A rheometer dedicated for the investigation of viscoelastic effects in commercial magnetic fluids

The investigation of viscoelastic properties of commercial ferrofluids base d on nanosized magnetite particles in various carrier liquids requires a de dicated rheometer allowing the detection of extremely small changes in visc ous and viscoelastic properties. The observation of magnetoviscoelastic beh avior in commercial ferrofluids may become particularly important since the y exhibit long-term stability allowing reproducibility of the experiments. In addition, they are of relatively simple composition reducing the problem s in theoretical description of the observed effects. We will present here the design and main performance data of a rheometer developed far the kind of investigations mentioned above. The quality of the performance will be d emonstrated with some new data on rheological properties of a commercial fe rrofluid. (C) 1999 Elsevier Science B.V. All rights reserved.