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Performance characterization of Bi_2O_3/Al nanoenergetics blasted micro-forming system

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Defence Technology（防务技术） 2019年第1期15卷 98-105页

作者： Vinay Kumar Patel Rishi Kant Anu choudhary Madhusudan Painuly Shantanu Bhattacharya Department of Mechanical Engineering Govind Ballabh Pant Institute of Engineering & Technology Pauri-Garhwal Department of Mechanical Engineering Indian Institute of Technology Kanpur

This paper reports a novel micro-blast driven manufacturing process for micro-forming of Aluminum foils. The micro-blast is realized by using a nanoenergetic material system comprising of Bi_2O_3 microrods and aluminum particles. There is an enhanced need of forming of thin aluminum foil structures in small regions from point of view of drug packaging etc. The process developed caters to this need by using a single shot forming process using a micro-blast source. The micro-blast that is generated from an energetic composite system is made highly tunable by modulating the peak pressure generated through the blasting process and their impact in micro-forming of thin aluminum foils is observed through parametric studies. The engineering challenge involved in these experiments is to tune the blast pressure properties in order to address the forming of thin metal sheets with limiting boundary values as defined by the failure criteria. A variety of characterization techniques related to a thorough analysis of the synthesized material viz. X-ray diffraction(XRD), Scanning Electron Microscopy(SEM) etc, are used to tune the functional properties like gauge blast pressure etc, of material system. We have found a material system that can generate a maximum peak pressure of 73.8 MPa with pressurization rate of 2460 GPas^(-1) and that is able to accomplish micro-forming on thin metal foils(around 0.3 mm thickness). Experimental investigations demonstrate that tunabilty aspect of the energetic composites when exercised can enable variant processes such as embossing, coining, drilling etc. which may be of significant utility to drug packaging industries. A proper mathematical modeling of the forming process and critical process parameters therein have also been detailed.

关键词： Microforming Aluminum Foil Bi2O3 Nanoenergetic tunability Process parameters

Computer aided design and analysis of a tunable muzzle brake

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Defence Technology（防务技术） 2019年第1期15卷 89-94页

作者： Ekansh Chaturvedi Ravi K.Dwivedi Department of Mechanical Engineering Maulana Azad National Institute of Technology

This research work deals with the design of a tunable muzzle brake [10] for a rifle chambered in 5.56 x 45 NATO ammunition. It proposes to solve the problem of handling differences from shooter to shooter by incorporating the feature of tunability. Beside this, it also solves the problem of requirement of optimum recoil in short recoil weapons. This innovation gives this design an edge over its already existing counterparts in the market. The product is designed using the internal ballistics calculations and the investigations been performed using solidworks flow simulation tool and ANSYS static structural to check the parameters like velocity distribution, pressure growth, and muzzle brake force along the series of ports and comparison of the so found results with those devised by the authors of the documents mentioned in references. This assures the market adaptability of the product for satisfactory performance, when brought among its already existing counterpart, though with a slight edge over them due to tunability. The results so found shall be concluded satisfactory regarding the performance of muzzle brake.

关键词： Flow simulation Innovation Muzzle brake tunability Set screws

Effect of external electric field on crystalline structure and dielectric properties of Bi_(1.5)MgNb_(1.5)O_(7) thin films

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Chinese Physics B 2021年第10期30卷 603-608页

作者： Zhongzhe Liu Libin Gao Kexin Liang Zhen Fang Hongwei Chen Jihua Zhang State Key Laboratory of Electronic Thin Films and Integrated Devices School of Electronic Science and EngineeringUniversity of Electronic Science and Technology of ChinaChengdu 610054China

Bismuth-based cubic pyrochlore materials have attractive dielectric properties,especially dielectric *** Bi_(1.5)MgNb_(1.5)O_(7) ceramic samples were prepared by solid state *** XRD results and SEM pictures prove the raw material are well mixed and co-fired and the BMN cubic pyrochlore is well crystallized,no second phase was found in the *** thin film were fabricated by depositing BMN ceramic nanoparticles on the *** BMN thin film has a high dielectric tunability of 43%at a bias voltage of 1.5 MV/cm,with loss tangent lower than 0.009.A Raman study of BMN cubic pyrochlore reveals O′-A-O′and O-A-O bending modes contribute to 80%of dielectric permittivity,obstructing these modes such as applying external electric field can have apparent influence on dielectric *** Phase calculation results shows that A2O′tetrahedrons are more easy to distort under an external *** A-site Mg have the highest displacement(0.765028 A),followed by A-site Bi cations(0.346317˚A).Compared to zero-bias thin film,˚the biased one with A-O and A-O′bonds being stretched and external coulomb force applied on cations and anions,the dielectric constant under bias field dramatically decreased.

关键词： cubic pyrochlore dielectric properties tunability DFT calculations

Tunable broadband metamaterial absorber consisting of ferrite slabs and a copper wire

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Chinese Physics B 2012年第3期21卷 504-508页

作者：杨拥军黄勇军文光俊钟靖平孙海斌 Oghenemuero Gordon Key Laboratory of Broadband Optical Fiber Transmission & Communication Networks School of Communication and Information EngineeringUniversity of Electronic Science and Technology of China

A tunable broadband metamaterial absorber is demonstrated at microwave frequencies in this paper. The meta- material absorber is composed of ferrite slabs with large resonance beamwidths and a copper wire. The theoretical analysis for the effective media parameters is presented to show the mechanism for achieving the perfect absorptivity characteristic. The numerical results of transmission, reflectance, and absorptivity indicate that the metamaterial ab- sorber exhibits a near perfect impedance-match to free space and a high absorptivity of 98.2% for one layer and 99.97% for two layers at 9.9 GHz. The bandwidth with the absorptivity above 90% is about 2.3 GHz. Moreover, the absorption band can be shifted linearly in a wide frequency range by adjusting the magnetic bias. This metamaterial absorber opens a way to prepare perfectly matched layers for engineering applications.

关键词： broadband metamaterial absorber tunability ferrite

Microwave characterization of two Ba_(0.6)Sr_(0.4)TiO_(3) dielectric thin films with out-of-plane and in-plane electrode structures

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Journal of Advanced Ceramics 2023年第8期12卷 1521-1532页

作者： Hanchi Ruan Theo Graves Saunders Henry Giddens Hangfeng Zhang Achintha Avin Ihalage Jonas Florentin Kolb Matthew Blunt Sajad Haq Haixue Yan Yang Hao School of Electronic Engineering and Computer Science Queen Mary University of LondonLondon E14NSUK School of Engineering and Materials Science Queen Mary University of LondonLondon E14NSUK Department of Chemistry University College LondonLondon WC1H 0AJUK Advanced Services and Products QinetiQFarnborough GU140LXUK

Ferroelectric(FE)thin films have recently attracted renewed interest in research due to their great potential for designing novel tunable electromagnetic devices such as large intelligent surfaces(LISs).However,the mechanism of how a polar structure in the FE thin films contributes to desired tunable performance,especially within the microwave frequency range,which is the most widely used frequency range of electromagnetics,has not been illustrated *** this paper,we described several straightforward and cost-effective methods to fabricate and characterize Ba_(0.6)Sr_(0.4)TiO_(3)(BST)thin films at microwave *** prepared BST thin films here exhibit homogenous structures and great tunability(h)in a wide frequency and temperature range when the applied field is in the out-of-plane *** high tunability can be attributed to high concentration of polar *** response to the applied direct current(DC)field was directly visualized using a novel non-destructive near-field scanning microwave microscopy(NSMM)*** results have provided some intriguing insights into the application of the FE thin films for future programmable high-frequency devices and systems.

关键词： ferroelectric(FE) microwave tunability polarization thin film

Extension/Compression-Controlled Complete Band Gaps in 2D Chiral Square-Lattice-Like Structures

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Acta Mechanica Solida Sinica 2018年第1期31卷 51-65页

作者： Y. L. Huang N. Gao W.Q. Chen R.H. Bao Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China State Key Lab of CAD & CG Zhejiang University Hangzhou 310058 China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China Soft Matter Research Center Zhejiang University Hangzhou 310027 China

Achieving tunable band gaps in a structure by external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability of band gaps in square-lattice-like elastic periodic structures that are usually not featured with notable band gaps. Endowed with chirality, the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very rich and, more importantly, can be efficiently and robustly tuned by applying appropriate mechanical loadings without inducing buckling. As expected, geometry plays a more significant role than material nonlinearity does in the evolution of band gaps. The dynamic tunability of band gaps through mechanical loading is further studied. Results show that closing, opening, and shifting of band gaps can be realized by exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral symmetry can be useful in the design of particular acoustic devices.

关键词： Band gap tunability Square-lattice-like periodic structure Chiral symmetry,Large deformation

2D materials for intelligent devices

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Science China(Physics,Mechanics & Astronomy) 2023年第11期66卷 44-54页

作者： Xuan Pan Yixiang Li Bin Cheng Shi-Jun Liang Feng Miao Institute of Brain-Inspired Intelligence National Laboratory of Solid State MicrostructuresCollaborative Innovation Center of Advanced MicrostructuresSchool of PhysicsNanjing UniversityNanjing210093China Institute of Interdisciplinary Physical Sciences School of ScienceNanjing University of Science and TechnologyNanjing210094China

Neuromorphic intelligent hardware technologies have undergone rapid advancement during the past decade,with the goal of building intelligent devices and systems capable of overcoming challenges associated with conventional *** of neuromorphic intelligent hardware depends on major advances in materials science,condensed matter physics,device physics and *** a revolutionary discovery,two-dimensional(2D)materials with atomically-thin thickness and exceptionally high tunability introduce a new physical paradigm and show great promise in the development of intelligent ***,we give prominence to three categories of tunable properties(i.e.,charge carrier,band structure,lattice structure)that are inherent for 2D materials and review their superiorities in constructing intelligent devices particularly in electronics and ***,we provide insight into how the unique physical mechanisms emerging in 2D materials offer a fertile ground for the design of diverse intelligence devices.

关键词： tunability 2D materials intelligent devices

Robustly Tuning Bandgaps in Two-Dimensional Soft Phononic Crystals with Criss-Crossed Elliptical Holes

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Acta Mechanica Solida Sinica 2018年第5期31卷 573-588页

作者： Nan Gao Yi-lan Huang Rong-hao Bao Wei-qiu Chen Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China State Key Lab of CAD & CG Zhejiang University Hangzhou 310058 China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China Soft Matter Research Center Zhejiang University Hangzhou 310027 China

Tuning band gaps in soft materials by post-buckling deformation is becoming an appealing means to manipulate elastic waves. As one of the most favorable topologies, two- dimensional soft structures with circular holes have been extensively studied. Based on the contrarian thinking, this paper starts from the two-dimensional soft structures with criss-crossed elliptical holes, which is close to the post-buckling configuration of soft structures with circular holes, and then proposes to tune the band gaps through elongating or stretching rather than compressing. Influences of the loading magnitude and loading pattern （i.e., uniaxial and biaxial elongations） on the band gaps are studied via the nonlinear finite element simulations. Effects of the geometric parameters （the major-to-minor half-axis ratio and the porosity of the structure） are also discussed. It is shown that, compared with the traditional circular hole case, the band gaps of the unloaded structure with criss-crossed elliptical holes are much richer, and they could be reversely and continuously tuned by tensile loadings. In particular, the deformation is very robust and is insensitive to small geometric imperfections, which is always necessary for triggering the post-buckling deformations. The present work provides a useful reference to the manipula- tion of elastic waves in periodic structures as well as the design of soft phononic crystals/acoustic devices.

关键词： Soft phononic crystal Criss-crossed elliptical holes Band gap tunability

Dielectric Properties of Multilayered Ba0.5Sr0.5TiO3 Thin Films Deposited on ITO-Coated Corning 1737 Glass by rf Magnetron Sputtering

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Chinese Physics Letters 2005年第11期22卷 2947-2949页

作者：林明通陈国荣杨云霞肖田徐毅楼均辉陈晨曦 Key Laboratory for Superfine Materials of Ministry of Education School of Materials Science and Engineering East China University of Science and Technology Shanghai 200237 SVA Electron Co. Ltd. Shanghai 200081

A new stacking method via variation ofsubstrate temperature in rfmagnetron sputter is used to fabricate polycrystalline/polycrystalline Ba0.5Sr0.5TiO3 thin films with higher dielectric constant, higher breakdown strength and lower leakage current densities than those prepared by a conventionM deposition method. The improved figure of merit G （ε0εrEb） of the Ba0.5Sr0.5TiO3 thin films implies that they are a feasible insulation layer for thin film electroluminescent devices.

关键词： tunability DEVICES LAYER