tailieunhanh - Báo cáo vật lý: "EFFECT OF FIELD STRENGTH IN THE VELOCITY ANISOTROPY OF FERROFLUIDS"

Tuyển tập các báo cáo nghiên cứu khoa học trên tạp chí khoa học vật lý quốc tế đề tài: EFFECT OF FIELD STRENGTH IN THE VELOCITY ANISOTROPY OF FERROFLUIDS | Journal of Physical Science Vol. 18 2 1-13 2007 1 EFFECT OF FIELD STRENGTH IN THE VELOCITY ANISOTROPY OF FERROFLUIDS B. Samuel Ebinezer1 and L. Palaniappan2 department of Physics Annamalai University - 608002 TN India 2School of Physics Universiti Sains Malaysia 11800 USM Pulau Pinang Malaysia Corresponding author lp_dde_au@ Abstract Ultrasonic velocity measurements were made on the starch coated magnetite particles in aqueous carrier under various external magnetic field strength. Density values are presented under no field condition and a few acoustical parameters were calculated. All the observations are interpreted in terms of grain-grain interaction and grain-field interaction that exist in the system. The field strength is found to enhance the structural formation in the system irrespective of its direction. Keywords Ultrasonic velocity ferrofluid magnetic field grain-grain interaction grainfield interaction 1. INTRODUCTION Ferrofluids which consist of 10 to 100 Â size particles suspended in various carrier fluids have been considered to have much more in common with liquid crystals and ordinary liquid mixtures than with various solid ferromagnetic materials. The behavior of ultrasonic wave propagation through magnetic fluids in the presence of magnetic fields is a relatively unexplored area. The significance of these fluids need not be emphasized as these are part of the expanding nano science and technology. Although ferrofluids consist of ferromagnetic particles suspended in a fluid the magnetic behavior is generally described by paramagnetic theories and the ultrasonic behavior of the fluids is approached from the view point of hydrodynamics. Many authors1-3 have followed such type of approaches for their interpretation even in studying the ultrasonic attenuation and velocity measurements. Further they have concluded that pulse-echo experiments were more suitable for attenuation measurements than for measuring changes in velocity due to a .