Hafnium
Forms & Grades Handled
​
-
Hafnium Crystal Bars (Zr <0.5%)
-
Hafnium solids (Zr <0.5%, Zr <1%)
-
Hafnium oxide (Zr <0.5%, Zr <1%)
Hafnium Facts
​
Hafnium 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 kg/m3
300 nΩ⋅m
78 GPa
25.73 J/K⋅mol
5.3 ppm
23 W/m⋅K
Hafnium 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 1:50 in Zircon sands [itself a by-product of Ilmenite]. Its main use over the last half century was almost exclusively in the nuclear industry where it is used as control rods; because of its ability to absorb neutrons.
With only approximately 85 mt a year of annual output, of which about 30 mt is extracted in France this is a rare metal. It is only produced at plants whose main work is dedicated to the production of 'de-hafniated' Zirconium fabrications for the nuclear industry (an example of which is the tubes which contain Uranium fuel in an assembly). The Hafnium arises as part of a complex process in which Fused Zirconia is chlorinated in the presence of carbon and then sublimed, to produce a solution of approx 50:50 Hafnium tetrachloride and Zirconium tetrachloride. The HfCl4 is then separated from this salt and follows its own path to market.
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 2233°C ) have grown in demand. Lipmann Walton usually stocks a range of Hafnium in metallic forms, such as Van Arkel crystal bars, suitable for the super alloy industry.
One of the other main uses of Hafnium, after alloy making, is in plasma cutting tips. 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 due to its high melting point, stability and ability to conduct electricity.
Hafnium is a good example of the co-dependency of an element with its host ore. As mentioned above, without the need for pure (Hf free) Zirconium, there would be no Hafnium output at all. It is therefore worth pointing out that, although claims have been made for other production routes of Hafnium-free Zirconium, none has been commercialised at the time of writing (2020). It means that if the nuclear industry was to draw to a close (which at the moment seems unlikely) Hf output would cease.
​
More articles: