Study of viscoelastic properties of magnetic nanofluids: an insight into their internal structure

Abstract

Three magnetic nanofluids were prepared as colloidal suspensions in ethylene glycol using two types of Fe 3 O 4 ferrimagnetic nanoparticles (MGMFs)-one of them commercial (CMGMFs) and the other synthesized in our laboratory (SMGMFs)-and from one type of Fe 2 O 3 nanoparticle (HMF). Using a shear stress controlling rheometer, they were characterized in order to comparatively analyze their viscoelastic behavior and structure. Effects of magnetic particle size and nature on elastic and viscous moduli were determined. The static yield stress and the percolation concentration were also obtained.The fractal dimension (D f ) was estimated from the suspension static yield-stress and volume fraction (f) dependence, and was determined to be D f z 2.3 for SMGMFs and CMGMFs, and D f z 1.5 for HMFs. The corresponding aggregation models and structures were discussed. Finally, master curves were obtained for the magnetic fluids under study, which provide valuable information to estimate the material response for any concentration.

Elemental substitution tuned magneto-elastoviscous behavior of nanoscale ferrite MFe2O4 (M = Mn, Fe, Co, Ni) based complex fluids

“…where, the shear stress (  ) is related to the yield stress ( y  ), the plastic viscosity ( pl  ) and the imposed shear rate ( ). The apparent viscosity app  for the MRF is defined as app     (7) Introducing the non-linear nature of the plastic viscosity, the apparent viscosity can be remodeled in terms of the infinite shear viscosity as app y pl…”

“…It has been theorized that attachment and detachment of the sidechains from dense clusters of particles is responsible for the dynamic viscoelastic behaviors of MRFs [6]. Some studies have shown that the dipole interactions among MNPs are primarily responsible for the difference in aggregation behavior [7,8], which in turn governs rheological features. Measurement techniques like neutron scattering [9,10] and X-ray scattering [11,12] have been employed by researchers to reveal information regarding the field induced microstructures of the MRFs.…”

Co3O4 ethylene glycol-based nanofluids: Thermal conductivity, viscosity and high pressure density

“…It is generally agreed that the combination of factors as the diversity of preparation processes, samples stability, particle size dispersion, non-uniformity of the particle shape, clustering, sedimentation or pH are related with those discrepancies [10][11][12][13]. Regarding transport properties, including viscosity and other viscoelastic properties, nanofluids also exhibit unusual behaviour [1,[14][15][16][17][18][19][20][21] and this represents a challenge, not only for to the difficulties associated to their experimental determination, but also for the very limited knowledge about the underlying physicochemical phenomena that might justify the observed trends.…”

Influence of the dispersion of Nanoclays on the cellular structure of foams based on polystyrene

“…This procedure is done for different values of . This equation can be used only in the proximities of the percolation threshold 56 . Finally, the value of for which the best fit is obtained is considered as the percolation threshold of the composite.…”