RESUMO
The 3D hollow hierarchical architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight, high-efficient and broadband absorbers. Herein, the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti3C2Tx nanosheets through electrostatic self-assembly. The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti3C2Tx nanoflakes. Based on the synergistic effects of multi-components and special well-constructed structure, NiCo layered double hydroxides@Ti3C2Tx (LDHT-9) absorber remarkably achieves unexpected effective absorption bandwidth (EAB) of 6.72 GHz with a thickness of 2.10 mm, covering the entire Ku-band. After calcination, transition metal oxide@Ti3C2Tx (TMOT-21) absorber near the percolation threshold possesses minimum reflection loss (RLmin) value of - 67.22 dB at 1.70 mm within a filler loading of only 5 wt%. This work enlightens a simple strategy for constructing MXene-based composites to achieve high-efficient microwave absorbents with lightweight and tunable EAB.
RESUMO
In this manuscript, we constructed a Ni/MWCNTs absorber and properly adjusted the permittivity resulted from absorber content in the PVDF to optimize impedance matching properties. Both ε' and εⳠincrease obviously with the increasing content of Ni/MWCNTs in PVDF, demonstrating that dielectric properties are dependent on the conductivity. Moderate dielectric properties and excellent impedance matching can be obtained for the filler content of 20 wt% Ni/MWCNTs. Reasonable impedance matching allows electromagnetic waves to propagate into the materials and finally realize energy dissipation through dielectric loss and interfacial polarization. As expected, the minimum reflection loss (RL) of -46.85 dB at 6.56 GHz with a low filler loading (20 wt%) and wide effective bandwidth (RL<-10 dB) of 14.0 GHz in the thickness range of 1.5-5.0 mm was obtained for the commercial Ni/MWCNTs composites, which is promising for mass production in industrial applications. Our findings offer an effective and industrialized way to design high-performance material to facilitate the research in microwave absorption.
RESUMO
Bi2Fe4O9(BFO) nanocubes were prepared in proportion using a simple and easy hydrothermal method, and were then assembled on reduced graphene oxide (rGO) multilayered sheets. The excellent microwave absorption properties of Bi2Fe4O9/rGO nanohybrids were achieved by properly adjusting the impedance matching and getting a high attenuation capability contributed from different ratios of the BFO and rGO. A minimum reflection loss value of -61.5 dB at 12.8 GHz was obtained with a Bi2Fe4O9/rGO ratio of 2:1, and the broadest bandwidth below -10 dB was up to 5.0 GHz (from 10.8 to 15.8 GHz) with a thickness of 2.4 mm. Additionally, the elementary mechanism of wave absorption performance is also investigated.
RESUMO
The preparation of nanoscale oxide/polyvinylidene fluoride (PVDF) composite hollow fiber membrane by phase transition process was introduced. The effects of nanoscale titania and alumina particles on structure and property of composite hollow fiber membrane were investigated. The separation property, microstructure and crystalline phase of composite membranes were characterized by bovine serum albumin (BSA) rejection experiment, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), respectively. The results show that the properties of composite membrane are improved greatly compared to the pure PVDF membranes. The BSA rejection ratios of pure PVDF, Al2O3/PVDF and TiO2/PVDF membranes were 3.27%, 67.20% and 86.67%, respectively. The pure water fluxes of Al2O3/PVDF and TiO2/PVDF membranes were 2.3 and 2.6 times higher than that of pure PVDF membranes. Moreover, the pore size and its distribution of composite membrane characterized by nitrogen isothermal absorption measurement are smaller and narrower than pure PVDF membranes.