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