Surfactant Effect on the Thermal and Electrical Behaviors of Sonochemically Synthesized Fe and Fe–PVP Nanofluids and Insight into the Magnetism of Their in Situ Oxidized α-Fe2O3 Analogues

Abstract

Magnetic nanofluids are dispersions of magnetic nanoparticles in a diamagnetic base liquid, which display distinct physical properties that can be tuned easily by an external magnetic field, electric current, and temperature. Iron nanofluids were synthesized sonochemically in a one-step process and were observed to oxidize in situ over prolonged air exposure, forming α-Fe2O3 nanofluids. The thermal conductivity measurements on these single-step fabricated magnetic nanofluids were performed for the first time and showed enhanced thermal transport. Hence, we present a new one-pot synthesis approach to improve the heat transfer. The electrical properties of the iron and ferric oxide nanofluids in the presence and absence of a surfactant are also newly reported in this paper. The different electrical conductivities among the two sets of nanofluids are interpreted, and mechanisms are proposed to account for the observed deviation. The heat transport by Fe2O3 nanofluids with respect to the magnetic flux was inv...