Interaction of oxygen functionalized multi-walled carbon nanotube nanofluids with copper

Abstract

As a measure to increase the heat transfer from a surface, the application of nanofluids made up of nanoparticles stably dispersed in traditional coolants is considered. Researchers have succeeded in preparing nanofluids, that remain stable when stored in glass vials for long periods of time. However, it is still not known whether these nanofluids remain stable in the presence of metals, which is inevitable to use them in industrial heat exchangers. In this article, we show that an ethanol-based nanofluid containing oxygen functionalized multi-walled carbon nanotubes remained stable for more than one year when in contact with copper and when boiled. We investigated the reason for this observation by measuring individual particle size with atomic force microscopy, solvent diffusion co-efficient by nuclear magnetic resonance spectroscopy and molecular interactions by Fourier transform infra-red spectroscopy. We understood that the exceptional stability of the ethanol-based nanofluid is due to the strong hydrogen bonding and polar interactions between the ethanol molecules and the oxygen-containing functional groups on functionalized carbon nanotubes. When tested for heat transfer enhancement, the stable ethanol-based nanofluid gave a 7% rise in cooling rate compared to that with pure ethanol.