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

Fang Chen,Shengnan Yan,Xiaobing Liu,Hao Fu,Zhaoqiang Yan,Zhenggui Li

doi:10.3390/nano11102653

Fang Chen, Shengnan Yan + Show 4 more

Open Access

https://doi.org/10.3390/nano11102653

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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.

Highlights

Ferrofluid, a functional fluid material, prepared by dispersing magnetic nanoparticles coated with surfactants in base liquids [1], which are widely used in sealing, biomedicine, aerospace, etc. [2,3,4], owing to its having both mobility and magnetism under magnetic fields
The rheological properties of ferrofluids play a significant role in various applications [5,6], for example, fluids of low viscosity are needed in high speed seals, or the heat induced by friction will make sealing pressure reduce [7]
The viscosity of silicon oil-based ferrofluids decreases with rising temperature, and increases with increasing magnetic field strength; the formation and destruction of chains and droplets are the key factors affecting magnetoviscous properties [15,16]

Summary

Introduction

Ferrofluid, a functional fluid material, prepared by dispersing magnetic nanoparticles coated with surfactants in base liquids [1], which are widely used in sealing, biomedicine, aerospace, etc. [2,3,4], owing to its having both mobility and magnetism under magnetic fields. The viscosity of silicon oil-based ferrofluids decreases with rising temperature, and increases with increasing magnetic field strength; the formation and destruction of chains and droplets are the key factors affecting magnetoviscous properties [15,16]. The viscosity of kerosene-based ferrofluid was related to the strength and direction of the magnetic field, due to the quasiperiodic chains or columns formed [18,19] Another category is the differences in ferrofluids (nanoparticle concentration, average particle size, particle size distribution, base liquid types, types of particles, etc.)—all these factors will have different effects on the rheological properties. The application conditions of ferrofluids, such as temperature, magnetic field strength and sealing ion speed in industry are often complex; viscosity and its alteration in PFPE oil-based ferrofluids could not be predicted—the influence mechanism is not clear and needs to be further researched. The findings on the rheological properties of Zn-ferrite/PFPE oil-based ferrofluids will provide the basis for theoretical investigation and will improve their application performance

Preparation of Zn-Ferrite Nanoparticles and PFPE Oil-Based Ferrofluid

Methods

The Internal Structures and Magnetism of Zn-Ferrite Nanoparticles

The Rheological Properties of PFPE Oil-Based Ferrofluids

It hasabeen reported that the viscosity ofin polymers asfact thethat

Conclusions