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Synthesis and characterization of nanocrystalline NaTaO_3

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Rare Metals 2006年第z2期25卷 69-72页

作者： CHEN Jingfang HU Long ZHAO Jianling TANG Chengchun LI Yangxian school of material Science and engineering Hebei University of Technology Tianjin 300130 China School of Material Science and Engineering Hebei University of Technology Tianjin 300130 China School of Material Science and Engineering Hebei University of Technology Tianjin 300130 China School of Material Science and Engineering Hebei University of Technology Tianjin 300130 China School of Material Science and Engineering Hebei University of Technology Tianjin 300130 China

Tantalum pentoxide reacts actively with concentrated NaOH solution under hydrothermal conditions at 180 ℃. In the reaction between NaOH solution and Ta2O5, the structure and composition of the tantalates depend on the reaction time, and the structure evolution results in a remarkable change in light absorption. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) diffused reflection spectrum were used to characterize various properties of the obtained solid products. At 180 ℃, the reaction proceeds rapidly. With the increase of time, the reflection peaks of unreacted Ta2O5 in the XRD patterns becomes weaker and weaker. Pure NaTaO3 is obtained after 60 min, which is well crystallized with a uniform cubic morphology.

关键词： NaTaO3 hydrothermal characterization crystal morphology

Numerical Simulation on Nugget Formation and Evolution in Spot Welding of Aluminum Alloy

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Transactions of Tianjin University 2011年第1期17卷 28-32页

作者：程方杰张建优胡绳荪单平 school of material Science and engineering Tianjin University Tianjin Key Lab of advanced Welding and Joining

With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical simulation.

关键词： aluminum alloy spot welding nugget oxide film contact resistance

Performance measurement and evaluation of an ionic liquid electrospray thruster

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Chinese Journal of Aeronautics 2023年第3期36卷 1-15页

作者： Chengjin HUANG Jianling LI Mu LI school of Power and Energy Northwestern Polytechnical UniversityXi’an 710072China Shenzhen Key Laboratory of Ultraintense Laser and advanced material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118China

As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising ***,performance measurement and evaluation of the Ionic Liquid Electrospray Thruster(ILET)is one of the most challenging issues for practical application,due to the difficulties in the development of a prototype and direct measurements of micro-thrust and small flow *** address this issue,a Modular Ionic Liquid Electrospray Thruster(MILET)prototype is constructed,and a diagnostic system for thrust and mass flow rate is specially developed based on an analytical balance *** the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as the propellant,a series of experiments is carried out on the MILET prototype under a wide operating condition through changing the applied voltage to control the *** different applied voltages,the thrust and the mass flow rate of the propellant are directly *** propulsive performance parameters of the thruster,such as thrust,specific impulse,thrust-to-power ratio,thruster efficiency,etc.,are comprehensively ***,a performance comparison is made between the MILET and other representative *** a relatively low applied voltage ranging from 1550 V to 2000 V,the MILET achieves a quasi-constant specific impulse of 1263 s with the averaged thrust-to-power ratio of 65.2μN/W and thruster efficiency of 40.7%.The performance of ILET is also compared with other typical electric *** results demonstrate that the ILET exhibits an excellent ability of minimalization with high specific impulse and thruster efficiency,which guarantees a great superiority in micro ***,the ways to further improve the performance of ILET are discussed,which further confirms the potential prospect of *** present result helps to advance the development and application of ILET.

关键词： Electrospray thruster Ionic liquids Performance measurement Performance estimation Micro-propulsion

Acoustic emission characterization methods of damage modes identification on carbon fiber twill weave laminate

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Science China(Technological Sciences) 2013年第9期56卷 2228-2237页

作者： HAN WenQin ZHOU JinYu school of material engineering Jiangsu University of Technology

In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of the large number of acoustic emission (AE) data obtained from the quasi-static tension test of carbon fiber twill weave composite. For this purpose, AE signals have been collected and post-processed for tension test, and are analyzed with three signal processing methods: Empirical Mode Decomposition (EMD), Hilbert-Huang Transform (HHT) and modified energy entropy algorithm. AE signals can be decomposed into a set of Intrinsic Mode Functions (IMF) components, results from this study reveal that the peak frequency of IMF components based on Fast Fourier Transform (FFT) corresponds to different damage mechanisms of composite. HHT of AE signals can clearly express the frequency distribution of IMF component in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition. The energy entropy based on EMD is introduced to act as a new relevant descriptor of composite damage modes in order to improve the characterization and the discrimination of the damage mechanisms.

关键词： carbon fiber twill weave composite acoustic emission EMD HHT energy entropy

Fabrication of flexible thin organic transistors by trace water assisted transfer method

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Chinese Chemical Letters 2018年第11期29卷 1681-1684页

作者： Junjie Kan Shuguang Wang Zhongwu Wang Shujing Guo Wenchong Wang Liqiang Li Institute of nanochemistry and nanobiology School of Environmental and Chemical EngineeringShanghai University advanced nano-materials Division Key Laboratory of Nano-Devices and ApplicationsSuzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of Sciences

The development of fabrication method for flexible thin organic electronic device is highly important for the flexible and wearable products. Herein, we develop a facile peel-off method to transfer organic thin film to various substrates. In this strategy, polyacrylonitrile （PAN） film can be easily peeled offwith trace water and further transferred to various substrates. Using PAN as supporting and dielectric layers, high performance flexible organic transistors are fabricated. Remarkably, the method uses only micro volume water as an assist to peel off PAN film, which reduces the risk of contamination by solvent and greatly contributes to the performance maintenance.

关键词： Transfer Flexible Thin film organic transistor Peel-off

Effects of Pressure during Preparation on the Grain Orientation of Ruddlesden-Popper Structured BaLa_2Ti_3O_(10) Ceramic

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Journal of materials Science & Technology 2014年第5期30卷 455-458页

作者： Xizhong Wang Lei Guo Hongbo Guo Guohui Ma Shengkai Gong school of materials Science and engineering Beihang University Beijing Key Laboratory for advanced Functional material and Thin Film Technology Beihang University

As potential thermal barrier coating （TBC） materials, Ruddlesden-Popper structured BaLn2Ti3010 （Ln = rare earth） compounds possess excellent phase stability and desirable thermo-physical properties as well as interesting anisotropic structure. In this paper, the effects of pressure during BaLa2Ti3010 （BLT） bulk preparation on the grain orientation were investigated. BLT grains exhibited lamellar structure, but the grain orientation depended strongly on the existence of pressure during bulk preparation. When pressure was applied, BLT grains preferentially grew along pressing direction, leading to formation of the texture parallel to pressing direction, but BLT grain orientation became relatively random when pressure was absent. However, in the small scale area, BLT grains grew preferentially along c-axis with independence on pressure during preparation. Pressure affected BLT grain orientation at the rapid growth stage according to the grain growth model of BLT.

关键词： Thermal barrier coating (TBC) Ceramics Pressure Grain growth

Synthesis and Properties of Water-soluble CdSe/ZnS nanocrystals with the Type-I Core/Shell Structure

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Journal of Wuhan University of Technology(materials Science) 2008年第5期23卷 600-605页

作者：王德平 school of material Science and engineering Tongji University

The synthesis of CdSe/ZnS core/shell nanocrystals though aqueous phase using the coprecipitation method was reported. The influences of factors such as injection methods and dosages of precursors, reaction duration of water-bathing and the initial CdSe：ZnS molar ratio were discussed. In comparison to the CdSe plain core nanocrystals, the CdSe/ZnS core/shell nanocrystals show much brighter photoluminescence demonstrated by the photoluminescence spectra. The epitaxial growth of the core/shell structures was verified by TEM and XRD.

关键词： nanocrystals CdSe/ZnS core/shell synthesis of aqueous phase fluorescence

Primary Solidification Phase and Lamellar Orientation in Directionally Solidified Ti-45Al-7Nb Alloy

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Chinese Journal of Aeronautics 2012年第3期25卷 489-492页

作者： YAN Jie ZHENG Lijing XIAO Zhixia YANG Lili ZHANG Hu Key Laboratory of Aerospace advanced materials and Performance of Ministry of Education school of material Science and engineering Beihang UniversityBeijing 100191China

Primary solidification phase and lamellar orientation are investigated in Ti-45Al-7Nb alloy at very high ratio of temperature gradient to growth rate （G/v） by a liquid-metal-cooled directionally solidified method. It shows that Ti-45Al-7Nb alloy solidifies with primary ct phase. Longitudinal （parallel to growth direction） microstructure shows that a dendrites in solid-liquid mushy zone are discontinuous and transverse mierostructure of a dendrites is worm-like feature. Growth direction of a phase is about 80° away from （0001）,a direction, and close to （1120） a direction. The corresponding lamellar orientation is aligned at the angle of about 10° to growth direction, which is consistent with a-dendrite growth direction according to Blackburn orientation relationship. Therefore, due to the altered growth direction of a phase, the lamellar orientation in Ti-45Al-7Nb alloy is controlled at the G/v ratio of 5 × 10^9 ***^-2.

关键词： metallic material titanium aluminides directional solidification crystal growth lamellar orientation

The Geometry-Induced Superhydrophobic Property of Carpet-like Zinc Films

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Chinese Physics Letters 2013年第10期30卷 203-206页

作者： LIANG Li-Xing DENG Yuan WANG Yao Beijing Key Laboratory for advanced Functional materials and Thin Film Technology School of Material Science and EngineeringBeihang UniversityBeijing 100191

Carpet-like zinc films with unique nanowires are fabricated by using a simple physical evaporation *** definite morphologies of the films endow the superhydrophobic material with a contact angle of about 157.9°,and by additional modification of CF_(3)(CF_(2))_(7)CH_(2)CH_(2)Si(OCH_(3))_(3)the water adhesive force could be tuned from 58.3μN to 14.6μ*** order to analyze the controllable adhesion of superhydrophobic Zn films,we study the microstructure and chemical compositions of the films by x-ray diffraction SEM,TEM,HRTEM and ***,a model based on the balance of micro-surface energy is proposed to illustrate the relationship of the geometry and wettability properties of the *** model provides new insights into how to design-oriented microchannels and micro-protuberance on material surfaces,which is of benefit for controlling their ability of caught-collection in air bubbles and water-pinning collection.

关键词： nanowires films microstructure