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Atomic Number: 40
Atomic Symbol: Zr
Atomic Weight: 91.22
Electron Configuration: [Kr]5s24d2
History
(Persian zargun, gold like) The name zircon probably originated from
the Persion word zargun, which describes the color of the gemstone now known as
zircon, jargon, hyacinth, jacinth, or ligure. This mineral, or its variations,
is mentioned in biblical writings. The mineral was not known to contain a new
element until Klaproth, in 1789, analyzed a jargon from Ceylon and found a new
earth, which Werner named zircon (silex circonius), and Klaproth called
Zirkonertz (zirconia). The impure metal was first isolated by Berzelius in 1824
by heating a mixture of potassium and potassium zirconium fluoride in a small
decomposition process they developed.
Sources
Zirconium is found in abundance in S-type stars, and has been
identified in the sun and meteorites. Analysis of lunar rock samples obtained
during the various Apollo missions to the moon show a surprisingly high
zirconium oxide content, compared with terrestrial rocks.
Isotopes
Naturally occurring zirconium contains five isotopes. Fifteen other
isotopes are known to exist. Zircon, ZrSiO4, the principal ore, is
pure ZrO2 in crystalline form having a hafnium content of about 1%.
Zirconium also occurs in some 30 other recognized mineral species. Zirconium is
produced commercially by reduction of chloride with magnesium (the Kroll
Process), and by other methods. It is a grayish-white lustrous metal. When
finely divided, the metal may ignite spontaneously in air, especially at
elevated temperatures. The solid metal is much more difficult to ignite. The
inherent toxicity of zirconium compounds is low. Hafnium is invariably found in
zirconium ores, and the separation is difficult.
Commercial-grade zirconium contains from 1 to 3% hafnium.
Zirconium has a low absorption cross section for neutrons, and is therefore used
for nuclear energy applications, such as for cladding fuel elements. Commercial
nuclear power generation now takes more than 90% of zirconium metal production.
Reactors of the commercial size, now being made, may use as much as a
half-million linear feet of zirconium alloy tubing.
Properties
Reactor-grade zirconium is essentially free of hafnium. Zircaloy®
is an important alloy developed specifically for nuclear applications. Zirconium
is exceptionally resistant to corrosion by many common acids and alkalis, by sea
water, and by other agents. Alloyed with zinc, zirconium becomes magnetic at
temperatures below 35° K.
Uses
It is used extensively by the chemical industry where corrosive
agents are employed. Zirconium is used as a getter in vacuum tubes, as an
alloying agent in steel, in surgical appliances, photoflash bulbs, explosive
primers, rayon spinnerets, lamp filaments, etc. It is used in poison ivy lotions
in the form of the carbonate as it combines with urushiol. With niobium,
zirconium is superconductive at low temperatures and is used to make
superconductive magnets, which offer hope of direct large-scale generation of
electric power. Zirconium oxide (zircon) has a high index of refraction and is
used as a gem material. The impure oxide, zirconia, is used for laboratory
crucibles that will withstand heat shock, for linings of metallurgical furnaces,
and by the glass and ceramic industries as a refractory material. Its use as a
refractory material accounts for a large share of all zirconium consumed.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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