Multidentate Cyclohexylphosphonic Acid as Corrosion Inhibitor for Structural Steel in 3.5% NaCl Solution: An Experimental and Computational Study

Protection of Metals and Physical Chemistry of Surfaces - The inhibition effect of cyclohexylphosphonic acid (CHPA) on the corrosion of structural steel (EN 10027) in 3.5% sodium chloride solution...     

Magnetohydrodynamic co-rotating flow in a vertical cylindrical container

ABSTRACT

The effect of an external axial magnetic field on the liquid metal flow produced by co-rotation of the top and bottom disks in a vertical cylindrical container with a vertical temperature gradient is numerically analyzed. The governing Navier–Stokes, energy, and potential equations along with appropriate boundary conditions are solved using the finite-volume method. Comparisons with the previous results were performed and found to be in excellent agreement. It was observed that the Reynolds number is increased, and the axisymmetric basic state loses stability for circular patterns of axisymmetric vortices and spiral waves. In the mixed convection case the axisymmetric mode disappears, giving an asymmetric mode m = 1. It was also found that the primary thresholds, Re_cr corresponding to modes m = 1 and 2, increase with an increase in Hartmann number (Ha). We can therefore conclude that when the magnitude of the magnetic field exceeds a certain value, the instability becomes a steady bifurcation. Finally, stability diagrams were established according to the numerical results of this investigation. These diagrams show the evolution of primary thresholds as a function of Hartmann number for various values of Richardson number.     

Synthesis and characterization of polystyrene coated iron oxide nanoparticles and asymmetric assemblies by phase inversion

Films with a gradient concentration of magnetic iron oxide nanoparticles are reported, based on a phase inversion membrane process. Nanoparticles with ～13 nm diameter were prepared by coprecipitation in aqueous solution and stabilized by oleic acid. They were further functionalized by ATRP leading to grafted polystyrene brush. The final nanoparticles of 33 nm diameter were characterized by TGA, FTIR spectroscopy, GPC, transmission electron microscopy, and dynanmic light scattering. Asymmetric porous nanoparticle assemblies were then prepared by solution casting and immersion in water. The nanocomposite film production with functionalized nanoparticles is fast and technically scalable. The morphologies of films were characterized by scanning electron microscopy and atomic force microscopy, demonstrating the presence of sponge‐like structures and finger‐like cavities when 50 and 13 wt % casting solutions were, respectively, used. The magnetic properties were evaluated using vibrating sample magnetometer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41368.     

Hydrogeological Behavior of a Store-and-Release Cover: A Comparison Between Field Column Tests and Numerical Predictions With or Without Hysteresis Effects

Non-hysteretic numerical codes are often used to design store-and-release (SR) cover systems. Hysteretic and non-hysteretic predictions were compared using field measurements with instrumented column tests, consisting of fine-grained SR material (phosphate limestone waste) with high hysteretic behavior (hysteretic ratio ≈11) placed over a capillary break layer. Transient unsaturated water flow was then predicted using a one-dimensional code (HYDRUS-1D) under semi-arid climatic conditions over 1 year. Non-hysteretic simulation based on the main wetting curve of the SR material and hysteretic simulation were validated with the measured data. The compared results showed better agreement between measured and predicted values for non-hysteretic simulation during wet periods, whereas the hysteretic scenario showed better agreement with field measurements during dry periods. The influence of hysteresis effects on the complex transient unsaturated water flow of the tested scenarios and conditions is considered minor.