Optical Rheometry of Suspensions

Publication Reference: 
Author Last Name: 
G G Fuller
Report Type: 
Research Area: 
Wet Systems
Publication Year: 
Publication Month: 
United States

Executive Summary

This report describes the research in the laboratory of Professor Fuller supported by I.F.P.R.I. on the development and application of techniques in optical rheometry to the study of structure and dynamics of dispersions subject to external fields. In the first three year funding period, four projects were completed. These were: (1) the structure of dense suspensions of spheres subject to electric flelds,2 (2) the microstructural basis for shear thickening in dense suspensions,3 (3) the electro-hydrodynamics of asymmetric particles, ’ and (4) the development of oblique angle pola- rimetiy. This latter project was aimed at devising an experimental capability of examining dense systems that are normally too opaque to test using standard optical flow cells. By using light that is sent through a sample at an oblique angle, the full refractive index tensor can be reconstructed for very thin samples. In this manner, the optical density of the samples can be significantly reduced. In the coming funding period, the technique of oblique angle polarimetry shall be extended and used to consider several dense particulate systems. Two possible systems would include dispersions of soft particles where the optical experiments can yield information concern- ing deformation by flow, and dispersions of magnetic particles. These latter systems are of interest due to their use in ferrofluid applications.