Eur. Phys. J. E (2012) 35: 109
https://doi.org/10.1140/epje/i2012-12109-7

Regular Article

Effect of temperature on rotational viscosity in magnetic nano fluids

Department of Physics, Sardar Vallabhbhai Patel Campus, Bhavnagar University, 364022, Bhavnagar, GJ, India

^* e-mail: rjp@bhavuni.edu
^** e-mail: rpat7@yahoo.com

Received: 24 March 2012
Revised: 5 July 2012
Accepted: 25 September 2012
Published online: 26 October 2012

Abstract

Flow behavior of magnetic nano fluids with simultaneous effect of magnetic field and temperature is important for its application for cooling devices such as transformer, loud speakers, electronic cooling and for its efficiency in targeted drug delivery and hyperthermia treatment. Using a specially designed horizontal capillary viscometer, temperature-sensitive and non-temperature-sensitive magnetic nano fluids are studied. In both these case the temperature-dependent rotational viscosity decreases, but follows a quite different mechanism. For temperature-sensitive magnetic nano fluids, the reduction in rotational viscosity is due to the temperature dependence of magnetization. Curie temperature (^T _c ) and pyromagnetic coefficient are extracted from the study. A fluid with low T _c and high pyromagnetic coefficient is useful for thermo-sensitive cooling devices and magnetic hyperthermia. For non-temperature-sensitive magnetic nano fluids, reduction in rotational viscosity is due to removal of physisorbed secondary surfactant on the particle because of thermal and frictional effects. This can be a good analogy for removal of drug from the magnetic particles in the case of targeted drug delivery.