Negative viscosity due to magnetic properties of a non-dilute suspension composed of ferromagnetic rod-like particles with magnetic moment normal to the particle axis

Control of the orientational characteristics of disk-like hematite particles by a simple shear flow

“…A suspension composed of hematite particles exhibit characteristic magneto-rheological properties completely different form those of ordinary ferromagnetic particles (Ozaki et al, 1988;Ozaki and Matijević, 1985;Varanda et al, 2001). That is, this suspension exhibits negative magneto-rheological effects in a certain situation of an applied magnetic field, which has already been verified by an experimental study using a cone-plate-type rheometer (Satoh and Ozaki, 2006;Satoh and Sakuda, 2007;Satoh, 2013;Sakuda et al, 2012). From this background, we understand that it is important to conduct a systematic series of studies in order to investigate the behaviors of non-spherical magnetic particles, which may be lead to new Satoh, Mechanical Engineering Letters, Vol.2 (2016) [DOI: 10.1299/mel.…”

Brownian dynamics simulation of a dispersion composed of disk-like hematite particles regarding aggregation phenomena

“…Another characteristic feature of a spindle-like particle dispersion is that the viscosity due to magnetic properties becomes negative under a certain condition of an applied magnetic field. This negative magneto-rheological effect was theoretically predicted from the theory based on the orientational distribution function in a simple shear flow [23][24][25]. Quite recently, by performing an experiment using a cone-plate type rheometer, we have succeeded in experimentally verifying that the negative magneto-rheological effect arises in an actual situation [26].…”

Brownian dynamics simulation of a dispersion composed of disk-like hematite particles regarding the orientational distribution and the magneto-rheological properties

“…In contrast, hematite particles exhibit quite different characteristics because they are magnetized in a direction normal to the particle axis direction, and exhibit much weaker magnetization than magnetite [32][33][34][35]. In hematite particles the magnetization direction gives rise to two degrees of freedom regarding the rotational motion, that is, the usual rotational motion about a line normal to the particle axis and the spin rotational motion about the particle axis direction [36][37][38][39]. Currently, by expanding the ordinary synthesis technology, the challenge of developing new magnetorheological fluids has created an interest in new hematite particles with a variety of shape such as rod-like, oblate spheroidal and cubic-like [40,41].…”

“…Moreover, the theoretical analysis based on the orientational distribution function had shown that a needle-like hematite particle suspension can exhibit a negative viscosity effect in certain situations [37,39,45]: the negative viscosity effect occurs when the viscosity component due to the magnetic properties of the particles becomes negative, but it is noted that the net viscosity of the fluid remains positive. From an experimental study using a cone-plate type rheometer, the predicted negative viscosity effect has been observed to arise in a sample suspension of hematite particles [46].…”