Magnetite (Fe3O4)/carbon (C) composite flowers with an average size of 4–6 μm were prepared through a facile route including a solvothermal approach and a carbon reduction process. The resultant Fe3O4/C composites are porous and exhibit a three-dimensional (3D) flower-like morphology with the core–shell Fe3O4@C nanoparticles hybridized by amorphous carbon sheets. The epoxy resin composites containing 50 wt % 3D porous Fe3O4/C composite flowers display an optimal reflection loss (RL) value of −54.6 dB at 5.7 GHz at a thin thickness of 4.27 mm and the effective bandwidth with RL < −10 dB reaches 6.0 GHz at a thickness of 2.1 mm. These enhanced EM wave absorption performances are attributed to the synergistic effects of Fe3O4 and carbon as well as the structural advantages, e.g., three-dimensional structure with large surface area, porous and core–shell structures of Fe3O4/C flowers. These results suggest the 3D porous Fe3O4/C composite flowers designed here can serve as ideal candidates for high-performance EM wave absorption.

No abstract

Nestlike 3D ZnO porous structures with size of 1.0-3.0 μm have been synthesized through annealing the zinc hydroxide carbonate precursor, which was obtained by a one-pot hydrothermal process with the assistance of glycine, Na(2)SO(4), and polyvinyl pyrrolidone (PVP). The nestlike 3D ZnO structures are built of 2D nanoflakes with the thickness of ca. 20 nm, which exhibit the nanoporous wormhole-like characteristic. The measured surface area is 36.4 m(2)g(-1) and the pore size is ca. 3-40 nm. The unique nestlike 3D ZnO porous structures provided large contacting surface area for electrons, oxygen and target gas molecules, and abundant channels for gas diffusion and mass transport. Gas sensing tests showed that the nestlike 3D ZnO porous structures exhibit excellent gas sensing performances such as high sensitivity and fast response and recovery speed, suggesting the potential applications as advanced gas sensing materials.

Developing high-performance and functional hydrogels that mimic biological materials in nature is promising yet remains highly challenging. Through a facile, scalable unidirectional freezing followed by a salting-out approach, a type of hydrogels composed of “trashed” MXene sediment (MS) and biomimetic pores is manufactured. By integrating the honeycomb-like ordered porous structure, highly conductive MS, and water, the electromagnetic interference (EMI) shielding effectiveness is up to 90 dB in the X band and can reach more than 40 dB in the ultrabroadband gigahertz band (8.2–40 GHz) for the highly flexible hydrogel, outperforming previously reported porous EMI shields. Moreover, thanks to the stable framework of the MS-based hydrogel, the influences of water on shielding performance are quantitatively identified. Furthermore, the extremely low content of silver nanowire is embedded into the biomimetic hydrogels, leading to the significantly improved multiple reflection-induced microwave loss and thus EMI shielding performance. Last, the MS-based hydrogels allow sensitive and reliable detection of human motions and smart coding. This work thus not only achieves the control of EMI shielding performance via the interior porous structure of hydrogels, but also demonstrates a waste-free, low-cost, and scalable strategy to prepare multifunctional, high-performance MS-based biomimetic hydrogels.

Ambient‐pressure‐dried (APD) preparation of transition metal carbide/nitrides (MXene) aerogels is highly desirable yet remains highly challenging. Here, ultrathin, high‐strength‐to‐weight‐ratio, renewable cellulose nanofibers (CNFs) are efficiently utilized to assist in the APD preparation of ultralight yet robust, highly conductive, large‐area MXene‐based aerogels via a facile, energy‐efficient, eco‐friendly, and scalable freezing‐exchanging‐drying approach. The strong interactions of large‐aspect‐ratio CNF and MXene as well as the biomimetic nacre‐like microstructure induce high mechanical strength and stability to avoid the structure collapse of aerogels in the APD process. Abundant functional groups of CNFs facilitate the chemical crosslinking of MXene‐based aerogels, significantly improving the hydrophobicity, water resistance, and even oxidation stability. The ultrathin, 1D nature of the CNF renders the minimal MXenes’ interlayered gaps and numerous heterogeneous interfaces, yielding the excellent conductivity and electromagnetic interference (EMI) shielding performance of aerogels. The synergies of the MXene, CNF, and abundant pores efficiently improve the EMI shielding performance, photothermal conversion, and absorption of viscous crude oil. This work shows great promises of the APD, multifunctional MXene‐based aerogels in electromagnetic protection or compatibility, thermal therapy, and oil‐water separation applications.