S.M.Morsy (Metallurgy Dept. Nuclear Research Center
,
Atomic Energy Authority
,
Cairo
,
Egypt) I.Z.Selim (Physical Chemistry Dept.
,
National Research Center
,
Dokki
,
Cairo
,
Egypt)S. H. Tantawi (Building Research Institute
,
Dokki
,
Cairo
,
Egypt)
材料科学技术（英文）
Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current method and potentiostatic polarization technique. The results of corrosion behaviour of the steel in both 5%NaCl and 5%MgSO4 show that each electrochemical technique provides some information about the condition of the steel bar or the corrosivity of the environment being evaluated, yet none provides a complete data regarding the corrosion resistance of reinforcing steel in aggressive media
关键词:
Zhenya Zhang
材料科学技术（英文）
This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy (RS P/M) processing system (S-RS P/M), which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 μm in width. TEM (transmission electron microscopy) observations illustrated nano-size magnesia particles (10{30 nm) constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZK60 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coe±cient of thermal expansion (CTE) mismatch because of the approximately same average grain size.
关键词:
Microstructure
Journal of Physics and Chemistry of Solids
The tetragonal distortion for the tetragonal V2+-V-M center in KBr:V2+ crystal is estimated by analyzing its EPR data from two theoretical models, one is the two spin-orbit (S.O.) parameter model where the contributions to EPR parameters from both the S.O. coupling of the central metal ion and that of the ligands are considered and another is the conventional one-S.O.-parameter model where only the contribution from the S.O. coupling of the central metal ion is included. The result from the two-S.O.-parameter model is more than ten times that of the one-S.O.-parameter model. The reasonableness of the former is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.
关键词:
inorganic compounds;crystal fields;defects;electron paramagnetic;resonance (EPR);epr parameters;transition;ions
Acta Chimica Sinica
The molal enthalpies of solution of VOSO(4)center dot 2.76H(2)O(s) with various molalities in water and in aqueous sulfuric acid (0.5 mol.kg(-1)) Delta(s)H(m), were measured by a solution-reaction isoperibol calorimeter at 298.15 K. The value of -Delta(s)H(m) in aqueous sulfuric acid was lower than that in water, which shows that energy state of VOSO(4) in aqueous H(2)SO(4) was higher than that in pure water. An improved Archer's method was put forward in terms of ionic association equilibrium of VOSO(4) and second dissociation equilibrium of H(2)SO(4). Using the improved method, the standard molal enthalpies of solution Delta(s)H(m)(circle minus) = 29.18 kJ.mol(-1) in pure water and Delta(s)H(m)(circle minus) = -25.79 kJ.mol(-1) in aqueous sulfuric acid were obtained, respectively. According to calculation, the molality of VO(2+) was larger in VOSO(4)-H(2)SO(4) mixed solution than that in water.
关键词:
vanadium redox flow battery;enthalpy of solution;vanadyl sulfate;sulfuric acid;vanadyl sulfate;sulfuric-acid;redox;v(iv)/v(v);battery;cell
Journal of Chemical and Engineering Data
The low-temperature heat capacities of VOSO(4)center dot 2.63H(2)O(s) which is a key component in the electrolyte of the vanadium redox flow battery were measured by adiabatic calorimetry in the temperature range of (78 to 388) K, and the experimental values of the molar heat capacities in the temperature regions of (78 to 372) K were fitted to a polynomial equation. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the compound relative to the standard reference temperature of 298.15 K were calculated at intervals of 5 K. Additionally, a dehydration process occurred in the temperature range of (372 to 382) K, and the peak temperature, T(de) = (378.895 +/- 0.309) K, molar enthalpy of dehydration, Delta(de)H(m) = (116.446 +/- 0.148) kJ.mol(-1), and molar entropy of dehydration, Delta(de)S(m) = (307.329 +/- 0.141) J.K(-1).mol(-1), were determined in terms of the heat capacity curve.
关键词:
synthetic sapphire alpha-al2o3;standard reference material;enthalpy;cell
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
Materials Letters
Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
M6C precipitation;aging;M7C3 carbide;superalloy
