Electrorheological (ER) and Magnetorheological (MR) fluids are a class of colloidal suspensions, typically consisting of polarizable solid particles dispersed in a relative non-polarizable liquid. Drastic enhancement in viscosity and shear stress results from the field-induced structures, when ER (or MR) fluids are subject to an external electric (or magnetic) field. This property offers ER and MR fluids many potential applications in various areas. In the thesis I report the experimental results on magnetic response of particulate materials with different compacting process and particle shapes. It is found the magnetic anisotropy largely depends on the compacting process and component particle shape: uniformly aligned rods show the largest magnetic anisotropy; while the field-oriented...[ Read more ]

Electrorheological (ER) and Magnetorheological (MR) fluids are a class of colloidal suspensions, typically consisting of polarizable solid particles dispersed in a relative non-polarizable liquid. Drastic enhancement in viscosity and shear stress results from the field-induced structures, when ER (or MR) fluids are subject to an external electric (or magnetic) field. This property offers ER and MR fluids many potential applications in various areas. In the thesis I report the experimental results on magnetic response of particulate materials with different compacting process and particle shapes. It is found the magnetic anisotropy largely depends on the compacting process and component particle shape: uniformly aligned rods show the largest magnetic anisotropy; while the field-oriented suspension of coated microrods obtained through the MR effect shows somewhat weaker magnetic anisotropy. The magnetic anisotropy drops significantly when the microrods were replaced by microspheres, even when they were aligned in chain-like formations. A simple model is employed to interpret the role of shape anisotropy of the constituting particles. In the thesis experimental results are also reported for rheological property of ER fluids with different particle shapes and the evolution of a single magnetic micro-rod in an external dc field.