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Advances in microwave absorbing materials with broad-bandwidth response

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Nano Research 2023年第8期16卷 11054-11083页

作者： Susu Bao Meixi Zhang zhiyuan jiang Zhaoxiong Xie Lansun Zheng State Key Laboratory for Physical Chemistry of Solid Surfaces College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China

Microwave absorbing materials(MAMs)are playing an increasingly essential role in the development of wireless communications,high-power electronic devices,and advanced target detection *** with a broad-bandwidth response are particularly important in the area of communication security,radiation prevention,electronic reliability,and military *** considerable progress has been made in the design and preparation of MAMs with a broad-bandwidth response,a number of challenges still remain,and the structure–function relationship of MAMs is still far from being completely ***,the advances in the design and research of MAMs with a broad-bandwidth response are *** main strategies for expanding the effective absorption bandwidth of MAMs are comprehensively summarized considering three perspectives:the chemical combination strategy,morphological control strategy,and macrostructure control *** important results as well as design principles and absorption mechanisms are highlighted.A coherent explanation detailing the influence of the chemical composition and structure of various materials on the microwave absorption properties of MAMs is *** main challenges,new opportunities,and future perspectives in this promising field are also presented.

关键词： microwave absorbing materials broad-bandwidth response magnetic-dielectric synergy morphology control macrostructure control

Energy-Optimal and Delay-Bounded Computation Offloading in Mobile Edge Computing with Heterogeneous Clouds

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China Communications 2020年第5期17卷 191-210页

作者： Tianchu Zhao Sheng Zhou Linqi Song zhiyuan jiang Xueying Guo Zhisheng Niu Beijing National Research Center for Information Science and Technology Department of Electronic EngineeringTsinghua UniversityBeijing 100080China Computer Science Department City University of Hong KongHongkong 999077China School of Communication and Information Engineering Shanghai UniversityShanghai 200444China Department of Computer Science University of CaliforniaDavisDavis 001313USA

By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.

关键词： mobile edge computing heterogeneous clouds energy saving delay bounds dynamic programming

A finite oxidation strategy for customizing heterogeneous interfaces to enhance magnetic loss ability and microwave absorption of Fe-cored carbon microcapsules

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Nano Research 2023年第8期16卷 11084-11095页

作者： Meixi Zhang Laisen Wang Susu Bao Zhijia Song Wenjiao Chen zhiyuan jiang Zhaoxiong Xie Lansun Zheng State Key Laboratory for Physical Chemistry of Solid Surfaces College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China College of Materials Xiamen UniversityXiamen 361005China

Metallic iron particles are of great potential for microwave absorption materials due to their strong magnetic loss ***,the oxidation susceptibility of metallic iron particles in the atmospheric environment is regarded as a major factor causing performance *** many efforts have been developed to avoid their oxidation,whether partial surface oxidized iron particles can improve the microwave absorbing performance is rarely *** order to explore the effect of partial surface oxidation of iron on its properties,the designed yolk–shelled(Fe/FeO_(x))@C composites with multiple heterointerfaces were synthesized via an in-situ polymerization and a finite reduction–oxidation process of Fe_(2)O_(3)*** performance enhancement mechanisms of Fe/FeO_(x)heterointerfaces were also *** is demonstrated that the introduction of Fe-based heterogeneous interfaces can not only enhance the dielectric loss,but also increase the imaginary part of the permeability in the higher frequency range to strengthen the magnetic loss ***,the yolk–shell structure can effectively improve impedance matching and enhance microwave absorption performances via increasing multiple reflection and scattering behaviors of incident *** to Fe@C composite,the effective absorption(reflection loss(RL)<−10 dB)bandwidth of the optimized(Fe/FeO_(x))@C-2 increases from 5.7 to 7.3 GHz(10.7–18.0 GHz)at a same matching thickness of 2 mm,which can completely cover *** work offers a good perspective for the enhancement of magnetic loss ability and microwave absorption performance of Fe-based microwave absorption materials with promising practical applications.

关键词： heterogeneous interfaces finite oxidation yolk-shell structure magnetic loss interface polarization microwave absorption

Synthesis and High Electrocatalytic Performance of Hexagram Shaped Gold Particles Having an Open Surface Structure with Kinks

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Nano Research 2011年第6期4卷 612-622页

作者： Qingning jiang zhiyuan jiang Lei Zhang Haixin Lin Ning Yang Huan Li Deyu Liu Zhaoxiong Xie Zhongqun Tian State Key Laboratory for Physical Chemistry of Solid Surfaces Department of Chemistry College of Chemistry and Chemical EngineeringXiamen University Xiamen 361005 China

Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammonium chloride） at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.

关键词： Hexagram shaped gold particles surface structure high index facets with kinks structure-property relationship electrocatalysis crystal growth

Origin of symmetry breaking in the seed-mediated growth of bi-metal nano-heterostructures

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Science Bulletin 2018年第14期63卷 892-899页

作者： Guifen Du Jun Pei zhiyuan jiang Qiaoli Chen Zhenming Cao Qin Kuang Zhaoxiong Xie Lansun Zheng State Key Laboratory of Physical Chemistry of Solid Surfaces Collaborative Innovation Center of Chemistry for Energy MaterialsDepartment of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University Pen-Tung Sah Institute of Micro-Nano Science and Technology Xiamen University

Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures. Despite successful instances through trial and error were reported, the way for second metal depositing on the seed. namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the ther- modynamic factor, i.e., the difference of equilibrium electrochemical potentials （corresponding to their Fermi levels） of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by revers- ing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant （L-ascorbic acid） in the growth solution, the structure of as-prepared prod- ucts successfully evolved from centrosymmetric Pd@Au core-shell trisoctabedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational con- struction of bimetal nano-heterostructures with soecific functions.

关键词： Symmetry breaking Bimetal nano-heterostructures Seed-mediated growth Equilibrium electrochemical potentials

Novel hydrogen storage properties of palladium nanocrystals activated by a pentagonal cyclic twinned structure

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Nano Research 2015年第8期8卷 2698-2705页

作者： Huang Huang Shixiong Bao Qiaoli Chen Yanan Yang zhiyuan jiang Qin Kuang Xiaoyin Wu Zhaoxiong Xie Lansun Zheng State Key Laboratory of Physical Chemistry of Solid Surfaces Collaborative Innovation Center of Chemistry for Energy Materials andDepartment of Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China

Researchers appear to have neglected a special form of crystallites, pentagonal cyclic twinning, in which an obvious two-dimensional lattice expansion exists leading to novel physical-chemical properties associated with the changes in geometric and electronic structures. Using the storage and release of hydrogen in Pd nanocrystals as a probe, we have found that icosahedral pentagonal cyclic twinned Pd nanocrystals had distinct hydrogen storage properties, due to the two-dimensional lattice expansions, quite different from those of the octahedral single crystalline counterpart. In addition, the two-dimensional lattice expansion in pentagonal cyclic twinned Pd nanocrystals causes a change in electronic structure, which results in novel catalytic properties involving in situ formation of PdHx pentagonal cyclic twinned nanocrystals.

关键词： hydrogen storage lattice expansion tweed structure palladium nanoparticles

Molecular hexagram and octagram:Position determined 3D metallo-supermolecules and concentration-induced transformation

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Chinese Chemical Letters 2021年第6期32卷 1911-1914页

作者： Tun Wu zhiyuan jiang Xiaobo Xue Shi-Cheng Wang Mingzhao Chen Jun Wang Haisheng Liu Jun Yan Yi-Tsu Chan Pingshan Wang Institute of Environmental Research at Greater Bay Area Key Laboratory for Water Quality and Conservation of the Pearl River DeltaMinistry of EducationGuangzhou UniversityGuangzhou 510006China Department of Organic and Polymer Chemistry College of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083China Department of Chemistry National Taiwan UniversityTaipei 10617

The reaction of a metallo-organic ligand(LA)in which two"V"-shaped bisterpyridines attaching to metaposition of"X"-shaped tetraterpyridine via connectivity and Zn^(2+)ions gave rise to 3D supramolecular architectures:octagram(Zn_(8)LA_(4)).However,a position varied ligand(LB)in which two"V"-shaped bisterpyridines locating at the ortho-position of"X"-shaped tetraterpyridine afforded a different 3D hexagram(Zn_(6)LB_(3)).Full characterizations included NMR(^(1)H,^(13)C,^(2)D COSY,NOESY and DOSY),ESI-MS,TWIM-MS,TEM and *** resulted structures were directly determined by the position of two"V"-shaped bisterpyridines attaching to"X"-shaped tetraterpyridine.

关键词： Self-assembly Terpyridine Supramolecular transformation Metal-organic ligand Metalla-cage

Engineering the Surface Structure of Functional Nanocrystalline Materials and their Corresponding Applications

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Engineering the Surface Structure of Functional Nanocrystall...

第二届海峡两岸功能材料科技与产业峰会（2015）

作者： Qin Kuang Yaqi jiang zhiyuan jiang Zhaoxiong Xie State Key Laboratory of Physical Chemistry of Solid Surfaces Collaborative Innovation Center of Chemistry for Energy MaterialsCollege of Chemistry and Chemical EngineeringXiamen University

The physical and chemical properties of nanocrystalline materials depend on the surface *** with high-energy facets exposed usually show high physical and chemical activities,due to abundant unsaturated coordination atoms and atomic steps and ***,in order to minimize the surface energy of the crystals,the high-energy facets quickly disappeared in the crystal growth ***,controllable synthesis of the nanocrystals exposed with high-energy facets is still a challenging topic.

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汉字超语符的数目表达研究

湖南师范大学社会科学学报 2020年第1期49卷 145-149页

作者：蒋志远湖南师范大学文学院

汉字超语符的数目表达,是指汉字可以在很多特殊的场合超越语言符号的性质,在交际中独立表达和它所记音义无关的数目。所表达的数目信息,可以来源于汉字形体结构的拆分重组、字形参数的映射转换以及特定文本的字序迁移等。这种特殊的汉... 详细信息

汉字超语符的数目表达,是指汉字可以在很多特殊的场合超越语言符号的性质,在交际中独立表达和它所记音义无关的数目。所表达的数目信息,可以来源于汉字形体结构的拆分重组、字形参数的映射转换以及特定文本的字序迁移等。这种特殊的汉字运用手段在中日等国有着悠久的历史,它扩展了个体汉字的信息含量,体现了使用者对汉字特性的独到理解。

关键词：汉字表达数目超语符