitable for microwave absorption applications [[25], [26], [27]]. Due to its beneficial properties, it has been widely used, both alone and in various composites and heterostructures with other materials [[28], [29], [30]]. While TiO2@NiCo2O4 composites have been explored in different application areas such as batteries, photocatalysis and supercapacitors, their application in MAMs has received comparatively no attention [[31], [32], [33], [34]]. A few studies have investigated other NiCo2O4-based heterostructures for microwave absorption and reported promising results [10,35,36]; however, the targeted integration of dual-phase (providing additional interfaces) TiO2 and NiCo2O4 into a rationally designed, morphology-controlled heterostructure remains largely unexplored in the MAMs context.
Herein, we report the successful fabrication of novel honeybee-leg-like TiO2@NiCo2O4 hierarchical structure, achieved by combining dual-phase electrospun TiO2 nanofibers with densely decorated needle-like NiCo2O4 nanostructures. To the best of our knowledge, this specific TiO2@NiCo2O4 configuration is investigated for microwave absorption performance for the first time in the literature. This study provides a comprehensive investigation into the structural, morphological, magnetic, and electromagnetic properties of these nanocomposites. Our findings clearly demonstrate that this unique heterostructure exhibits exceptional microwave absorption properties, which are directly attributed to the intricate interplay of its structure, morphology, and electrical characteristics, highlighting the critical role of interface engineering. Furthermore, we conducted a detailed investigation into the formation mechanism governing the assembly of these nanocomposites. Overall, the findings highlight the significant potential of this engineered morphology for next-generation absorber technologies, with prospective applicability across a wide range of electromagnetic interference (EMI) mitigation and stealth-related applications.
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