Niobium and it
Niobium and its applications:


Niobium and its alloys are remarkably resistant to corrosion by certain liquid metals, notably lithium metal and sodium-potassium alloys, and to high temperatures (900 oC to 1010 oC). This resistance is coupled with a low-capture cross section for thermal neutrons renders niobium materials most attractive for reactor applications.

Typical Analysis in PPM:

Fe                <20              Ni                <20

Cr                <20             Cu               <10

Si                <20              Ti                <10

Mo               <20              W               <200

Ta               <200             Al               <20

Zr                <10              Hf               <20

 

Typical Physical Properties:

Atomic Number: 41

Atomic Weight : 92.91

Atomic Volume : 10.83 cm3/g-atom

Lattice Type: Body centered cubic

Lattice Constant (Angstroms) : 3.30

Covalent Radius (Angstroms) : 1.34

Thermal Neutron Absorption Cross Section (Barns/Atom) : 1.1

Density (20 oC, g/cm3): 8.57

Melting Point: 2468 oC

Boiling Point : 4927 oC

Thermal Conductivity:

0 oC J (sec cm oC): 0.523

1600 oC J (sec cm oC): 0.691

Coefficient of Thermal Expansion at 20 oC (x 10-6/oC): 7.1

Temperature Coefficient (x 10-3/oC) : 3.95

Specific Heat:

15 oC (J/g): 0.268

1227 oC (J/g): 0.320

Heat Capacity (J/mol oC):

0 oC:             24.9

1200 oC:        29.7

2700 oC:        33.5

Electronegativity (Paulings): 1.6

Electrical Resistivity (Microhm) : 15

Volume Electrical Conductivity (%IACS*) : 13.3

*International Annealed Copper Standard

Typical Mechanical Properties:

Modulus of Elasticity (x 10-6 kg/cm2): 1.05

Poissons Ratio : 0.38

Hardness (VHN) : 60-100

Resistance to Thermal Shock: Good

Workability (Ductile to Brittle Transition) : -150 oC

Recrystallization Temperature: 900-1300 oC

Stress Relieving Temperature : 800 oC

Chemical Properties:

Niobium is moderately to highly resistant to corrosion in most aqueous mediums that are usually considered highly corrosive, such as dilute mineral acids, organic acids, and organic liquids. Notable exceptions are dilute strong alkalies, hot concentrated mineral acids, and hydrofluoric acid, all of which attack the metal rapidly. Gaseous atmospheres at high temperatures attack niobium rapidly, primarily by oxidation, although oxygen contents may be very low.

Applications:

Niobium has a variety of uses. It is used to produce high-grade steel and in superalloys for items such as jet engine components and heat and combustion resistant equipment. It is also used for superconducting magnets, and some medical devices like pacemakers.

 

 

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