Physics For Civil Engineering: Unit IV: New Engineering Materials
Ferromagnetic Ceramics
Classification, Hexagonal Ferrites, Oxide ceramics
We know that soft magnetic (ferro magnetic) materials are easy to magnetise with low value of magnetic field. On the other hand, the hard magnetic materials require larger magnetic field for magnetization as well as demagnetization
FERROMAGNETIC CERAMICS
We know that soft magnetic (ferro
magnetic) materials are easy to magnetise with low value of magnetic field. On
the other hand, the hard magnetic materials require larger magnetic field for
magnetization as well as demagnetization
Therefore, the coercive field is very
high and hence, used to make hard magnets for apploication such as recording
media and permanent magnet. The soft magnetic ceramics, exhibits similar
properties as that of soft magnetic materials (metal counter parts.)
However, soft magnetic ceramics are good
electrical insulators. The eddy current losses of the soft magnetic ceramics
are very low. Therefore, the magnetic ceramic materials are used whenever there
is a requirement of reduction in the eddy current losses.
The magnetic ceramic materials are
classified into three types namely,
• Spinel
• garnets
• hexagonal ferrites
Hexagonal Ferrites
Hexagonal
ferrities are ferromagnetic materials. The general formula for hexagonal
ferrites is BaO 6Fe2 O3 The structure of ferrities is in line with magneto
plumbite and hence. It is called magneto ferrites.
In
this structure, all magnetic spins are parallel. Based on the arrangement of
grains, hexagonal ferrites are classified as isotropic and anisotropic
ferrites.
The
grains are arranged in random manner in isotropic ferrites, while in anisotropy
crystals they are aligned in a regular manner. One can obtain the anisotropy by
the influence of magnetic field.
Thus,
hexagonal ferrites have high anisotropy constants and hence, are used to
fabricate hard magnets with high coercive fields.
In
view of its low conductivity, high coercive fields, easy Istem) alsrijem
manufacturing, etc., hexagonal ferrites is one of the important permanent
magnets. It finds wide application like loudspeaker and compact dc motors,
where a large field is required.
Oxide
ceramics
There are two important oxide ceramics –
aumina and zirconua.
Physics For Civil Engineering: Unit IV: New Engineering Materials : Tag: : Classification, Hexagonal Ferrites, Oxide ceramics - Ferromagnetic Ceramics
Physics For Civil Engineering: Unit IV: New Engineering Materials
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Physics for Civil Engineering
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