Hafnium
Atomic Number: 72
Atomic Symbol: Hf
Atomic Weight: 178.49
Electron Configuration: 2-8-18-32-10-2
History
(Hafinia, Latin name for Copenhagen) Many years before its discovery in 1932 (credited to D. Coster and G. von Hevesey), Hafnium was thought to be present in various minerals and concentrations. On the basis of the Bohr theory, the new element was expected to be associated with zirconium.
It was finally identified in zircon from Norway, by means of X-ray spectroscope analysis. It was named in honor of the city in which the discovery was made. Most zirconium minerals contain 1 to 5 percent hafnium.
It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process).
Uses
Because the element not only has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), but also excellent mechanical properties and is extremely corrosion-resistant, hafnium is used for reactor control rods. Such rods are used in nuclear submarines.
Hafnium is used in gas-filled and incandescent lamps, and is an efficient getter for scavenging oxygen and nitrogen.
Cost
The price of the metal is in the broad range between $100/lb and $500/lb, depending on purity and quantity. The yearly demand for hafnium in the U.S. now exceeds 100,000 lb.
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