Controllable Synthesis of Cu_xFe_3−xO₄@Cu Core–Shell Hollow Spherical Chains for Broadband, Lightweight Microwave Absorption

Abstract

CuxFe3−xO4@Cu (0<x<1.30) core–shell hollow spherical chains (HSCs) with tunable composition were prepared through magnetic‐field‐induced solvothermal and liquid‐phase reduction approach. The influence of [Cu2+] on composition, phase, morphology, and microstructure of the products was confirmed by energy‐dispersive X‐ray spectrometry, X‐ray diffraction, X‐ray photoelectron spectrometry, scanning electron microscopy, and transmission electron microscopy analyses. Cu0 content, Cu2+ substitution, and crystal size in CuxFe3−xO4@Cu HSCs can be adjusted by changing [Cu2+]. Increasing [Cu2+] decreases the mean crystal size and increases the Cu0 content and Cu2+ substitution. The saturation magnetization (Ms) of CuxFe3−xO4@Cu HSCs linearly decreases, and the coercivity (Hc) varies in the Boltzmann mode. The microwave‐absorbing properties of CuxFe3−xO4@Cu HSCs decline first and then increase, and the sample with x=1.300 exhibits the optimal properties. Cu1.300Fe1.700O4@Cu HSCs with 44 wt % mass fraction obtain the minimum resonance loss (RL) of −45.1 dB at 3.44 GHz and the absorption bandwidth (RL≤−20 dB) of 9.9 GHz. Cu1.300Fe1.700O4@Cu HSCs exhibits stronger absorption, lighter weight, and a broader absorption band than the other samples. The improved absorption performance may be ascribed to the hollow/porous core–shell structures, Cu2+ substitution, and Cu0 shell with high conductivity, leading to enhanced permittivity, matching, and resonance absorption.

Composition-Tunable Ultrasmall Manganese Ferrite Nanoparticles: Insights into their In Vivo T1 Contrast Efficacy

“…The peak positions of Fe 2p and Mn 2p are consistent with previously reported values for Fe 3+ and Mn 2+ 7, 23, 26. With increasing Mn 2+ , the intensities of the Fe 2p peaks decrease, and those of the Mn 2p peaks increase, which is consistent with the literature results 27. These data suggest that 3 nm Mn x Fe 3-x O 4 nanoparticles, where x = 0.32, 0.37, 0.75, 1, 1.23 and 1.57, were successfully synthesized by the DSTD method.…”

Dimensional Design and Core–Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption

“…[92] Guided by the foregoing, cores such as CNT, CNF, CNC, SiC nanofibers, and magnetic nanochains were decorated with magnetic nanoparticles, dielectric TiO 2 and ZnO, and conductive polymer to prepare various types of excellent 1D composite absorbents. [118,[186][187][188][189][190][191] For example, SiC-Fe 3 O 4 core-shell nanowires have a higher RL value of −51.0 dB than pure SiC nanowires. [186] Oriented Cu/Co and Cu/Ni core-shell nanochains have maximum RL values/EABs of −49.7 dB/5.2 GHz and −43.5 dB/7.3 GHz, respectively; these values are better than those of random nanowires.…”

Defect Engineering in Two Common Types of Dielectric Materials for Electromagnetic Absorption Applications

“…In view of the importance of dielectric materials to improve the microwave absorption performance, lots of researches about dielectrics‐based microwave absorption have been done . Decades of experimental researches have generated a huge body of knowledge on the links between processing and microstructural properties, as well as how they relate to microwave absorption . So far, it has been widely recognized that conduction loss and polarization (CaP) are two of the dominant factors in determining complex permittivity .…”