Microscopic phenomena found within enclosed surface laser ablation of 20 nm thick aluminium films

This paper investigates the microscopic features which occur when a four-layered film is ablated using Q-switched Nd:YAG laser. The four-layered films consist of a vacuum-deposited aluminium layer (0.02 μm) upon an oriented polypropylene (OPP) film (30 μm) which has been laminated using an inert adhesive and a second OPP film. Laser radiation is absorbed principally by the aluminium layer, melting and/or vaporising it. Upon cooling, the aluminium layer is rearranged into discrete microscopic particles, which give laser-treated areas of the film a transparent appearance. Within the films are found microscopic features, which can be divided into three distinct types: aluminium demetallisation features, polymer distortion features and particle features. Features from each of these categories can exist within a single laser track depending upon the laser parameters used for transparentisation.     

Effect of film thickness on interface and electric properties of BiFeO3 thin films

Bismuth ferrite (BFO) thin films were fabricated by RF-magnetron sputtering deposition method on Pt/Ti/SiO₂/Si(1 0 0) substrate. The effect of the thickness of BFO films varying from 85 to 280 nm on electrical properties was investigated. Saturated coercive fields were found to increase with the BFO film thickness. The dielectric constant of BFO thin films measured at 1 kHz decreased with decreasing thickness from 98 to 86, while tangent losses increased from 0.013 to 0.021. The presence of bismuth oxide at the interface between BFO films and Pt bottom electrodes was responsible for the high leakage currents in thin BFO thin films as was demonstrated by X-ray diffraction, grazing-incident X-ray diffraction, and secondary ion mass spectroscopy analysis.     

Growth of Pt thin films on WSe2

The morphology and structure of Pt deposited on a WSe₂(0 0 0 1) van der Waals surface have been investigated by reflection high energy electron diffraction and scanning tunneling microscopy. At room temperature, the initial growth is characterized by the formation of three-dimensional fcc Pt islands with (1 1 1) orientation. In contrast, at higher temperatures of about 450 °C the formation of a novel chemically ordered Pt-Se alloy is observed. Based on the diffraction patterns, a tetragonal DO₂₂-type structure of a Pt₃Se compound is suggested. With increasing Pt thickness, this chemically ordered alloy disappears and an additional superstructure occurs, which is accompanied by the coalescence of the islands. The observed superstructure is attributed to a strong Se diffusion towards the growth surface, forming most likely a PtSe₂ alloy with the CdI₂-type layered structure on the top surface. Due to the lateral lattice mismatch between the Pt(1 1 1) layers and the PtSe₂(1 1 1) top layer, a Moiré pattern with a period of 1.1 nm is created, which might be used as a long-range atomic pattern for further nanostructure growth.     

Properties of mixed protein/surfactant adsorption layers

The adsorption isotherms, adsorption kinetics and surface rheological properties of β-lactoglobulin, β-casein, in the absence and presence of Tween 20 were measured. To study the adsorption process (isotherms and kinetics) at the water–air interface the pendant drop technique (axial drop shape analysis, ADSA), and ring tensiometry were used. The surface shear rheological parameters were measured with a torsion pendulum set-up. Also, data of the equilibrium film thickness and surface diffusion coefficients obtained from fluorescence recovery after photobleaching (FRAP) measurements are used to understand the competitive adsorption mechanism. The adsorption process and shear rheological behaviour of the studied systems show a rather complex behaviour which depends most of all on the system's composition. At high protein or surfactant content the behaviour is controlled by the main component while for the more mixed systems the adsorption process is complex and consists of partial adsorption, surfactant–protein interaction and protein rearrangement as a function of surface coverage. The results obtained illustrate that all these processes must be taken into account in future new theoretical models to be derived for such systems.     

Film forming kinetics and reaction mechanism of γ-glycidoxypropyltrimethoxysilane on low carbon steel surfaces

The film forming kinetics and reaction mechanism of γ-GPS on low carbon steel surfaces was investigated by FTIR-ATR, AFM, NSS and theoretical calculation method. The results from experimental section indicated that the reaction of γ-GPS on low carbon steel surfaces followed the conventional reaction mechanism, which can be described as reaction (I) (Me (Metal)-OH + HO-Si → Me-O-Si + H₂O) and reaction (II) (Si-OH + Si-OH → Si-O-Si + H₂O). During film forming process, the formation of Si-O-Fe bond (reaction (I)) exhibited oscillatory phenomenon, the condensation degree of silanol monomers (reaction (II)) increased continuously. The metal hydroxyl density had significant influence on the growth mechanisms and corrosion resisting property of γ-GPS films. The results from theoretical calculation section indicated that the patterns of reaction (I) and reaction (II) were similar, involving a nucleophilic attack on the silicon center. The formation of Si-O-Fe bond (reaction (I)) was kinetically and thermodynamically preferred, which had catalytic effect on its condensation with neighboring silanol monomers (reaction (II)). Our DFT calculations were good consistent with the experimental measurements.     

Segmented gas–liquid flow characterization in rectangular microchannels

We used optical methods such as Laser Induced Fluorescence (LIF) and confocal Laser Scanning Microscopy (LSM) to characterize gas–liquid phase distribution in rectangular microchannels. Using a 2 m long microchannel with a hydraulic diameter of 200 μm enables the precise measurement of important parameters such as liquid slug length, bubble length, pressure drop and film thickness at the wall as well as in the corner of the microchannel for low Capillary numbers (Ca) ranging from 2 × 10⁻⁴ to 1 × 10⁻². This range of Ca was obtained by using different fluid pairs such as ethanol, water and different concentrated aqueous solutions of glycerol in combination with nitrogen.     

Confining effect on the bearing capacity of circular footings on a purely cohesive soilEffet du confinement sur la capacité portante d'une fondation circulaire sur un sol purement cohérent

The bearing capacity of axially symmetrical footings acting on a purely cohesive soil foundation contained by a rigid wall at a finite distance is investigated within the framework of the Yield design theory. Following the same tracks as in a preceding paper devoted to strip footings, the analysis is performed by referring to already existing results concerning the bearing capacity of a circular footing on a soil layer with limited thickness. It comes out that the bearing capacity factor determined by Eason and Shield for a rough circular footing on an unlimited soil foundation is increased by a correction factor that increases when the diameter of the container decreases. Comparison with the results obtained for strip footings acting on a purely cohesive soil in the same conditions shows that the confining effect is significantly lower for a circular footing than for a strip footing. To cite this article: J. Salençon, C. R. Mecanique 330 (2002) 521–525.     

同位镀铋膜电极测定爆米花中的痕量铅

采用同位镀铋膜法修饰铂电极,用差分脉冲溶出伏安法对爆米花中痕置铅进行了测定,并优化了实验条件.在优化的实验条件下,分别对2.0×10<'8>-6.0×10<'-7>mol/L和6.0×10<'-7>-1.0×10<'-4>mol/L的pb<'2+>进行了测定,Pb<'2+>溶出峰电流与Pb<'2+>浓度呈良好的线性关系...     

无沸腾喷雾冷却技术的研究进展

文中简述了无沸腾喷雾冷却技术近年来国内外的研究进展。着重介绍了关于影响无沸腾区换热各参数的实验研究,如壁面温度、介质体积通量、喷雾流量、喷雾倾角和喷雾高度等,为寻求最佳换热提供了指导。并对无沸腾区的理论研究内容进行了归纳,主要是模拟不同喷雾条件下的换热过程及特性参数(如液膜厚度)的大小和分布,并将理论值与实验数据进行比较分析;总结了影响无沸腾区换热的喷雾特性参数和外部特性。