Investigation of the Rheological Properties of Zn-Ferrite/Perfluoropolyether Oil-Based Ferrofluids

Abstract

The rheological properties of ferrofluids are related to various applications, such as sealing and loudspeakers, and have therefore attracted widespread attention. However, the rheological properties and their influence on the mechanisms of perfluoropolyether oil (PFPE oil)-based ferrofluids are complicated and not clear. Here, a series of PFPE oil-based ferrofluids were synthesized via a chemical co-precipitation method, and their rheological properties were revealed, systematically. The results indicate that the prepared Zn-ferrite particles have an average size of 12.1 nm, within a range of 4–18 nm, and that the ferrofluids have excellent dispersion stability. The activity of the ferrofluids changes from Newtonian to non-Newtonian, then to solid-like with increasing w from 10 wt% to 45.5 wt%, owing to their variation in microstructures. The viscosity of the ferrofluids increases with increasing Mw (the molecular weight of base liquid PFPE oil polymer), attributed to the increase in entanglements between PFPE oil molecules. The magnetization temperature variation of Zn-ferrite nanoparticles and viscosity temperature variation of PFPE oil together contribute to the viscosity temperature change in ferrofluids. The viscosity of the ferrofluids basically remains unchanged when shear rate is above 50 s−1, with increasing magnetic field strength; however, it first increases and then levels off when the rate is under 10 s−1, revealing that the shear rate and magnetic field strength together affect viscosity. The viscosity and its alteration in Zn-ferrite/PFPE oil-based ferrofluids could be deduced through our work, which will be greatly significant in basic theoretical research and in various applications.

Size Effect of Fe3O4 Nanoparticles on Magnetism and Dispersion Stability of Magnetic Nanofluid

“…The conventional ferrofluids possess low saturation magnetization due to their small average particle size (i.e., ∼10 nm) and the differences of particle morphology and types of magnetic component (López-López et al, 2012). Even though some magnetorheological fluids contain larger average particle size (i.e., ∼ 1 µm) with higher saturation magnetization (Tang, 2011), they exhibit unsatisfied dispersion stability compared to ferrofluids (Chen et al, 2021). Therefore, the two critical parameters, saturation magnetization and stability, must be considered simultaneously for different nanofluids application occasions.…”

Experimental Investigation of Magnetorheological Behavior of Fe3O4@PVP@OA Ferrofluid for Potential Application in Gas Condensate Blockage Reduction

“…As shown in Figure (a), the samples experienced a slight increase in shear viscosity with nanoparticle concentrations in the absence of an external magnetic field. Indeed, the polymeric chains were coated on the surfaces of magnetic nanoparticles, leading to increases hydrodynamic volumes, followed by increases in shear viscosities of the prepared ferrofluids up to 3.5% in Ferrofluid 2. , Based on the obtained results, the magnetic Fe 3 O 4 nanoparticles coated with PVP and OA showed acceptable efficiencies, so that the ferrofluids comprising kerosene and Fe 3 O 4 @PVP@OA nanoparticles were considered for further magnetorheological studies in the presence of an external magnetic field. As shown in Figure (b) and (c), once the magnetic fields were applied at various intensities to Ferrofluids 1 and 2 there was no linear relationship between shear stress and shear rate, indicating non-Newtonian behaviors of the ferrofluids under magnetic fields with various intensities.…”

“…Indeed, the polymeric chains were coated on the surfaces of magnetic nanoparticles, leading to increases hydrodynamic volumes, followed by increases in shear viscosities of the prepared ferrofluids up to 3.5% in Ferrofluid 2. 41,70 Based on the obtained results, the magnetic Fe 3 O 4 nanoparticles coated with PVP and OA showed acceptable efficiencies, so that the ferrofluids comprising kerosene and Fe 3 O 4 @PVP@OA nanoparticles were considered for further magnetorheological studies in the presence of an external magnetic field. As shown in Figure 15 not suitable owing to the differences between experimental data and the model when an external magnetic field was applied.…”

“…In fact, the modified nanoparticles adhered on the surface can cause a complex dynamic wetting property and consequently a change in flow property. 70,77 In addition to this point, it is obvious that the pressure drop has reduced in the presence of the magnetic field creating an external force at the end of the micromodel which accelerated movement of the ferrofluid near the magnet. This can be referred to the fact that the external magnetic field might alter the boundary layer thickness and the flow pattern as shown in the magnetorheological behavior study of the ferrofluids (Section 3.7) during the flow through the micromodel.…”

“…This may be related to a change in liquid–solid wetting properties because the surfactant used to stabilize nanoparticles tends to lower the surface tension in comparison to a pure carrier (kerosene). In fact, the modified nanoparticles adhered on the surface can cause a complex dynamic wetting property and consequently a change in flow property. , In addition to this point, it is obvious that the pressure drop has reduced in the presence of the magnetic field creating an external force at the end of the micromodel which accelerated movement of the ferrofluid near the magnet. This can be referred to the fact that the external magnetic field might alter the boundary layer thickness and the flow pattern as shown in the magnetorheological behavior study of the ferrofluids (Section ) during the flow through the micromodel. , It can be concluded that loading magnetic nanoparticles into kerosene associated with the presence of external magnetic field led to a decrease in pressure drop within the micromodel apparatus.…”