Cluster formation of ferromagnetic nano-particles in micro-capillary flow

This paper reports the experimental research on the growth and dispersion processes of cluster formation in a water-based magnetic fluid in micro-capillary flow. The magnetic fluids are suspensions of ultra fine particles coated with a molecular layer of dispersant in a liquid carrier, such as water or kerosene. The ultra fine particles are coated with single- or double-layer surfactants to attain stable dispersion. However, numerous experimental studies have indicated the existence of primary cluster of ferromagnetic nano-particles in a water-based magnetic fluid. The purpose of this research is to observe the characteristics of primary clusters in micro-capillary flow. The thermal behavior of ferromagnetic nano-particles in micro-capillary flow was observed through micro-visualization using the optical dark-field microscope system and particle tracking velocimetry (PTV) data processing system. Real-time visualization of the Brownian motion of primary clusters in a water-based magnetic fluid in micro-capillary flow was carried out. Furthermore, the effect of magnetic field on the growth process and dispersion process of cluster formation in micro-capillary flow was investigated.