TANG Hong
,
XIANYU Ze
,
HU Qianli
,
QIAO Guiwen
,
WANG Yongzhong
,
ZHUANG Yuzhi1 1) Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
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China 2) Northeastern University
,
Shenyang
,
China Manuscript Received 7 March 1995
金属学报(英文版)
In this study, high-Tc YBaCuO superconductors with high Jc value were prepared using MTG(melting-textured growth) method. These superconductors with high density have Jc value in excess of 1.6×104 A/cm2 (77K, zero field) determined by using a d.c. standard four terminal method with the criterion of lμV/cm. The XRD and fractograph analysis revealed that the texture existed in whole MTG-processed YBaCuO sample which consists of the layered and plate-like grains of matrix phase YBa2Cu3Oy unidirectionally aligned along its (103) planes. The experimental results indicated that the connectivity between superconducting grains has been improved greatly and the weak-link problem has been overcome essentially.
关键词:
: YBaCuO high-Tc superconductor
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null
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null
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null
Shihong XU Pengshou XU Mingrong JI Xianming LIU Maosheng MA Jingsheng ZHU Yuheng ZHANG Structure Research Laboratory
,
University of Science and Technology of China
,
Hefei
,
230026
,
ChinaZhenjia XU Institute of Semiconductor
,
Academia Sinica
,
Beijing
,
100083
,
China
材料科学技术（英文）
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxide growth have been investigated by means of thermal desorption,work function,Auger electron spectroscopy and photoemission electron spectroscopy.The experimental data showed that there was a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It was found that the presence of Na always caused an increase of the oxygen initial uptake whereas the promotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A new mechanism of Na-promoted Si oxide growth is suggested in this paper.
关键词:
adsorption
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null
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null
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null
Nabil S. Youssef
,
K.H.Hegab
材料科学技术（英文）
Some transition metal chelates of two ligands L1 and L2 were prepared and characterized by elemental analysis. The IR and 1H NMR spectra of several chelates of two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 were coordinated either in the enol or the keto form. IR spetra also showed that Fe(III)-, Ni(II)-, Mn(II)-, VO(II)-L1 and Cu(II)-L2 chelates behaved in a bidentate manner, in contrast with the two (1:1) M:L cobalt chelates with the two ligands are tridentate. TG analysis indicated the presence of three to twelve water molecules of hydration eliminated on heating up to 150°C and one or two coordinated water molecules removed at 150-180°C. The octahedral structure is proposed for all the chelates, except Cu(II)-L2 and Ni(II)-L1 chelates which have square planar geometry, based on their electronic spectra.
关键词:
Chinese Journal of Organic Chemistry
2,5-Dihydrazino-1,3,4-thiadiazole was prepared by 2,5-dimecapto-1,3,4-thiadiazole and hydrazine, and then the six novel different 2,5-bis(benzylidenehydrazino)-1,3,4-thiadiazole compounds were obtained by a condensation reaction of 2,5-dihydrazino-1,3,4-thiadiazole with substituted benzaldehyde and structurally confirmed by elemental analysis, IR, H-1 NMR and mass spectra. The result indicates that the six 2,5-bis(benzylidenehydrazino)-1,3,4-thiadiazole compounds are of definite inhibition against silver surface in corrosion jet fuel.
关键词:
2,5-dimercapto-1,3,4-thiadiazole;hydrazine;benzaldehyde;aldehyde-hydrazone;synthesis;anti-corrosion;derivatives
TAO Peng
,
ZHANG Chi
,
YANG Zhi-gang
,
et al
钢铁研究学报(英文版)
Transformation and coarsening of carbides in 2.25Cr-1Mo steel weld metal during tempering at 700 oC for different time intervals ranging from 1 to 150 h has been examined by transmission electron microscopy and scanning electron microscopy. M3C carbides were observed in the as-welded specimens and when tempered the precipitates were mainly composed of M3C, M7C3 and M23C6 carbides. A sequence for corresponding carbide transformation during tempering with initial precipitation of M3C and followed by M7C3 and M23C6 has been proposed. The precipitation of M7C3 with higher Cr content is the main factor contributing to the decrease of coarsening rate of precipitates after prolonged tempering. The decrease of hardness in the tempered specimens agreed well with the prediction of the weakening of precipitation strengthening due to the coarsening of carbides.
关键词:
weld metal;carbide;tempering;coarsening
Journal of Physical Chemistry C
We study the chemical nature of the bonding of an oxide layer to the parent metal. In order to disentangle chemical effects from strain/misfit, the Ti(10 (1) over bar0)/TiO2(100) interface has been chosen. We use the density functional pseudopotential method which gives good agreement with experiment for known properties of bulk and surface Ti and TiO2. Two geometries, a film-like model (with free surface in the structure) and a bulk-like model (with no free surface in the structure), are used to simulate the interface, in each case with different terminations of Ti and TiO2. For the single-oxygen interfaces, the interface energies obtained using these two models agree with each other; however, for the double-oxygen ones, the relative stability is quite different. The disturbance to the electronic structure is confined within a few atomic layers of the interface. The interfacial bonding is mainly ionic, and surprisingly, there is more charge transfer from Ti to 0 in the interface than in the bulk. In consequence, the Ti/TiO2 interface has stronger binding than the bulk of either material. This helps to explain why the oxide forms a stable, protective layer on Ti and Ti alloys.
关键词:
total-energy calculations;wave basis-set;titanium-dioxide;thermal-oxidation;100 surface;rutile;corrosion;films;microscopy;interfaces
Yongtao Zhao Junhui Dong Yonglin Ma Liping Zhao Xiaobing Pei
材料科学技术（英文）
The purpose of this study is to discuss the microstructure and properties variation of the weld metal in the dissimilar stainless steels during the argon tungsten-arc welding process. Because of the existence of different materials and chemistry variation within welds, properties, such as tensile and fracture properties and so on, are expected to show spatial variation. In the study, microstructures were observed by optical and electron microscopy. Good appearance and uniform structure and typical dendrite structure were observed in welding joint. The micro-hardness tester and electronic universal stretcher were used to measure the mechanical properties of the weldments and base metals. The heat affected zone (HAZ) near 1Cr13 hardness is up to peak value of 1150 HV, the strength of weldments is nearly same as austenite stainless steel. In addition,
through seawater immersion test, polarization curves and AC impedance spectroscopy of the weldments and base metals are obtained. It was found that corrosion resistance at welding joint lies between 1C13 and 1Cr18Ni9Ti.
关键词:
1Cr13
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1Cr18Ni9Ti
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welding joint
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mechanical and galvano－chemistry
MA Zongyi YAO Zhongkai Harbin Institute of Technology
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Harbin
,
China
金属学报(英文版)
The SiC_w/Al composite prepared by squeeze casting has a combination of superior room temperature specific strength and modulus together with excellent thermal properties.The extrusion can make an improvement on the strength and ductility of the composite from 582 MPa as squeeze casted up to 639 MPa,and on the transformation from isotropic to the anisotropic structure.This seems to be explained by the orientation of whiskers and the densification of dislocations in matrix.TEM observation indicates that the stacking fault is the usual planar defect on the SiC_w surface. composite;;SiC whisker;;Al alloy;;microstructure
关键词:
composite
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null
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null
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null
Q. Gao
,
Y.X. Zhao and L.X. Cai (Institute of Applied Mechanics
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Southwest Jiaotong University
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Chengdu 610031
,
China)
金属学报(英文版)
Based on the test results obtained from the single-step test and the incremental-step test at room temperature and 240℃, a probabilistic assessment of temperature effects on the cyclic stress-strum response and the fatigue life of 1Cr18Ni9Ti steel weld metal is performed. In orber to assess the temperature effect on cyclic stress amplitude where there is a scatter of the material cyclic constitution, a probabilistic assessment approach on the basis of probabilistic modified Ramberg-Osgood relations is introduced.The investigation shows that the cyclic stress amplitude and the scatter of cyclic stress amplitude data are decreased at 240℃. Similarly, from the consideration of the fatigue life scatter a probabilistic assessment of temperature effect on the fatigue life is suggested on the basis of probabilistic Langer S-N relations. The investigation shows that the crack initiation life is increased and the scatter of crack initiation life data is decreased at 240℃.
关键词:
1Cr_(18)Ni_9Ti stainless steel
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null
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null
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null
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null
