| dc.description.abstract |
Magnetism and magnetic materials have been an ever-attractive
subject area for engineers and scientists alike because of its versatility in
finding applications in useful devices. They find applications in a host of
devices ranging from rudimentary devices like loud speakers to sophisticated
gadgets like waveguides and Magnetic Random Access Memories (MRAM).The one and only material in the realm of magnetism that has been at the
centre stage of applications is ferrites and in that spinel ferrites received the
lions share as far as practical applications are concerned.It has been the endeavour of scientists and engineers to remove
obsolescence and improve upon the existing so as to save energy and
integrate in to various other systems. This has been the hallmark of material
scientists and this has led to new materials and new technologies.In the field of ferrites too there has been considerable interest to
devise new materials based on iron oxides and other compounds. This means
synthesising ultra fine particles and tuning its properties to device new
materials. There are various preparation techniques ranging from top- down
to bottom-up approaches. This includes synthesising at molecular level, self
assembling,gas based condensation. Iow temperature eo-precipitation, solgel
process and high energy ball milling. Among these methods sol-gel
process allows good control of the properties of ceramic materials. The
advantage of this method includes processing at low temperature. mixing at
the molecular level and fabrication of novel materials for various devices.Composites are materials. which combine the good qualities of one
or more components. They can be prepared in situ or by mechanical means
by the incorporation of fine particles in appropriate matrixes. The size of the
magnetic powders as well as the nature of matrix affect the processability
and other physical properties of the final product. These plastic/rubber
magnets can in turn be useful for various applications in different devices.
In applications involving ferrites at high frequencies, it is essential that the
material possesses an appropriate dielectric permittivity and suitable
magnetic permeability. This can be achieved by synthesizing rubber ferrite
composites (RFC's). RFCs are very useful materials for microwave
absorptions. Hence the synthesis of ferrites in the nanoregirne.investigations on their size effects on the structural, magnetic, and electrical
properties and the incorporation of these ferrites into polymer matrixes
assume significance.In the present study, nano particles of NiFe204, Li(!5Fe2S04 and
Col-e-O, are prepared by sol gel method. By appropriate heat treatments,
particles of different grain sizes are obtained. The structural, magnetic and
electrical measurements are evaluated as a function of grain size and
temperature. NiFel04 prepared in the ultrafine regime are then incorporated
in nitrile rubber matrix. The incorporation was carried out according to a
specific recipe and for various loadings of magnetic fillers. The cure
characteristics, magnetic properties, electrical properties and mechanical
properties of these elastomer blends are carried out. The electrical
permittivity of all the rubber samples in the X - band are also conducted. |
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