NIU Yan
,
F.GESMUNDO
,
WU Weitao
,
ZENG Chaoliu
,
F.VIANI
,
(State Key Laboratory for Corrosion and Protection
,
Institute of Corrosion and Protection of Metals
,
Chinese Academy of Sciences
,
Shenyang.110015
,
China)(Istituto di Chimica
,
Facolta'di Ingegneria
,
Universita'di Genova
,
Fiera del Mare
,
Pad.D
,
16129 Genova
,
Italy)Manuscript received 3 July 1995
金属学报(英文版)
The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to sulfur attack at high temperatures.The alloy is nearly single-phase.containing mostly the intermetallic compound Co17Y2 plus a little amount of the solid solution of Y in cobalt.At 600-700℃ and at 800℃ under 10-2 Pa of S2 the alloy forms multi-layered scales consisting of an outer region of pure cobalt sulfide,an intermediate region of a mixture of the sulfides of the two metals and finally an innermost layer of a mixture of yttrium sulfide with metal cobalt.At 800℃ under 10-3Pa of S2,below the dissociation pressure of cobalt sulfide, the alloy forms only a single layer composed of a mixture of metallic cobalt with yttrium sulfide.Pure Y produces only the oxysulfide Y2O2S, as a result of the good stability of this compound and of the presence of some impurities in the gas mixtures used The corrosion kinetics is generally rather complex and irregular except al 800℃under 10-3 Pa of S2.The addition of yttrium always reduces the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of yttrium sulfide is never achieved.The internal sulfidation of Y in Co-15% Y is not associated with a depletion of Y in the alloy.This kind of diffusionless internal attack is typical of alloys with a very small solubility of the most reactive component Y in the base metal A.which restricts severely the Y flux from the alloy towards the alloy-scale interface.
关键词:
:cobalt-yttrium alloy
,
null
,
null
Fuquan LI
,
Chunqing WANG
,
Yanhong TIAN
材料科学技术（英文）
The interfacial phenomena of the Sn-Pb solder droplet on Au/Ni/Cu pad are investigated. A continuous AuSn2 and needle-like AuSn4 are formed at the interface after the liquid state reaction (soldering). The interfacial reaction between the solder and Au layer continues during solid state aging with AuSn4 breaking off from the interface and felling into the solder. The kinetics of Au layer dissolution and diffusion into the solder during soldering and aging is analyzed to elucidate intermetallic formation mechanism at the solder/Au pad interface. The concentration of Au near the solder/pad interface is identified to increase and reach the solubility limit during the period of liquid state reaction. During solid state reaction, the thickening of Au-Sn compound is mainly controlled by element diffusion.
关键词:
Sn-Pb solder droplet
,
老化
,
溶解
,
钎料熔滴
金云学
,
稀有金属材料与工程
选用A356/SiC复合材料与Semi-metallic pad材料进行干滑动摩擦磨损试验,并采用SEM、XRD、EDS等手段分析了复合材料的摩擦磨损特点及磨损机制.铝基复合材料与该pad问表现出非常出色的耐摩擦磨损特性,在lm/s的低滑动速度下,即使载荷增加到700 N也几乎不发生磨损;载荷不大于500 N时,磨损率与滑动速度无关,保持非常小的范围.只有在高载荷、高滑动速度下才会有较为明显的磨损.摩擦系数则随载荷增大产生无规则变化,而随滑动速度的增加而减少,但变化幅度在0.1之内.复合材料耐磨特性好的主要原因是,磨损过程中磨损面上迅速形成以氧化物和石墨为主的润滑膜,减少磨损.高载荷、高滑动速度下磨损的主要特点为,复合材料表层形成塑性流动层,大的塑性流动变形使得较软的铝合金基体沿磨损方向以片状形式挤出,形成特殊的磨屑.而不易变形的SiC颗粒则留在磨损面上形成SiC聚集区,该区域又能在一定程度上减少进一步的磨损.
关键词:
SiC
,
铝合金
,
滑动
,
磨损机制
,
摩擦磨损
J. Li
,
W. Liu
,
Y.Q. Lai
,
null
,
null
金属学报(英文版)
Two full 3D steady mathematical models are developed by finite element method (FEM) to calculate coupled physics fields: the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad.
关键词:
coupled simulation
,
null
,
null
,
null
,
null
Physical Review B
In the investigation of the optical and magnetic properties of the semiconductors containing transition-metal ions, the one-electron orbital cannot be treated with a pure d orbital because of a strong covalence. This paper presents the energy matrix of the d*(8) and d*(2) (d* means a modified d function) system, in which the covalence is described by two covalent factors. The differences between the matrix diagonal elements of the t(2)(m)e(n) term of the d*(8) system and the t(2)(6-m)e(4-n) term of the d*(2) system vary with m and n. The d(N) electron system can be explained with the d(10-N) hole system because the difference between the energy matrix of the d(N) and d(10-N) systems has a fixed value. However, this kind of simple relation does not exist for the d*(N) and d*(10-N) systems when the covalence is considered. A numerical calculation shows that the variation of the energy levels with the covalence for Ni2+ in the d*(8) electron system is larger than that in the d*(2) hole system. The calculated energy levels obtained from the d*(8) matrix are in good agreement with the experimental data of the Ni2+ ion for ZnS:Ni and ZnSe:Ni. This suggests that the d*(8) electron system instead of the d*(2) hole system should be used in the investigation of optical and magnetic properties of semiconductor containing Ni2+ ions.
关键词:
zns-ni;absorption;vanadium;impurities;spectra;ions
张兴
,
郑成武
,
李宁
,
周兴丹
,
李正强
,
华瑞茂
液晶与显示
doi:10.3788/YJYXS20122704.0448
介绍了3D显示的基本原理,重点介绍了目前3D显示的主流技术类型,包含了眼镜式3D技术以及裸眼式3D技术,其中眼镜式3D技术包含色差式3D技术、偏光式3D技术和主动快门式3D技术;裸眼式3D技术包含视差屏障式3D技术、柱状透镜式3D技术、指向光源式3D技术和多层显示式3D技术.阐述了各种3D显示技术的基本实现原理和应用领域、并对涉及液晶显示的几种3D技术的优缺点进行了对比.结合液晶材料的特点与3D液晶显示的实际要求,阐述了3D液晶面板对液晶材料快速响应方面的要求,以及液晶透镜对液晶材料光学各向异性参数的要求.
关键词:
3D显示
,
眼镜式3D显示
,
裸眼式3D显示
,
液晶材料
