Environment and energy are the eternal hot topics in the world,multiloculated microscale materials have attracted great attention in the field of electromagnetic interference(EMI)shielding and lithium ions storage.Herein,a novel flower-like NiFe_(2)O_(4)/graphene composite with adjustable structure was fabricated as EMI shielding material and anode material of lithium-ion batteries.NiFe_(2)O_(4)/graphene composite is a potential green EMI shielding material.The EMI shielding effectiveness(SE)increases with the increase of graphene content in NiFe_(2)O_(4)/graphene composite,and the total EMI SE of NiFe_(2)O_(4)/graphene with 73.6 wt.%graphene increases from 26.5 to 40.6 d B with the increase of frequency in 2–18 GHz.Furthermore,it exhibits long-life and large capacity lithium storage performance at high current density.The capacity reaches 732.79 m Ah g^(-1)after 100 cycles at 0.1 A g^(-1),recovering to more than 139%from the minimum capacity value.After 300 cycles at 0.5 A g^(-1),the capacity increases to 688.5 mAh g^(-1).The initial capacities at 2 and 5 A g^(-1)are 704.9 and 717.8 mAh g^(-1),and remain 297.9 and 203.2 m Ah g^(-1)after 1000 cycles.The distinguished EMI shielding performance and electrochemical performance are mainly ascribed to the structure regulation of NiFe_(2)O_(4)/graphene composite,as well as the synergistic effect of graphene and NiFe_(2)O_(4).This research opens up infinite opportunities for the application of multifunctional and interdisciplinary materials.
The electronic structures and optical properties of N-doped Zn O bulks and nanotubes are investigated using the firstprinciples density functional method. The calculated results show that the main optical parameters of Zn O bulks are isotropic(especially in the high frequency region), while Zn O nanotubes exhibit anisotropic optical properties. N doping results show that Zn O bulks and nanotubes present more obvious anisotropies in the low-frequency region. Thereinto, the optical parameters of N-doped Zn O bulks along the [100] direction are greater than those along the [001] direction, while for N-doped nanotubes, the variable quantities of optical parameters along the [100] direction are less than those along the[001] direction. In addition, refractive indexes, electrical conductivities, dielectric constants, and absorption coefficients of Zn O bulks and nanotubes each contain an obvious spectral band in the deep ultraviolet(UV)(100 nm～ 300 nm). For each of N-doped Zn O bulks and nanotubes, a spectral peak appears in the UV and visible light region, showing that N doping can broaden the application scope of the optical properties of Zn O.
Silicon carbide nanotubes(SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs' dopants.
Dedicating to the exploration of efficient electromagnetic(EM)absorption and electromagnetic interference(EMI)shielding materials is the main strategy to solve the EM radiation issues.The development of multifunction EM attenuation materials that are compatible together EM absorption and EMI shielding properties is deserved our exploration and study.Here,the graphenewrapped multiloculated NiFe_(2)O_(4) composites are reported as multifunction EM absorbing and EMI shielding materials.The conductive networks configurated by the overlapping flexible graphene promote the riched polarization genes,as well as electron transmission paths,and thus optimize the dielectric constant of the composites.Meanwhile,the introduction of magnetic NiFe_(2)O_(4) further establishes the magnetic-dielectric synergy effect.The abundant non-homogeneous interfaces not only generate effective interfacial polarization,also the deliberate multiloculated structure of NiFe_(2)O_(4) strengthens multi-scattering and multi-reflection sites to expand the transmission path of EM waves.As it turns out,the best impedance matching is matched at a lower filled concentration to achieve the strongest reflection loss value of−48.1 dB.Simultaneously,green EMI shielding based on a predominantly EM absorption and dissipation is achieved by an enlargement of the filled concentration,which is helpful to reduce the secondary EM wave reflection pollution to the environment.In addition,the electrocatalytic properties are further examined.The graphene-wrapped multiloculated NiFe_(2)O_(4) shows the well electrocatalytic activity as electrocatalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),which is mainly attributed to the interconnected structures formed by graphene and NiFe_(2)O_(4) connection.The structural advantages of multiloculated NiFe_(2)O_(4) expose more active sites,which plays an important role in optimizing catalytic reactions.This work provides an excellent jumping-off point for the development of multifunction EM absorb
With first-principles virtual-crystal approximation calculations, we systematically investigate the geometric and elec- tronic structures as well as the phase transition of lead zirconate titanate (PbZr1-xTixO3 or PZT) as a function of Ti content for the whole range of 0 ≤ x Ti ≤ 1. It can be found that, with the increase of the Ti content, the PbZr1-xTixO3 solid solu- tions undergo a rhombohedral-to-tetragonal phase transition, which is consistent with the experimental results. In addition, we also show the evolution in geometric and electronic structures of rhombohedral and tetragonal PbZr1-x TixO3 with the increasing content of Ti.
Advanced electromagnetic devices,as the pillars of the intelligent age,are setting off a grand transformation,redefining the structure of society to present pluralism and diversity.However,the bombardment of electromagnetic radiation on society is also increasingly serious along with the growing popularity of"Big Data".Herein,drawing wisdom and inspiration from nature,an eco-mimetic nanoarchitecture is constructed for the first time,highly integrating the advantages of multiple components and structures to exhibit excellent electromagnetic response.Its electromagnetic properties and internal energy conversion can be flexibly regulated by tailoring microstructure with oxidative molecular layer deposition(oMLD),providing a new cognition to frequency-selective microwave absorption.The optimal reflection loss reaches≈−58 dB,and the absorption frequency can be shifted from high frequency to low frequency by increasing the number of oMLD cycles.Meanwhile,a novel electromagnetic absorption surface is designed to enable ultra-wideband absorption,covering almost the entire K and Ka bands.More importantly,an ingenious self-powered device is constructed using the eco-mimetic nanoarchitecture,which can convert electromagnetic radiation into electric energy for recycling.This work offers a new insight into electromagnetic protection and waste energy recycling,presenting a broad application prospect in radar stealth,information communication,aerospace engineering,etc.
Healthy and livable living environments,as well as anti-electromagnetic(EM)radiation buildings,are the long-term goals of human beings.The introduction of advanced EM wave absorbing materials into buildings is one of the most feasible ways to address the increasing EM pollution in building spaces.High-efficiency,broadband,low-cost and good building performance EM wave absorbing materials,as an important support in the field of sustainable building,has gradually become the hotspot research.Here,we review the research progress of building materials with EM wave absorption functions,and comb their classification,including cement,concrete,ceramics,and prefabs,especially highlighting the advanced coating materials.We objectively outline and evaluate the latest technology of building materials with EM wave absorption performance,and discuss the main problems and bottlenecks,highlighting potential research opportunities.
Ting-Ting LiuMao-Qing CaoYong-Sheng FangYu-Hang ZhuMao-Sheng Cao
We investigate the dielectric properties of multi-walled carbon nanotubes(MWCNTs) and graphite filling in SiO2 with the filling concentration of 2-20 wt.% in the frequency range of 10 2-10 7 Hz.MWCNTs and graphite have general electrical properties and percolation phenomena owing to their quasi-structure made up of graphene layers.Both permittivity ε and conductivity σ exhibit jumps around the percolation threshold.Variations of dielectric properties of the composites are in agreement with the percolation theory.All the percolation phenomena are determined by hopping and migrating electrons,which are attributed to the special electronic transport mechanism of the fillers in the composites.However,the twin-percolation phenomenon exists when the concentration of MWCNTs is between 5-10 wt.% and 15-20 wt.% in the MWCNTs/SiO2 composites,while in the graphite/SiO2 composites,there is only one percolation phenomenon in the graphite concentration of 10-15 wt.%.The unique twin-percolation phenomenon of MWCNTs/SiO2 is described and attributed to the electronic transfer mechanism,especially the network effect of MWCNTs in the composites.The network formation plays an essential role in determining the second percolation threshold of MWCNTs/SiO2.
