Heating characteristics of transformer oil-based magnetic fluids of different magnetic particle concentrations

Abstract

The heating ability of mineral oil-based magnetic fluids with different magnetic particle concentrations is studied. The calorimetric measurements were carried out in an alternating magnetic field of 500A·m -1 to 2500A·m -1 amplitude and of 1500 kHz frequency. The revealed H n law-type dependence of the temperature increase rate, (dT/dt)t=0, on the amplitude of the magnetic field indicates the presence of superparamagnetic and partially ferromagnetic particles in the tested samples since n > 2. The specific absorption rate (SAR) defined as the rate of energy absorption per unit mass increases with a decrease of the volume fraction of the dispersed phase. This can be explained by the formation of aggregates in the samples with a higher concentration of magnetic particles. © The Author(s) 2010.