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High-performance microwave absorption enabled by Co_(3)O_(4) modified VB-group laminated VS_(2) with frequency modulation from S-band to Ku-band

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Journal of Materials Science & Technology 2022年第12期107卷 155-164页

作者： Zehao Huang Junye Cheng Huibin Zhang Yingfei Xiong Zhanxin Zhou Qingbin Zheng Guangping Zheng Deqing Zhang Maosheng Cao School of Materials Science and Engineering Qiqihar UniversityQiqihar 161006China Department of Materials Science and Engineering Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina School of Science and Engineering The Chinese University of Hong KongShenzhen 518172China School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

High performance microwave absorption(MA)materials especially those with tunable frequency are highly desirable for telecommunication industries and military camouflage in the information era.Herein,we constructed hierarchical heterostructures based on VB-group laminated vanadium disulfide(VS_(2))nanosheets embedded with cobalt tetroxide(Co_(3)O_(4))nanoparticles.The highly dispersed Co_(3)O_(4)nanoparticles generate strong electromagnetic coupling networks that could enhance the loss properties of MA materials.Moreover,the interconnected VS_(2)layered network results in dipolar/interfacial polarization,multiple reflection and scattering favorable for the enhanced MA performance.Impressively,the maximum reflection loss of the VS_(2)/Co_(3)O_(4)hybrids containing 10%Co_(3)O_(4)can reach 57.96 dB at a thin thickness of 1.57 mm,and the bandwidth with an RL value less than-10 dB is as large as 3.5 GHz.The effective MA band could be adjusted in a range of 15.1 GHz(2.9-18 GHz)from S to Ku bands by the increase in thickness from 1.2 mm to 5.5 mm.The results show that the synergistic effect of multiple loss mechanisms and good impedance matching could be the reasons for strong MA capability in nearly all frequency bands,and thus,the high-performance and lightweight MA materials could be developed by the VS_(2)/Co_(3)O_(4)hybrids.

关键词： VS2 nanosheets Co_(3)O_(4)nanospheres hetero-structure Microwave wave absorption

NiSe_(2)-CoSe_(2) with a Hybrid Nanorods and Nanoparticles structure for Efficient Oxygen Evolution Reaction

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Chinese Journal of Structural Chemistry 2022年第1期41卷 19-24页

作者： Meng Li Ligang Feng School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225002China

hetero-structure induced high performance catalyst for oxygen evolution reaction(OER)in the water splitting reaction has received increased attention.Herein,we demonstrated a novel catalyst system of NiSe_(2)-CoSe_(2) consisting of nanorods and nanoparticles for the efficient OER in the alkaline electrolyte.This catalyst system can be easily fabricated via a low-temperature selenization of the solvothermal synthesized NiCo(OH)x precursor and the unique morphology of hybrid nanorods and nanoparticles was found by the electron microscopy analysis.The high valence state of the metal species was indicated by X-ray photoelectron spectroscopy study and a strong electronic effect was found in the NiSe_(2)-CoSe_(2) catalyst system compared to their counterparts.As a result,NiSe_(2)-CoSe_(2) exhibited high catalytic performance with a low overpotential of 250 mV to reach 10 mA·cm^(-2) for OER in the alkaline solution.Furthermore,high catalytic stability and catalytic kinetics were also observed.The superior performance can be attributed to the high valence states of Ni and Co and their strong synergetic coupling effect between the nanorods and nanoparticles,which could accelerate the charge transfer and offer abundant electrocatalytic active sites.The current work offers an efficient hetero-structure catalyst system for OER,and the results are helpful for the catalysis understanding.

关键词： oxygen evolution reaction NiSe_(2) CoSe_(2) hetero-structure electrocatalysis

Comparison of band-to-band tunneling models in Si and Si–Ge junctions

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Journal of Semiconductors 2013年第9期34卷 6-10页

作者：矫亦朋魏康亮王泰寰杜刚刘晓彦 Shenzhen Graduate School Peking University Institute of Microelectronics Peking University

We compared several different band-to-band tunneling （BTBT） models with both Sentaurus and the two-dimensional full-band Monte Carlo simulator in Si homo-junctions and Si-Ge hetero-junctions. It was shown that in Si homo-junctions, different models could achieve similar results. However, in the Si-Ge hetero-junctions, there were significant differences among these models at high reverse biases （over 2 V）. Compared to the nonlocal model, the local models in Sentaurus underrated the BTBT rate distinctly, and the Monte Carlo method was shown to give a better approximation. Additionally, it was found that in the Si region near the interface of the Si-Ge hetero-junctions, the direct tunneling rates increased largely due to the interaction of the band structures of Si and Ge.

关键词： hetero-structure Monte Carlo device simulation carrier transport band-to-band tunneling