Graphene modification for preparation of stable nanofluids
Résumé
Carbon-based nanomaterials, such as carbon nanotubes or graphene, are recognized to be excellent
candidates for high performance materials. Graphene which is a layer of sp2 hybridized carbon atoms
with a thickness of only one atom possesses various magnificent properties that are not shared by
other materials [1]. Their excellent intrinsic thermal properties have, in particular, led a strong
interest for heat transfer applications [2]. However, dispersion of such material in water to prepare
stable nanofluids is highly difficult. And the dispersion issue is pointed out to be the main reason for
the reported disappointing and contradictory results in term of performance of such nanofluids [3].
Indeed carbon nanoparticles are usually strongly hydrophobic and tend to separate from the liquid
medium, aggregate and sediment. Graphene being a new material, its efficient and controlled surface
modification is still challenging. Our paper proposes different ways to chemically modify the
properties of graphenic materials in order to increase their hydrophilic character improving that way
their dispersion. Chemical reactivity of graphene upon the applied treatments was deeply analyzed
based on the carried out multi-scale characterization of the modified graphene. We will discuss
graphene reactivity in comparison with other nanostructured carbon materials. Rheological
properties of the prepared graphene dispersions will be presented and discussed regarding the
practical use of such dispersions under flowing conditions for heat transfer applications.