Tantalum



73 tungsten
Db
General
Number tantalum, Ta, 73
transition metals
Block d
Appearance gray blue
(2)  g·mol−1
Xe] 4f14 5d3 6s2
shell 2, 8, 18, 32, 11, 2
Physical properties
Phase solid
r.t.) 16.69  g·cm−3
Liquid m.p. 15  g·cm−3
F)
F)
kJ·mol−1
kJ·mol−1
Heat capacity (25 °C) 25.36  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 3297 3597 3957 4395 4939 5634
Atomic properties
Crystal structure cubic body centered
acidic oxide)
Electronegativity 1.5 (Pauling scale)
Ionization energies 1st: 761 kJ/mol
2nd: 1500 kJ/mol
Atomic radius 145  pm
Atomic radius (calc.) 200  pm
Covalent radius 138  pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (20 °C) 131 n Ω·m
Thermal conductivity (300 K) 57.5  W·m−1·K−1
Thermal expansion (25 °C) 6.3  µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 3400 m/s
Young's modulus 186  GPa
Shear modulus 69  GPa
Bulk modulus 200  GPa
Poisson ratio 0.34
Mohs hardness 6.5
Vickers hardness 873  MPa
Brinell hardness 800  MPa
CAS registry number 7440-25-7
Selected isotopes
Main article: Isotopes of tantalum
iso NA half-life DM DE (MeV) DP
177Ta syn 56.56 h ε 1.166 177Hf
178Ta syn 2.36 h ε 1.910 178Hf
179Ta syn 1.82 a ε 0.110 179Hf
180Ta syn 8.125 h ε 0.854 180Hf
180Ta syn 8.125 h β- 0.708 180W
180mTa 0.012% >1.2×1015 y ε 0.929 180Hf
β- 0.783 180W
IT 0.075 180Ta
181Ta 99.988% Ta is neutrons
182Ta syn 114.43 d β- 1.814 182W
183Ta syn 5.1 d β- 1.070 183W
References

Tantalum (tantalite.

Characteristics

Tantalum is dark, dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to carbon.

Applications

The major use for tantalum, as the metal powder, is in the production of electronic components, mainly capacitors and some high-end audio-grade resistors. Tantalum electrolytic capacitors exploit the tendency of tantalum to form a protective oxide surface layer, using tantalum powder, pressed into a pellet shape, as one "plate" of the capacitor, the oxide as the dielectric, and an electrolytic solution or conductive solid as the other "plate". Because the dielectric layer can be very thin (thinner than the similar layer in, for instance, an aluminium electrolytic capacitor), a high capacitance can be achieved in a small volume. Because of the size and weight advantages, tantalum capacitors are attractive for portable telephones, pagers,personal computers, and automotive electronics.

Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, and missile parts. Because of its ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminium.

Due to the fact that it resists attack by body fluids and is nonirritating, tantalum is widely used in making surgical instruments and implants. For example, porous tantalum coatings are used in the construction of orthopedic implants due to tantalum's ability to form a direct bond to hard tissue. The oxide is used to make special high refractive index glass for camera lenses. The metal is also used to make vacuum furnace parts.

Shaped charge liners have been constructed from tantalum.

History

Tantalum was discovered in Sweden in 1802 by Anders Ekeberg and isolated in 1820 by tungsten replaced it.

Its name is derived from the character Tantalus, father of Niobe in Greek mythology, who was punished after death by being condemned to stand knee-deep in water with perfect fruit growing above his head, both of which eternally tantalized him - if he bent to drink the water, it drained below the level he could reach, and if he reached for the fruit, the branches moved out of his grasp. This was considered similar to tantalum's general non-reactivity—it sits among reagents and is unaffected by them. The English word tantalize was named after Tantalus, and tantalum was named after the tantalizing problems posed by the inertness of the element and its compounds.

For many years, the commercial technology for separating tantalum from niobium involved the fractional crystallization of potassium heptafluorotantalate away from potassium oxypentafluoroniobate monohydrate, that had been discovered by Marignac in the 1860s. The method has been supplanted by solvent extraction from fluoride-containing solutions.

Occurrence

Tantalum occurs principally in the minerals fergusonite).

Tantalum ores are mined in Ethiopia, Australia, Brazil, Egypt, Canada, the Democratic Republic of the Congo, Mozambique, Nigeria, Namibia, Portugal, Malaysia and Thailand. A comprehensive, 2002 picture of non-Australian mines is reasonably current.

Tantalite is largely found mixed with coltan).

Several complicated steps are involved in the separation of tantalum from tin smelting.

Compounds

Los Alamos National Laboratory scientists have developed a graphite composite material that is one of the hardest materials ever synthesized. Korean researchers have developed an amorphous tantalum-tungsten-copper alloy which is more flexible and two to three times stronger than traditional steel alloys.[1]

See also tantalum compounds.

Isotopes

Main article: isotopes of tantalum

Natural tantalum consists of two isotopes. Ta-181 is a stable isotope, and Ta-180m has a half life of over 1015 years (see scientific notation) and is a nuclear isomer of Ta-180. Ta-180 has a ground state half life of only 8 hours.

Tantalum has been proposed as a "fallout for several months. Such a weapon is not known to have ever been built, tested, or used.

Precautions

Compounds containing tantalum are rarely encountered, and the metal does not normally cause problems in the laboratory, but it should still be handled with care, taking the usual laboratory precautions. There is some evidence that tantalum compounds can cause tumors, and its metal dust is a fire and explosion hazard.

References

  • Los Alamos National Laboratory - Tantalum
  • T.I.C. industry site - Tantalum uses, ore mining and extraction
  • R. Cohen (2006). Applications of porous tantalum in total hip arthroplasty. Journal of the American Academy of Orthopaedic Surgeons, 14:646-655.
  1. ^ http://english.chosun.com/w21data/html/news/200505/200505060005.html
  • WebElements.com - Tantalum
  • Tantalum-Niobium International Study Center
 
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