Changes to the microstructure of joints of welded iron superalloys IN 519 and H39WM during operation

Steam reforming is one method of producing hydrogen. The endothermic decomposition process of mixtures consisting of methane and water vapour under pressures of up to 4.0 MPa is conducted at a temperature of up to 780°C in austenite pipes cast centrifugally and filled with nickel catalytic agent. The results of microstructure tests on the welded joints of centrifugally cast catalytic pipes, made of second generation alloy IN 519 and third generation alloy H39WM, are presented in this article. The tests were conducted on butt welds drawn from the area of the substrate inlet of an approx. 500°C temperature, and from the area of maximum speed of pipe creep. The temperature of the pipe's external wall at the outlet of the products approaches 900°C under the operating conditions of ammonia reformers when internal pressure reaches up to 4.0 MPa. Long-lasting operational results in phase and structural changes depend on the local temperature of the pipe material. These changes affect the mechanical properties of the pipe material and contribute to initiation of the creep process, which manifests itself in macroscopic aspect as a local increase in the diameter of the pipes. The extreme stage of the high-temperature degradation of the microstructure reveals itself as macro-cracks leading to a loss of pipe leak-tightness.     

Cyclic voltammetry and impedance studies of undoped diamond films

The undoped, polycrystalline diamond films were deposited on tungsten wire substrates by hot filament chemical vapor deposition (HF CVD), using a precursor gas mixture of methanol with excess of hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy (SEM) and Raman spectroscopy. The surface morphology analyzed by SEM resembles a continuous and well faceted diamond film. Raman results showed essential differences in qualities of diamond films grown at different hydrocarbon concentrations. The electrochemical properties of diamond electrodes were examined with cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). The CV experiments revealed a large chemical window (>～4.3 V) of undoped diamond. Analysis of the ferrocyanide-ferricyanide couple at a diamond electrode suggests some extent of electrochemical quasi-reversibility, but the rates of charge transfer across the diamond substrate interface vary with diamond quality.     

亚烃基二胺-N，N’-双（1-芳甲基磷酸）用于工业水系统的综合抑制保护

本文介绍了在IVB标准水中St3软钢的腐蚀效果的研究结果,该水含有亚烃基二胺-N,N’-双（1-芳甲基磷酸）及它们与锌离子和邻苯二甲酸酐的混合物,这个研究使用电化学和电位动力学技术完成。使用重量分析法对水中含有的两种被选择的50mg／dm^3 1,5-戊二胺-N,N’-双（1-戊甲基磷酸）和1mg／dm^3邻苯二甲酸酐的混合物进行测试,确定它们对腐蚀和沉积形成的抵抗力。     

Influence of constant magnetic field on the electrodeposition of Co–Mo–W alloys

The aim of this study was to investigate the effect of a constant magnetic field (CMF) on the electrodeposition of Co–Mo–W alloys, and to observe changes in the topography of the alloy surface and its chemical composition. The investigation included the use of Cyclic Voltammetry (CV), Coulometry (C), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX). At higher electrolyte concentrations (so-called II), the CV method revealed an increase in cathode current density in a CMF environment. During crystallisation of the Co–Mo–W alloy, fractures appeared on the surface due to internal stresses. The application of CMF reduced the fracture widths resulting from the increased concentration of electroactive particles at the working electrode and the greater deposited alloy mass. Electrolyte motion under the influence of CMF caused an increase in the percentage of the main ferromagnetic component (Co) in the alloy.     

Bootstrap beacon creation for overcoming the effects of beacon anisoplanatism in a laser beam projection system

We address the problem of using adaptive optics to deliver power from an airborne laser platform to a ground target through atmospheric turbulence under conditions of strong scintillation and anisoplanatism. We explore three options for creating a beacon for use in adaptive optics beam control: scattering laser energy from the target, using a single uncompensated Rayleigh beacon, and using a series of compensated Rayleigh beacons. We demonstrate that using a series of compensated Rayleigh beacons distributed along the path provides the best beam compensation.     

Comparison of the high vacuum standard parameters computed from two models

The paper presents the results of analyses of the high vacuum standard obtained with the use of two models: traditional and the new, so-called ‘global’. It was found that the assumptions used in the traditional approach i.e. uniform and cosine gas flux density distribution at the orifice plane and the uniform distributions of the gas flux on the calibration and pumping chamber walls, are not fully fulfilled. These effects cause the effective pumping speed calculated with both models to differ and the relative difference equals 4×10⁻⁴. Additionally it was found that the uncertainty of the vacuum standard due to the orifice dimensions measurements being imprecisely computed using the global model is twice smaller taking into account the gas beaming effect.     

Applications of fullerene beams in analysis of thin layers

Molecular dynamics computer simulations have been employed to model ejection of particles from Ag{1 1 1} metal substrate and thin benzene overlayer bombarded by fullerene cluster projectiles. The sputtering yields are analyzed depending on the size (from C₂₀ up to C₅₄₀) and the kinetic energy (5-20 keV) of a projectile. It has been found that for clean metal substrate bombarded by 15 keV projectiles the maximum ejection is stimulated by the impact of the C₆₀ cluster. However, the size of the cluster projectile maximizing the yield depends on the kinetic energy of the cluster, shifting towards larger clusters as the impact energy increases. For a thin benzene overlayer, the yield increases monotonically with the size of the cluster within investigated range of fullerene projectiles and kinetic energies.