F.F.Hammad
,
M.Sh.Khalil
,
A. H. Salama
材料科学技术（英文）
The electrical conductivity of pure CaTiO3 and that containing 0.5 similar to5.0 mole fraction CuO as dopant were measured in the temperature range 291 similar to 773 K. The conductivity values varied as a function of temperature and dopant concentration. The activation energy in the lower temperature range depended on the impurity content while in the high temperature range it indicated a value of energy gap width. The infrared absorption spectra in the range of 100 similar to 4000 cm(-1) revealed the presence of two main bands at 340 and 570 cm(-1) which were assigned to TiO6 octahedral normal mode. Bands in the range of 106 similar to 270 cm(-1) were due to the vibration of anion TiO3-2. Some bands were observed at higher values due to the presence of lattice imperfections. There was a slight shift in band position with increasing dopant concentration which favors the formation of orthorhombic modification.
关键词:
Acta Chimica Sinica
Passive film formed on 304 stainless steel in 2.5 mol/L H2SO4 solution by using alternating voltage (A. V.) passivation have been investigated by measuring capacitance and photoelectrochemical parameters. The investigation of the effect of measure frequency on the slope of Mott-Schottky curve has been carried out. The photoelectrochemical measurements were consistent with the capacitance measurement. Analysis of the experimental results showed that the passive film formed 304 stainless steel by using A. V. passivation exhibits semiconducting properties. Using the simple model of semiconductor rather than the multi-donor level model can explain satisfactorily the semiconducting behavior of the film formed on 304 stainless steel by using A.V. passivation.
关键词:
A. V. passivation;passive film;semiconducting properties;stainless;steel;model;electrodes
Fatigue & Fracture of Engineering Materials & Structures
Fatigue data for welded joints subjected to an explosion treatment (ET) were obtained using rotary bending fatigue specimens. The fatigue fracture surfaces were observed by SEM and the dislocation morphologies by TEM. Mechanical properties have been quantitively studied by considering elastic and plastic shock wave characteristics. The test results indicate that the fatigue strength of welded joints subjected to ET is apparently improved due to the action of elastic or plastic stress waves while the ductility of the welded joints, i.e., reduction in area, is greatly increased.
关键词:
Materials Characterization
Dendritic coarsening of gamma' was investigated in a directionally solidified Ni-base superalloy during exposure at 1173 K for 24,000 h. Chemical homogeneity along different directions and residual internal strain in the experimental superalloy were measured by electronic probe microanalysis (EPMA) and electron back-scattered diffraction (EBSD) technique. It was indicated that the gradient of element distribution was anisotropic and the inner strain between dendrite core and interdendritic regions was different even after 24,000 h of exposure at 1173 K, which influenced the kinetics for the dendrite coarsening of gamma' phase. (C) 2010 Elsevier Inc. All rights reserved
关键词:
Superalloy;Coarsening;Exposure;Segregation;ni-base superalloy;evolution;field
王琴萍
,
吕殿祯
,
孙雪丽
应用化学
doi:10.3969/j.issn.1000-0518.2003.02.011
在恒定溶液总离子强度I＝1.00 mol/kg,改变甘油在混合溶剂中的质量分数为5、15和20的条件下,测定了无液体接界电池(A)和电池(B)的电动势.Pt,H2 (105 Pa)│HCl(c),C3H8O3(w),H2O(1-w)│AgCl-Ag(A)Pt,H2 (105 Pa)│HCl(cA),NaCl(cB),C3H8O3(w),H2O(1-w)│AgCl-Ag(B)根据测得电池 (A)的电动势,确定混合溶剂中Ag-AgCl电极的标准电极电势,讨论了HCl 的迁移性质. 利用测得电池(B)的电动势,计算了混合溶液中HCl 的活度系数γA. 结果表明, 在溶液中总离子强度保持恒定为I＝1.000 mol/kg时,HCl的活度系数服从Harned规则. 在溶液组成恒定时,log γA对热力学温度的倒数1/T作图,是一条直线. 进一步讨论了混合物中HCl的相对偏摩尔焓和介质效应.
关键词:
活度系数
,
电动势
,
电极电势
,
HCl
,
无液接电池
Yan NIU
,
Weitao WU and Chaoliu ZENG (State Key Lab. for Corrosion and Protection
,
Institute of Corrosion and Protection of Metals
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)F. Gesmundo and F. Viani (Instituto di Chimica
,
Facolta di Ingegneria
,
Un
材料科学技术（英文）
The corrosion of an Fe-based alloy containing 15 wt pct Y in H2-H2S mixtures under 10-3 Pa S2 was studied at 600~800℃ in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneflcial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus,Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition. but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12~17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe
关键词:
FANG Zheng CHEN Xinmin(H.M.Chen) Central South University of Technology
,
Changsha
,
China FANG Zheng
,
Associate Professor
,
Department of Chemistry
,
Central South University of Technology
,
Changsha
,
China
金属学报(英文版)
By taking the effect of oxygen contents into account,a new set of formulae which represents the oxygen potentials of H_2O-H_2 and H_2O-H_2-inerts gas mixtures has been derived.Classi- cal representation is only a particular case of it.Some of the variables affecting equilibrium atmosphere when trace oxygen is present and optimum preparation of the gas mixtures to min- imize errors have been discussed.The reliability of some of previous equilibrium experiments under the oxygen potentials controlled by H_2O-H_2 or H_2O-H_2-inerts gas mixtures has also been criticized.
关键词:
gas equilibration method
,
null
,
null
,
null
材料科学技术（英文）
The corrosion of an Fe-based alloy containing 15 wt pet Y in H-2-H2S mixtures under 10(-3) Pa S-2 was studied at 600 similar to 800 degrees C in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneficial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus, Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition, but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12 similar to 17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe.
关键词:
high-temperature sulfidation;most-reactive component;ni-nb alloys;h2-h2s mixtures;behavior;600-degrees-c-800-degrees-c;oxidation
Applied Physics Letters
ZnCoO:H nanocrystals are weak ferromagnetic at room temperature with a small coercivity and a small remanence, whereas ZnCoO nanocrystals are paramagnetic. The thermal irreversibility of zero-field cooling and field cooling magnetizations of ZnCoO:H nanocrystals corresponds to the existence of superparamagnetism due to the nanosize effect. X-ray photoelectron spectra show the incorporation of Co(2+) ions inside the ZnO lattice without changing the wurtzite structure. Our data suggest that hydrogen can induce ferromagnetism in ZnCoO and that ferromagnetic ZnCoO:H crystals with small particle size can show the superparamagnetism. (C) 2008 American Institute of Physics.
关键词:
magnetic semiconductors;zno;hydrogen;cobalt
