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Saturday, July 20, 2013

Presentation On Electromagnetic Interference

PPT On Electromagnetic Interference

Electromagnetic Interference Presentation Transcript: 
1.Effect of annealing temperature of nano-sized BaFe12O19 in Novolac Phenolic Resin on microwave properties for use as EMI shielding material in X-band

Theory of microwave absorption
Preparation of ferrite nanoparticles and magnetodilectric composite
Results and discussion

Leakages of electromagnetic wave in various communication systems lead to electromagnetic interference (EMI). Shielding materials minimize the external electromagnetic waves from interfering in functioning of electronic devices.

 A good absorber should have two essential characteristics, low impedance mismatch at the air-absorber interface to get low reflection and extent of the microwave entering into the materials and secondly, should sufficiently attenuate and absorb the wave passing through it.

Microwave absorption characteristic of the absorbing material in a frequency range depends on complex permittivity, (er= er?- jer?) and complex permeability (µr =µr?- jµr" ).

Ferrite is a metal oxide, which contains magnetic ions arranged in such a manner that it produces spontaneous magnetization while maintaining good dielectric properties. Saturation magnetization and permeability depend strongly on the particle size, morphology, and microstructure of the materials.
In the present investigation barium ferrite particles are annealed with varying temprature and used as the magnetic inclusions in the Novolac Phenolic Resin (NPR) matrix for microwave absorption study.

4.Electromagnetic Interference and its origin
Vast use of this spectra leads to electromagnetic pollution in the environment affecting proper functioning of electronic devices.
This interference leads to problems such as jamming of signal, inaccuracy in target detection in warfare and also less camouflaging etc. Due to electromagnetic interference, electromagnetic compatibility becomes a prime concern.

5.How to minimize the electromagnetic interference (EMI)
Shields are used to isolate a region, to prevent interference from outside sources and to avoid the leakage of unwanted radiation due to internal sources.
Shielding can be done by placing the device in an enclosure which will reflect all the electromagnetic wave thus protecting the device from external electromagnetic interference or it could be done by placing material on the device which will absorb the electromagnetic wave incident on it.

6.Theory of microwave absorption
Microwave absorption mechanism require two conditions:
    Low reflection at the air-absorber interface and
    High attenuation within the bulk of the material.


8.Synthesis of  nano-sized barium ferrite (BaFe12O19) particles and BaFe12O19/NPR composites

9.X-Ray Diffraction Pattern

10.Transmission Electron Micrograph results
With increasing temperature, the ferrite particles showing an elongated, rod shaped structure:
The nanoparticle growth occurs at unit cell level along preferential directions.

 The surface energy of barium ferrite is different along different directions of the unit cell, particle growth would not occur in all directions equally.

 The growth of the nanoparticles along [0001] direction i.e. the c-axis, as it is energetically favourable due to minimum surface energy at higher temperature and hence, the formation of elongated nanostructure is observed  at 9000C.

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