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Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

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science china(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2, CHEN ZhengHao3.& ZHANG XiaoZhong4,5 1 key laboratory of Beam Technology & materials Modification of the {3. of education, Institute of Low Energy Nuclear Physics, Beijing Normal university, Beijing 100875, china 2 Beijing Radiation Center, Beijing 100875, china 3.laboratory of Optical Physics, Institute of Physics, Chinese Academy of sciences, Beijing 100080, china 4 key laboratory of advanced materials of the ministry of education, department of materials science and engineering,{13., Beijing 100084, china 5 Beijing National Center for Electron Microscopy,{13., Beijing 100084, china 1. key laboratory of Beam Technology & materials Modification of the {3. of education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing 100875 China 2. Beijing Radiation Center Beijing 100875 China 3. laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China 4. key laboratory of advanced {3. of the ministry of education Department of Materials Science and Engineering Tsinghua University Beijing 100084 China 5. Beijing National Center for Electron Microscopy Tsinghua University Beijing 100084 China

The LaMn1-xTexO3.δ (x=0.1, 0.2, 0.3. were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3. ions are partly converted into Mn2+ and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2+, Mn3. and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3. is much larger or less than the sum of Mn2+ and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3. is close to the sum of Mn2+ and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

Probing the hydration of composite cement pastes containing fly ash and silica fume by proton NMR spin-lattice relaxation

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science china(Technological sciences) 2010年第6期53卷 1471-1476页

作者： SHE AnMing & YAO Wu key laboratory of advanced Civil {3. materials (Tongji university),ministry of education,Shanghai 200092,china 1. key laboratory of advanced Civil {3. materials (Tongji university) Ministry of Education Shanghai 200092 China

Proton NMR spin-lattice relaxation (T1) was used as a prober for observing the hydration process of composite cement pastes blending fly ash and silica fume during the early *** distribution at initial time,evolution curves and signals intensity of T1 were shown in this *** demonstrate that the T1 distribution curves at initial time exhibit two peaks,which are regarded as two different water phases in the *** evolution curves of T1 are in good agreement with the hydration process of composite pastes and could be roughly divided into four stages:initial period,dormant period,acceleration period and steady *** hydration mechanism for each stage was *** hydration of the composite cement pastes was retarded by the addition of fly ash and silica fume when compared to that of pure ***,the hydration degree of the cement in the blends was promoted.

关键词： NMR relaxation cement fly ash silica fume hydration

A Time-saving Method for Assessing the Corrosion Inhibitor Efficiency

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Journal of Wuhan university of Technology(materials science) 2010年第5期25卷 856-861页

作者：耿春雷翁端 key laboratory of advanced {3. Department of Materials Science and Engineering Tsinghua University

Corrosion inhibitor is one of the most important technologies to enhance the durability of steel reinforced concrete. A kind of time-saving method was developed to assess the inhibitor efficiency by using a 16 voltage electric field to accelerate the chloride ion diffusion in concrete and inducing corrosion. Both macrocell and microcell current measurements were used to confirm the corrosion initiation status of steel. The comprehensive efficiency of inhibitor shall be assessed in three aspects. The results clearly show the efficiency of different inhibitors, which indicate the reliability of this time-saving method.

关键词： inhibitors efficiency chloride ions diffusion steel reinforced concrete

Effects of different pack aluminizing fillers on the aluminide coatings of Ti-6Al-4V alloy and their high-temperature oxidation behaviors

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Rare Metals 2007年第S1期26卷 306-312页

作者： ZHOU Wei,ZHAO Yuguang,and MEI Xuelian key laboratory of Automobile materials of {3. of education,department of materials science and engineering,Jilin university,Changchun 13.025,china Jilin Univ Dept Mat Sci & Engn Key Lab Automobile Mat Minist Educ Changchun 130025 Peoples R China

The aluminide coating process of Ti-6Al-4V alloys with different fillers(100wt.% Al_2O_3.50wt% Y_2O_3.50wt.% Al_2O_3.and 100wt.% Y_2O_3. for improvement of the oxidation resistance were *** results show that the filler does not only participate in the aluminizing process,but also has much effect on the coating *** XRD analysis reveals that the aluminide coating with filler Al_2O_3.is predominant with TiAl_3.and TiAl phases;while the aluminide coatings with filler Y_2O_3.Al_2O_3.are predominant with Ti_3.l *** oxidation kinetics shows that different fillers affect greatly the oxidation resistance of aluminide coating,and the oxidation resistance of aluminized specimens with pack aluminizing filler Al_2O_3.are about 5-8 times than that of the aluminized specimens with other pack aluminizing fillers.

关键词： Ti-6Al-4V alloy aluminide coating fillers oxidation

Molecular dynamics simulations of non-Fourier heat conduction

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Progress in Natural science:materials International 2008年第8期18卷 999-1007页

作者： Qixin Liu, Peixue Jiang *, Heng Xiang key laboratory for Thermal science and Power {3. of ministry of education, department of Thermal {3., tsinghua university, Beijing 100084, china key laboratory for Thermal science and Power {3. of ministry of education Department of Thermal Engineering Tsinghua University Beijing 100084 China

Unsteady heat conduction is known to deviate significantly from Fourier’s law when the system time and length scales are within certain temporal and spatial windows of relaxation. Classical molecular dynamics simulations were used to investigate unsteady heat conduction in argon thin films with a sudden temperature increase or heat flux at one surface to study the non-Fourier heat conduction effects in argon thin films. The studies were conducted with both pure argon films and films with vacancy defects. The temperature profiles in the argon films showed the existence of mechanical waves when the thin film was suddenly heated and the wave nature of the heat propagation. The flux phase relaxation time, sq, and the temperature phase relaxation time, st, were calculated from the temporal variations of the energy flux and temperature distribution in the film. Comparisons of the MD temperature profiles with temperature profiles predicted by Fourier’s law show that Fourier’s law is not able to predict the temperature variations with time. Different film thicknesses were also studied to illustrate the variation of the time needed for the films to reach steady-state temperature profiles after a sudden temperature rise at one surface and to illustrate the finite speed of the energy waves.

关键词： Molecular dynamics simulation Non-Fourier heat conduction Argon thin film

Effects of Current Frequency on the Microstructure and Wear Resistance of Ceramic Coatings Embedded with SiC Nano-particles Produced by Micro-arc Oxidation on AZ91D Magnesium Alloy

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Journal of materials science & Technology 2010年第10期26卷 865-871页

作者： Yue Yang and Hua Wu key laboratory of advanced Structural {3.,ministry of education,Changchun university of Technology,Changchun 13.012,china [a] key laboratory of advanced Structural {3. ministry of education Changchun university of Technology Changchun 13.012 china

To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation （MAO） on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency （500 Hz,700 Hz,and 900 Hz） were produced during the MAO *** morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM）,field emission scanning electron microscopy （FESEM）,and X-ray diffraction （XRD）.The surface roughness of the coatings was characterized by confocal laser scanning microscopy （CLSM）.Simultaneously,the tribological properties of the composite coatings were evaluated by using a universal materials tester （UMT）.The results shows that the wear resistance of the ceramic coatings with SiC nano-particles was improved significantly compared to the ceramic coatings without SiC ***,the composite coating formed at current frequency 900 Hz showed the better wear resistance than the others.

关键词： Magnesium alloy Micro-arc oxidation SiC nano-particles Wear resistance

Development of New Type Mn-Series Bainitic Steels in china

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Journal of Iron and Steel Research International 2011年第S1期18卷 112-120页

作者： BAI Bing-zhe,GAO Gu-hui,ZHENG Yan-kang,YANG Zhi-gang (key laboratory of advanced {3. of ministry of education,department of Material science and engineering,tsinghua university,Beijing 100084,china) tsinghua Univ Dept Mat Sci & Engn Minist Educ Key Lab Adv Mat Beijing 100084 Peoples R China

The alloying design idea,strengthening-toughening mechanism,microstructure,mechanical performances,development and application in china of new type Mn-series bainitic steels are ***-series air-cooling bainitic steels including granular bainitic steels,FGBA /BG duplex steels,CFB/M duplex steels,medium carbon bainite/martensite steels,cast bainitic steels are *** invented idea mechanical performances,development and application of second generation of Mn-series bainitic steels,*** quenching Mn-series bainitic steels invented by the authors newly are *** water quenching Mn-series bainitic steels cover severe series steels containing ultra-low carbon,low-low carbon,medium-low carbon,and high-low carbon content etc,which can reduce the amount of alloying content,increase hardening capability and improve *** should be pointed out that the application of both air cooling and water quenching Mn-series bainitic steels are complementary and mutually reinforcing,and the new type Mn-series bainitic steels can meet the performance requirements of most steels used in engineering *** newest technologies of Mn-series bainitic steels in china are discussed in this *** is suggested that the significance of the development of the Mn-series bainitic steels can be summarized as:significantly reducing costs of both raw {3. and production;good combination of strength and toughness;excellent weldability;simple procedure;large savings in energy resources and reduced environmental pollution.

关键词： bainitic steels strengthening-toughening mechanism low cost,high performances air cooling bainitic steel water quenching bainitic steel

Chloride transference during electrochemical chloride extraction process

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science china(Technological sciences) 2010年第6期53卷 1466-1470页

作者： YAO Wu & ZHAO Zheng key laboratory of advanced Civil {3. materials (Tongji university),ministry of education of china,Shanghai 200092,china 1. key laboratory of advanced Civil {3. materials (Tongji university) Ministry of Education of China Shanghai 200092 China

Chemical titration method and lab-made chloride probes were jointly adopted to investigate the effects of water-to-cement (W/C) ratio and the impressed current density on chloride transport for cement-based materials during electrochemical chloride extraction (ECE) *** dissolution of bound chlorides and the effect of current density on dissolution were *** variations of chloride concentration at different depths and the chloride transference process were *** results show that W/C ratios adopted have slight influence on chloride extraction,while chloride extraction efficiency is mainly determined by the impressed current *** ECE process a portion of bound chloride ions dissolved and the amount of bound chlorides released is directly proportional to current density.

关键词： electrochemical chloride extraction transference bound chloride current density

Theoretical calculation and experimental study of influence of oxygen vacancy on the electronic structure and hemocompatibility of rutile TiO_2

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science china(Technological sciences) 2009年第9期52卷 2742-2748页

作者： LEI YiFeng,LENG YongXiang,YANG Ping,WAN GuoJiang & HUANG Nan key laboratory of advanced {3. Technology of ministry of education,department of {3. science and engineering,Southwest Jiaotong university,Chengdu 61003.,china key laboratory of advanced {3. Technology of ministry of education Department of Materials Science and Engineering Southwest Jiaotong University Chengdu 610031 China

In this work,the relationship between electronic structure and hemocompatibility of oxygen deficient rutile TiO2-x was studied by both theoretical calculation and experimental study. Based on the local density functional theory,first-principals method was performed to calculate the electronic structure of rutile TiO2 with different oxygen vacancy concentration. In the range of less than 10% of (or equal) physically realistic O vacancy concentration,the band gap of rutile TiO2 increases with increasing O vacancy concentration,leading the TiO2 changes from a p-type to an n-type semiconductor. The valance band of TiO2 is predominated by O 2p orbital,while the conduction band is occupied by Ti 3. orbital for different O vacancy concentration. The O vacancy results in the occupation of electrons at the bottom of conduction band of TiO2,and the donor density increases with increasing O vacancy concentration. When materials come in contact with blood,the n-type semiconductor feature of oxygen deficient TiO2-x with the bottom of conduction band occupied by electrons would prevent charge transfer from fibrinogen into the surface of materials,thus inhibiting the aggregation and activation of platelets,therefore improving the hemocompatibility of rutile TiO2-x.

关键词： rutile TiO2 oxygen vacancy electronic structure hemocompatibility