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The Innovation 2024年第2期5卷 79-87页

作者： Huan Ma Yueyue Jiao Wenping Guo Xingchen Liu Yongwang Li Xiaodong Wen State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SciencesTaiyuan 030001China University of Chinese Academy of Sciences Beijing 100049China National Energy Center for Coal to Liquids Synfuels China Co.Ltd.Beijing 101400China Beijing Advanced Innovation Center for Materials Genome Engineering IndustryUniversity Cooperation Base between Beijing Information S&T University and Synfuels China Co.Ltd.Beijing 100101China

Solid surfaces usually reach thermodynamic equilibrium through particle exchange with their environment under reactive conditions.A prerequisite for understanding their functionalities is detailed knowledge of the surface composition and atomistic geometry under working conditions.Owing to the large number of possible Miller indices and terminations involved in multielement solids,extensive sampling of the compositional and conformational space needed for reliable surface energy estimation is beyond the scope of ab initio calculations.Here,we demonstrate,using the case of iron carbides in environments with varied carbon chemical potentials,that the stable surface composition and geometry of multielement solids under reactive conditions,which involve large compositional and conformational spaces,can be predicted at ab initio accuracy using an approach that combines the bond valence model,Gaussian process regression,and ab initio thermodynamics.Determining the atomistic structure of surfaces under working conditions paves the way toward identifying the true active sites of multielement catalysts in heterogeneous catalysis.

关键词： surfaces solids environments

Acoustic Bilayer Gradient Metasurfaces for Perfect and Asymmetric Beam Splitting

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Chinese Physics Letters 2024年第1期41卷 39-50页

作者：权家琪孙宝印伏洋洋高雷徐亚东 Institute of Theoretical and Applied Physics School of Physical Science and TechnologySoochow UniversitySuzhou 215006China College of Physics Nanjing University of Aeronautics and Astronautics&Key Laboratory of Aerospace Information Materials and Physics(NUAA)MIITNanjing 211106China School of Optical and Electronic Information Suzhou City UniversitySuzhou 215104China

We experimentally and theoretically present a paradigm for the accurate bilayer design of gradient metasurfaces for wave beam manipulation,producing an extremely asymmetric splitting effect by simply tailoring the interlayer size.This concept arises from anomalous diffraction in phase gradient metasurfaces and the precise combination of the phase gradient in bilayer metasurfaces.Ensured by different diffraction routes in momentum space for incident beams from opposite directions,extremely asymmetric acoustic beam splitting can be generated in a robust way,as demonstrated in experiments through a designed bilayer system.Our work provides a novel approach and feasible platform for designing tunable devices to control wave propagation.

关键词： surfaces splitting asymmetric

Understanding the Thermal Impedance of Silicone Rubber/Hexagonal Boron Nitride Composites as Thermal Interface Materials

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Chinese Journal of Polymer Science 2024年第3期42卷 352-363,I0008页

作者： Yuan Ji Shi-Da Han Hong Wu Shao-Yun Guo Feng-Shun Zhang Jian-Hui Qiu The State Key Laboratory of Polymer Materials Engineering Sichuan Provincial Engineering Laboratory of Plastic/Rubber Complex Processing TechnologyPolymer Research InstituteSichuan UniversityChengdu 610065China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Department of Mechanical Engineering Faculty of Systems Science and TechnologyAkita Prefectural UniversityAkita 015-0055Japan

Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.

关键词： Thermal interface materials Hexagonal boron nitride Thermal impedance surfaces

Programmable structured surfaces can change the future of wireless communications

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Light(Science & Applications) 2022年第7期11卷 1341-1342页

作者： Lei Xu Mohsen Rahmani Advanced Optics and Photonics Laboratory Department of EngineeringSchool of Science and TechnologyNottingham Trent UniversityNottingham NG118NSUK

An innovative time-varying metasurface has been reported to realise dual-channel data transmissions for light-to-microwave signal conversion.Such a novel technique is a remarkable step forward to realise full-spectrum networks for catering for the growing demand for wireless communications.Moreover,this technique enriches the functionalities of tunable metasurfaces and stimulates new information-oriented applications.

关键词： wireless tunable surfaces

Free Cyclic Actions on surfaces and the Borsuk-Ulam Theorem

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1803-1822页

作者： Daciberg Lima GONCALVES John GUASCHI Vinicius Casteluber LAASS Departamento de Matematica IMEUniversidade de Sao PauloRua do Matao 1010 CEP:05508-090Sao Paulo-SPBrazil Normandie Univ. UNICAENCNRSLMNO14000 CaenFrance Universidade Federal da Bahia IMEDepartamento de MatematicaAv.Milton SantosS/N Ondina CEP:40170-110Salvador-BABrazil

Let M and N be topological spaces,let G be a group,and letτ:G×M→M be a proper free action of G.In this paper,we define a Borsuk-Ulam-type property for homotopy classes of maps from M to N with respect to the pair(G,τ)that generalises the classical antipodal Borsuk-Ulam theorem of maps from the n-sphere S^(n) to R^(n).In the cases where M is a finite pathwise-connected CWcomplex,G is a finite,non-trivial Abelian group,τis a proper free cellular action,and N is either R^(2) or a compact surface without boundary different from S^(2) and RP^(2),we give an algebraic criterion involving braid groups to decide whether a free homotopy class β∈[M,N]has the Borsuk-Ulam property.As an application of this criterion,we consider the case where M is a compact surface without boundary equipped with a free actionτof the finite cyclic group Zn.In terms of the orient ability of the orbit space Mof M by the actionτ,the value of n modulo 4 and a certain algebraic condition involving the first homology group of M,we are able to determine if the single homotopy class of maps from M to R^(2) possesses the Borsuk-Ulam property with respect to(Z_(n),τ).Finally,we give some examples of surfaces on which the symmetric group acts,and for these cases,we obtain some partial results regarding the Borsuk-Ulam property for maps whose target is R^(2).

关键词： Borsuk-Ulam theorem cyclic groups braid groups surfaces

Class-specific diffractive cameras based on deep learning-designed surfaces

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Light(Science & Applications) 2022年第10期11卷 2262-2263页

作者： Xuxi Zhou Shuming Wang National Laboratory of Solid-State Microstructures School of PhysicsNanjing UniversityNanjing 210093China

Recently,a new diffractive camera design based on transmissive surfaces structured using deep learning is proposed.It performs class-specific imaging of target objects and all-optical deletion of other classes of obje... 详细信息

关键词： specific surfaces preserving

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces fabricated by double rolling

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International Journal of Minerals,Metallurgy and Materials 2013年第12期20卷 1170-1175页

作者： Xi-yong Wang Xue-feng Liu Wen-jiang Zou Jian-xin Xie School of Materials Science and Engineering University of Science and Technology Beijing Beijing Laboratory of Metallic Materials and Processing for Modern Transportation University of Science and Technology Beijing Key Laboratory for Advanced Materials Processing Ministry of Education) University of Science and Technology Beijing

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.

关键词： copper foils rolling surfaces gradient structure fatigue of materials

Normal Contact Model for Elastic and Plastic Mechanics of Rough surfaces

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Acta Mechanica Solida Sinica 2019年第2期32卷 148-159页

作者： Dong Wang Zhousuo Zhang Fan Jin Xuanhua Fan State Key Laboratory for Manufacturing and Systems Engineering School of Mechanical Engineering XVan Jiaotong University Xi'an 710049 China Institute of Systems Engineering China Academy of Engineering Physics Mianyang 621999 China

An elastic and plastic mechanical model is proposed to characterize the normal contact of rough surfaces. The contact process is considered as three separated contact regimes, i.e., the fully elastic, mixed elastic一plastic and fully plastic ones. The Hertzian elastic contact solutions and the classical fully plastic contact model of Abbott and Fires tone are used to model the contact behaviors of fully elastically deformed asperities and fully plastically deformed ones, respectively. For the mixed elastic-plastic regime, an improved Hermit interpolation method is applied to enforce the continuity and smoothness at the critical contact interference, and to decrease the interpolation waving effect by transforming the physical quantities of contact load into logarithmic coordinates. The contac t model of rough surfaces is formula ted by using the Greenwood and Williamson^ statistics analysis. Comparisons with the CEB, ZMC and KE models are then performed to examine the effects of plasticity index and mean separation. Agreeing well with the ZMC model, our results show that the total contact load of rough surfaces decreases with the increase in mean separation, and the difference between the prediction results of elastic models and the plastic ones also decreases, indicating that the contact behaviors mainly dominated by plastically deformed asperities have been changed to be controlled by elastically deformed ones. Larger plasticity index represents more plastically deformed asperities, inducing normal contact behaviors mainly dominated by plastic solutions.

关键词： Rough surfaces Elastic plastic Asperity contact Logarithm transformation Statistics analysis

Biomimetic Superlyophobic Metallic surfaces: Focusing on Their Fabrication and Applications

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Journal of Bionic Engineering 2020年第1期17卷 1-33页

作者： Zhongxu Lian Jinkai Xu Zuobin Wang Huadong Yu Ministry of Education Key Laboratory for Cross-Scale Micro and Nano Manufacturing Changchun University of Science and TechnologyChangchun 130022China International Research Centre for Nano Handling and Manufacturing of China Changchun University of Science and TechnologyChangchun 130022China

Metals are indispensable engineered materials for day-to-day life.Researches focused on metallic surfaces with superlyophobicity(superhydrophobicity,superoleophobicity,underwater superoleophobicity and slippery characteristic)have attracted much attention recently.Nature is a magician that gives each organic life a unique advantage.Researchers have created a large number of biomimetic superlyophobic metallic surfaces through various approaches.These biomimetic superlyophobic metallic surfaces exhibit advantages in many applications,such as self-cleaning,corrosion resistance,anti-icing,and drag reduction.In this review,the specific fabrication and applications of biomimetic superlyophobic metallic surfaces were reported.The remaining challenges and future outlook of biomimetic superlyophobic metallic surfaces were preliminarily analyzed.It is hoped that the review will be essential for broadening the scope of potential applications of metals and providing a powerful reference for future research on metal-based advanced functional materials.

关键词： biomimetic metallic surfaces superhydrophobicity superoleophobicity underwater superoleophobicity slippery characteristic

Surface Structure and Reconstructions of HgTe(111)surfaces

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Chinese Physics Letters 2018年第2期35卷 71-74页

作者：杨心怡王观勇赵晨晓朱朕董璐李爱民吕洋洋姚淑华陈延彬管丹丹李耀义郑浩钱冬刘灿华陈宇林贾金锋 Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education) Department of Physics and AstronomyShanghai Jiao Tong University National Laboratory of Solid State Microstructures & Department of Materials Science and Engineering Nanjing University National Laboratory of Solid State Microstructures & Department of Physics Nanjing University Collaborative Innovation Center of Advanced Microstructures Clarendon Laboratory Department of PhysicsUniversity of Oxford

Hg Te（111） surface is comprehensively studied by scanning tunneling microscopy/spectroscopy（STS）.In addition to th√e prim√itive（1 × 1）√ hexagonal lattice,six reconstructed surface structures are observed：（2 × 2）,2 × 1,4 × 1,3 ×（1/2）3,2（1/2）2 × 2 and （1/2）11 × 2.The（2 × 2） reconstructed lattice maintains the primitive hexagonal symmetry,whi√le the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the3 ×（1/2）3 reconstruction are bias dependent,indicating that they have both topographic and electronic origins.The STSs obtained at different reconstructed surfaces show a universal dip feature with size ～100 mV,which may be attributed to the surface distortion.Our results reveal the atomic structure and complex reconstructions of the cleaved Hg Te（111） surfaces,which paves the way to understand the rich properties of Hg Te crystal.

关键词： In STS Hg Surface Structure and Reconstructions of HgTe surfaces