Rheology of a ferrofluid based on nanodisc cobalt particles

Abstract

Rheological investigations as well as theoretical studies on ferrofluids have shown strong field and shear dependent changes in viscosity, which are correlated with the formation of chain-like clusters of magnetic nanoparticles. Moreover, the formation of these clusters leads to the appearance of viscoelastic effects or other non-Newtonian features in ferrofluids in the presence of a magnetic field. Previous investigations were carried out with differently composed ferrofluids, all of them containing particles of nearly spherical shape, but differing in the size of the nanoparticles, the volume concentration and the magnetic material. In the work presented here a ferrofluid with non-spherical cobalt nanoparticles is used, to get more information about the influence of the shape of the nanoparticles on their interparticle interaction and the resulting rheological behaviour of the suspension. For the experiments an especially designed stress controlled rheometer has been used. Experiments on yield stress as well as measurements of the magnetoviscous effect have been performed for this ferrofluid with nanodisc particles for different magnetic field strengths. The results from the yield stress experiments have been compared with those achieved for a cobalt-based ferrofluid containing spherical nanoparticles.

Thermal conductivity measurements on ferrofluids with special reference to measuring arrangement

“…The effect of this interaction can be seen, for example, in changes in the viscosity of ferrofluids [8], which depends on interparticle interaction and differs depending on the material of the components and the size and shape of the particles [9].…”

Rheological Study of Dextran-Modified Magnetite Nanoparticle Water Suspension

“…The colloidal stability of magnetic nanofluids with respect to the phase separation phenomenon depends on a variety of factors such as the magnetic nanoparticle concentration, the size and size polydispersity, the colloidal stabilization efficiency, the temperature, and the magnetic field intensity [5]. The formation of drop-like clusters leads to the appearance of viscoelastic effects or other non-Newtonian features in the magnetic nanoparticle suspension in the presence of a magnetic field [8,9].…”

Thermal convection thresholds in a Oldroyd magnetic fluid

“…An important application of ferrofluids lies in the biomedicine area where the carrier liquid is blood [2][3][4][5][6] which is known to have also special rheological proprieties [7][8][9]. In addition, when a magnetic field is applied, the ferrofluid can exhibit additional rheological properties such as magneto-viscosity, adhesion properties, non-Newtonian behavior, among others [10][11][12][13][14][15][16][17][18][19][20]. Hence, a detailed study of viscoelastic magnetic fluids is quite important and in order.…”