Controlled synthesis and size-dependent thermal conductivity of Fe3O4 magnetic nanofluids

The effect of nanoparticle size (4 similar to 44 nm) on the thermal conductivities of heat transfer oils has been systematically examined using iron oxide nanoparticles. Such Fe3O4 nanoparticles were synthesized by a simple one-pot pyrolysis method. The size (16 similar to 44 nm), shape and assembly patterns of monodisperse Fe3O4 nanoparticles were modulated by only controlling the amount of Fe(acac)(3). After the as-prepared Fe3O4 NPs were dispersed in heat transfer oils, the prepared magnetic nanofluids exhibit higher thermal conductivity than heat transfer oils, and the enhanced values increase with a decrease in particle size. In addition, the viscosities of all nanofliuids are remarkably lower than that of the base fluid, which has been found for the first time in the nanofluid field. The promising features offer potential application in thermal energy engineering.