Nuclear magnetic resonance visualization of anomalous flow in cone-and-plate rheometry

We demonstrate the use of nuclear magnetic resonance (NMR) microscopy to image the velocity distribution for fluids sheared within the gaps (4 degrees and 7 degrees) of cone-and-plate rheometers. These measurements employ a specially constructed rheogoniometer, which fits within the NMR probe system. While the uniform shear rate assumption is verified in the case of simple Newtonian and non-Newtonian fluids, a range of anomalous behavior (apparent slip, shear banding, and fracture) is observed in other systems, including wormlike surfactants, semidilute solutions of 18 MDa polyacrylamide, and dispersed silica in silicone grease. (C) 1997 The Society of Rheology.