材料期刊网

SLOW PROPAGATION OF FATIGUE CRACK NEAR THRESHOLD

DENG Rongying ZHOU Aihua JIANG Huaiqing LI Chunxiu Institute of Mechanics , Academia Sinica , Beijing , ChinaZHANG Liqing , SUN Yutian Beijing Institute of Engineering , Beijing , China [Originally published in ACTA METALL SIN(CHINESE EDN)25(3)1989 pp A219—A225 , Associate Profes sor , Institute of Mechanics , Academia Sinica , Beijing , China

金属学报(英文版)

The effect of pearlite interlamellar spacing(d)from 0.31 to 0.77 μm of T8 steel on fatigue crack propagation near threshold has been investigated at different stress ratios(R).The closure stress intensity factor(K_(cl)),the threshold value(ΔK_(th))and crack tip opening dis- placement range(ΔCOD)were measured.The results show that pearlite interlamellar spac- ing in this range has no effect on K_(cl),but has effect on the threshold value in low stress ratio. The threshold value is higher for materials with larger interlamellar spacing.No matter what the stress ratio is,during the propagation near threshold,the propagation rate will be the same,provieded the crack tip opening displacement range is the same. Metallurgical examinations were also carried out to show that the crack propagation path is sensitive to mierostructure.The crack always propagates along either boundary of pearlite colony or ferrite lamellar in pearlite.

关键词: pearlitic steel , null , null , null

SUBSTRUCTURE ALTERATION OF STAINLESS STEEL DURING CONSTANT STRAIN FATIGUE

WANG Jingyi Xi'an Institute of Technology , Xi'an , ChinaTAN Yuxu MA Zenghai Xi'an Jiaotong University , Xi'an , China Institute of Mealic Materials and Strength , Xi'an Jiaotong University , Xi'an 710049 , China

金属学报(英文版)

The alteration of substructure of an austenitic stainless steel has been investigated during con- stant strain fatigue.No plateau stage on the cyclic stress-strain curve was observed for the stainless steel in contrast with a monocrystalline pure copper specimen.This may relate to its low stacking fault energy.During strain fatigue under various amplitudes the substructure of dislocation in austenite alterates correspondingly.It revealed to associate with the appearance change of the cyclic stress-strain curve.

关键词: austenitic strainless steel , null , null

FLOTATION-SPECTROPHOTOMETRIC DETERMINATION OF TRACES OF PHOSPHORUS IN IRON, NICKEL, COBALT, COPPER AND ZINC USING MOLYBDATE AND MALACHITE GREEN

Fresenius Journal of Analytical Chemistry

A sensitive method for the determination of traces of P in Fe, Ni, Co, Cu and Zn is based on the formation of an ion-associate with molybdate and malachite green, whose absorbance is measured at 620 nm. The calibration curve is linear up to 0. 1 0-mu-g/ml; molar absorptivity is 2.7 x 10(5) l mol-1 cm-1. It was found that commonly coexisting elements did not interfere.

关键词:

Inhibition effect of AC-treated, mixed self-assembled film of phenylthiourea and 1-dodecanethiol on copper corrosion

Journal of the Electrochemical Society

A new method for preparing effective inhibition film on copper has been developed. Phenylthiourea was first adsorbed to a copper surface to form a self-assembled film. 1-Dodecanethiol was then self-assembled on the surface for subsequent modification. Finally, ac voltage was loaded on copper covered with the mixed film to further modify the film. After these procedures, an effective inhibition film was obtained as indicated by the low corrosion current density in polarization curves. High charge-transfer resistance in electrochemical impedance spectra reveals that the film hinders corrosion electrochemical reaction between the copper surface and NaCl solution. Film coverage on the copper surface is more than 99.0%, and inhibition efficiency is more than 97.2% in 0.5 mol dm(-3) NaCl solutions. The mixed films before and after ac treatment are stable in a wide region of potentials. X-ray photoelectron spectroscopy analysis reveals that the effect of ac treatment may associate with the formation of a new complex compound. (C) 2003 The Electrochemical Society.

关键词: impedance spectroscopy;gold;monolayers;protection;electrode;alkanethiols;behavior;thiourea;electrodissolution;mechanisms

Electrochemical investigation of dynamic interfacial processes at 1-octadecanethiol-modified copper electrodes in halide-containing solutions

Electrochimica Acta

1-Octadecanethiol (C18SH) monolayers were self-assembled on the fresh and active copper surface pretreated by nitric acid etching method. The surface properties of the alkanethiol-modified copper electrode in halide-containing solutions were characterized systematically by using several electrochemical methods, including polarization curves, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN). The results show that C18SH self-assembled monolayers (SAMs) onto copper provide a flexible method that can protect the underlying copper against corrosion. With the immersion time of SAMs-coated copper electrode in NaCl and HCl corrosive solutions increasing, a slow loss of corrosion protection ability of SAMs indicates dynamic processes occurring at the electrode/solution interface and in the monolayers, such as expansion of the defects and transport of corrosive ions through defects of SAMs. Electrochemical noise (EN) is employed to detect the alkanethiol-modified copper surfaces immersed in HCl solution. This observation suggests the pitting process associate with dynamic processes in the I-octadecanethiol layer. (C) 2003 Elsevier Ltd. All rights reserved.

关键词: self-assembled monolayers (SAMs);electrochemical impedance spectroscopy;(EIS);electrochemical noise (EN);defect;pitting;self-assembled monolayers;scanning-tunneling-microscopy;2-dimensional;polymer-films;hydrochloric-acid solution;n-alkanethiol monolayers;alkyl thiol monolayers;impedance spectroscopy;chemical modification;anodic-dissolution;schiff-bases

Theoretical investigations of the spin Hamiltonian parameters for the two trigonal Cr3+ centers in GASH

Journal of Magnetism and Magnetic Materials

The spin Hamiltonian (SH) parameters (zero-field splitting D. anisotropic g factors g(1), g(2), the hyperfine structure constants A(parallel to), A(perpendicular to), the nuclear quadrupole interaction constant Q' and the effective nuclear g value g(n)') for the two trigonal Cr-53(3+) centers I and II in guanidinium aluminum sulfate hexahydrate are theoretically investigated by using the perturbation formulas of the SH parameters for a 3d(3) ion in trigonal symmetry. According to the studies, the impurity-ligand bonding angles beta(i) in center I (or II) are found to be about 1degrees (or 0.9degrees) smaller than the corresponding metal-ligand bonding angles beta(i)(H) of the host Al3+ sites, and then the trigonal distortions for the impurity centers are also smaller than those in the hosts. The calculated SH parameters based oil the above local angles are in good agreement with the observed values of EPR and ENDOR measurements. Meanwhile, the negative D values for both centers are theoretically verified. Further, the quantitative expressions are established to associate the orbital coefficients a and h in the formula of A(parallel to) (or A(perpendicular to)) with the trigonal distortion of the studied impurity centers for the first time. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.

关键词: electron-nuclear double resonance (ENDOR);crystal fields and spin;Hamiltonians;impurity structures;Cr3+;guanidinium aluminum sulfate;hexahydrate (GASH);aluminum sulfate hexahydrate;electron-paramagnetic-resonance;hyperfine;interaction;ions;crystal;temperature;pressure;spectra;transition;chromium

Design of Slant-Form Tool in Precision Reuse of Digital Paper Display

Pai-Shan Pa

材料科学技术（英文）

A reuse fabrication module using micro electroetching as a precision machining process with a new design of a slant-form tool to remove the defective indium-tin-oxide (ITO) nanostructure from the optical poly-ethyleneterephthalate (PET) surfaces of digital paper display is presented in current studies. The low yield of ITO thin film deposition is an important factor in optoelectronic semiconductor production. The adopted precision reuse process requires only a short period of time to remove the ITO nanostructure easily and cleanly, which is based on technical and economical considerations and is highly efficient. In the current experiment, a large inclined angle of the cathode and a small end radius of the anode take less time for the same amount of ITO removal. A higher feed rate of the optical PET diaphragm combines with enough electric power to drive fast micro electroetching. A small rotational diameter of the anode accompanied by a small width of the cathode corresponds to a higher removal rate for the ITO nanostructure. A pulsed direct current can improve the effect of dreg discharge and is advantageous to couple this current with the fast feed rate of the workpiece. This improvement is associated with an increase in current rating. High rotational speed of the slant-form tool can improve the effect of dregs discharge and is advantageous to associate with the fast feed rate of the workpiece (optical PET diaphragm).

关键词: Reuse fabrication

Design of Slant-Form Tool in Precision Reuse of Digital Paper Display

Pai-Shan Pa

材料科学技术（英文）

A reuse fabrication module using micro electroetching as a precision machining process with a new design of a slant-form tool to remove the defective indium-tin-oxide (ITO) nanostructure from the optical poly-ethyleneterephthalate (PET) surfaces of digital paper display is presented in current studies. The low yield of ITO thin film deposition is an important factor in optoelectronic semiconductor production. The adopted precision reuse process requires only a short period of time to remove the ITO nanostructure easily and cleanly, which is based on technical and economical considerations and is highly efficient. In the current experiment, a large inclined angle of the cathode and a small end radius of the anode take less time for the same amount of ITO removal. A higher feed rate of the optical PET diaphragm combines with enough electric power to drive fast micro electroetching. A small rotational diameter of the anode accompanied by a small width of the cathode corresponds to a higher removal rate for the ITO nanostructure. A pulsed direct current can improve the effect of dreg discharge and is advantageous to couple this current with the fast feed rate of the workpiece. This improvement is associated with an increase in current rating. High rotational speed of the slant-form tool can improve the effect of dregs discharge and is advantageous to associate with the fast feed rate of the workpiece (optical PET diaphragm).

关键词: Reuse fabrication

Synthesis and properties of one-dimensional aluminum nitride nanostructures

Nano

This article presents a brief review of the recent research progresses achieved in the field of one-dimensional (1D) aluminum nitride (AlN) nanostructures. It mainly covers three aspects: The first one is to introduce the synthetic strategies for several classic 1D AlN nanostructures (such as nano fibers, nanobelts, nanorods, nanowires, nanotips, etc.) including template-confined reaction, arc discharge, catalyst-assisted growth, and vapor transport and related growth methods. The second is to elaborate some special physical properties, such as field emission and photoluminescence, which associate with the uniqueness of 1D AlN nanostructures. It is revealed that aligned AlN 1D nanostructures have low turn-on and threshold voltages, high emission current and small current fluctuation, and that the photoluminescence of AlN nanobelts are different from those of conventional AlN material. The third is to briefly illustrate the potential application of these 1D AlN nanostructures in composite materials. It is found that AlN nanowire is a good reinforcement for improving the mechanical and thermal properties of metal matrix composites, which can be expected to be utilized as packaging material with high strength and low thermal expansion. Finally, we summarize the major challenges in this field. Among them, a thorough understanding of the growth mechanism of 1D AlN nanostructures is the most important issue, and more precisely controlled growth is required to obtain tailored AlN nanostructures according to device applications.

关键词: one-dimensional nanostructures;AlN;synthesis;properties;al-aln composites;field-emission properties;carbon-nanotube-template;metal-matrix composites;si-doped aln;semiconductor nanowires;electron-affinity;thermal-expansion;vapor-deposition;low-temperature

北京城区夏季PM2.5中碳组分和二次水溶性无机离子浓度特征

安欣欣 , 张大伟 , 冯鹏 , 富佳明 , 景宽 , 王琴 , 魏强 , 刘保献

环境化学 doi:10.7524/j.issn.0254-6108.2016.04.2015090801

为探索北京城区大气细颗粒物浓度水平及其碳组分和二次水溶性无机离子的浓度特征,于2014年6月1日至7月15日在车公庄地区使用微量振荡天平(TEOM+FDMS)、EC/OC在线分析仪以及水溶性离子在线分析仪对PM2.5质量浓度及其主要化学组分(OC、EC、SO42-NO3-和NH4+)进行了实时监测.研究结果表明,北京市城区夏季PM2.5质量浓度平均值为69.0±47.9 μg· m-3,PM2.5中OC、EC、SO2-、NO3-和NH4+所占的比例分别为15.8％、2.4％、23.0％、15.7％和19.2％,SNA(SO42-、NO3-和NH4+)合计达到了PM2.5质量浓度的57.9％.研究各组分的日变化特征发现,OC和SO42-白天浓度变化较小,夜晚浓度稍高;NO3-和NH4+则随着光照和温度的增加面逐渐降低;EC呈现出夜晚浓度高白天浓度低的特点.研究各组分的相关性及比值发现,OC和EC的相关系数为0.62,OC/EC大于2.0,说明北京城区夏季存在着较为严重的二次污染;此外,NO3-/ SO42-平均比值为0.68,SOR和NOR的变化趋势基本一致,两者的平均值分别为0.55和0.14.通过分析北京市城区夏季不同浓度级别各组分的变化发现,随着PM2.5质量浓度的增加,OC和EC所占的比例不断降低,而SNA比例则不断升高,其中NO3-浓度水平的增加最为显著.

关键词: PM2.5 , 北京城区 , 碳组分 , 二次水溶性无机离子