Porous metal materials are widely used for preventing electromagnetic interference, control of heat conduction and impact absorbing. However, a limitation associated with porous metals is that their irregular and non‐uniformal microstructures make their functions non‐desirably tunable. In this report, the authors propose a microlattice material with precisely controlled microstructures for electromagnetic (EM) shielding. An effective medium model taking into account of the EM stimulated surface current of the metal wires is developed to characterize the EM shielding effect of the microlattice metal. In addition, a compact and integrated measuring device is constructed by using a 3D printing method for experimental verification. The theoretical predictions agree well with the experimental measurement. The influence of the geometrical parameters of the microlattice metals on EM shielding effect is also studied. The theoretical model and the compact measuring system provide robust and efficient tools for the design of EM shielding materials. 相似文献
The Fe–Ni–P–Cu alloys with different copper content (0, 0.5, 1, and 2 wt%) are fabricated by liquid phase sintering (LPS) at 950 °C. The nano‐Cu powder is mechanically mixed for 90 min with Fe–Ni–P composite powder using the ethanol as the medium. The microstructure, microhardness and compressive properties of Fe–Ni–P–Cu alloys are investigated. The results indicate that the copper is beneficial to improve the mechanical properties of sintered specimens. The sample contains a small amount of γ‐(Fe, Ni) phase when the copper content is 1 wt%, which results in its the highest compressive yield strength (948.1 MPa). The highest microhardness of 371 HV is accessible in Fe–Ni–P–Cu alloy with 2 wt% Cu. The fracture surface analysis indicates that sintered specimens with Cu addition exhibit a typical intergranular mode. 相似文献
Synthesizing ultrathin 2D metal–organic framework nanosheets in high yields has received increasing research interest but remains a great challenge. In this work, ultrathin zirconium‐porphyrinic metal–organic framework (MOF) nanosheets with thickness down to ≈1.5 nm are synthesized through a pseudoassembly–disassembly strategy. Owing to the their unique properties originating from their ultrathin thickness and highly exposed active sites, the as‐prepared ultrathin nanosheets exhibit far superior photocatalysis performance compared to the corresponding bulk MOF. This work highlights new opportunities in designing ultrathin MOF nanosheets and paves the way to expand the potential applications of MOFs. 相似文献
Advanced biocompatible and robust platforms equipped with diverse properties are highly required in biomedical imaging applications for the early detection of atherosclerotic vascular disease and cancers. Designing nanohybrids composed of noble metals and fluorescent materials is a new way to perform multimodal imaging to overcome the limitations of single-modality counterparts. Herein, we propose the novel design of a multimodal contrast agent; namely, an enhanced nanohybrid comprising gold nanorods (GNRs) and carbon dots (CDs) with silica (SiO2) as a bridge. The nanohybrid (GNR@SiO2@CD) construction is based on covalent bonding between SiO2 and the silane-functionalized CDs, which links the GNRs with the CDs to form typical core–shell units. The novel structure not only retains and even highly improves the optical properties of the GNRs and CDs, but also possesses superior imaging performance in both diffusion reflection (DR) and fluorescence lifetime imaging microscopy (FLIM) measurements compared with bare GNRs or fluorescence dyes and CDs. The superior bioimaging properties of the GNR@SiO2@CD nanohybrids were successfully exploited for in vitro DR and FLIM measurements of macrophages within tissue-like phantoms, paving the way toward a theranostic contrast agent for atherosclerosis and cancer.
Atomic composition tuning and defect engineering are effective strategies toenhance the catalytic performance of multicomponent catalysts by improvingthe synergetic effect; however, it remains challenging to dramatically tune the active sites on multicomponent materials through simultaneous defect engineeringat the atomic scale because of the similarities of the local environment. Herein,using the oxygen evolution reaction (OER) as a probe reaction, we deliberatelyintroduced base-soluble Zn(II) or Al(III) sites into NiFe layered double hydroxides(LDHs), which are one of the best OER catalysts. Then, the Zn(II) or Al(III) siteswere selectively etched to create atomic M(II)/M(III) defects, which dramaticallyenhanced the OER activity. At a current density of 20 mA·cm?2, only 200 mV overpotential was required to generate M(II) defect-rich NiFe LDHs, which is the best NiFe-based OER catalyst reported to date. Density functional theory(DFT) calculations revealed that the creation of dangling Ni–Fe sites (i.e., unsaturated coordinated Ni–Fe sites) by defect engineering of a Ni–O–Fe site at the atomic scale efficiently lowers the Gibbs free energy of the oxygen evolutionprocess. This defect engineering strategy provides new insights into catalysts atthe atomic scale and should be beneficial for the design of a variety of catalysts.
The two-dimensional self-assembly behaviors of tetraphenylethylene (TPE) molecules are significant for further applications, but reports are rare. The self-assembled structures of two C2-symmetry TPE derivatives (H4TCPE and H4ETTC) possessing propeller structures and their stimulus responses to the addition of vinylpyridine derivatives were thoroughly studied with the assistance of scanning tunneling microscopy (STM) technique in combination with density functional theory (DFT) calculations. Although their chemical structures were similar, the H4TCPE and H4ETTC molecules self-assembled into closely packed lamellar and quadrilateral structures, respectively, at the 1-heptanoic acid/HOPG interface. After the addition of pyridine derivatives (DPE, PEBP-C4, and PEBP-C8), H4TCPE and H4ETTC showed different responsiveness resulting in different co-assembly structures. The results indicated that the structures of pyridine derivatives—including backbones and substituents—affected the intermolecular interactions of both H4TCPE/pyridine and H4ETTC/pyridine systems. The modification of the self-assembly behaviors of propeller-shaped H4TCPE and H4ETTC would contribute to the construction of more complex multilevel nanostructures.
Nano Research - A spin-coating method was applied to obtain thinner and smoother PEO/LiClO4 polymer electrolyte films (EFs) with a lower level of crystallization than those obtained using a... 相似文献