Neutron and thermodynamic studies of magnetic fluids stabilized by monocarboxylic acids

Abstract

The results of neutron and thermodynamic studies of a non-polar magnetic fluid stabilized by surfactants (monocarboxylic acids) are presented in the paper. As a result of the study of neutrons it was revealed that in the investigated range of concentrations of oleic and myristic acids the aggregation in the liquid system does not occur due to the liquid-surfactant interaction. It is shown that in the presence of magnetic particles in a liquid system the force of attraction between the molecules of the surfactant decreases. Experimental P-V-T data for the ferrofluid based on lauric acid, such as baric and temperature dependence on density, isobaric thermal expansion coefficient, and isothermal entropy increment are described by means of the semi-empirical Tait-Tammann equation. It has been established that the investigated ferrofluid has a significantly lower thermal expansion coefficient as compared with water due to a change in energy of interparticle interaction and the changing of water structure when the magnetic particles add to water.