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Influence of modulation ratio on structure and properties of nanoscale ZrB_2/ZrAlN multilayered coatings

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Science China(Technological Sciences) 2010年第3期53卷 772-775页

作者： LI DeJun 1,KANG YuanBin 1,DONG Lei 1,DENG XiangYun 1,LIU Hao 2 &SUN XueLiang 2 1College of Physics and Electronic Information Science,Tianjin Normal university,Tianjin 300387,China 2 department of mechanical&materials engineering,university of western ontario,london on,canada 1. College of Physics and Electronic Information Science Tianjin Normal University Tianjin 300387 China2. Department of Mechanical & Materials Engineering University of Western Ontario London ON Canada

ZrB2/ZrAlN multilayered coatings with various modulation ratios(t ZrB2:t ZrAlN)and constant modulation periods were prepared by magnetron sputtering system at room ***,XRD,surface profiler and nano-indenter were employed to investigate the influences of tZ rB 2:tZrAlNon the microstructure and mechanical properties of the *** interfaces and nanoscale multilayered modulation were confirmed by *** multilayer with modulation period of 40 nm and ratio of 3:1 displayed the highest hardness(36.4 GPa)and critical fracture load(76.477 mN)with lower *** polycrystalline structure and multilayered modulate structure were directly responsible for the enhanced mechanical properties.

关键词： ZrB2/ZrAlN multilayered coating magnetron sputtering modulation ratio nanoscale

Kinetics of Zr(CrFe)_2 Precipitation in a Beta-quenched and Aged Zr-Cr-Fe Alloy

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Rare Metals 1992年第3期11卷 165-176页

作者： Sun Xi-chen and Derek O.Northwood engineering materials Group,department of mechanical engineering,university of Windsor,Windsor,ontario,canada N9B 3P4

A Zr-1.15wt% Cr-0.10wt% Fe alloy was beta-quenched from 1050℃ to produce a supersaturated α′-phase, and then heated for varying times at temperatures from 650℃ to 760℃ to precipitate Zr(CrFe)_2.A thermoelectric power(TEP)technique and transmission electron microscopy(TEM)were used to monitor this precipitation *** the Johnson-Mehl-Avrami equation,the TEP results and a line regression method,the activation energy for diffusion and the diffusion coefficient of chromium(and Fe)in α-Zr have been calculated over 650℃～760℃.The temperature dependence of the diffusion coefficient,D_(Cr/α)(cm^2/s)is described at 650℃～760℃ by the relationship *** coarsening of the Zr(CrFe)_2 particles shows a t^(1/2)dependence of mean particle size on aging time,*** a time dependence is typical of coarsening where atom transfer across the interface is rate-controlling.

关键词： Zirconium-base alloy Heat treatment Precipitation Kinetics

GAS-SOLIDS FLOW BEHAVIOR WITH A GAS VELOCITY CLOSE TO ZERO

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Particuology 2006年第Z1期 167-177页

作者： H. Zhang and J.-X. Zhu* department of Chemical engineering, university of western ontario, london, ontario, canada N6A 5B9, canada

In a 9.3 m high and 0.10 m i.d. gas-solids downflow fluidized bed (downer), the radial and axial distribu- tions of the local solids holdups and particle velocities along the downer column were measured with the superficial gas velocity set to zero. A unique gas-solids flow structure was found in the downer system with zero gas velocity, which is completely different from that under conditions with higher gas velocities, in terms of its radial and axial flow structures as well as its micro flow structure. The gas-solids flow pattern under zero gas velocity conditions, together with that under low gas velocity conditions, can be considered as a special regime which differs from that under higher gas velocity conditions. According to the hydrodynamic properties of the two regimes, they can be named the “dense annulus” regime for the flow pattern under zero or low gas velocity conditions and the “dense core” regime for that under higher gas ve- locity conditions.

关键词： downer reactor gas-solids cocurrent downflow fluidized bed hydrodynamics flow development particle velocity solids holdup solids flux flow regime

CRITERION　OF　STOCHASTIC　LAYER　NEAR　A　PLANAR　HOMOCLINIC　ORBIT　OF　NONLINEAR　DYNAMICAL　SYSTEM

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Journal of Hydrodynamics 1995年第2期7卷 35-50页

作者： Albert C. J. Luo(department of mechanical & Industrial engineering university of Manitoba. Winnipeg, Manitoba, R3T 2N2,canada) Univ of Manitoba Winnipeg Canada

A new analytic method is developed for nonlinear dynamical system, to investigate the mathematical structure and physical characteristics of the stochastic layer near a homoclinic or heteroclinic orbit. This method is based on the subharmonic resonant condition and an energy increment along the separatrix of the system. The critical conditions for the disappearance of stochastic layer are presented, which are associated with all control parameters of the system including initial conditions, excitation frequencies excitatiom amplitudes ***, using this method, we analyze two simple nonlinear dynamical systems, namely,Duffing-Holmes's equation and a forced planar pendulum. As their stochastic layers begin to disappear, their critical amplitudes are also obtained for the given excitation frequency and other chosen parameters. By means of these conditions, we carry out numerical simulations for the two simple models. Their stochastic layer will be shown using Poincare mapping section. Our theoretical results are subeequently shown to be in a good agreement with numerical simulations.

关键词： nonlinear dynamical system stochastic layer numerical simulation

Influence of nanometric CeO2 coating on high temperature oxidation of Cr

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Progress in Natural Science:materials International 2007年第5期17卷 601-606页

作者： Jin Huiming , Zhang Linnan and Liu Xiaojun (materials Research Center, department of mechanical engineering, Yangzhou university, Yangzhou 225009, China College of materials Science and engineering, North-East university, Shenyang 110014, China) [a]materials Research Center Department of Mechanical Engineering Yangzhou University Yangzhou China [b]College of materials Science and engineering North-East University Shenyang China

Isothermal and cyclic oxidation behavior of chromium and its superficially applied nanometric CeO2 samples were studied at 900℃in air. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and high resolution electronic microscopy (HREM) were used to examine the morphology and micro-structure of oxide films. It was found that ceria addition greatly improved the anti-oxidation ability of Cr both in isothermal and cyclic oxidizing experiments. Acoustic emission (AE) technique was used in situ to monitor the cracking and spalling of oxide films, and AE signals were analyzed in time-domain and number-domain according to the related oxide fracture model. Laser Raman spectrometer was also used to study the stress status of oxide films formed on Cr with and without ceria. The main reason for the improvement in anti-oxidation of chromium was that ceria greatly reduced the growing speed and grain size of Cr2O3. This fine-grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of compressive stress by means of creeping, and maintained the ridge character and relatively low internal stress level. Meanwhile, ceria application reduced the size and the number of interfacial defects, while remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.

关键词： oxidation stress CeO2 nanoparticle coating chromium.

Interfacial Microstructure and Properties of Ti(C, N)/Ni Bonded by Transient Liquid-phase Diffusion

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Journal of Wuhan university of Technology(materials Science) 2009年第3期24卷 432-439页

作者：周世权熊惟皓 School of mechanical Science and engineering Huazhong University of Science and Technology department of mechanical engineering University of Waterloo School of materials Science and engineering Huazhong University of Science and Technology

Effects of the main process parameters（temperature and time） on microstructure and properties of Ti（C, N）/Ni interface bonded by （Cu＋Nb） interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3Nb metallic compound and eutectic of Ni3Nb ＋ CuNiss, and finally transformed to （Ti, Nb）（C, N）＋Ni3Nb near Ti （C, N） and NiCuss ＋ Ni3Nb near Ni when diffusion bonding temperature was 1 523-1 573 K. It was clear that Cu was a constituent in the transient liquid phase （TLP） into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti （C, N） conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little （Ti, Nb）（C, N） solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3Nb accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53 mm/s^1/2.

关键词： vacuum diffusion bonding transient liquid phase (TLP) diffusion bonding interlayer activation energy

Advances in numerical methods for the solution of population balance equations for disperse phase systems

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Science China Chemistry 2009年第8期52卷 1063-1079页

作者： SU JunWei1,GU ZhaoLin2,3 & XU X.Yun41 department of mechanical engineering and Automation,School of mechanical engineering,Xi’an Jiaotong university,Xi’an 710049,China 2 Key Laboratory of Mechanics on Disaster and Environment in western China,Ministry of Education,Lanzhou 730000,China 3 department of Environmental Science and Technology,School of Human Settlements and Civil engineering,Xi’an Jiaotong university,Xi’an 710049,China 4 department of Chemical engineering,Imperial College london,london SW7 2AZ,UK 1. department of mechanical engineering and Automation School of Mechanical Engineering Xi’an Jiaotong University Xi’an 710049 China 2. Key Laboratory of Mechanics on Disaster and Environment in western China Ministry of Education Lanzhou 730000 China 3. department of Environmental Science and Technology School of Human Settlements and Civil Engineering Xi’an Jiaotong University Xi’an 710049 China 4. department of Chemical engineering Imperial College London London SW7 2AZ UK

Accurate prediction of the evolution of particle size distribution is critical to determining the dynamic flow structure of a disperse phase system.A population balance equation(PBE),a non-linear hyperbolic equation of the number density function,is usually employed to describe the micro-behavior(aggregation,breakage,growth,etc.) of a disperse phase and its effect on particle size *** solution is the only choice in most *** this paper,three different numerical methods(direct discretization methods,Monte Carlo methods,and moment methods) for the solution of a PBE are evaluated with regard to their ease of implementation,computational load and numerical *** attention is paid to the relatively new and superior moment methods including quadrature method of moments(QMOM),direct quadrature method of moments(DQMOM),modified quadrature method of moments(M-QMOM),adaptive direct quadrature method of moments(ADQMOM),fixed pivot quadrature method of moments(FPQMOM),moving particle ensemble method(MPEM) and local fixed pivot quadrature method of moments(LFPQMOM).The prospects of these methods are discussed in the final section,based on their individual merits and current state of development of the field.

关键词： population balance equation direct discretization method Monte Carlo method moment methods disperse phase system

Rolling Element Bearing Diagnostics by Combination of Envelope Analysis and Wavelet Transform

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Journal of university of Science and Technology Beijing 2001年第1期8卷 69-74页

作者： Ying Tang, Qiao Sun mechanical engineering School, university of Science and Technology Beijing, Beijing 100083, China department of mechanical engineering, university of Calgary Calgary Alberta T2N 1N4, canada Univ Sci & Technol Beijing Sch Mech Engn Beijing 100083 Peoples R China Univ Calgary Dept Mech Engn Calgary AB T2N 1N4 Canada

Rolling element-bearing diagnostics has been studied over the last thirty years, and envelope analysis is widely recognized as being the best approach for detection and diagnosis of rolling element bearing incipient failure. But one of the on-going difficulties with envelope technique is to determine the best frequency band to envelop. Here, wavelet transform technique is introduced into envelope analysis to solve the problem by capturing bearing defects-sensory scales (i.e. frequency bands). A modulated Gaussian function is chosen to be the analytical wavelet because it coincides well with bearing defect-induced vibration signal patterns. Vibration signals measured from railway bearing tests were studied by the proposed method. Cases of bearings with single and multiple defects on inner and outer race under different testing conditions are presented. Experimental results showed that the proposed method allowed a more accurate local description and separation of transient signal part, which were caused by impacts between defects and the mating surfaces in the bearing. The combination method provides an effective signal detection technique for rolling element-bearing diagnostics.

关键词： continuous wavelet transform envelope analysis rolling element bearing diagnostics

STUDY on THE OPTICAL FLAT PROFILE HIGH PRECISION MEASURING TECHNOLOGY IN THE METHOD OF LASER DATUM

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Chinese Journal of mechanical engineering 1999年第4期12卷 312-316页

作者： Liu Haijiang Wan De’an department of mechanical engineering,Tongji university 同济大学机械工程系上海 200092 同济大学机械工程系上海

The physical datum method that uses the laser beam as the physical datum is proposed.A high accuracy of the straight movement on the line above 0.01 μm/100 mm is achieved through applying the method of the closed loop feedback control that uses the laser beam as the *** measuring accuracy above 0.05 μm is obtained by applying the self making electric eddy displacement sensor to detect the geometric accuracy of the optical *** proves that the laser beam datum method can achieve the high accurcy of the straight movement and has the huge advantage.

关键词： Laser beam datum Optical flat Profile precision measurement