Electro-rheological  and Magneto-rheological fluids
 This kind of systems are dispersions of micrometric particles in inert oils. In the presence of an externalfield they suffer dramatic changes in several of their physical properties,especially in the mechanical ones ( video ).  

 The suspended micrometric particles have dielectric or soft magnetic properties. We have obtained particles  of iron oxide and bismuth titanate to prepare ER and MR fluids. We have used chemical coprecipitation methods.   
Structure in MR fluid 
We have preparedmagneto-rheological  fluids dispersing in some oils particles of ironoxide.
Structure in a ER fluid 
For electro-rheological  fluids we prepared particles of bismuth titanate with a sharp size distribution about 10 micrometers. Some other people have used glass, zeolites, starch, ferroelectrics. Some biological materials like blood also exhibits electro-rheological properties.

The following are some photographs of aggregates in rheologicals fluids
structure               structure                  structure

Electro-rheological fluid basedon iron-oxide. By an optical microscope and by means of a digital videocamera we can observe directly the structure formed by the particles(video).
structure      structure               structure           structure
Some pictures of an electro-rheological fluid based on bismuth titanate ceramics powders.
     structure        structure        structure        structure  

Complex structures formed in a magneto-rheological fluid based on iron oxide particles.


We have studied some of the physical properties of rheological fluids like elastic, structural, and thermal properties.

magneto-rheological fluid    magneto-rheological fluid

These pictures shows the magnetorheological effect (Video)





sound propagation
Sound speed ina MR fluid as a function of the intensity of the applied field. Continuousline are theoretical results obtained by means of an effective media aproximation.Dots and squares are experimental results. These and other related resultscan be found in  Articles (PDF)

These results are in the Fernando Donado Thesis . This thesis and complementary documents, photos and videos can be obtained asking for them to Fernando e-mail address     fdonadop@sirio.ifuap.buap.mx.

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