Effect of substrate bias voltage on corrosion of TiN/Ti multilayers deposited by magnetron sputtering

Austenitic stainless steel can be attack by localized corrosion in saline environments, such as seawater. TiN/Ti multilayers can improve the corrosion resistance of the stainless steel better than TiN monolayers, because the titanium layers improve the impermeability of TiN/Ti multilayers. In this work, 1.75-4.55 μm thick layers were deposited on to grounded or −100 V biased substrates of 304 stainless steel substrates by reactive magnetron sputtering. The corrosion resistance of the layers was studied by means of potentiodynamic polarization in 0.5 M NaCl solutions. It was found that the pitting corrosion resistance was dependent on the bias and period number of the multilayers.     

Vibration-induced granular segregation: a phenomenon driven by three mechanisms

The segregation of large spheres in a granular bed under vertical vibrations is studied. In our experiments, we systematically measure rise times as a function of density, diameter, and depth, for two different sinusoidal excitations. The measurements reveal that, at low frequencies, inertia and convection are the only mechanisms behind segregation. Inertia (convection) dominates when the relative density is greater (less) than one. At high frequencies, where convection is suppressed, fluidization of the granular bed causes either buoyancy or sinkage and segregation occurs.     

Sequenced elimination-reduction and elimination-cyclopropanation reactions of 2,3-epoxyamides promoted by samarium diiodide. Synthesis of 2,3-dideuterioamides and cyclopropanamides

An easy and general sequenced elimination/reduction or elimination/cyclopropanation process promoted by samarium diiodide or/and CH₂I₂/Sm provide an efficient method for synthesising 2,3-dideuterioamides 3 or cyclopropanamides 8, respectively. The transformations take place in high yields and with total or high selectivity from the easily available 2,3-epoxyamides.     

Attraction-driven disorder in a hard-core colloidal monolayer

Monte Carlo simulation techniques were employed to explore the effect of short-range attraction on the orientational ordering in a two-dimensional assembly of monodisperse spherical particles. We find that if the range of square-well attraction is approximately 15% of the particle diameter, the dense attractive fluid shows the same ordering behavior as the same density fluid composed of purely repulsive hard spheres. Fluids with an attraction range larger than 15% show an enhanced tendency to crystallization, while disorder occurs for fluids with an attractive range shorter than 15% of the particle diameter. A possible link with the existence of "repulsive" and "attractive" states in dense colloidal systems is discussed.     

E-CUSP scheme for the equations of ideal magnetohydrodynamics with high order WENO Scheme

An E-CUSP (energy-convective upwind and split pressure) scheme is developed to solve the equations of magnetohydrodynamics. Fifth order WENO reconstructions are employed to calculate the fluxes in order to achieve high order spacial accuracy. A characteristic speed of sound by averaging the fast wave speed and the acoustic speed of sound is suggested to evaluate the Mach number, which will yield robust and accurate solutions. The numerical experiments have demonstrated the accuracy and the capability of the new scheme to capture complex interactions of multiple shocks and vortices.     

A simple shock‐capturing technique for high‐order discontinuous Galerkin methods

This article presents a novel shock‐capturing technique for the discontinuous Galerkin (DG) method. The technique is designed for compressible flow problems, which are usually characterized by the presence of strong shocks and discontinuities. The inherent structure of standard DG methods seems to suggest that they are especially adapted to capture shocks because of the numerical fluxes based on suitable approximate Riemann solvers, which, in practice, introduces some stabilization. However, the usual numerical fluxes are not sufficient to stabilize the solution in the presence of shocks for large high‐order elements. Here, a new basis of shape functions is introduced. It has the ability to change locally between a continuous or discontinuous interpolation depending on the smoothness of the approximated function. In the presence of shocks, the new discontinuities inside an element introduce the required stabilization because of numerical fluxes. Large high‐order elements can therefore be used and shocks captured within a single element, avoiding adaptive mesh refinement and preserving the locality and compactness of the DG scheme. Several numerical examples for transonic and supersonic flows are studied to demonstrate the applicability of the proposed approach. Copyright © 2011 John Wiley & Sons, Ltd.     

Use of Magnetic Resonance Imaging as a Tool for the Study of Foamy Oil Behavior for an Extra‐Heavy Crude Oil. T2 /Viscosity Correlation with Respect to Pressure

The purpose of this work is to present the results of the phase behavior study for a live heavy oil during a pressure depletion process using magnetic resonance imaging (MRI) as a tool to characterize foamy oil phenomena. The experiments were carried out in the pressure range of 13.1 to 1.4MPa. Signal intensity images were obtained at each pressure and with respect to time, that is, approximately for a total time of 3h after each pressure change. It is possible to see a variation in intensity across the sample. These changes can be associated with changes in mobility as well as segregation of the oil. It was also possible to observe that what we trust is the formation of gas channels at the last two pressure values, as it comes out of solution. A correlation between the transverse relaxation time T2 and temperature was established with the aim of producing one between T2 and viscosity. In this way viscosity maps for the live oil were obtained as a function of pressure and time. It was observed that above the bubble point, the viscosity maps varied from low to high to low with respect to time for the same pressure. Below the bubble point the situation is reverse. The viscosity map changes from high to low to high with respect to time for the same pressure. The study shows the potential use of MRI to follow viscosity changes during pressure depletion test in a PVT MRI cell.     

The order of addition of corn starch/lithium perchlorate/glycerol affects the optical,mechanical, and electrical properties of a solid polymer electrolyte

Optical, mechanical, and electric properties of solid polymer electrolyte (SPE) were affected by the order of addition of corn starch (S), lithium perchlorate (Li), and glycerol (G) during the preparation process. Four formulations were made based on whether Li was added prior to S gelatinization (simultaneous formulations SGLi and SLi+G) or whether it was added after S was gelatinized (sequential formulations SG+Li and S+LiG). Simultaneous formulations produced films with smaller elongation-at-break response (60–75%) relative to their sequential counterparts (75–82%). The simultaneous formulations exhibited higher electrical conductivity (～0.7 mS cm^?1) and capacitance (～0.017 F cm^?2) and electrochemical stability than the sequential formulations (～0.9 mS cm^?1 and ～0.012 F cm^?2) at room temperature. Results from FTIR and DSC analyses indicated that starch re-crystallization in casting phase could lead to variations on electrical properties for the different SPE formulations. It was postulated that Li cations replace hydrogen ions inside starch molecules, retarding the re-crystallization of starch molecules.     

A primitive model for hexamethylpararosaniline (crystal violet) monomolecular adlayer: a Monte Carlo simulation study

The NVT Monte Carlo simulation results are reported for a model of two-dimensional (2D) chemically associating fluid with six attractive sites per monomer disc. Three of these sites are of the type α and the other three of the type β. The sites α and β are fixed inside a hard core, they follow each other anticlockwise, with a `valence' angle of 60°. It is assumed that only α+β site–site association of two different discs occurs. Complex formation, dependent on the density and association energy, is much more sophisticated, in comparison to previously studied models of dimerizing and polymerizing discs. An analysis of complexes in terms of the fractions of singly, doubly,…, hexa-bonded particles is performed, and the dimensions and distributions of complexes are studied. We obtained the pair distribution functions of particles and structure factor in the fluid layer. The model was inspired by experiments on visualization of organic monolayers in the framework of scanning tunneling microscopy (STM). Currently it yields a preliminary insight into the molecular organization of crystal violet molecules on the iodine covered (111) single-crystal surface plane observed experimentally. Extensions of the model and methodology are discussed.