Zirconium

Main article: Isotopes of zirconium
iso	NA	half-life	DM	DE (MeV)	DP
⁸⁸Zr	syn	83.4 d	ε	-	⁸⁸Y
⁸⁸Zr	syn	83.4 d	γ	0.392D	-
⁸⁹Zr	syn	78.4 h	ε	-	⁸⁹Y
			β⁺	0.902	⁸⁹Y
			γ	0.909D	-
⁹⁰Zr	51.45%	⁹⁰Zr is stable with 50 neutrons
⁹¹Zr	11.22%	⁹¹Zr is stable with 51 neutrons
⁹²Zr	17.15%	⁹²Zr is stable with 52 neutrons
⁹³Zr	syn	1.53×10⁶y	β⁻	0.060	⁹³Nb
⁹⁴Zr	17.38%	1.1 × 10¹⁷ y	β⁻β⁻	-	⁹⁴Mo
⁹⁶Zr	2.8%	2.0×10¹⁹y ^[3]	β⁻β⁻	3.348	⁹⁶Mo

References

Image:Zirconium rod.jpg

Zirconium rod

Zirconium (pronounced /zɚˈkoʊniəm/, /ˌzɝˈkoʊniəm/) is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is never found as a native metal, but is instead obtained mainly from the mineral zircon. Zirconium is used as an alloying agent due to its high resistance to corrosion.

1 Characteristics
2 Applications
3 History
4 Occurrence
5 Isotopes
6 Toxicity
7 References
8 External links

Characteristics

Zirconium is a lustrous, grayish-white metal which is solid at room temperature. In powder form, zirconium is highly flammable, but the solid form is far less prone to igniting.^[4] Zirconium is highly resistant to corrosion by alkalis, acids, salt water, and other agents.^[5] Alloys with zinc become magnetic below 35 K.^[6]

The melting point of zirconium is at 1852°C, and the boiling point is at 4377°C.^[7] Zirconium has an electronegativity of 1.33 on the Pauling scale. Of the elements within d-block, Zirconium has the fourth lowest electronegativity after yttrium, lutetium, and hafnium.^[8]

Applications

Because of Zirconium's excellent resistance to corrosion, it is often used as an alloying agent in materials that are exposed to corrosive agents, such as surgical appliances, explosive primers, vacuum tube getters and filaments. Zirconium dioxide (ZrO₂) is used in laboratory crucibles, metallurgical furnaces, and as a refractory material.^[6] Zircon (ZrSiO₄) is cut into gemstones for use in jewelry. Zirconium carbonate (3ZrO₂·CO₂·H₂O) is used in lotions to treat poison ivy. Zirconium is also used in nuclear reactors because of its low neutron-capture cross-section and resistance to corrosion.^[9]

History

Zirconium (from Syriac zargono,^[10] Arabic zarkûn from Persian zargûn زرگون meaning "gold like") was discovered in 1789 by Martin Heinrich Klaproth, isolated in 1824 by Jöns Jakob Berzelius, and finally put in a pure form in 1914.^[9]

The zirconium-containing mineral zircon, or its variations (jargoon, hyacinth, jacinth, ligure), were mentioned in biblical writings. The mineral was not known to contain a new element until Klaproth analyzed a jargoon from the island of Ceylon in the Indian Ocean. He named the new element Zirkonertz (zirconia). The impure metal was isolated first by Berzelius by heating a mixture of potassium and potassium-zirconium fluoride in a small decomposition process conducted in an iron tube.^[5]

The crystal bar process (or Iodide process), discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, was the first industrial process for the commercial production of pure metallic zirconium. It was superseded by the Kroll process, developed in the 1940s.^[11]

Occurrence

Image:2005zirconium.PNG

Zirconium output in 2005

Image:Zirconium mineral concentrates - world production trend.svg

World production trend of zirconium mineral concentrates

Zirconium has a concentration of about 130 mg/kg within the earth's crust and about .026 μg/L in sea water,^[12] though it is never found in nature as a native metal. The principal commercial source of zirconium is the zirconium silicate mineral, zircon (ZrSiO₄), which is found in deposits located in Australia, Brazil, India, Russia, and the United States. Zirconium and hafnium are both contained in zircon and they are quite difficult to separate chemically.^[13] Zircon resources exceed 60 million metric tons worldwide^[14] and annual worldwide zirconium production is approximately 900,000 metric tons.^[12]

Zircon is a by-product of the mining and processing of the titanium minerals ilmenite and rutile, as well as tin mining.^[15] From 2003 to 2007, zircon prices have steadily increased from $360 to $840 per metric ton.^[14] Zirconium also occurs in more than 140 other recognized mineral species including baddeleyite and kosnarite.^[16] This metal is commercially produced mostly by the reduction of the zirconium(IV) chloride with magnesium metal in the Kroll process. Commercial-quality zirconium for most uses still has a content of 1% to 3% hafnium.^[7]

This element is relatively-abundant in S-type stars, and it has been detected in the sun and in meteorites. Lunar rock samples brought back from several Apollo program missions to the moon have a quite high zirconium oxide content relative to terrestrial rocks.^[5]^[13]

See also zirconium minerals.

Isotopes

Main article: Isotopes of zirconium

Naturally-occurring zirconium is composed of five isotopes. ⁹⁰Zr, ⁹¹Zr, and ⁹²Zr are stable. ⁹⁴Zr has a half-life of 1.10 × 10¹⁷ years. ⁹⁶Zr has half-life of 2.4 × 10¹⁹ years, making it the longest-lived radioisotope of zirconium. Of these natural isotopes, ⁹⁰Zr is the most common, making up 51.45% of all zirconium. ⁹⁶Zr is the least common, comprising only 2.80% of zirconium.^[17]

28 artificial isotopes of zirconium have been synthesized, ranging in atomic mass from 78 to 110. ⁹³Zr is the longest-lived artificial isotope, with a half-life of 1.53 × 10⁶ years. ¹¹⁰Zr, the heaviest isotope of Zirconium, is also the shortest-lived, with an estimated half-life of only 30 milliseconds. Radioactive isotopes at or above mass number 93 decay by β^-, whereas those at or below 89 decay by β⁺. The only exception is ⁸⁸Zr, which decays by ε.^[17]

Zirconium also has six metastable isomers, ^83mZr, ^85mZr, ^89mZr, ^90m1Zr, ^90m2Zr, and ^91mZr. Of these, ^90m2Zr has the shortest half-life at 131 nanoseconds. ^89mZr is the longest lived with a half-life of 4.161 minutes.^[17]

Toxicity

Inhalation of zirconium compounds can cause skin and lung granulomas. Zirconium aerosols can cause pulmonary granulomas. Persistent exposure to zirconium tetrachloride resulted in increased mortality in rats and guinea pigs and a decrease of blood hemoglobin and red blood cells in dogs. OSHA recommends a 5 mg/m³ time weighted average limit and a 10 mg/m³ short-term exposure limit.^[18] Ingestion or inhalation of ⁹³Zr, a radioactive isotope, causes a slight increase in the likelihood of developing cancer.^[12]

References

^ Zirconium: zirconium(III) iodide compound data. WebElements.com. Retrieved on 2007-12-10.
^ Zirconium: zirconium(I) fluoride compound data. OpenMOPAC.net. Retrieved on 2007-12-10.
^ Pritychenko, Boris; V. Tretyak. Adopted Double Beta Decay Data. National Nuclear Data Center. Retrieved on 2008-02-11.
^ Winter, Mark (2007). Key Information. Zirconium. University of Sheffield. Retrieved on 2008-02-12.
^ ^a ^b ^c Zirconium. Los Alamos Chemistry Division (2003-12-15). Retrieved on 2008-02-12.
^ ^a ^b Winter, Mark (2007). Uses. Zirconium. University of Sheffield. Retrieved on 2008-02-12.
^ ^a ^b
^ Winter, Mark (2007). Electronegativity (Pauling). University of Sheffield. Retrieved on 2008-03-05.
^ ^a ^b Gagnon, Steve. Zirconium. It's Elemental. Jefferson Lab. Retrieved on 2008-02-12.
^ Pearse, Roger (2002-09-16). Syriac Literature. Retrieved on 2008-02-11.
^ Hedrick, James B. (1998), "Zirconium", Metal Prices in the United States through 1998, US Geological Survey, pp. 175-178, <http://minerals.usgs.gov/minerals/pubs/metal_prices/metal_prices1998.pdf>. Retrieved on {{#iferror:2008 |2008-02-26 |25 February 2008}}
^ ^a ^b ^c
^ ^a ^b
^ ^a ^b (January 2008) "Zirconium and Hafnium" (PDF). Mineral Commodity Summaries: 192-193. US Geological Survey. Retrieved on 2008-02-24.
^ Callaghan, R. (2008-02-21). Zirconium and Hafnium Statistics and Information. US Geological Survey. Retrieved on 2008-02-24.
^ Ralph, Jolyon; Ida Ralph (2008). Minerals that include Zr. Mindat.org. Retrieved on 2008-02-23.
^ ^a ^b ^c (2003) "Nubase2003 Evaluation of Nuclear and Decay Properties". Nuclear Physics A 729: 3-128. Atomic Mass Data Center. Retrieved on 2008-03-04.
^ Zirconium Compounds. National Institute for Occupational Health and Safety (2007-12-17). Retrieved on 2008-02-17.