Tantalum

Tantalum is one of the refractory metals, so-called for their ability to withstand extremely high temperatures. As a refractory metal tantalum stands out for a combination of high melting point, low ductile-to-brittle transition temperature and corrosion resistance. Tantalum is used for electrolytic capacitors, chemical process equipment such as heat exchangers, condensers, thermowells, and lined vessels, and to produce containers for working with acids including nitric, hydrochloric and sulfuric. Tantalum is also used in heating elements and heat shields, prosthetic devices and surgical staples, and in specialized aerospace, nuclear and military applications.

 

Typical Properties

Atomic Number: 73

Atomic Weight: 180.95

Atomic Volume: 10.9

Crystal Structure: Body-centered cubic, a = 0.33026

Isotope (Natural): 181

Density at 20 ^oC, g/cc: 16.6, .600 lb/in³

Melting Point: 2,996 ^oC

Boiling Point: 5,430 ^oC

Linear Coefficient of Expansion: 6.5 x 10^-6 per ^oC

Thermal Conductivity at 20 ^oC: 0.130 cal/cm ²/cm/^oC/sec

Specific Heat at 20 ^oC: 0.036 cal/g/^oC

Electrical Conductivity : 13% IACS

Electrical Resistivity at 20 ^oC: 135.0 nΩ ⋅ m

Temperature Coefficient of Electrical Resistivity(0-100 ^oC): 0.0038 per ^oC

Tensile Strength: 

              at Room Temperature:  35,000-70,000 psi

              at 500 ^oC:                       25,000-45,000 psi

              at 1000 ^oC:                     13,000-17,000 psi

Young's Modulus of Elasticity:

              Room Temperature:   27 x 10⁶ lb/in²

              500 ^oC:                        25 x 10⁶ lb/in²

              1000 ^oC:                      22 x 10⁶ lb/in²

Poisson's Ratio: 0.35

Thermionic Work Function: 0.657 aJ (4.10 eV)

Magnetic Susceptibility: 0.93 10^-6 cgs

Spectral Emissivity: .46 (900 ^oC) (Wave Length Approx. 0.65 micron)

Total Emissivity:

              at 1500 ^oC:         .21

              at 2000 ^oC:         .26

Working Temperature: Room temperature

Recrystallization Temperature: 1200 ^oC - 1400 ^oC

Stress Relieving Temperature: 850 ^oC

Thermal Neutron Cross Section: 21.3 b

Polishing: Emery to 000 levigated alumina to finish.

Etchant: Hf-NH₄F Solution. Etch and Polish repeatedly until grain boundaries appear.