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Thermal property and microstructure of Al nanopowders produced by two evaporation routes

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中国有色金属学会会刊：英文版 2009年第1期19卷 187-191页

作者：陈亮宋武林郭连贵谢长生 State key laboratory of Material Processing and Die and Mould Technology Huazhong University of Science and Technology Analytical and testing Center Huazhong University of Science and Technology

Al nanopowders with diameters ranging from 20 to 50 nm passivated by Al2O3 coatings were produced by two different evaporation routes: induction heating evaporation (IHE) and laser-induction complex heating evaporation (LCHE). Thermal property of the nanopowders was investigated by differential thermal analysis (DTA) in dry oxygen environment. The results show that Al nanopowders produced by LCHE have the oxidation enthalpy change (△H) of 3.54 kJ/g, while the △H of Al produced by IHE is 1.18 kJ/g. The phase constitution and microstructures of these nanopowders were revealed using X-ray diffraction (XRD) analysis, transmission electronic microscopy (TEM) and high-resolution transmission electronic microscopy (HRTEM). The results show that the two powders have the same composition and mean particle size, as well as the thickness of Al2O3 coatings (3-5 nm). Defects were observed on the surfaces of the particles by LCHE. However, the defects were not detected by HRTEM on the surfaces of the particles by IHE. The results prove that there exists excessive stored energy in Al nanopowders by LCHE because of the nonequilibrium condition brought by laser and the defects are the storage area of the excessive stored energy. Propellants composed of Al nanopowders by LCHE show higher energy level and specific impulse.

关键词：高性能材料铝型材加工金属材料

Tunable negative-index photonic crystals using colloidal magnetic fluids

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Chinese Physics B 2015年第12期24卷 352-357页

作者：耿滔王新王岩董祥美 Engineering Research Center of Optical instrument and System Ministry of Education Shanghai Key Laboratory of Modern Optical SystemUniversity of Shanghai for Science and Technology

The model of using colloidal magnetic fluid to build tunable negative-index photonic crystal is established. The effective permittivity εe and permeability μe of the two-dimensional photonic crystal are investigated in detail. For transverse magnetic polarization, both εe and μe exhibit a Lorentz-type anomalous dispersion, leading to a region where εe and μe are simultaneously negative. Then, considering a practical case, in which the thickness of photonic crystal is finite, the band structures for odd modes are calculated by the plane wave expansion method and the finite-difference time-domain method. The results suggest that reducing the external magnetic field strength or slab thickness will weaken the periodic modulation strength of the photonic crystal. Simulation results prove that the negative-index can be tuned by varying the external magnetic field strength or the slab thickness. The work presented in this paper gives a guideline for realizing the flat photonic crystal lens with tunable properties at optical frequencies, which may have potential applications in tunable near-field imaging systems.

关键词： tunable negative-index photonic crystals colloidal magnetic fluids

Homomorphic partial differential equation filtering method for electronic speckle pattern interferometry fringes based on fringe density

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Chinese Optics Letters 2009年第3期7卷 210-213页

作者：张芳刘文耀夏琳王晋疆朱越 College of Precise instrument and Optical Electronic Engineering Tianjin University key laboratory of Opto-Electronics Information Technical science Ministry of Education

Noise reduction is one of the most exciting problems in electronic speckle pattern interferometry. We present a homomorphic partial differential equation filtering method for interferometry fringe patterns. The diffusion speed of the equation is determined based on the fringe density. We test the new method on the computer-simulated fringe pattern and experimentally obtain the fringe pattern, and evaluate its filtering performance. The qualitative and quantitative analysis shows that this technique can filter off the additive and multiplicative noise of the fringe patterns effectively, and avoid blurring high-density fringe. It is more capable of improving the quality of fringe patterns than the classical filtering methods.

关键词： Computational fluid dynamics Image quality Interferometers Interferometry Moire fringes Partial differential equations Speckle

Evaluation of vibration stress of TA11 titanium alloy blade by quantitative fractography

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Rare Metals 2014年第3期33卷 263-269页

作者： Xin-Ling Liu Yuan-Ming Xu Chun-Hu Tao Beijing Institute of Aeronautical Materials Aviation Industries of China key laboratory of Aeronautical Materials testing and Evaluation ChinaTao Failure Analysis Center of Aviation Industries of China School of Aeronautical science and Engineering Beijing University of Aeronautics and Astronautics Beijing key laboratory of Aeronautical Materials testing and Evaluation

Vibration fatigue is the main failure mode of compressor blade. Evaluating the vibration stress of blade that leads to cracking is very useful for analysis of vibration fatigue. In this paper, fatigue stress estimation methods by quantitative fractography were studied through experimental blade and in-service first-stage compressor blade in order to evaluate the initiation vibration stress of in-service blade. The analysis process of initiation vibration stress was established. The evaluating result of vibration stress of in-service blade subjected to centrifugal force and bending vibration stress agrees with aero engine test result. It is shown that the evaluation method can not only evaluate the equivalent fatigue stresses of different crack depths but also yield the initiation equivalent fatigue stress.

关键词： Compressor blade Bending vibration Stress evaluate Quantitative fractography

Passively Mode-Locked Fiber Laser with a Sub-Megahertz Repetition Rate

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Chinese Physics Letters 2011年第11期28卷 110-112页

作者： CHEN Jiong JIA Dong-Fang WU Yong-Chao WANG Chang-Le WANG Zhao-Ying YANG Tian-Xin key laboratory of Optoelectronics Information and Technical science(Ministry of Education) and College of Precision Instrument and Optoelectronics EngineeringTianjin UniversityTianjin 300072

We demonstrate an ultra-long cavity by which an all-fiber erbium-doped fiber laser is passively mode-locked by nonlinear polarization *** length of the resonant cavity amounts to 466 m,which can be achieved by incorporating a 420m highly nonlinear *** laser generates stable mode-locked pulses with a 444 kHz fundamental repetition rate.A near transform-limited subpicosecond pulse is obtained without any dispersion *** maximum average power of the output pulses is 5.16mW,which corresponds to a per-pulse energy of 11.62 nJ.

关键词： fiber polarization pulse

New multiplexed system for synchronous measurement of out-of-plane deformation and two orthogonal slopes

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Chinese Physics B 2022年第3期31卷 259-264页

作者： Yonghong Wang Xiao Zhang Qihan Zhao Yanfeng Yao Peizheng Yan Biao Wang School of instrument science and Opto-electronics Engineering Hefei University of TechnologyHefei 230009China Anhui Province key laboratory of Measuring Theory and Precision instrument Hefei University of TechnologyHefei 230009China

We propose a novel system for synchronous measurement of out-of-plane deformation and two orthogonal slopes using a single camera. The linearly polarized reference beam introduced by an optical fiber interferes with the unpolarized object beam to measure the out-of-plane deformation. A modified Mach–Zehnder interferometer is used to measure the two orthogonal slopes of the out-of-plane deformation. One of the object beams of the Mach–Zehnder interferometer is an unpolarized beam, and the other object beam is split into two orthogonal linearly polarized object beams by a polarizing prism. The two beams are orthogonally polarized. Hence, they will not interfere with each other. The two polarized beams respectively interfere with the unpolarized beam to simultaneously measure the two orthogonal slopes of the out-of-plane deformation. In addition, the imaging lens and apertures are respectively placed in three optical paths to independently control the carrier frequencies and shearing amounts. The effectiveness of this method can be proved by measuring two pressure-loaded circular plates.

关键词： digital speckle pattern interferometry digital shearography simultaneous measurement of displacement and two orthogonal slopes

Molecular dynamics study on splitting of hydrogen-implanted silicon in Smart-Cut~ technology

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Journal of Semiconductors 2015年第3期36卷 144-149页

作者：王冰古斌潘荣莹张思佳沈建华 key laboratory of testing Technology for Manufacturing Process Southwest University of Science and Technology-Ministry of Education School of Manufacturing Science and Engineering Southwest University of Science and Technology

Defect evolution in a single crystal silicon which is implanted with hydrogen atoms and then annealed is investigated in the present paper by means of molecular dynamics simulation. By introducing defect density based on statistical average, this work aims to quantitatively examine defect nucleation and growth at nanoscale during annealing in Smart-Cut technology. Research focus is put on the effects of the implantation energy, hydrogen implantation dose and annealing temperature on defect density in the statistical region. It is found that most de- fects nucleate and grow at the annealing stage, and that defect density increases with the increase of the annealing temperature and the decrease of the hydrogen implantation dose. In addition, the enhancement and the impediment effects of stress field on defect density in the annealing process are discussed.

关键词： Smart-Cut molecular dynamics hydrogen implantation defect density

dynamic stability of parametrically-excited linear resonant beams under periodic axial force

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Chinese Physics B 2012年第11期21卷 94-101页

作者：李晶樊尚春李艳郭占社 School of instrument science&Opto-electronics Engineering Beihang University key laboratory of Precision Opto-mechatronics Techonology Ministry of Education key laboratory of Inertial science and Technology for National Defence School of Information and Communication Engineering North University of China

The parametric dynamic stability of resonant beams with various parameters under periodic axial force is studied. It is assumed that the theoretical formulations are based on Euler-Bernoulli beam theory. The governing equations of motion are derived by using the Rayleigh-Ritz method and transformed into Mathieu equations, which are formed to determine the stability criterion and stability regions for parametricallyexcited linear resonant beams. An improved stability criterion is obtained using periodic Lyapunov functions. The boundary points on the stable regions are determined by using a small parameter perturbation method. Numerical results and discussion are presented to highlight the effects of beam length, axial force and damped coefficient on the stability criterion and stability regions. While some stability rules are easy to anticipate, we draw some conclusions： with the increase of damped coefficient, stable regions arise; with the decrease of beam length, the conditions of the damped coefficient arise instead. These conclusions can provide a reference for the robust design of parametricallyexcited linear resonant sensors.

关键词： resonant beams dynamic stability parametrically excitation periodic axial force

Effects of surface adsorbed oxygen, applied voltage, and temperature on UV photoresponse of ZnO nanorods

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Chinese Physics B 2015年第10期24卷 501-506页

作者：宗仙丽朱荣 State key laboratory of Precision Measurement Technology and instruments Department of Precision InstrumentTsinghua University

The ultraviolet（UV） photoresponses of ZnO nanorods directly grown on and between two micro Au-electrodes by using electric-field-assisted wet chemical method are measured comprehensively under different conditions, including ambient environment, applied bias voltage, gate voltage and temperature. Experimental results indicate that the photoresponses of the ZnO nanorods can be modulated by surface oxygen adsorptions, applied voltages, as well as temperatures. A model taking into account both surface adsorbed oxygen and electron-hole activities inside ZnO nanorods is proposed. The enhancement effect of the bias voltage on photoresponse is also analyzed. Experimental results shows that the UV response time（to 63%） of ZnO nanorods in air and at 59°C could be shortened from 34.8 s to 0.24 s with a bias of 4 V applied between anode and cathode.

关键词： ZnO nanorods UV photoresponse surface effect applied voltage effect