Zirconium

Zirconium is a hard, lustrous, silvery coloured metal which is extracted from its ores (the oxide or zircon, ZrSiO₄) by conversion to the tetrahalide followed by reduction with magnesium. The metal is extremely corrosion resistant due to the formation of a stable oxide film and is unaffected by acids (with the exception of HF) and alkalis. As a result of its corrosion resistance, zirconium is widely used in the chemical industry where corrosive agents are used. Also, due to its excellent high temperature properties, coupled with its low neutron absorption, it is used in the construction of nuclear reactors. The pure metal is also used as a lining in jet engines. Zirconium is used as an alloying element, the resultant alloys having improved mechanical properties. The chemical properties of zirconium are very similar to those of hafnium. As a result, the normal chemical processes used for the extraction of zirconium will not remove hafnium, which can be present in commercial grades of zirconium at levels as high as 4.5%.

Symbol

Zr

Discovered

Berlin, Germany, in 1789 by M.H. Klaproth, but was not isolated until 1824 by J.J. Berzelius in Stockholm, Sweden.

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Atomic number	40		Clip
Atomic / Molecular Weight	91.224	gmol-1	Clip
Density	6507	kgm-3	Clip
Crystal Structure	hcp / bcc at 1100K		Clip
Lattice constant	323	fm	Clip
Melting Point	2123	K	Clip
Boiling Point	4773	K	Clip
Tensile strength	260e6 (annealed) 1e9 (hard drawn)	Nm-2	Clip
Specific heat capacity	276	Jkg-1K-1	Clip
Thermal conductivity	23	Wm-1K-1	Clip
Acoustic wave velocity (longitudinal bulk waves)	4650	ms-1	Clip
Acoustic wave velocity (Shear waves)	2250	ms-1	Clip

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See also: Hafnium, Periodic Table, Zirconium Oxide.