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Preparation of nanoparticles with an environment-friendly approach

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Journal of Environmental Sciences 2009年第6期21卷 727-730页

作者： YAO Kefu,PENG Zhen,FAN Xiaolin key laboratory of {2. {2. processing technology,Ministry of Education of China,Department of Mechanical Engineering,tsinghua university,beijing 100084,China. key laboratory of {2. {2. processing technology Ministry of Education of China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers. Despite that many methods have been developed for preparing nanomaterials, developing simple and environment-friendly ways for preparing nanomaterials is very attractive. Here a simple approach of synthesizing Fe3O4 nanoparticles by arc-discharge submerging in water was reported. The results showed that by this method Fe3O4 nanoparticles can be synthesized at large scale. The as-prepared Fe3O4 nanoparticles exhibited uniform spherical shape and their diameters varied with arc-discharging parameters. The experimental results showed that the size of the synthesized Fe3O4 nanoparticles can be controlled through adjusting the processing parameters. Since no vacuum system has been used, the synthesizing process is greatly simplified. In addition, only cheap deionized water and industrial iron bar are used and no pollution or harmful byproducts are found in the synthesis process. It indicated that the present approach is a simple, low-cost and environment-friendly one for preparing nanoparticles.

关键词： nanoparticles preparation approach Fe3O4

LATTICE BGK MODEL SIMULATION OF ASYMMETRIC FLOW INSIDE A CONTINUOUS SLAB CASTING MOLD

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Journal of Hydrodynamics 2006年第4期18卷 431-435页

作者： ZHANG Xiao-jun SHEN Hou-fa key laboratory for {2. {2. by materials processing technology Department of Mechanical Engineering Tsinghua University Beijing 100084 China

The incompressible lattice Bhatnager-Gross-Krook （BGK） model of computational fluid dynamics, from which the unsteady incompressible Navier-Stokes equations can be exactly derived with the limit of small Mach number, was established in continuous casting mold. An asymmetric flow pattern in the two-dimensional central plane of continuous slab casting mold was simulated, and the flow pattern is not stationary but changes over frequently if the Reynolds number is larger than 3000 or so. The results are found to be in excellent agreement with previous experimental results.

关键词： lattice Bhatnager-Gross-Krook (BGK) method incompressible Navier-Stokes equation continuous slab casting mold

Plastic deformation behavior of Fe_(40)Ni_(40)P_(14)B_6 bulk metallic glass investigated by nanoindentation

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International Journal of Minerals,Metallurgy and materials 2007年第S1期15卷 68-72页

作者： Changqing Zhang and Kefu Yao key laboratory for {2. {2. by materials processing technology, Department of Mechanical Engineering, tsinghua university, beijing 100084, China

Fe40Ni40P14B6 bulk metallic glass rods have been prepared by water quenching the fluxed alloy. The deformation behavior was investigated by nanoindentation tests and compressing tests. The average hardness and elastic modulus of the as-prepared Fe40Ni40P14B6 BMG (bulk metallic glass) measured by nanoindentation tests are 8.347 and 176.61 GPa respectively. The displace- ment-load curve shows “pop-in” characteristics which correspond to the loading rate bursts. Many shear bands around the indent were observed. The as-prepared Fe-based BMG exhibits a compressive plastic strain of 5.2.%, which is much larger than that of other Fe-based glassy alloys and most of other BMGs.

关键词： Fe40Ni40P14B6 bulk metallic glass nanoindentation tests compressing tests, "pop-in" characteristics, shear bands, com- pressive plastic strain

Numerical Simulation of Macrosegregation During Steel Ingot Solidification Using Continuum Model

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Journal of Shanghai Jiaotong university(Science) 2011年第2期16卷 145-148页

作者：王励石伟 key laboratory for {2. {2. processing technology Ministry of Education Department of Mechanical Engineering Tsinghua University

A continuum model is adopted to study the macrosegregation phenomena during solidification of large steel *** of temperature,melt velocity,and compositional concentration field during a 2. t steel ingot solidification are illustrated by using the finite volume *** results of temperature distribution are validated by *** influence of local permeability relates to the friction that the melt experienced in mushy region is *** is shown that the continuum model is able to predict the temperature field,and the variation of permeability obviously affects the melt flowing behavior and the final compositional distribution.

关键词： continuum model steel ingot macrosegregation convection permeability

Improvement of water resistance of long afterglow SrAl_2._4: Dy, Eu phosphor by coating with SiO_2.film

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Rare Metals 2002年第2期21卷 152-155页

作者： ZHANG Junying, CHEN Qingming, LIN Yuanhua, and ZHANG ZhongtaiState key laboratory of New Ceramics and Fine {2., Department of {2. Science and Engineering, tsinghua university,beijing 100084, China Department of materials Science and Engineering Tsinghua University State Key Laboratory of New Ceramics and Fine Processing 北京 100084

The long afterglow SrAl_2._4: Dy, Eu phosphor is liable tohydrolyze in water with deterioration of the lumin- escent ***_2._4: Dy, Eu phosphors were therefore heated at 60-90 deg. C inTEOS sol to form a surface gel and then heat-treated at 400 deg. C toobtain SiO_2.coated phosphors. Observation by ?Transmission ElectronMicroscope (TE) and X- ray photoelectron spectroscopy (XPS) showsthat a thin silica film forms on the surface of the phosphors. Thecoating procedure can be illustrated by a four-step process and thetransparent silica film can suppress the hydrolysis process, so thatthe luminescent properties of the phosphors are unimpaired or evenbetter.

关键词： phosphors coating luminescent materials SrAl_2._4

Effects of solidification parameters on microstructure and mechanical properties of continuous columnar-grained Cu-Al-Ni alloy

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Progress in Natural Science:materials International 2011年第5期21卷 368-374页

作者： Zhen WANG,Xue-feng LIU,Jian-xin XIE key laboratory for {2. {2. processing,Ministry of Education, university of Science and technology beijing,beijing 100083,China key laboratory for {2. {2. processing Ministry of Education University of Science and Technology Beijing Beijing 100083 China

Effects of melt temperature and casting speed on microstructure and mechanical properties of Cu-14%Al-3.8%Ni(mass fraction) alloy wires fabricated by continuous unidirectional solidification technology were *** was found that the average size of columnar grain in the alloy decreased and grain boundary turned clear and straight with increasing the casting speed at a given melt *** the melt temperature was up to 1 2.0℃,theβ1phase gradually transformed into lozenged and lanciformγ’1martensite,as well as parallel-sided plateβ’*** alloy with numerous coarsely dendriticγ2.hase has poor mechanical properties due to the difficulty of stress-induced martensitic *** the amount of theγ2.hase reduced and the coarse dendriteγ2.hase evolved into the fine square particles,the elongation of the alloy increased gradually with a decrease in tensile ***,the plasticity of the alloy could also be improved by increasing the amount and size of martensites,particularly the lanciformγ’*** the alloy was almost composed of coarse lanciformγ’1martensite,the tensile strength and elongation of the alloy could be up to 772.MPa and 18.9%,respectively,and the tensile curve consisted of three transformation platforms.

关键词： shape memory alloy continuous unidirectional solidification columnar grain martensitic transformation

Mold Filling Analysis in Vacuum Infusion Molding Process Based on a High-Permeable Medium

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Journal of materials Science & technology 2003年第5期19卷 467-471页

作者： Yingdan ZHU, Hua TAN and Jihui WANGState key laboratory of {2. {2. for materials Synthesis and processing, Wuhan university of {2., Wuhan 430070, China State key laboratory of {2. {2. for materials Synthesis and processing Wuhan University of Technology Wuhan 430070 China

The objective of this paper is to understand the flow mechanism through visualization experiments and discuss theinfluence of process parameters on mold filling process. A 2. leakage flow model is developed to simulat... 详细信息

关键词： Vacuum infusion molding process (VIMP) High-permeable medium Mold filling Simulation

Microstructures and characteristics of deep trap levels in ZnO varistors doped with Y_2._3

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Science China(Technological Sciences) 2009年第12期52卷 3668-3673页

作者： LIU Jun 1 ,HU Jun 1 ,HE JinLiang 1 ,LIN YuanHua 2.&LONG WangCheng 1 1State key laboratory of Power Systems,Department of Electrical Engineering,{2. {2.,beijing 100084,China 2.tate key laboratory of New Ceramics and Fine processing,Department of Material Science and Engineering,{2. {2., beijing 100084,China State key laboratory of Power Systems Department of Electrical Engineering Tsinghua University

In this paper discussions on ZnO based varistor ceramics doped with different ratios of Y2.3 are *** on the phase and microstructures of the samples indicates that an additional phase is detected in the samples doped with Y2.3,and the average grain size of the specimens decreases from about 9.2.m to 4.5μm,with an increase in the addition of Y2.3 from 0 mol%to 3 mol%.The corresponding varistor’s voltage gradient markedly increases from 462.V/mm to 2.40 V/mm,while the nonlinear coefficient decreases from 2..3 to 11.5,***,the characteristics of deep trap levels in these ZnO samples are investigated by measuring their dielectric *** trap energy level and capture cross section evaluated by relaxation peak of the Cole-Cole plot vary slightly as the addition of Y2.3 *** traps may be ascribed to the intrinsic defects of ZnO lattice.

关键词： ZnO varistors Y2.3 electrical properties deep trap levels

Analysis micro-mechanism of burrs formation in the case of nanometric cutting process using numerical simulation method

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Science China(Technological Sciences) 2007年第2期50卷 129-137页

作者： HAN XueSong & HU YuanZhong State key laboratory of Tribology,{2.,{2., China State key laboratory of Tribology Tsinghua University

Burrs (exit failure), being one of the important factors influencing the final precision of workpiece, have been widely studied. Today, with the development of manufacturing technology, the depth of cut falls into the range of nanometer or subnanometer, there may be some different disciplines dominating the burrs generation process. Molecular dynamics (MD) emthod, which is different from continuous mechanics, plays an important role in describing microscopic world. Take the example of single crystal copper, this paper carries out MD analysis micro-mechanism of burrs generation process. The results show that the burrs geometry depends on the type of workpiece (ductile or brittle). The depth of cut is decreased in the case of positive burrs generation process while the depth of cut is increased in case of negative burrs generation process. {2.words burr - molecular dynamics - micro-mechanism Supported by China Postdoctor Science Foundation (Grant No. 2.060390458)

关键词： burr molecular dynamics micro-mechanism