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Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

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 ministry 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, tsinghua university, beijing 100084, china 5 beijing National Center for Electron Microscopy, tsinghua university, beijing 100084, china key laboratory of Beam Technology & materials Modification of the ministry of education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing China key laboratory of advanced materials of the ministry of education Department of Materials Science and Engineering Tsinghua University Beijing China beijing National Center for Electron Microscopy Tsinghua University Beijing 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

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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 advanced materials Processing Technology,ministry of education of china,department of Mechanical engineering,tsinghua university,beijing 100084,china. key laboratory of advanced materials 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

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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 materials 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

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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 engineering of ministry of education, department of Thermal engineering, tsinghua university, beijing 100084, china key laboratory for Thermal science and Power engineering 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

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Thermodynamic Functions and Phase Transformation of Metal Nanocrystals

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Journal of materials science & Technology 2005年第5期21卷 705-709页

作者： Jinping GAO, Xiaoyan SONG , Jiuxing ZHANG, keyong YANG and Xuemei LIUCollege of materials science and engineering, the key laboratory of advanced Functional materials of the education ministry,beijing university of Technology, beijing 100022, china key laboratory of advanced Functional materials College of Materials Science and Engineering Beijing University of Technology Beijing 100022 China

A model to calculate the thermodynamic functions of the pure metal nanocrystals has been developed, with the consideration of the effects of both the interfaces and the crystal in the nano-grain interior. As an example, the enthalpy, entropy and Gibbs free energy, as functions of the excess free volume at interfaces, temperature and grain size, are calculated for the Co nanocrystals. Furthermore, the characteristics of β-Co→α-Co phase transformation are studied, and the transformation temperatures at different levels of grain size, as well as the critical grain sizes at different temperatures, are predicted. The calculation results show that, the nano-grained β-Co （fcc） is thermodynamically stable at temperatures much lower than that for the conventional coarse-grained materials, and may also stably exist at room temperature when the grain size is reduced to be small enough. The present model is verified by comparisons between the experimental findings and the theoretical predictions.

关键词： Thermodynamic function Nanocrystal Phase transformation

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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 materials 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 materials 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

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CO_2 Mitigation in Coal Gasification Cogeneration Systems with Integration of the Shift Reaction, CO_2 Absorption and Methanol Production

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Journal of Thermal science 2004年第3期13卷 193-198页

作者： Yuanyuan DUAN Jin ZHANG key laboratory of Thermal science and Power engineering, department of Thermal engineering, tsinghua university, beijing 100084, china key laboratory of Thermal science and Power engineering Department of Thermal Engineering Tsinghua University Beijing China

Cogeneration of electricity and liquid fuel can achieve higher efficiencies than electricity generation alone in Integrated Gasification Combined Cycle (IGCC), and cogeneration systems are also expected to mitigate CO2 emissions. A proposed methanol-electricity cogeneration system was analyzed in this paper using exergy method to evaluate the specified system. A simple cogeneration scheme and a complicated scheme including the shift reaction and CO2 removal were compared. The results show that the complicated scheme consumes more energy, but has a higher methanol synthesis ratio with partial capture of *** those methanol and electricity cogeneration systems, the CO2 mitigation is not merely an additional process that consumes energy and reduces the overall efficiency, but is integrated into the methanol production.

关键词： cogeneration system methanol synthesis CO2 mitigation exergy analysis

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Improvement of water resistance of long afterglow SrAl_2O_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 Processing, department of materials 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_2O_4: Dy, Eu phosphor is liable tohydrolyze in water with deterioration of the lumin- escent ***_2O_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_2O_4

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Investigation of heavy metal partitioning influenced by flue gas moisture and chlorine content during waste incineration

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Journal of Environmental sciences 2010年第5期22卷 760-768页

作者： Qinghai Li,Aihong Meng,Jinyan Jia,Yanguo Zhang department of Thermal engineering,key laboratory for Thermal science and Power engineering of the ministry of education of china,tsinghua university,beijing 100084,china. department of Thermal engineering Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education of China Tsinghua University

The impact of moisture on the partitioning of the heavy metals including Pb,Zn,Cu and Cd in municipal solid waste （MSW） was studied in a laboratory tubular furnace.A thermodynamic investigation using CHEMKIN software was performed to compare the experimental *** waste,representative of typical MSW with and without chlorine compounds,was burned at the background temperature of 700 and 950°C,*** the absence of chlorine,the moisture content has no evident effect on the volatility of Pb,Zn and Cu at either 700 or 950°C,however,as flue gas moisture increasing the Cd distribution in the bottom ash increased at 700°C and reduced at 950°C,*** the presence of chlorine,the flue gas moisture reduced the volatility of Pb,Zn and Cu due to the transformation of the more volatile metal chlorides into less volatile metal oxides,and the reduction became significant as chlorine content *** Cd,the chlorine promotes its volatility through the formation of more volatile CdCl *** a result,the increased moisture content increases the Pb,Zn,Cu and Cd concentrations in the bottom ash,which limits the utilization of the bottom ash as a construction ***,in order to accumulate heavy metals into the fly ash,MSW should be dried before incineration.

关键词： heavy metals partitioning moisture chlorine municipal solid waste incineration

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Effects of surface modification on isothermal oxidation behavior of HVOF-sprayed NiCrA1Y coatings

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Progress in Natural science:materials International 2011年第2期21卷 173-179页

作者： Li-yong NI,Zi-long WU,Chun-gen ZHOU key laboratory of Aerospace materials and Performance(ministry of education), department of materials science and engineering,Beihang university,beijing 100191,china key laboratory of Aerospace materials and Performance (ministry of education) Department of Materials Science and Engineering Beihang University

NiCrAlY coatings were deposited on Ni-based superalloy by high-velocity oxygen-fuel spraying(HVOF).Surface modification by means of grit-blasted,shot-peened and ground methods was used in order to study the effect of surface conditions on the isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings at 1 050℃.The results showed that surface modification had an obvious effect on the isothermal oxidation behavior of the *** was a large decrease in growth rate compared with the as-sprayed *** scale formed on the grit-blasted and shot-peened coatings was a mixture of Al2O3and NiCr2O4,while the oxide formed on the ground coating was composed mainly of *** surface modification,the content of NiCr2O4spinels decreased compared with the as-sprayed coating.

关键词： NiCrAlY HVOF isothermal oxidation thermal barrier coating

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