Nuclear magnetic resonance-based study of ordered layering on the surface of alumina nanoparticles in water

Layering of water molecules on the surface of alumina nanoparticles in an alumina/water nanofluid is studied using nuclear magnetic resonance (NMR). The data suggest that a thin ordered layer (similar to 1.4 nm) of water molecules surrounds each nanoparticle. This ordered layer increases the nanoparticle effective volumetric fraction; however, the nanofluid thermal conductivity appears to be unaffected by this layer, and in good agreement with Maxwell's effective medium theory. Furthermore, the NMR data suggest that the nanoparticles do not enhance, but rather stifle micromixing in the base fluid. (C) 2009 American Institute of Physics. [doi:10.1063/1.3276551]