材料期刊网

Molecular Dynamics Simulation of Liquid Noble Metals Au and Ag

LI Qingchun CHEN Kuiying ** Dept.of Metals and Technology , Harbin Institute of Technology , Harbin , 150006 , China+ To whom correspondence should be addressed

材料科学技术（英文）

关键词: molecular dynamics simulation , null , null

用DEPT135测定Resol的组成及微细结构参数

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

Calculation of theoretical strengths and bulk moduli of bcc metals

Physical Review B

A first-principles method based on the local-density approximation using discrete variational clusters has been used to study the electronic structure of bcc metals, Li, Na, K, VI Nb, Ta, Cr, Mo, end W. The binding energy of these metals was calculated, and the relationship! between the binding energy and the volume of a unit cell for a given metal was determined. The results show that the contribution of the interaction beyond the third nearest-neighbor atoms to the binding energy is small for transition metals, but large for alkali metals, The theoretical triaxial tensile strength and bull; modulus of these metals were estimated from the electronic structure and binding-energy calculations. The present results of the bulk modulus for Li, Na, K, Nb, Tu, Mo, and W are in good agreement with experiments and other available theoretical data, but the bulk modulus for V and Cr is somewhat overestimated. The theoretical strength obtained in the present work is in good agreement with the results of the linear muffin-tin-orbitals method. [S0163-1879(99)14521-1].

关键词: density;potentials;accurate;energy

Chen系统的状态变量周期性反馈控制

李开明 , 李亚洲 , 冯维贵 , 林长

量子电子学报 doi:10.3969/j.issn.1007-5461.2007.05.014

采用非线性反馈控制,用附加了带参数的正弦项对Chen系统进行了有效的控制.随着参数k的逐渐增大,系统的动力学行为呈现出一系列的变化.数值研究结果表明:随控制参数的增大,驱动信号的强度渐大,混沌系统由混沌运动到周期轨道,最终到一相点.

关键词: 混沌 , Chen系统 , 不动点 , Lyapunov指数 , 反馈控制

Prospects for Variable Gauge Rolling: Technology, Theory and Application

LIU Xianghua

钢铁研究学报(英文版)

Rolling of gauge changeable (RGC) is a new technology to produce flat with different thickness (FDT), which could be used to replace conventional flat products in order to save metals and reduce structure weight. This paper introduced the method of RGC, investigated new problems in rolling theory of RGC, proposed the new formulas for caluclating parameters of RGC, and described some results of numerical simulation by FEM. As example, the products applications of FDT in bridge construction, ship building and auto manufacturing were presented. Finally the prospect for RGC and FDT was discussed.

关键词: variable gauge rolling;longitudinal profile plate;tailor rolled blank

Influence of biofilms growth on corrosion potential of metals immersed in seawater

Materials and Corrosion-Werkstoffe Und Korrosion

The changes of corrosion potential (E-corr) of metals immersed in seawater were investigated with electrochemical technology and epifluoresence microscopy. In natural seawater, changes of E-corr were determined by the surface corrosion state of the metal. E-corr of passive metals exposed to natural seawater shifted to noble direction for about 150 mV in one day and it didn't change in sterile seawater. The in-situ observation showed that biofilms settled on the surfaces of passive metals when E-corr moved in noble direction. The bacteria number increased on the metal surface according to exponential law and it was in the same way with the ennoblement of E-corr. The attachment of bacteria during the initial period played an important role in the ennoblement of E-corr and it is believed that the carbohydrate and protein in the biofilm are reasons for this phenomenon. The double layer capacitance (C-dl) of passive metals decreased with time when immersed in natural seawater, while remained almost unchanged in sterile seawater. The increased thickness and reduced dielectric constant of C-dl may be reasons.

关键词: stainless-steels;diminution;reduction;oxygen

Microstructures and Dielectric Properties of Ba_1-xSr_xTiO₃ Ceramics Doped with B₂O₃-Li₂O Glasses for LTCC Technology Applications

Xiujian Chou

材料科学技术（英文）

Ba_1-xSr_xTiO₃ ceramics, doped with B₂O₃-Li₂O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 °C using liquid-phase sintering aids. The microstructures and dielectric properties of B₂O₃-Li₂O glasses doped Ba_1-xSr_xTiO₃ ceramics have been investigated systematically. The temperature dependence dielectric constant and loss reveals that B2O3-Li₂O glasses doped Ba_1-xSr_xTiO₃ ceramics have diffusion phase transformation characteristics. For 5 wt% B₂O₃-Li₂O glasses doped Ba0:55Sr0:45TiO₃ composites, the tunability is 15.4% under a dcpplied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics (LTCC) and potential microwave tunable devices applications.

关键词: Sintering

Nanocrystal Model for Liquid Metals and Amorphous Metals

X.L. Tian C.W. Zhan J.X. Hou X.C. Chen J.J. Sun

材料科学技术（英文）

A nanocrystal model for liquid metals and amorphous metals has been developed. With the nanocrystal model, the broadening peak profiles (BPPs) of Cu, Al, Al₆₅Cu₂₀Fe₁₅ alloy, Cu₇₀Ni₃₀ alloy and Fe₅₀Si₅₀ alloy were gained by broadening the X-ray diffraction (XRD) peaks of a crystal lattice. By comparing the BPPs with the XRD intensity curves measured on the liquid metals, it is found that the BPPs are closely in agreement with the XRD intensity curves, respectively, except the Fe₅₀Si₅₀ alloy. Therefore, the nanocrystal model can be used to determine if the atomic cluster structure of the liquid metal is similar to the structure of its crystal lattice.

关键词: Liquid metal , Atomic Cluster , Structure , Crystal Lattice

Titanium technology in the USA - an overview

D.Eylon , S.R.Seagle

材料科学技术（英文）

The state of Ti research, development and industry is reviewed in this article. The fifty-year anniversary of Ti technology commercialization in the USA provides an opportunity for a historical perspective. Incorporation of "information-age" tools into alloy development, processing, and production invigorates the technology. Consolidation, diversification and globalization have been transforming the Ti industry in the recent years.

关键词:

Twinnability Predication for fcc Metals

B.Q. Li

材料科学技术（英文）

Inherent twinnability of face-centered-cubic (fcc) metals was analyzed based on the direct competition between twinning partial dislocation nucleation and trailing partial dislocation nucleation, with which the twinnability of fcc metals can be simply expressed as function of the stacking-fault energy, the unstable stacking-fault energy, and the unstable twinning-fault energy of fcc metals. The predicted twinnability ranking matched well with former experimental results and provided a physical insight to understand twinnability from crystallographic orientation and fault energy parameters.

关键词: Deformation twinning