Highly-dispersed Fe3O4@ZrO2 yolk–shell structures with a ZrO2 shell of homogeneous shell thickness was successfully prepared via a polymer surfactant (hydroxypropyl cellulose) assisted sol–gel method.

No abstract

Rational designing of one-dimensional (1D) magnetic alloy to facilitate electromagnetic (EM) wave attenuation capability in low-frequency (2–6 GHz) microwave absorption field is highly desired but remains a significant challenge. In this study, a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method. The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique, indicating the excellent magnetic loss ability under an external EM field. Then, the in-depth analysis shows that many factors, including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy, primarily contribute to the enhanced EM wave absorption performance. Therefore, the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm. Thus, this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.

As a typical 2D (two dimensional) material, Ti3C2T x , has been used as a promising microwave absorber (MA) because of its massive interface architecture, abundant natural defects, and chemical surface functional groups. However, its single dielectric-type loss and excessive high conductivity seriously restrict the further enhancement of MA performance. Herein, we first describe a simple spray-drying routine to reshape the 2D MXene into a confined and magnetized microsphere with tightly embedded Fe3O4 nanospheres (designated as M/F), contributing to the enhanced specific interfaces and strong dielectric polarization. These Fe3O4 magnetic units are highly dispersed into the dielectric Mxene framework, leading to the optimized impedance balance and electromagnetic coordination capability. This composite way effectively exceeds the conventionally physical mixing, simple loading, and local phase separation method. Meanwhile, strong magnetic loss capability with significantly improved magnetic flux line density is achieved from microscale MXene and nanoscale Fe3O4, confirming our 3D multiscale magnetic coupling network. Accordingly, the M/F composites hold distinct microwave absorption property with the strong reflection loss (−50.6 dB) and effective absorption bandwidth (4.67 GHz) at the thickness as thin as only 2 mm. Our encouraging strategy provides important designable implications for MXene-based functional materials and high-performance absorbers.