Solid Surface In Presence Research Articles

Probing the interaction mechanism between oil droplets with asphaltenes and solid surfaces using AFM

Wetting phenomena of oil/water/solid systems are fundamentally governed by the stability of confined water film and interaction mechanism between oil droplet and solid surface in water. Herein, droplet probe AFM was used to quantify the surface forces of model oil droplets including toluene and heptol in presence of interfacial asphaltenes interacting with mica surfaces of varied hydrophobicity in different water environments. It was found that adsorption of asphalenes at oil/water interface could result in the enhanced electrical double layer (EDL) repulsion at low salinity while strengthen the steric repulsion at high salinity, both of which contributed to a more stable water film between oil droplets and mica surfaces, inhibiting oil droplet attachment. Addition of heptane strengthened the repulsive EDL force and steric hindrance since more asphaltenes were adsorbed onto the interface. For hydrophobized mica surface, the attractive hydrophobic interaction could overcome steric hindrance due to interfacially adsorbed asphaltenes, thereby inducing strong attachment and adhesion of oil droplet. Our results demonstrate the nanomechanical mechanism underlying the interactions between oil droplets and solid surfaces in presence of interfacial materials, which can further explain the wetting of oil/water/solid systems in many engineering applications such as oil fouling and corrosion, and oil/water separation.

Role of viscogens on the macromolecular assemblies of fibrinogen at liquid/air and solid/air interfaces.

In this study, an attempt has been made to understand the organization and association of fibrinogen (Fg) in solvent environment induced by viscogens such as 1-ethyl 3-methyl imidazolium ethyl sulfate (IL-emes), Ficoll, and Trehalose. The author observed that Fg in IL-emes adsorbed on solid surface shows higher β-sheet conformation. Shear viscosity measured using quartz crystal microbalance, for Fg in IL-emes was highest with a corresponding higher adsorbed mass 3.26 μg/cm(2). Associated assemblies of the protein at the liquid/air interface were monitored with changes in surface tension and were used to calculate work of adhesion. Changes in work of adhesion were used as a tool to measure the adsorption of Fg to solid surfaces in presence of viscogens and highest adsorption was observed for hydrophilic surfaces. Scanning electron microscopy images show Fg in trehalose forms elongated bead like structures implying organization of the protein at the interface. Crowding in the solvent environment induced by viscogens can slow down organization of Fg, leading to macromolecular assemblies near the interface.

Numerical Treatment of the MHD Convective Heat and Mass Transfer in an Electrically Conducting Fluid over an Infinite Solid Surface in Presence of the Internal Heat Generation

Numerical solutions of a set of non-linear partial differential equations are investigated. We obtained the velocity distribution of a conducting fluid flowing over an infinite solid surface in the presence of an uniform magnetic field and internal heat generation. The temperature and concentration distributions of the fluid are studied as well as the skin-friction, rate of mass transfer and local wall heat flux. The effect of the parameters of the problem on these distributions is illustrated graphically.