Nanofluids Alter the Surface Wettability of Solids

Abstract

We report the results of our studies on the changes in the contact angle and interfacial tension using a nanofluid composed of silica nanoparticles dispersed in water on three different solid substrates: gold (partially hydrophobic), glass (hydrophilic), and a silicon wafer (hydrophilic). We used both the goniometric method and drop-shape analysis to make the measurements. On the basis of the results of the drop-shape analysis using the Laplace equation, we evaluated the contributions of the interfacial tension change to the equilibrium contact angle and the presence of nanoparticles near the solid substrate, thereby elucidating the change in the wettability of the solid substrate. We found that the nanoparticles decrease the contact angle of the substrate with the increase in the nanoparticle concentration. To rationalize our experimental observations on the decrease in the contact angle of the solid substrate in the presence of nanoparticles, we calculated the surface volume fraction of the nanoparticles in the layer near the solid substrate using the particle layering model (based on the nanoparticles' excluded volume effect). We found that the volume fraction of the nanoparticles in the layer close to the substrate increased with an increase in the nanoparticle volume fraction in the bulk and correlated qualitatively with the change in the substrate wettability. The extent of the wettability alteration depends on the volume fraction of the nanoparticles, their size, and the type of substrate. We found a strong correlation between the change in the substrate wettability and the nanoparticle volume fraction in the layer closer to the substrate surface.

Review on enhanced oil recovery by nanofluids

“…Note that IFT will definitely be reduced if nanoparticles are doped with surfactant groups and surface modified. As pointed out by Lim et al (2015), a study using a pure nanofluid system (just nanoparticles, without any surface-active impurities) needs to be conducted in order to establish conclusively the role of the nanoparticles in altering IFT and surface wettability. Hu et al (2016) conducted such a study and found little effect of nanoparticle addition on IFT.…”

Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration

“…Obviously, simple nanofluid flooding (containing only nanoparticles) at low concentration (0.01 wt % or less) shows the greatest potential from the environmental and economic perspective. Several corresponding oil displacement mechanisms have also been introduced, including reduction of oil-water interfacial tension (6,7), alteration of rock surface wettability (8)(9)(10), and generation of structural disjoining pressure (11)(12)(13). However, the oil recovery factor is below 5% with 0.01% nanoparticle loading in core flooding tests in a saline environment (2 wt % or higher NaCl content).…”

Performance Evaluation and Lubrication Mechanism of Water-Based Nanolubricants Containing Nano-TiO2 in Hot Steel Rolling

“…In this case, the nanolubricant with better dispersibility, stronger wettability and higher concentration is more inclined to decrease rolling force to a larger extent. Many researchers have reported that the wettability of nanolubricant improves with increasing the concentration of NPs into base liquid [26][27][28]. Therefore, when the concentration of nano-TiO 2 is lower than 4.0 wt%, there are insufficient TiO 2 NPs left to form lubricating film and make rolling effect due to loss of nanolubricants when contacting the hot steel surface.…”