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17. Topological Lattice Metamaterials -- A Platform For Novel Electromagnetic Material Design Based On An Artificial Topological 'Atom'

Author

Zhang, Wenjin, Meng, Ziyuan, Zhang, Zidong, Bi, Ke, Fan, Runhua, Du, Yi, and Hao, Weichang

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

In nature, most materials are composed of atoms with periodic structures. Hence, it's impossible to introduce topological structures into their lattice compose, because the atoms as basic blocks cannot be modulated. However, the lattice compose of metamaterials can be designed conveniently. In our work, we propose to introduce topological non-trivial structures, Mobius unknots, as the basic block (the artificial chiral "atoms") to design metamaterials. A 5.95 GHz intrinsic peak, in addition to the electrical resonance peak near 11 GHz on the transmission coefficient spectrum was confirmed by theoretical calculations, finite-difference time-domain (FDTD) simulations and experiments when electromagnetic waves transfer to a chiral Mobius unknot. Theoretical analysis indicates that this intrinsic peak originates from the phase transition caused by the electromagnetic waves propagate along the Mobius unknot non-trivial structure. It is similar to the state of spin-splitting of electron levels. Take the artificial chiral "atoms" - Mobius unknots as the basic block, we can construct two-dimensional and even three-dimensional ordered metamaterials. The simulation and experimental results showed that the response to electromagnetic wave in the GHz band can be modulated by the coupling between the periodic potential and the spin-like of energy levels., Comment: 9 pages, 5 figures

Published
2019

29. Enhanced dielectric properties of Sr2+ and Zr4+ doped BaTiO3 colossal permittivity metamaterials

Author

Tang Qingyang, Shi Zhicheng, Xia Shuimiao, Bie Xiaohan, Yang Yujie, Bian Dedong, Xu Daofeng, and Fan Runhua

Subjects
metamaterial, dielectric property, breakdown strength, barium titanate, simulation, Electrical engineering. Electronics. Nuclear engineering, TK1-9971, Physics, QC1-999
Abstract

BaTiO3, as one of the most important functional materials of perovskite structure, is widely used in the electronic industry. However, the dielectric permittivity of BaTiO3 remains relatively low, which greatly limits its practical application in metamaterials with colossal dielectric permittivity. In this work, (Ba100−xSrx)(Ti100−yZry)O3 composite ceramics are fabricated via the solid sintering method. Surprisingly, the dielectric properties of (Ba100−xSrx)(Ti100−yZry)O3 composite ceramic materials are strongly dependent on the occupancy of Sr2+ and Zr4+ at the A-sites and B-sites, respectively. Consequently, via adjusting the doping amount of SrTiO3 and BaZrO3, a greatly enhanced dielectric permittivity of 28287 (65 °C, 1 kHz), along with a high breakdown strength of 84.47 kV/cm is achieved in (Ba90Sr10)(Ti90Zr10)O3 composite ceramics, which are 2144% and 13 % higher than those of (Ba99Sr1)(Ti99Zr1)O3 composite ceramics, respectively. Moreover, the reasons for the significant increase in dielectric permittivity are identified through finite element simulations, and the breakdown mechanism of composite ceramic materials is explored. This work provides a facile approach to constructing high dielectric permittivity composite ceramics, the (Ba100−xSrx)(Ti100−yZry)O3 composite ceramics have broad application prospects in electronics and electrostatic energy storage capacitors.

Published
2024
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44. Core‐shell TiO2@Au Nanofibers Derived from a Unique Physical Coating Strategy for Excellent Capacitive Energy Storage Nanocomposites.

Author

Ren, Zengliang, Shi, Zhicheng, Tang, Qingyang, Xia, Shuimiao, Sun, Liang, Fan, Runhua, Cui, Hongzhi, and Wang, Hong

Subjects
PULSED power systems, COULOMB blockade, ENERGY storage, ENERGY density, GOLD nanoparticles
Abstract

Polymer dielectrics have been widely employed in pulsed power systems, but their applications are severely restricted by the low energy density. Incorporating core‐shell nanofillers is one promising strategy to enhance the energy density of polymer dielectrics. Nowadays, core‐shell nanofillers are mainly prepared via chemical coating strategies, which always involve complex chemical synthesis procedures. Herein, a unique physical coating strategy is developed to prepare core‐shell TiO2@Au nanofibers consisting of monodispersed Au nanoparticles homogeneously anchored on the TiO2 nanofibers. Interestingly, the TiO2@Au nanofibers show outstanding dielectric energy storage boosting capability. Specifically, with merely introducing 0.1 wt.% TiO2@Au nanofillers, the TiO2@Au/PVDF composite exhibits a substantially enhanced breakdown strength of 749 MV m−1, which reaches 152.8% of PVDF. Meanwhile, a high dielectric constant of 10.2 (114.1% of PVDF) is obtained. Consequently, an ultrahigh energy density of 18.6 J cm−3, which is 250.1% of PVDF, is achieved. It is further revealed that the significant energy storage boosting effect is originated from the Coulomb blockade and micro‐capacitor effects of the TiO2@Au nanofibers. This work establishes a unique paradigm for the facile preparation of core‐shell nanomaterials, which have huge potential for both dielectric energy storage and other functional nanocomposites. [ABSTRACT FROM AUTHOR]

Published
2024
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