Behavior of Magnetorheological Fluids Utilizing Nanopowder Iron

Iron nanopowders for use in magnetorheological (MR) fluids were synthesized using a Microwave Plasma Synthesis technique developed at Materials Modification Inc (Fairfax VA). Transmission electron microscopy and surface area analysis measured iron particle size at 15–25 nm. The nanopowders were mixed into hydraulic oil to create nano-scale MR fluid. A micro-scale fluid was created using 45 μm iron particles as well as a hybrid fluid using a 50/50 mix of micro- and nanoparticles. All three fluids had a solids loading of 60% (w/w or weight by weight fraction). The fluids were tested in a flow mode rheometer fabricated from a modified damper using a sinusoidal input dynamometer over a speed range of 12.7 to 177.8 mm/s (0.5 to 6 in/s) and an input current range of 0 to 2 A. The yield stress and plastic viscosity of the MR fluid were characterized using a Bingham plastic model.