| Nanofluids comprising nanoparticle suspensions in liquids have significant industrial applications. Recent experiments and modeling conducted in our laboratory have demonstrated that the spreading of nanofluids, liquid suspensions of nanosized particles, on solids are enhanced due to self-structuring of nanoparticles in the confined three-phase oil-nanofluid-solid contact region.;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, glass, and a silicon wafer. Based on 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. We found that the concentration of the nanoparticles in the layer close to the substrate increased with an increase in the nanoparticle concentration and correlated qualitatively with the change in the substrate wettability.;We report here our results of the effects of several parameters, such as the nanoparticle concentration, liquid salinity, temperature, and the substrate contact angle, on the motion of the two contact lines and their effects on the detachment of the oil droplet. We employed the frictional model to predict the outer contact line velocity and our previous theoretical model to predict the inner contact line velocity. The theoretical predictions agreed quite well with the experimentally measured values of the velocities.;In the present work, we explore the application of a new mechanism for the solid particle detachment using latex particles on glass and a copper-coated wafer substrate using nanofluids.;Our results showed that the detachment of the particulate solid particles on the solid substrate was clearly enhanced by the nanofluids, compared to using only pure liquids. The detachment efficiency was increased with the increase in the nanoparticle volume fraction. Our nanofluids also showed a greater detachment efficiency for the particulate soil removal from the copper-coated wafer substrates compared to that of pure liquids.;Our findings in this thesis provide new insights for the novel application of the structural disjoining energy mechanism for cleaning hard surfaces. |
