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 (Pauling’s): 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

Poisson’s 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.

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.