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177 results on '"Yuan, Jujun"'

21. Preparation of ZnO/Co/C/RGO Composites for Enhanced Microwave Absorption.

Author

Yu, Jing, Mu, Meiqi, Lin, Sisi, Ding, Jie, Xiong, Bing, Mou, Jirong, Zhu, Xiurong, Li, Xiaokang, Xiong, Zuzhou, Zhang, Xianke, and Yuan, Jujun

Abstract

ZnO/Co/C/reduced graphene oxide (RGO) composites are synthesized through carbonization of ZnCo-MOF-5/GO under an Ar/H2 flow. The abundant active sites (e.g., functional groups and lattice defects), copious heterointerfaces (among Co, ZnO, C, and RGO), and wrinkled architecture trigger multiple dipole polarization, interface polarization, and enhanced conductive loss. By adjusting the content of RGO, the electromagnetic parameters for ZnO/Co/C/RGO composites were effectively regulated. The minimum reflection loss (RLmin) of ZnO/Co/C/RGO-50 composites is −52.72 dB at 1.70 mm, and the EAB is 3.57 GHz. Futhermore, CST simulation results further confirm the remarkable RCS reduction capacity for ZnO/Co/C/RGO-50 composites. The reduction value of RCS is 22.84 dB m2, and effective absorption can reach the entire angle range. The superior microwave absorption property for ZnO/Co/C/RGO composites is benefited from cooperative action of dielectric loss (dipole polarization, interface polarization, conductive loss) and magnetic loss (natural resonance and exchange resonance). [ABSTRACT FROM AUTHOR]

Published
2024
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34. Co Nanoparticles Embedded in N‑Doped Carbon Nanotubes for Broadband Microwave Absorption.

Author

Xu, Suqiong, Liao, Peng, Zhu, Jiawei, Ling, Wei, Zhang, Xianke, Yuan, Jujun, Rong, Chuicai, Liu, Xiaoqing, and Xiong, Zuzhou

Abstract

Herein, an efficient one-dimensional (1D) N-doped Co/C nanotube absorber was designed by a cobalt source and solvent ratio comodulation strategy. First, we explored the influences of different cobalt sources (CoCl2, Co-(OAc)2, Co-(NO3)2, and CoSO4) on the morphology and microwave absorption (MA) property, which showed that CoCl2 facilitated the formation of nanotubes with a relatively uniform diameter and length. Notably, the Co/C nanotubes displayed an ultrawide effective absorption bandwidth (EAB) of 6.885 GHz at 2.2 mm when the filling ratio was only 8 wt %. Then, by adjusting the solvent ratio of isopropanol (IPA) and water, Co/C showed a strong absorption of −44.51 dB with an EAB of 5.44 GHz at 2.35 mm. The outstanding MA performance is ascribed to the synergistic effect of dielectric and magnetic components, which is conducive to optimizing the impedance matching, thus broadening the EAB. In addition, the 1D nanostructure is good for constructing three-dimensional (3D) conductive networks and enhancing conductive loss. Since Co nanoparticles are wrapped in carbon nanotubes (CNTs), the confinement effect can effectively prevent the agglomeration of ferromagnetic nanoparticles, adjusting the MA performance. It is worth mentioning that the maximum Radar cross section (RCS) value of Co/C can be reduced by 28.8 dB m2. Furthermore, the RCS values are all lower than −10 dB m2 from −90 to 90° and the minimum RCS value can reach −46.8 dB m2. This work provides a strategy for designing lightweight MA absorbers with strong RL and ultrawide EAB. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Construction of Porous Carbon Nanosheet/Cu 2 S Composites with Enhanced Potassium Storage.

Author

Mu, Meiqi, Li, Bin, Yu, Jing, Ding, Jie, He, Haishan, Li, Xiaokang, Mou, Jirong, Yuan, Jujun, and Liu, Jun

Subjects
COPPER, IONIC conductivity, SUPERIONIC conductors, CARBON, NANOSTRUCTURED materials, VULCANIZATION
Abstract

Porous C nanosheet/Cu2S composites were prepared using a simple self-template method and vulcanization process. The Cu2S nanoparticles with an average diameter of 140 nm are uniformly distributed on porous carbon nanosheets. When used as the anode of a potassium-ion battery, porous C nanosheet/Cu2S composites exhibit good rate performance and cycle performance (363 mAh g−1 at 0.1 A g−1 after 100 cycles; 120 mAh g−1 at 5 A g−1 after 1000 cycles). The excellent electrochemical performance of porous C nanosheet/Cu2S composites can be ascribed to their unique structure, which can restrain the volume change of Cu2S during the charge/discharge processes, increase the contact area between the electrode and the electrolyte, and improve the electron/ionic conductivity of the electrode material. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Fabrication of nano-solid spherical Nb2O5/nitrogen-doped carbon composite for high-performance sodium-ion battery anodes.

Author

He, Haishan, Gan, Yunfei, Mu, Meiqi, Yuan, Jujun, Zhang, Chao, Zhang, Xianke, Li, Xiaokang, Ma, Xiangdong, Yu, Huanjun, Mou, Jirong, and Liu, Jun

Subjects
CARBON composites, SODIUM ions, METALLIC oxides, CHARGE exchange, NANOCRYSTALS, SUPERIONIC conductors, STORAGE batteries, ANODES
Abstract

Nano-solid spherical Nb2O5/nitrogen-doped carbon (NC) composite is obtained by the hydrothermal method followed by a calcination procedure. The Nb2O5/NC composite exhibits good rate performance and sustainable cyclic stability (144 mAh g−1 at 1000 mAh g−1 upon 2000 charge–discharge cycles) as an anode material in Na-ion batteries (SIBs). The excellent performance of the Nb2O5/NC composite is attributed to its unique nanosphere structure, in which Nb2O5 nanocrystals embedded in porous NC matrix can restrain agglomeration of Nb2O5 nanocrystals and ensure electrolyte accessibility, and the NC matrix can provide effective active sites and increase ions/electrons transfer. This work offers a new method to fabricate nano-solid spherical Nb2O5/NC composite with good Na+ storage property, which can be extended for synthesizing other metal oxide/NC composite as SIB anode. [ABSTRACT FROM AUTHOR]

Published
2023
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