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Hafnium

HafniumHafnium was first separated in 1923 by the Hungarian chemist, George Charles de Hevesy working with Dirk Coster at the University of Copenhagen – hence its name which is derived from the Latin name for that town – Hafnia.

Like a number of other elements, nowhere is Hafnium mined for itself and usually arises at the rate of 50 : 1 in Zircon sands [itself sometimes a by-product of Ilmenite]. Its main use over the last half century has been almost exclusively in the nuclear industry where it is used as control rods; because of its ability to absorb neutrons.

With only approximately 55mt a year of supply, of which about 25mt is extracted in France this is a rare metal. It is only produced at plants whose main work is dedicated to the production of Zirconium rods / tubes and fabrications for the nuclear industry (the tubes which contain Uranium fuel in an assembly). The Hafnium arises through the need to produce very pure, Hafnium-free, Zirconium.

Over the years, non-nuclear uses have become more significant. Perhaps one of the most important is in complex super alloys where 1.5% Hf is a typical constituent of MAR-M-247, a Nickel base directionally solidified (DS) casting alloy developed by Martin-Marietta Corp. for use in gas turbine engines. As operating temperatures have risen, elements such as Hafnium (melting point 2233oC ) have grown in demand. Lipmann Walton concentrates on the supply of Hafnium pieces in metallic form suitable for the super alloy industry.

One of the other main uses of Hafnium, after alloy making, is in plasma cutters. Plasma* cutters operate at very high temperatures, generated by a spark between a negative electrode and the metal to be cut. Hafnium is an ideal material for this negative electrode as it has one of the highest melting points out of all of the metals in the periodic table, 2233oC, and can conduct electricity.

                                                                                                 For video, credit www.periodictable.co.uk

                                      Credit www.plasma-cutter.com

*Plasma is a fourth state of matter (solid, liquid, gas, plasma) that can be reached by electrically heating a gas to the point at which the molecules no longer behave like gas molecules. When harnessed, this high energy state can be used for the precision cutting of metals.

Hafnium FACTS

It was first reported by Urbain in 1911 and its existence was finally established by D. Coster and G.C de Hevesey in 1923.

Hafnium is a lustrous, silvery, ductile metal that resists corrosion due to an oxide film on its surface. The element is found with zirconium and is extracted by formation of the chloride and reduction by the Kroll process.

The metals structure is HCP. In contrast to Zirconium it is a strong neutron absorber and is used as a control rod material for nuclear reactors. It is also used in high temperature alloys as discussed.

Atomic no.
Relative atomic mass
Melting point
Boiling point
Density
Electrical resistivity
Young’s modulus
Heat capacity
Abundance
Thermal conductivity
72
178.49
2233°C
4603°C
13310 kgm-3
300 nΩm
78 Gpa
25.73 J/K/mol
5.3 ppm
23 W/m/K