Dirk Coster, a Danish chemist, and Charles de Hevesy, a Hungarian chemist, jointly discovered hafnium in 1923 in the mineral zircon. The element's name stems from the Latin word for the city of Copenhagen, Hafnia. Most zirconium minerals contain about 1 to 3% hafnium.
Hafnium is a ductile metal with a brilliant silver lustre and its properties are influenced considerably by any impurities of zirconium present. Of all the elements, zirconium and hafnium are two of the most difficult to separate. It has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties and is extremely corrosion resistant.
APPLICATIONS OF HAFNIUM
Energy: Hafnium's excellent mechanical, corrosion-resistance and nuclear absorption properties allow its use in the harsh environment of pressurized water nuclear reactors, in particular in fission control rods.
Alloys: Small additions of hafnium increase the adherence of protective oxide scales on nickel based alloys. It improves the corrosion resistance especially under cyclic temperature conditions that tend to break oxide scales by inducing thermal stresses between the bulk material and the oxide layer. Hafnium is also used in iron, titanium, niobium, tantalum, and other metal alloys.
C103 is an alloy, consisting of 89% niobium, 10% hafnium and 1% titanium, is used for liquid rocket thruster nozzles and was used for example, in the engine of the Apollo Lunar Lander Modules.
Electronics: Hafnium-based compounds can be employed in gate insulators in the 45 nm generation of integrated circuits from Intel, IBM and others. Hafnium oxide-based compounds have high dielectric constants making practical capacitors which allow reduction of the gate leakage current which improves performance at these scales. It is also being substituted for silicon in computer chips allowing for smaller sizes and hence faster functioning.
Other uses: Hafnium is a good scavenger for oxygen and nitrogen in gas-filled and incandescent lamps. Similarly it is also used in vacuum tubes as a "getter"; a metal that combines with and removes traces of gases such as oxygen from vacuum tubes.
Hafnium is also used as the electrode in plasma cutting. Hafnium carbide is the most refractory binary composition known. Hafnium, tantalum carbides have the highest known melting temperature of 4,2150 C.
LINKS: For chemical and physical properties: www.webelements.com or http://education.jlab.org/itselemental/ele072.html
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