Magnetically controllable nanofluid with tunable thermal conductivity and viscosity

Abstract

We report the viscosity (η) and thermal conductivity (k) enhancement in a stable magnetic nanofluid containing particles size <10 nm as a function of volume fraction (vol %), shear rate, magnetic field, and time. Without field, the η enhancement of nanoparticle is much larger than that of k. In a nanofluid with 0.078 vol %, the k/η ratio is tunable from 0.725 to 2.35 by controlling the applied field. Our results show that magnetic nanofluids with tunable k/η ratio can be used as multifunctional “smart materials” for miniature cooling cum damping applications.

Enhanced magnetic response of fluids using self-assembled petal-like iron oxide particles

“…When 10 wt % of the spherical particles were added, there is a moderate increase in the storage modulus under the magnetic field, which is previous studies. 4,15,16 At same solid content and magnetic field, as shown in Fig. 3͑b͒, the storage modulus of SAIO fluids is two times as large as that of the spherical particles.…”

“…3 This tunable rheology is intensively investigated for their use in biomedical and mechanical application such as targeted drug delivery, biomolecule separation, and heat transfer. 2,4 Recently, the separation methods using magnetic particle have been developed to easily isolate target biomolecules from sample solution with minimum efforts. This direct separation of biomolecules may save resources and time, compared with traditional separation methods.…”

The Viscosity of Nanofluids: A Review of the Theoretical, Empirical, and Numerical Models

“…Magnetic nanofluids, also called ferrofluids, magnetic fluids and/or MRNF [217,218], are a type of nanofluids in which the suspended nanoparticles are ferromagnetic nanoparticles, ferrimagnetic nanoparticles and metallic nanoparticles that are influenced by magnetic fields [219]. These fluids have been proved to be tuneable to produce the desired thermophysical characteristics in the presence of an external magnetic field [181,220,221]. Issues about its stability are of great concern owing to the fact that magnetic nanoparticles (α-and -Fe2O3, Fe3O4, CoFe2O4, Co, Fe-C, MnFe2O4, MgFe2O3, Fe3N, Ni, Fe, Fe-Co or Ni-Fe) are very heavy.…”

“…Even with relatively viscous basefluids [43], they display non-Newtonian characteristics, which can be attributed to the formation of agglomerates. This is one way to measure the stability of the magnetic nanofluids [181,219]. To overcome the stability problem, different methods of synthesising magnetic nanoparticles have been explored, some of which are wet-grinding [222], chemical co-precipitation [223][224][225] and solvothermal [43] methods.…”

“…Some researchers have also deduced that rheological characteristics, i.e. Newtonian, signify stable nanofluids and non-Newtonian characteristics signify otherwise [181]. All these characterisation procedures have their deficiencies, which are still preventing the report of either qualitative results or a report that represents the actual situation that is encountered in real-life application.…”