Negative magneto-rheological effect of a dispersion composed of spindle-like hematite particles

Abstract

We have experimentally investigated the negative magneto-rheological effect that is theoretically predicted to appear in a dispersion composed of spindle-like hematite (-Fe 2 O 3 ) particles. The spindle-like hematite particles were synthesized by aging a solution of FeCl 3 and KH 2 PO 4 for 72 h at 373 K. The particle size distribution was determined by digital image analysis from electronic microscope observation of the particles. In the present study we considered a glycerol-water-based dispersion in order to clarify the influence of the shear rate and the magnetic field strength on the negative magneto-rheological effect. Measurement of the viscosity was carried out using a rotational-type rheometer in an external magnetic field generated by Helmholtz coils. The main results obtained can be summarized as follows. The viscosity of a hematite/glycerol-water dispersion relative to that with no applied magnetic field decreases with increasing magnetic field strength: that is, we observed the negative viscosity effect that has previously been predicted from theoretical considerations. Moreover, the negative magneto-rheological effect is observed to decrease with increasing shear rate, which also agrees qualitatively with the theoretical prediction.

Magnetorheology: a review

“…† An exception is the so-called negative MR effect reported by Sakudaet al145 on elongated particles magnetized along the short axis.…”

On aggregate structures in a rod-like haematite particle suspension by means of Brownian dynamics simulations

“…From these theoretical studies, we have been able to predict that a negative magneto-rheological effect arises in the case of an eternal magnetic field applied in the direction normal to the C shearing plane [47,48]: the negative magneto-rheological effect implies that the viscosity contribution due to magnetic properties of the dispersed particles becomes negative and dependent on the applied magnetic field strength. Quite recently, by performing an experiment using a cone-platetype rheometer, we have succeeded in experimentally verifying that the negative magneto-rheological effect arises in an applied magnetic field and this effect becomes larger with decreasing Peclet number [49], as was predicted by the theoretical work. Moreover, we have developed the basic equation of the orientational distribution function that takes into account the spin Brownian motion, and have discussed the influence of the spin Brownian motion on the negative magneto-rheological effect in detail based upon numerical solutions of the basic equation [50].…”

The soft-landing features of a micro-magnetorheological fluid damper

“…MR damper is a kind of semi-active control devices, [1][2][3][4][5] which was developed based on rapidly reversible magneto-rheological effect of MRF under the magnetic field. [6][7][8][9] Not only because of its simple structure, low power consumption, fast response, and durability but also because the damping force can be adjusted in a largely dynamic range according to the need of engineering controls, it can be easily combined with computer to implement intelligent control based on the continuous and reversible control process. [10][11][12][13][14][15] Recently, a small MRF damper has been developed by Lord Corporation.…”