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Novel ferrofluid

Ferrofluid is a colloidal mixture composed of nanoparticles suspended in a fluid such as an organic solvent or water. Different methods of preparation of ferrofluid involve steps of precipitation of the magnetic particles, their surface treatment and the use of dispersing mediums to obtain the fluid.

Prof. D. Bahadur and his student of Department of Metallurgical Engineering and Materials Science have developed a novel two stage process for the preparation of a ferrofluid that is superior in terms of achievable sizes of the superparamagnetic (SP) particle. In the first stage, precipitation happens in the presence of surface modifying agents to obtain dried SP particles that can be stored and transported in a non-hazardous manner. The particles depending on their application, are dispersed in a known volume of carrier liquid to obtain tailored ferrofluid. In the second stage of the novel method, bypassing the typical dilution process that may destabilize the fluid is done.

To prepare the SP particles (SPP), Fe2+ / Fe3+ based substances in an acetone and ammonia added solution, are stirred and heated. Magnetic particles collected under the influence of a magnet field are finally washed with water and acetone several times and dried. This procedure performed is half the task completed quicker. In another embodiment of the invention, the required weight of the dried SPP is added to the carrier liquid and after centrifugation, gives the required magnetization ferrofluid; removing the bad particles, which may destabilize under the influence of gravity and external magnetic, centrifugal forces.

Chemical tests showed successful creation of ferrofluids using their patented method with measured magnetization from 12 - 30 emu/cc at room temperatures. Besides electronic devices where nanotechnology is applied in a large scale, ferrofluids have found use in mechanical, military and aerospace in a variety of uses from simple friction-reduction seals to decreasing the electromagnetic signal of an aircraft and spaceship control. This can be applied in medicinal instruments today not only assisting doctors in detecting critical cancers, but can also take shape in the form of art that can promote science in schools and museums.

Indian patent application no. 475/MUM/2004 Patent grant no. 210641
Inventors: D Bahadur and J Giri