Ultrasonic study of ferrofluids

S. C. Bhatt¹ - Om Prakash Nautiyal²

¹ Department of Physics, H.N.B. Garhwal University Srinagar Garhwal, Uttarakhand-246174, India
² Uttarakhand Science Education and Research Centre (USERC) 33 Vasant Vihar, Phase II, Dehradun, Uttarakhand-248006, India

Abstract
Different acoustic parameters like adiabatic compressibility, acoustic impedance, stiffness constant, viscous relaxation time, attenuation and intermolecular free length have been calculated by using measured values of ultrasonic velocity, density and viscosity for water and a water-based ferrofluid and for kerosene and a kerosene-based ferrofluids at 1 MHz frequency. Ultrasonic velocity measurements have been made with the help of a variable path ultrasonic interferometer. The results are summarized in the tabular form. It is observed that density, viscosity, ultrasonic velocity, acoustic impedance and stiffness constant are higher for the water-based ferrofluid than their values for pure base material liquid, i.e. for water, whereas isentropic compressibility, viscous relaxation time, attenuation and intermolecular free length have lower values for the water-based ferrofluid if compared to pure base material liquid. In case of kerosene-based ferrofluid, viscosity, ultrasonic velocity, viscous relaxation time and attenuation have their values higher than the pure base material liquid, i.e. kerosene, whereas acoustic impedance and stiffness constant have lower values than the pure base material liquid. Tables 1, Refs 8.