Graphene for Water-Based Nanofluid Preparation: Effect of Chemical Modifications on Dispersion and Stability
Résumé
Graphene, whatever its number of layers, is recognized for heat and thermal transfer ability. As it is widely known to be highly hydrophobic, its use in water-based nanofluid development requires first to improve both their dispersion and stability properties. Here, we have investigated several ways to chemically modify the surface properties of multi-layer graphene in order to increase their hydrophilic character. Chemical reactivity of graphene was deeply analyzed based on a multi-scale characterization using TEM, Raman spectroscopy and TGA-MS coupled technique. By optimizing and combining both covalent and non-covalent functionalization, stable graphene-based nanofluids under static conditions could be prepared with a straightforward approach. Moreover, we have investigated their flowing behavior. Contrary to graphene nanosheets strongly attacked by HNO3, under a gentler oxidation treatment using KMnO4, stability is well preserved under flowing conditions. Such high-stability nanofluids could help toward the practical use of graphene-based dispersions as heat transfer fluid in flowing systems.