On the deformation and fracture behaviour of a Zr-based glassy alloy

The deformation behaviour of Zr₆₀Cu₁₆Ni₁₄Al₁₀ glassy alloy was found to exhibit cleavage-like fracture relief paired with typical vein patterns. The mirror-like cleavage area fraction is found to be comparable with that of vein areas. These two types of patterns alternate on the fracture surface in a direction normal to shear deformation. The structure of the studied alloy was characterised by X-ray diffractometry and scanning and transmission electron microscopy. A small volume fraction of crystals in the form of eutectic colonies were found here and there in the specimen. No distinct difference in the glassy structure of the cleavage-like fracture areas and the areas corresponding to vein patterns was found within the resolution of experimental techniques employed.     

On the critical behaviour of a surface interacting linear polymer chain

A method based on a real space renormalization group transformation is developed to describe the critical behaviour of a surface interacting linear flexible polymer chain, represented by a self-avoiding walk. It is shown that a lattice model based on a central rule in which the starting point of the walk and the surface are taken to be in the middle of one cell, provides a suitable framework to study both the penetrable and impenetrable surfaces. In contrast to this, a method based on a corner rule in which the starting point of the walk and the surface are fixed to be one corner of a cell cannot describe the behaviour of a chain interacting with an impenetrable surface. The value of crossover exponent found by us for a square lattice are in agreement with those expected to be exact for both the cases.     

On the stability of the CO adsorption-induced and self-organized CuPt surface alloy

The stability of the recently discovered CO-induced and self-organized CuPt surface alloy was explored at near ambient pressures of O₂ (200 mbar) at room temperature, in a CO + H₂ mix (P_tot = 220 mbar, 4% CO) from room temperature to 573 K, as well as in a CO + H₂O mix (P_tot = 17 mbar, 50% CO) from room temperature to 673 K. No indications of substantial changes in surface structure were observed under the latter conditions compared to CO alone whereas the O₂ oxidation resulted in CO removal and the build-up of an ultrathin CuO_x-film. However, the oxidized CO/CuPt surface alloy could be regenerated by reducing the CuO_x in 100 mbar CO for 10 min at room temperature. The results show, amongst others, the stability of the CuPt surface alloy in various environments containing CO and how a novel coinage/Pt-group bimetallic surface alloy catalyst induced by CO adsorption can be reactivated before use in applications such as electrochemistry at ambient temperatures.     

On the surface structure of MoO3 crystals used in catalytic oxidation of hydrocarbons

The occurrence of atomic steps and kinks on MoO₃ crystal surfaces was evidenced by electron microdiffraction techniques; the alternate appearance of forbidden reflections matched the structure factor calculations for several step heights and implications for catalytic reactions on MoO₃, surfaces were considered.     

Annealing behaviour of ion-implanted nickel-aluminium alloy

The time evolution of the aluminium concentration profiles in ion-implanted nickel-aluminium alloys during annealing has been studied in the temperature range 550–800°C using the (p, γ) resonance broadening method. The surface enrichment of aluminium has been found to be balanced by a corresponding uniform decrease in the bulk concentration and hence the bulk concentration profiles can be described by the modified solution of the second diffusion equation, when the implanted concentration does not exceed the solubility limit. When the solubility limit is exceeded the time evolution follows the solubility controlled flow of the solutes. The dependence of the degree of surface enrichment on the extra irradiation of⁵⁸Ni⁺ before and after the aluminium implantation is demonstrated and is found to be significant only in the post-irradiation cases. This is taken as evidence of the importance of interstitials in the development of the bulk concentration profiles. The linear Arrhenius plot extracted from the measurements indicates that the diffusion of A 1 in Ni can be described by the activation energyE=2.69 eV and the pre-exponential factorD ₀=0.6 cm²/s. Solid solubilities of aluminium in nickel from the implanted distribution are found to agree with those obtained using conventional metallographical methods.     

Electron spectroscopy studies of surface In-Ag alloy formation on the tungsten surface

XPS and UPS investigations of ultrathin films of In/Ag and Ag/In, deposited onto the W(1 1 0) surface in the ultrahigh vacuum conditions have been performed. Indium and silver films were formed by “in-situ” evaporation on W(1 1 0) substrate. XPS and UPS studies have been performed by means of SCIENTA ESCA200 instrument. The changes of In4d core-level and Ag4d valence band emissions with increasing Ag and In coverage were monitored to observe the energy shift and shape of the spin-orbit doublet of In4d and Ag4d lines in the Ag/In/W and In/Ag/W systems. UPS (HeI and HeII) measurements were supported by XPS AlK_α measurements of In3d and W4p levels, as well as by investigations of Ag3d levels. XPS and UPS data allowed to evaluate the coverage and make conclusions concerning intermixing and surface alloying in the In/Ag/W and Ag/In/W systems. W(1 1 0) substrate can be cleaned after each deposition by thermal desorption and no alloying in the In/W and Ag/W systems is observed.     

A new solar selective surface

A new waveguide method of providing a selective surface for solar energy applications is described. Some measurements of a vacuum-deposited mesh are given, and elementary theory indicates that ratios of solar absorptance to thermal emittance of 30:1 should be possible at temperatures of about 200°C.     

Fermi surface and band mapping of the cerium/palladium surface alloy

X-ray and UV excitation angle-resolved photoemission spectroscopy of ultra-thin films of cerium deposited on Pd(1 1 1) single-crystal surface has been carried out. Photoelectron diffraction pattern showed that deposition of 1 ML of Ce led to a formation of Ce-Pd substitutional alloy. Valence band spectra measured with high angular resolution permitted to plot valence band maps and Fermi surface scans and showed formation of surface alloy exhibiting d- and f-electron orbital hybridization. A shift of Pd 4d-derived states to higher binding energy in the Ce-Pd systems was observed.     

Noncollinear surface spin density by surface reconstruction in the alloy NiMn

At the (001) surface of the alloy Ni(50)Mn(50), a noncollinear spin density is observed in real space by spin-polarized scanning tunneling microscopy. The spin density of individual atoms also varies in both size and direction as a function of bias voltage, indicating a noncollinearity in the energy domain. The noncollinearity is driven by a surface reconstruction which breaks the otherwise high surface symmetry. First-principles electronic-structure calculations support the experimental observations and evidence the interplay of reconstruction and spin-orbit coupling.     

能量选择表面的瞬态响应

为实现强电磁脉冲防护和信号收发的兼容,研究了一种基于能量选择机制的强电磁防护结构,即能量选择表面。该防护表面利用半导体压控导电特性,实现了强场辐照时防护表面由高阻态向低阻态的转变,具有能量低通特性和超宽带特性。利用场路协同仿真方法,分析了能量选择表面瞬态响应与PIN二极管阻抗特性、强电磁脉冲峰值场强及脉冲前沿的关系,结果显示：尖峰泄漏功率和响应时间与Ⅰ层厚度、强电磁脉冲峰值场强成正比,与少数载流子寿命成反比变化。     

能量选择表面的瞬态响应

为实现强电磁脉冲防护和信号收发的兼容,研究了一种基于能量选择机制的强电磁防护结构,即能量选择表面。该防护表面利用半导体压控导电特性,实现了强场辐照时防护表面由高阻态向低阻态的转变,具有能量低通特性和超宽带特性。利用场路协同仿真方法,分析了能量选择表面瞬态响应与PIN二极管阻抗特性、强电磁脉冲峰值场强及脉冲前沿的关系,结果显示:尖峰泄漏功率和响应时间与Ⅰ层厚度、强电磁脉冲峰值场强成正比,与少数载流子寿命成反比变化。     

Research of the behaviour of O chemisorption on the (110) surface of Rhx--Pt1－x alloy

An atomic group model of the disordered binary alloy Rhx-Pt1-x has been constructed to investigate surface segregation. According to the model, we have calculated the electronic structure of the Rhx-Pt1-x alloy surface by using the recursion method when O atoms are adsorbed on the Rhx-Pt1-x （110） surface under the condition of coverage 0.5. The calculation results indicate that the chemical adsorption of O changes greatly the density of states near the Fermi level, and the surface segregation exhibits a reversal behaviour. In addition, when x 〈 0.3, the surface on which O is adsorbed displays the property of Pt; whereas when x 〉 0.3 it displays the property of Rh.     

Effect of precipitating agent on the catalytic behaviour of precipitated iron catalysts

Hyperfine Interactions - Iron precipitated catalysts have been prepared using different precipitating agents (NH4OH, K2CO3) at different pH values. In situ Mössbauer (MES) study of the reduced...     

Effect of the surface free energy on the behaviour of surface and guided waves

The aim of this paper is to evaluate the influence of the surface free energy upon the propagation of the eigenmodes of structures, by studying successively (a) the Rayleigh wave for an elastic half-space, (b) the Lamb waves for an elastic layer, and (c) the guided modes for a tri-layer structure (e.g., metal/adhesive/metal). The surface free energy is a parameter which appears in the jump conditions of stresses and displacements at each interface, and which consequently modifies the eigenmodes, solutions of the boundary conditions system. As expected, the Rayleigh wave is dispersive and its velocity increases when the surface free energy increases. In the same way, the velocity of Lamb waves also increases except at normal angle of propagation where the surface free energy does not arise. Moreover, near the Rayleigh angle, the behaviour of the A₀ and S₀ Lamb modes varies strongly according to the surface free energy. Similar results are observed for the tri-layer structure.     

The surface composition of the gold-palladium binary alloy system

The surface composition of the AuPd alloy system has been determined by Auger electron spectroscopy. Measurements were performed on polished polycrystalline alloy foils. After cleaning, the intensities of the 71 eV and 2024 eV gold Auger transitions, and the intensity of the 330 eV palladium transition were measured, and then converted to atom concentrations in the surface layer. The surfaces of the annealed samples were found to be significantly enriched in gold with respect to the bulk. This result disagrees with the regular solution theory prediction. After extensive sputtering of the AuPd alloys with 1.5 keV Ar⁺ ions, a slight surface enrichment with palladium was found, as predicted by the simple theoretical model for sputtering.     

On the nodal behaviour of eigenfunctions

The generic behaviour of the nodal pattern of the eigenfunctions of the Schrödinger equation depending on parameters is discussed. Numerical examples are presented for the case of a hard-walled parallelogram.     

光学透明频率选择表面的研究

运用谱域Galerkin法对光学透明带通频率选择表面(FSS)进行了分析计算,研究了透明导电膜的电导率对光学透明带通FSS频率选择特性的影响. 计算及实验结果表明：在雷达波段,透明导电膜的电导率主要影响光学透明带通FSS在中心频率处的透过率,光学透明带通FSS在透可见反雷达波的同时,还具有选择性透过雷达波段的特性. 关键词： 频率选择表面 透明导电膜 电导率