S. X. Wang
,
D. S. Zheng and Y. L. Liu 1) Department of Material Engineering
,
Luoyang Institute of Technology
,
Luoyang 471039
,
China 2) Luoyang Copper (Group) Co.
,
Ltd
,
Luoyang
,
China
金属学报(英文版)
The model established in this paper for calculating the unsteady temperature field, in which physical parameters varies with temperatures, is simplified as compared with the classical one by defining the heat conductivity as function of temperature and dealing with the latent heat of phase transformation and boundary conditions. The results show that the probability of absolute error less 2℃ between the calculated and measured values in temperature field calculation reaches above 80%.
关键词:
temperature field
,
null
,
null
Communications in Theoretical Physics
Calculations have been performed to investigate the pressure-induced solid-solid phase transitions and the mechanical stability for three zinc-blende II-VI semiconductor compounds: ZnS, ZnSe, ZnTe by ab initio plane-wave pseudopotential density functional theory (DFT). Using the generalized gradient approximation (GGA) for exchange and correlation in the scheme of Perdew-Wang 1991 (PW91), the ground state properties and equation of state are obtained, which are well consistent with the experimental data available and other calculations. On the basis of the forth-order Birch-Murnaghan equation of states, the transition pressures P(t) are determined through the analysis of enthalpy variation with pressure. A linear-response approach is used to calculate the frequencies of the phonon dispersion. Finally, by the calculations of phonon frequencies, some thermodynamic properties such as the vibrational contribution to the Helmholtz free energy (F), enthalpy (H), entropy (S), and the heat capacity (C(V)) are also successfully obtained
关键词:
phase transition;elasticity;phonon dispersion;order elastic constants;ab-initio calculations;high-pressure phase;optical-properties;electronic-structure;molecular-dynamics;crystal-structure;absorption-edge;zinc selenide;znte
孙新阁
,
霍立兴
,
张玉凤
腐蚀科学与防护技术
采用楔形张开加载恒位移实验研究了X65管线钢在H2S溶液中的应力腐蚀开裂行为，并得出了X65管线钢母材、焊缝和热影响区的临界应力强度因子KISCC分别为55.7093 MPa•m 1/2、33.3189 MPa•m1/2和38.0711 MPa•m1/2；平台处的裂纹扩展速率da/dt分别为3.38×10－9m/s、3.5×10－9 m/s和3.5×10－9m/s.研究结果还表明，焊缝比母材具有更高的应力腐蚀敏感性.
关键词:
管线钢
,
null
,
null
Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences
The electron paramagnetic resonance (EPR) parameters g and the hyperfine structure constants A of CO2+ in ZnX (X = S, Se, Te) and CdTe are studied, using the perturbation formulas of the EPR parameters for a 3d(7) ion in tetrahedra based on two mechanism models. In these formulas, both the contributions from the conventional crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. According to the investigations, the sign of the g-shift DeltagCT from the CT mechanism is the same as DeltagCF from the CF mechanism, whereas the contributions to the A value from the CF and CT mechanisms have opposite signs. Particularly, the contributions to the EPR parameters from the CT mechanism increase rapidly with increase of the spin-orbit coupling coefficient of the ligand and the covalency effect of the systems, i.e. S2- < Se2- < Te2-.
关键词:
crystal-fields and Spin Hamiltonians;EPR;Co2+;ZnX (X = S, Se, Te);CdTe;atomic screening constants;scf functions;field theory;cr2+ ion;spectra;znse;complexes;crystal;liyf4;znte
危兆玲
,
李天保
,
赵君芙
,
梁建
,
马淑芳
,
许并社
材料导报
PbX(X=S,Se)纳米结构材料因其良好的光电性能,在太阳能电池等方面有着较好的应用前景,目前已成为半导体领域的研究热点.概括和总结了几种制备PbX纳米材料的经典和新型方法,其中包括水热法、溶剂热法、化学气相沉积法、中孔材料模板法、熔盐籽晶法、纳米晶的取向附属物法和微波法等,并分析和讨论了各方法的特点及对应产物的特征.
关键词:
PbS
,
PbSe
,
制备方法
,
纳米结构
Physica Scripta
The spin Hamiltonian parameters (zero-field splitting D, g factors and hyperfine structure constants) and local structure as well as their concentration dependences for Cd(1-x)Mn(x)S quantum dots are theoretically investigated from the perturbation formulae of these parameters for a 3d(5) ion under trigonally distorted tetrahedra. The impurity Mn(2+) is found not to occupy exactly the host Cd(2+) site in the CdS quantum dots but to experience an inward displacement 0.041 angstrom towards the ligand triangle along the C(3)-axis because of the size mismatching substitution and the internal stress. As compared with bulk CdS : Mn(2+), the larger impurity displacement and stronger Mn(2+) 3d-3s orbital admixture in the Cd(1-x)Mn(x)S quantum dots suitably account for the higher zero-field splitting and hyperfine structure constant, respectively. The impurity axial displacement and the Mn(2+) 3d-3s orbital admixture in the Cd(1-x)Mn(x)S quantum dots may exhibit an approximately cubic increase with increasing the Mn concentration x from 0.001 to 0.15.
关键词:
electron-paramagnetic-resonance;transition-metal impurities;atomic;screening constants;optical-properties;defect structures;scf;functions;crystals;ions;nanocrystals;semiconductor
张雁
,
蔡庆伍
,
谢广宇
腐蚀科学与防护技术
通过扫描电镜（SEM）、透射电镜（TEM）等方法，研究了X65～X70级别管线钢在饱和H2S溶液中的氢致开裂行为，及不同显微组织、位错与析出对氢致开裂（HIC）的作用.结果表明：组织均匀的珠光体/铁素体型X65管线钢和铁素体/针状铁素体型X70管线钢均具有良好的抗H2S腐蚀性能；带状组织是裂纹萌生和扩展的主要途径；合金元素的弥散析出作用可以提高管线钢的抗硫化氢腐蚀性能.
关键词:
管线钢
,
null
,
null
