Temperature dependence of interface tension of drop-like aggregates in magnetic fluids

Abstract

Experimental investigation of interface tension temperature dependence of drop-like aggregates in magnetic fluids undergoing first-order phase transition of the “gas-liquid” type was carried out. Visual observation of the condensed phase drops (drop-like aggregates) was performed in a thermostatically controlled transparent horizontal Hele-Shaw cell.  The interface tension coefficient was defined according to the standard technique of a drop elongation in a homogeneous constant applied magnetic field. It is shown that the interface tension grows with the rise of temperature. The anomalous behavior (if compared to ordinary one-component fluids) of surface tension can be explained in the framework of the granulometric aspect of the temperature-dependent phase transition: at high temperatures only the largest particles are capable of aggregating into drops of the new phase. The enlargement of the average diameter of aggregating particles inside the condensed phase drops leads to the increase of magneto-dipole and van der Waals interparticle attraction, what results in the growth of the effective interface tension coefficient.