Nanoparticle in a Nanofluid Film Spreading on a Surface
Original entry by Hyerim Hwang, AP 226, Spring 2012. not finished
Alex Nikolov, Kirti Kondiparty, and Darsh Wasan, "Nanoparticle Self-Structuring in a Nanofluid Film Spreading on a Solid Surface", Langmuir 2010 26(11), 7665-7670
This research shows the solid-oil interactions in the presence of a silica nanoparticle aqueous suspension, using a combined differential and common reflected light interferometry by observing the three-phase contact region as presented in Figure 1. Figure 2 shows a sequence of photomicrographs depicting the development of the particle layering phenomenon during the film thinning process. It is shown that a photomicrograph depicting four different particle structural transitions inside the nanofluid film in Figure 3. Here, the experiments revealed that the nanofluid film thickness stability on a solid substrate depends on the film size. Figure 4 presents an example of a small oil drop, that shows that the nanofluid film formed between oil drop and the glass surface surrounded by the meniscus, indicated by the consecutive dark and bright Newton interference rings around the perophery of the film. The interferogram depicting the film-meniscus profile is shown in Figure 4C. Figure 5 shows the film-meniscus region profile corresponding to the maxima and minima in the interferogram.
The film-meniscus microscopic contact angle is related to the disjoining pressure, given by the equation above which is Frunkim-Derjaguin equation. The second term on the right side of the equation is the interaction energy between the film surfaces. Thus, the film energy can be calculated from the measured values of the contact angle versus film thickness using the equation. Figure 6 is what this research got as experimental results.
In this paper, the experimental results of the nanoparticle self-ordering and stepwise thinning of the nanofluid film fromed between an oil drop and a solid surface are reported. This also presents the measured contact angle of film-meniscus and thickness corresponding to the number of particle layers on a solid surface. These were used for getting the film energy due to the nanoparticle layering within the nanofluid film.