Applied Physics Letters
In this letter, it is found that when the critical electric current pulse (ECP) passes through a Cu-Zn alloy with lead inclusions, those inclusions will disappear and transfer into grain boundaries or defects, forming many dispersed small particles of lead. Such kind of lead transfer can be produced by no other heat treatments than ECP. The theoretical analysis points out that this phenomenon is attributed to its specific effect on reducing considerably the diffusion activation energy of lead in the alloy. Therefore, the ECP treatment would provide a promising method to refine materials and to improve their physical properties. (c) 2006 American Institute of Physics.
关键词:
electromigration;transformation;diffusion;metals
Huanyan XU
,
Lei YANG
,
Peng WANG
材料科学技术（英文）
Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite (CHap) are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage increases with decreasing pH values and reaches a maximum at pH=2–3. Under some conditions, the lead residual concentration is below national integrated wastewater discharge standard, even drinking water standard. The removal behavior is a complicated non-homogeneous solid/liquid reaction, which can be described by two stages from kinetic point of view. At the earlier stage, reaction rate is so fast that its kinetic course is intricate, which requires further study. At the latter stage, the rate of reaction becomes slow and the process of reaction accords with one order reaction kinetic equation. Experimental results show that the relationship between reaction rate constant k1 and temperature T accords to Arrhenius Equation, and the activation energy of sorption (Ea) is 11.93 kJ/mol and frequency factor (A) is 2.51 s-1. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive X-ray fluoresence spectrometer (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) test were conducted in this work. It is indicated that the main mechanism is dissolution-precipitation, accompanying with superficial sorption.
关键词:
Carbonate hydroxyapatite
,
铅离子
,
动力学
,
机理
,
溶解－沉淀
W.H.Tian
,
C.K.Yan
,
M.Nemoto
金属学报(英文版)
Transmission electron microscopy(TEM) observations were carried out for examining the precipitation behavior in a Cu-Sn-Zn-P lead frame material.TEM observations revealed that the precipitate is hexagonal Ni5P2 and the orientation relationship between the Cu matrix and Ni5P2 precipitate is (111)fcc//(0001)hcp,[101]fcc//[1120]hcp,where the suffix fcc denotes the Cu matrix and hcp denotes the hexagonal Ni5P2 precipitate.The Ni5P2 precipitate is ovoidal in shape at the beginning of aging at lower temperature.By prolonging the aging time or increasing the aging temperature,Ni5P2 precipitate grows and shows a rod-like shape.The Ni added Cu based lead frame material has a comparative mechanical properties with that of TAMAC15 which has been developed and used in electrical industry.
关键词:
lead frame materials
,
null
,
null
Journal of Physics-Condensed Matter
High resolution transmission electron microscopy (HRTEM) observations show evidence for the formation of disorder Al zones around some faceted Pb inclusions embedded in an Al matrix in immiscible lead-aluminium samples, which were prepared by a melt-spun method and then aged for about two months at room temperature. Furthermore, it is found that, both before and after ageing, all such Pb inclusions have a cube-cube orientation relationship with the Al matrix. The results of molecular dynamics (MD) simulations give an extensive analysis of the formation of the disorder Al zones and provide a reasonable explanation for the HRTEM finding: the existence of oxygen soluted in the Pb inclusions at higher temperatures may lead to the formation of the disorder Al zone in the aged sample. The dependence of the thickness of the disorder Al zone on the amount of oxygen soluted in the Pb inclusion at higher temperatures, and the average stress in the equilibrium configuration of a MD cell, is discussed.
关键词:
solid-state reaction;y-mo system;heterogeneous nucleation;structural;relaxation;al;pb;inclusions;alloys;solidification;potentials
Advanced Functional Materials
A binary surfactant mixture of cetyltrimethylammonium bromide and polyvinyl pyrrolidone is used as the tailoring agent in the fabrication of lead micro/nanostructures. Electron microscopy studies indicate that the morphologies of the products can be efficiently controlled in this simple one-step synthetic procedure. Intriguingly, well-defined asymmetric functional colloids, Pb hemispheres are obtained for the first time, and a dual-activity-controlled growth process is proposed to explain their formation. The magnetization measurements show that the as prepared samples are superconducting with the same transition temperature as bulk Pb. These findings prove the unique morphology tailoring efficacy of mixed surfactants, which could be used to obtain more vairform structures or architectures in the fabrication of advanced materials.
关键词:
nanowire arrays;size control;growth;nanoparticles;single;electrodeposition;microstructure;nanocrystals;polyaniline;morphology
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
In this study the authors present and discuss the results of the investigation on the fatigue fracture behaviors in a series of as-soldered and thermal-aged copper/lead-free solder joints deformed under both monotonic and cyclic loadings. The observation results showed that fatigue cracks generally initiate around the IMC/solder interface when the loading axis is vertical to the interface. The intrinsic deformation behaviors are little different for different solder joints resulting from strain localization induced by the stain mismatch. Fracture surface observations revealed the crack propagation path and fatigue resistance of the solder joints to be affected by the yield strength and mechanical property of the solder. When the copper/solder interface is parallel to the loading axis, the interfacial IMC layer failed approximately perpendicular to the interface when the cumulative strain exceeded the fracture strain, then the cracks propagated to the IMC/solder interface, leading to the fracture along the interface. The failure mechanisms and factors influencing interfacial fatigue are discussed. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Lead-free solder;Fatigue fracture;Interface;Strain localization;Vertical cracks;lead-free solders;pb-free solders;deformation-behavior;joints;tensile;cu;embrittlement;temperature;sn-3.5ag;alloy
H.F.Sun
,
W.B.Fang
,
F.Han
,
W.X.He
,
E.D.Wang
金属学报(英文版)
The method of manufacturing the composite wire by extruding lead to coated glass fiber is described. The different composite wire that diameter is from 0.5 to 1.0mm has been produced by two kinds of different extruding technology (getting wire along horizontal direction and getting wire along perpendicular direction). The optimal extruding technological parameter has been given in different extruding technology by the physical simulation (H: 300℃, 550kN, 0.16mm. P: 300℃, 215kN, 0.16mm). The effect on the coating speed by other extruding technological parameters in the different extruding technology has been discussed. The extruding temperature and extruding force is higher, the coating speed is faster. It has been pointed, that the affection on the extruding technology by the extruding temperature has also behaved as the extruding temperature rising up spontaneously. The reason for exiting the minimum extruding force and maximum extruding force also has been discussion in this paper. It is also important to the extruding process and coating speed that is the coating clearance.
关键词:
composite
,
null
,
null
