Material Technology

Nanoparticle complex fluids

These materials form a class of advanced and smart materials that exhibits dramatic changes in their rheological behaviour with a rapid, reversible and tunable transition from a liquidlike, free-flowing state to a solidlike state upon the application of an external field.

Electrorheological fluids are fluids which increase viscosity in response to an external electric field. These fluids are colloidal suspensions of high-dielectric nanoparticles in a low-dielectric base fluid. Electric field causes the fluid to stiffen in 1 to 10 milliseconds. Practical applications include quick-response adaptive systems – for example, a hydraulic damper filled with electrorheological fluid would react differently depending on the fluid's viscosity at a given instant.

For magnetorheological fluids the viscosity increases in response to a magnetic field. Most such fluids are colloidal suspensions of nm-mm sized ferromagnetic particles in a base carrier fluid such as kerosene, polymer, or water. As with electrorheological fluids, the response time is very quick. MR-fluids provide variable control of energy dissipation for commercial and industrial devices and systems. Current applications include some magnetic clutch designs, shock absorbers, sealings, pneumatic control, seismic mitigation and prosthetics.

Some of the goals of this project are:

  • Study the electrorheological and magnetorheological properties of suspensions of carbon nanotubes and carbon nanocones
  • Develope methods for carbon nanocone separation
  • Understand the static structures and the dynamic processes taking place in nanoparticle ferrofluids and magnetic hole systems.
  • Manipulate and control magnetic holes with sub-micrometer presicion.

The tools used in this research include small-angle neutron scattering (SANS), X-ray scattering, optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), optical tweezers and rheology tools.

The picture below shows SEM images of carbon disks and three of the five possible forms of carbon cones (cone diameters approximately 1 micrometre).

Some of the possible forms of carbon nanocones