Journal of Advanced Materials in Engineering (Esteghlal)

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The cross-stream migration of a deformable drop in two-dimensional Poiseuille flow at finite Reynolds numbers is studied numerically. In the limit of a small Reynolds number (<1), the motion of the drop depends strongly on the ratio of the viscosity of the drop fluid to the viscosity of the suspending fluid. For a viscosity ratio 0.125, the drop moves toward the centre of the channe while for the ratio 1.0, it moves away from the centre until halted by wall repulsion. The rate of migration increases with the deformability of the drop. At higher Reynolds numbers (5-50), the drop either moves to an equilibrium lateral position about halfway between the centerline and the wall according to the so-called Segre-Silberberg effect or undergoes oscillatory motions. The steady-state position depends only weakly on the various physical parameters of the flow but the length of the transient oscillations increases as Reynolds number is raised, the density of the drop is increased, or the viscosity of the drop is decreased. Once the Reynolds number is high enough, the oscillations appear to persist forever and no steady state is observed. The numerical results are in good agreement with experimental observations, especially for drops that reach steady-state lateral position.

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In this research, Glass Form Ability (GFA) has been investigated in the new class of Fe-based amorphous
alloys. Indeed, the main purpose is to evaluate the effects of alloying with niobium on glass form ability of Fe_55-xCr₁₈Mo₇B₁₆C₄Nb_x (X=0, 3, 4, 5) alloys. Vacuum induction melting (VIM) was utilized for production of primary ingots and melt spinning process was used for production of thin ribbons required for kinetic and structural investigations. Kinetic analysis was done using
the data obtained from Differential Scanning Calorimetry (DSC) tests. Results showed that GFA and viscosity were enhanced by Nb alloying. It was also determined that devitrification transformation was accomplished in alloys by nucleation and growth mechanisms.

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Electrophoretic Deposition (EPD) weight is highly affected by electrophoretic mobility of powders in suspension. In theoretical aspect, electrophoretic mobility is influenced by suspension viscosity in opposite direction, and increasing in viscosity can decrease electrophoretic mobility and consequently can decrease EPD weight. In non-aqueous suspension, viscosity is determined by ion strengths of suspension. In this study, viscosity, electrical conductivity and deposit weight were determined for electrophoretic deposition (EPD) of alumina suspended in ethanolic solvent of Y-, Mg-, Ce- and La- salts, prepared in dispersant level between 350 to 1350 ppm. The concentration of XCly, (X: Mg, Y, Ce and La), is also found to be a critical factor to control  the viscosity. It is shown that the deposit weight is influenced by precursor concentration, and on the other hand, electrical conductivity, viscosity or the pH of the suspension cannot change the yield. All concentrations interactions, except Mg × Ce concentration are significant in ANOVA model. The viscosity of suspension reached 2.5 mPa.s with Mg-, Y-, La- and Ce- decreased to 100, 100, 100 and 0 ppm in low iodine concentration (400 ppm). The reason is that heavier cations can be adsorbed to alumina surface with iodine adsorption, but lighter Mg- cations can be adsorbed under the influence of OH groups excited on alumina surface.