材料期刊网

INTERGRANULAR CORROSION AND PHOSPHOR SEGREGATION AT GRAIN BOUNDAR1FS OF NON-SENSITIZED SUPERPURE AUSTENITIC STAINLESS STEEL 00Cr25Ni22Mo2N

FANG Yaohua Nanjing Institute of Chemical Technology , Nanjing , ChinaXU Yuan ZHANG Wenqi University of Science and Technology Beijing , Beijing , China FANG Yaohua Associate Professor , Dept.of Applied Chemistry , Nanjing Institute of Chemical Technology , Nanjing 210009 , China

金属学报(英文版)

The corrosion behaviour and mechanism of superpure austenitic stainless steel 00Cr25Ni22Mo2N in urea processing environment was studied using metallography,SEM, TEM,SIMS and AES techniques.The results show that the gas extraction tube made of non-sensitized 00Cr25Ni22Mo2N steel suffered intergranular corrosion.Corrosive media penetrated not only into the tube wall through grain boundaries but also expanded from the boundary towards the interior of the grain.Neither depletion of Cr nor precipitates were found at the grain boundaries.However,P(and Si)was segregated at the grain boundaries to a great extent.Semiquantitative calculation indicates that the P content at the grain boundaries is about 25 wt-%,three orders of magnitude higher than the content within the grain.Sugges- tion is made that the potential difference between the grain and its boundary due to the segre- gation results in the observed intergranular corrosion.

关键词: superpure austenitic stainless steel , null , null

用DEPT135测定Resol的组成及微细结构参数

杨金瑞 , 余尚先 , 顾江楠

高分子材料科学与工程

通过对resol(羟甲基酚化合物和低分子量羟甲基酚树脂)DEPT135图谱的分析讨论,得到一系列计算resol微细结构参数的经验公式.根据DEPT135图谱可判断是否发生缩聚反应,根据经验公式可计算酚单体各个活性点参与反应百分率或酚羟基导入率、不同类型缩聚所占百分率及低分子量羟甲基酚树脂的平均核体数.

关键词: 羟甲基酚化合物 , 羟甲基酚树脂 , DEPT135 , 结构参数

Metal-Free Heterogeneous Catalysis for Sustainable Chemistry

Chemsuschem

The current established catalytic processes used in chemical industries use metals, in many cases precious metals, or metal oxides as catalysts. These are often energy-consuming and not highly selective, wasting resources and producing greenhouse gases. Metal-free heterogeneous catalysis using carbon or carbon nitride is an interesting alternative to some current industrialized chemical processes. Carbon and carbon nitride combine environmental acceptability with inexhaustible resources and allow a favorable management of energy with good thermal conductivity Owing to lower reaction temperatures and increased selectivity, these catalysts could be candidates for green chemistry with low emission and an efficient use of the chemical feedstock This Review highlights some recent promising activities and developments in heterogeneous catalysis using only carbon and carbon nitride as catalysts The state-of-the-art and future challenges of metal-free heterogeneous catalysis are also discussed.

关键词: carbon;catalyst;heterogeneous catalysis;selectivity;sustainable;chemistry;graphitic carbon nitride;modified activated carbon;nanofiber/graphite-felt composite;ordered mesoporous carbons;oxygen;reduction reaction;nitrogen-doped graphite;fuel cell cathode;onion-like carbon;oxidative dehydrogenation;hydrogen-production

SERS and Quantum Chemistry Studies of Adsorption of Thiourea and Ethylthiourea on Silver Electrode

Acta Physico-Chimica Sinica

Adsorption of thiourea (TU) and ethylthiourea( ETU) on roughened silver electrode was investigated using in situ surf. enhanced Raman spectroscopy(SERS) Using quantum chemistry and HSAB theories, the influences of electrode potential and the different substituent groups on SERS were disc i. TU is chemisorbed perpendicularly by Ag-S bond on silver at E = -0.3 V and adsorption of TU turns into a parallel orientation at E = -0.9 V. ETU is always chemisorbed at an angle from Ag. The adsorption of ETU is through and C=C and C=O groups at E = -0.3 V, and mainly through C=C at E = -0.9V.

关键词: Surface enhanced Raman spectroscopy;Adsorption;Quantum chemistry;Thiourea;Inhibitor

LOCAL CHEMISTRY AND THE COHESIVE STRENGTH OF GRAIN BOUNDARIES IN Ni_3Al

Shanthi Subramanian , David Muller , John Silcox and Stephen L.Sass (Department of Materials Science and Engineering and Department of Applied and Engineering Physics , Cornell University , Ithaca. NY 14853)

金属学报(英文版)

Local chemistry plays an important role in determining the cohesive strength of grain boundaries in Ni3Al. Doping with B increases the room temperature ductility and changes the fracture mode from intergranular to transgranular, while doping with Zr increases the ductility but leaves the fracture mode predominantly intergranular.Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive X-ray Spectroscopy (EDS) were used to probe the changes in local bonding (and hence the cohesive strength) produced by changes in local chemistry at large angle boundaries in Ni3Al.In addition , small angle tilt boundaries were studied to correlate structure with Nienrichment at the interface. B segregation to Ni-rich grain boundaries was shown to make the bonding similar to that of the bulk, thereby increasing their fracture resistance. Ni-enrichment does not occur in the presence of Zr segregation to grain boundaries. Ni-enrichment to antiphase boundaries (APB) in small angle tilt boundaries lowers the APB energy by reducing the number of high energy Al-Al interactions across the interface. Ni-enrichment to large angle boundaries is expected to produce a similar effect on energy.

关键词: : grain boundary chemistry , null , null , null

Effects of Applied Stresses on Martensite Transformation in AISI4340 Steel

ZHAO Hongzhuang , Seokjae LEE , Youngkook LEE , LIU Xianghua , WANG Guodong

钢铁研究学报(英文版)

This study aims at the experimental analysis of the transformation induced plasticity (TRIP) phenomenon. Experiments are conducted in which martensite is allowed to grow under the influence of a series of externally applied stresses. The magnitude of the applied stresses is less than 67% of the yield strength of austenite σγ(Ts). Since there is no obvious difference between the transformation plasticity under tension and the compression for the lower applied stresses, only compressive stresses are applied. The results confirm that the transformation plasticity is proportional to the applied stress if the latter does not exceed 67% of σγ(Ts). The TRIPstrain, the kinetics, and their dependence on the applied stresses are studied. The comparison between calculated results and experimental results shows that the model accurately describes the phenomenon.

关键词: applied stress;TRIP;martensite transformation;lowalloy steel

Influence of applied stress on the gamma ' directional coarsening in a single crystal superalloy

Materials & Design

It was found in a commercial single crystal superalloy CMSX-4 that preferential orientation of the gamma' rafting in dendrite core was not dependent on the sign of the applied stress sigma(A), but on the sign of the sum of the applied stress sigma(A) and a critical equivalent stress sigma(c). This critical equivalent stress sigma(c) caused by material inhomogeneity has been predicted previously; however it was first determined experimentally to be in the range 39.8-47.2 MPa in the present study. Moreover, it qualitatively demonstrated that the critical equivalent stress sigma(c) played a significant role in the creep behavior of superalloys at high temperature and low stress. (C) 2009 Elsevier Ltd. All rights reserved.

关键词: nickel-base superalloy;temperature creep-properties;uniaxial stress;alloy;parameters;morphology;apparent

Influences of externally applied potential on the properties of microscopic particles in nonlinear quantum systems

Physica B-Condensed Matter

When the Schrodinger equation in quantum mechanics is replaced by the nonlinear Schrodinger equation to describe microscopic particles in nonlinear quantum systems, it has been verified that the nature of the particles differs considerably from those in quantum mechanics, where they are localized and have also wave-corpuscle duality due to the nonlinear interactions. In this case the influences of externally applied potentials in the nonlinear Schrodinger equation on the natures of the microscopic particles have been studied by a perturbation theory. The studied results show that the external potential can change the states of the microscopic particles, such as the positions, amplitude and wave forms, but cannot change the wave-corpuscle duality. In the meanwhile, we find further that the relationship between the external potential and change of positions of the particle satisfies the rule of motion of classical particles. Thus we know from this study that the kinetic energy term, ((h) over bar (2)/2m)del(2)phi, in the nonlinear Schrodinger equation can only make the microscopic particles have a wave feature, but the nonlinear interaction b vertical bar phi vertical bar(2)phi determines its corpuscle feature, their combination makes the microscopic particles have a wave-corpuscle duality, and the potential V((r) over right arrow, t)phi changes only the positions, amplitude and wave form of the particles. Therefore the nonlinear interaction plays an important role in determination of the wave-corpuscle duality of microscopic particles in quantum theory. (C) 2010 Published by Elsevier B.V.

关键词: Microscopic particle;Schrodinger equation;External potential;wave-corpuscle duality;Nonlinear interaction;Quantum mechanics;schrodinger-equation

STRUCTURES OF γ Al_2O_3 AND AlON STUDIED BY ~(27)Al NMR AND QUANTUM CHEMISTRY CALCTLATIONS

X.M.Min , Y. Daiand C.W.Nan National Key Laboratory of Advanced Technology for Materials Synthesis and Processing , Wuhan University ofTechnology , Wuhan 430070 , China

金属学报(英文版)

Al NMRand quantum chemistry calculation have been used to study thestructureof γ Al2O3 and AlON. The NMRspectra arecharacterized bythree distinctresonance peaksat114 , 66 and 12 , corresponding to 〔AlN4〕,〔AlO4〕and 〔AlO6〕respectively. The uantum chemistrycalculationsshowqd thatthe models with vacancieslocated at octahedralsitein B block are morestablethanthose with vacancieslocated attetrahedralsitein A blockforboth of γ Al2 O3 and AlON. In AlON, nitrogen atoms preferentially replace oxygen atoms in〔AlO4〕tetrahedrons, and the model with 〔AlN4〕is morestablethan that with 〔AlO4 xNx〕(x= 1 ,2 and 3) and 〔AlO6 - yNy〕(y= 1 ,2 ,3 and 4) , which isin agreement with theexperimental analysisby NMR.

关键词: Al2 O3 and AlON , null , null , null

Applied Strain Field on Microstructure Optimization of Ti-Al-Nb Alloy Computer Simulated by Phase Field Approach

Wei GUO , Yaping ZONG , Gang WANG , Liang ZUO

材料科学技术（英）

The effects of applied tensile strain on the coherent α2 →O-phase transformation in Ti-Al-Nb alloys are explored by computer simulation using a phase-field method. The focus is on the influence of the applied strain direction on the microstructure and volume fraction of the O-phase precipitates. It is found that altering applied strain direction can modify microstructure of Ti-25Al-10~12Nb (at.~pct) alloy duringα2 →O-phase transformation effectively and full laminate microstructure in the Ti-25Al-10Nb (at. pct) alloy can be realized by an applied strain only along the direction 30° away from theα2 phase <10 0> in magnitude equivalent to the stress-free transformation strain. The simulation also shows that not only the magnitude of applied strain but also the applied strain direction influences the O-phase volume fraction and the effect of strain direction on the volume fraction is up to 25%.

关键词: Phase field simulation , null , null