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Introduction
Niobium
is a metallic, shiny gray element. It is a chemical
element of the 5th group of the periodic system
with an atomic number of 41. The 33 isotopes are
known from 81Nb until 113Nb.
The one of these isotopes are stable: 93Nb.
The Niobium is never found as a free element. It
fall into composition of the minerals: columbite
((Fe,Mn)(Nb,Ta)2O6), columbite-tantalite
or coltan ((Fe,Mn)(Ta,Nb)2O6), pyrochlore ((Na,Ca)2Nb2O6OH,F),
and euxenite ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6).
The unique physical properties of niobium and related
alloys have found many applications in modern industry.
Physical
Properties of Niobium
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Atomic
weight
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92.91
amu
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Atomic
radius (Goldschmid)
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147pm
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Electronic
structure
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[Kr]
4d45s1
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Crystal
structure
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Body
centred cubic
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Oxidation
number
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2,
3, 4, 5
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Electronegativities
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1.6
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Density
(20 °C)
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8.57
g•cm-3
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Melting
point
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2468
°C
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Boiling
point
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4742
°C
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Molar
volume
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9.38•10-6
m3/mol
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Electrical
resistivity (20 °C)
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16
μΩ•cm
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Temperature
coefficient (0-100 °C)
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0.0026
K-1
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Superconductivity
critical temperature
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9.25K
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Coefficient
of termal expansion (0°C - 100°C)
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7.2•10-6K-1
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Latent
heat of evaporation
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7360
J•g-1
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Latent
heat of fusion
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290
J•g-1
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Thermal
conductivity (0-100 °C)
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53.7
Wm-1K-1
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Special
features of Niobium
Niobium
is a transition metal. The pure niobium is gray,
heavy, ductile, a very hard, easily fabricated,
highly resistant to corrosion by acids, and is a
good conductor of heat and electricity. In fact,
at temperatures below 150°C niobium is almost
completely immune against acids attack and can only
be attacked by hydrofluoric acid. With a melting
point of 2468°C, it qualifies as a refractory
metal. It has many properties that make it an excellent
candidate for fabricated parts that must be made
of a refractory metal. Niobium offers good ductility
and weldability under a clean, dry, inert gas or
a vacuum. Niobium has the lowest melting point of
all the refractory metals, the lowest modulus of
elasticity and thermal conductivity, and the highest
thermal expansion, lowest strength and lowest density
of the refractory metals. Also this metal has the
low thermal neutron capture cross-section required
for nuclear applications. Niobium is a component
of some stainless steels and an alloy of other nonferrous
metals. The latest investigation of Niobium has
shown that it can use as a replacement to tantalum
in capacitor production since niobium is much more
abundant and costs substantially less than tantalum.
Advantages
- Niobium
can withstand very high temperatures.
- Niobium
has a high melting point.
- Niobium
can withstand many acids.
- Niobium
is a ductile and soft metal at elevated
temperatures.
- Niobium
has the low thermal neutron capture cross-section.
- Niobium
is a good component for alloys.
Applications
- Is
a component of some stainless steels and
an alloy of other nonferrous metals.
- As
a material for units in nuclear industry.
- Is
a preferred construction material for the
reactors in the space power systems;
- Used
in its pure form for semiconductor equipment
components and corrosion resistant parts.
- Fabrication
of corrosion resistant equipment: reaction
vessels, columns, bayonet heaters, shell
and tube heat exchangers, U-tubes, thermowells,
spargers, rupture diaphragms, orifices.
- Arc
welding rods for some grades of stainless
steel;
- Body
piercing jewelry (usually as an alloy);
- Is
an alternative to tantalum in capacitors;
- Medical
devices.
Flokal
can provide the niobium alloys:
 Nb1Zr
(Niobium1Zirconium)
One
niobium alloy has 8 names: NB-1Zr; Nb-Zirc; Niobium-Zirc,
Niobium Zirconium, Niobium - 1 Zirconium, Niobium
1% Zirconium, NB-1%Zr, Niobium 1% Zirc. The alloy
of the niobium with 1% zirconium increases the strength
of niobium, and decreases slightly its elongation.
Commonly this alloy is used in lighting and chemical
processing. Also this high temperature alloy used
for coating the inside of Stainless Steel tubes
to improve corrosion resistance. This alloy combines
moderate strength with good fabrication properties
and is used in nuclear applications because it has
a good resistance to radiation damage, and low thermal
neutron absorption cross section.
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