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Nov 15, 2013 (3 years and 9 months ago)

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Superconductivity

Lai Yi
-
Hsuan

PY
-
336X

HR: none


Introduction



In the culture of physics, quantum mechanics has developed and influenced the
community of physics.
Moreover,
its

applications have improved certain aspects in human
life.
Superconductivity is one of them.
Since

the
finding

of

the
superconductivity
,
the

research
popularity

has been shaped and its expectation
of future

applications is
growth.

Superconductivity

has bee
n one of the focuses on quantum mechanics


world.


Background


What

is

superconductivity?
Superconductivity

is a
phenomenon that

can
occur

on
certain material which can behave with

zero

electrical resistance

and expulsion of

magnetic
fields

when

the material is

cool
ed

below
the

characteristic

critical temperature

(Tc)
.

The

behavior

of
expulsion

of magnetic field on superconductor is explained as the Meissner
effect.
T
he related current to the magnetic field around the superconductor can be
express
in London equation
s

[1]
.




j
s

t
=
n
s
e
2
m
E











,









×
j
s
=

n
s
e
2
mc
B



(1) London Equation
s


The

first equation expressed the

electric
superconduct

in the superconductor.
T
he second
equation expressed the relativity of conducting current to the magnetic field within
superconductor.
T
he type of superconductor can be
recognized

in two different types by
single and
single

and double
critical

field; Type
I

super
conductor and type
II

superconductor

[2]
.
H
owever, the process of it
s development
is slow because of some
limits

on the
materials:
the limit of low
temperature
, restricted range of electrical current density and magnetic
field.



Motivati
on


In
this
civilizations

and cultures essay I choose superconductivity as my specific topic.
S
ince it has been researched and developed in society use, such as MRI, NMR and induction
heating.
I
t provided the change of the human society. Therefore, it is
worth to take more
look at it and give more positive attitude for the future development.


T
he
finding


T
he first finding of the
superconductivity

is observed by

Dutch
physicist

called Heike
Kamerlivgh Onnes

at the University of Leiden
.
T
he
phenomenon

of superconductivity was
accidently

discovered three years after the first liquefie
d helium was created by Onnes [3
].
T
he material mercury was used in observation.
After
the
temperature

was lowered below
from 4.3k to 1.5k, the abrupt vanishing of electric
al
resistance

was measured around 4.
2k [3
].
The superconducting state was formed.
Unfortunately
, when he
discovered

the
superconductivity

on magnet

was destroyed at very low critical field (Hc),

his technology
dream was

destroyed

also [4
].


Development
and a
pplication


After the difficulty on

technology

development
of the superconductivity was going
down for years, Ted Berlincourt brought back the interest. New crystal
structure, Nb3Sn
, was
applied to have higher Tc, 18k. Also, higher current

density (Jc) and higher magnetic field
is
available on this material [4
].
T
he
magnets made from it then
have been used in many
machines
, such as MRI, NMR, laboratory magnets and accelerators



A
nd in the past few years,
the

exciting
development

was revealed.
I
n
2001, the
compound
, MgB
2
, was

found to superconduct at 39k [4
].
And

in 2008, Fe
-
based compounds
found much
higher

Tc to behave superconductivity, 56k, and can

be developed to have high
Hc [4
].
T
he age of developing high
-
temperature

superc
onductors has
coming
. The use of
superconductivity

will be less restricted in technology use.

C
onclusion

and future


The

technology of

superconductivity is still
ongoing
,

e
specially

the improvement of the
compound

materials

of the
superconductor
.
A
s the high
-
temperature superconductor is
invent, there will be less restriction on
maintaining

critical temperature, current density and
magnetic.
T
herefore,
it
can be use
d

to
develop

more stable an
d cheaper
in
superconductivity application.















References

[1].
Wikipedia
:

Superconductivity.
http://en.wikipedia.org/wiki/Superconductivity
.

[2].

Wikipedia
: London equations.
http://en.wikipedia.org/wiki/London_equations
.

[3
].
Dirk van Delft, Peter Kes: The discovery of superconductivity.2010. American Institute of
Physics

[4
]. David Larbalestier, Paul C. Canfield: Su
perconductivity at 100


Where we

ve been and
where we

re going. 2011. Materials Research Society