- Zirconium
Zirconium (pronEng|zɚˈkoʊniəm, IPA|/ˌzɝˈkoʊniəm/) is a
chemical element with the symbol Zr andatomic number 40. It is a lustrous, gray-white, strongtransition metal that resemblestitanium . Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal, but is instead obtained mainly from the mineralzircon , which can be purified bychlorine . Zirconium was first isolated in an impure form in 1824 by Jöns Jakob Berzelius.Zirconium has no known biological role. Zirconium forms both inorganic and organic compounds, such as
zirconium dioxide andzirconocene dibromide , respectively. There are five naturally-occurringisotope s, three of which are stable. Short-term exposure to zirconium powder causes minor irritation, and inhalation of zirconium compounds can cause skin and lunggranulomas .Characteristics
Zirconium is a lustrous, grayish-white, soft,
ductile , andmalleable metal which is solid at room temperature, though it becomes hard andbrittle at lower purities. In powder form, zirconium is highly flammable, but the solid form is far less prone to igniting. Zirconium is highly resistant to corrosion by alkalis, acids, salt water, and other agents.cite web |title=Zirconium|publisher=Los Alamos Chemistry Division|date=2003-12-15|url=http://periodic.lanl.gov/elements/40.html| accessdate = 2008-02-12] However, it will dissolve in hydrochloric andsulfuric acid , especially whenfluorine is present.Citation|contribution=Zirconium|year=2005|title=Van Nostrand's Encyclopedia of Chemistry| editor-last = Considine| editor-first = Glenn D.|pages=1778–1779|place=New York|publisher=Wylie-Interscience|isbn=0-471-61525-0 ] Alloys with zinc become magnetic below 35 K.The melting point of zirconium is at 1855°C, and the boiling point is at 4409°C.Citation|contribution=Zirconium|year=2007–2008|title=CRC Handbook of Chemistry and Physics|editor-last=Lide|editor-first=David R.|volume=4|pages=42|place=New York|publisher=CRC Press|id=978-0-8493-0488-0] Zirconium has an
electronegativity of 1.33 on the Pauling scale. Of the elements withind-block , Zirconium has the fourth lowest electronegativity afteryttrium ,lutetium , andhafnium . [cite web|last=Winter|first=Mark|title=Electronegativity (Pauling)|publisher=University of Sheffield| year = 2007| url = http://www.webelements.com/webelements/properties/text/image-flash/electroneg-pauling.html| accessdate = 2008-03-05]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
getter s and filaments. Zirconium dioxide (ZrO2) is used in laboratory crucibles, metallurgical furnaces, and as a refractory material.Zircon (ZrSiO4) is cut into gemstones for use in jewelry. Zirconium carbonate (3ZrO2·CO2·H2O) was used in lotions to treat poison ivy, but this was discontinued as it caused bad skin reactions in some cases.cite book| last = Emsley| first = John| title = Nature's Building Blocks| publisher = Oxford University Press| year = 2001| location = Oxford| pages = 506–510| isbn = 0-19-850341-5 ] 90% of all zirconium produced is used in nuclear reactors because of its low neutron-capturecross-section and resistance to corrosion.cite web| title = Zirconium| work = How Products Are Made| publisher = Advameg Inc.| year = 2007| url = http://www.madehow.com/Volume-1/Zirconium.html| accessdate = 2008-03-26] Zirconium alloys are used in space vehicle parts for their resistance to heat, an important quality given the extreme heat associated withatmospheric reentry .cite book|last=Stwertka|first=Albert|title=A Guide to the Elements|publisher=Oxford University Press|year=1996|pages=117–119| isbn = 0-19-508083-1] Zirconium is also a component in someabrasive s, such as grinding wheels andsandpaper .cite book|last=Krebs|first=Robert E.|title=The History and Use of our Earth's Chemical Elements|publisher=Greenwood Press|year=1998|location=Westport, Connecticut|pages=98–100|isbn=0-313-30123-9] Zirconium is used in weapons such as theBLU-97/B Combined Effects Bomb for incendiary effect. Zirconium in the oxidized form is also used in dentistry for crowning of the teeth because of its biocompatibility, strength and appeareance.Refining
Upon being collected from coastal waters, the solid mineral
zircon is purified by spiral concentrators to remove excess sand and gravel and by magnetic separators to removeilmenite andrutile . The byproducts can then be dumped back into the water safely, as they are all natural components of beach sand. The refined zircon is then purified into pure zirconium bychlorine or other agents, thensinter ed until sufficiently ductile for metalworking. Zirconium andhafnium are both contained in zircon and they are quite difficult to separate due to their similar chemical properties.History
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 1789, when Klaproth analyzed a jargoon from the island ofCeylon in the Indian Ocean. He named the new element Zirkonerde (zirconia).Humphry Davy attempted to isolate this new element in 1808 through electrolysis, but failed. Zirconium (from Syriac "zargono", [cite web| last = Pearse| first = Roger| title = Syriac Literature| date = 2002-09-16| url = http://www.tertullian.org/rpearse/oriental/syriac.htm| accessdate = 2008-02-11] Arabic "zarkûn" from Persian "zargûn" "زرگون" meaning "gold like") was first isolated in an impure form in 1824 by Berzelius by heating a mixture of potassium and potassium-zirconium fluoride in a small decomposition process conducted in an iron tube.The "
crystal bar process " (or "Iodide process"), discovered byAnton Eduard van Arkel and Jan Hendrik de Boer in 1925, was the first industrial process for the commercial production of pure metallic zirconium. The process involved thermally decomposing zirconium tetraiodide. It was superseded in 1945 by a much cheaper process developed byWilliam Justin Kroll , in which zirconium tetrachloride is broken down by magnesium.Citation|first=James B.|last=Hedrick|contribution=Zirconium|title=Metal Prices in the United States through 1998|year=1998|pages=175–178|publisher=US Geological Survey|url=http://minerals.usgs.gov/minerals/pubs/metal_prices/metal_prices1998.pdf|format=PDF |accessdate=2008-02-26]Occurrence
Geological
Zirconium has a concentration of about 130 mg/kg within the
earth 's crust and about .026 μg/L insea water , though it is never found in nature as anative metal . The principal commercial source of zirconium is the zirconiumsilicate mineral ,zircon (ZrSiO4), which is found primarily in Australia, Brazil, India, Russia, South Africa, and the United States, as well as in smaller deposits around the world. 80% of zircon mining occurs in Australia and South Africa.Zircon resources exceed 60 million metric tons worldwidecite journal| title = Zirconium and Hafnium| journal = Mineral Commodity Summaries| pages = 192–193| publisher = US Geological Survey| month = January | year = 2008| url = http://minerals.usgs.gov/minerals/pubs/commodity/zirconium/mcs-2008-zirco.pdf| format = PDF| accessdate = 2008-02-24] and annual worldwide zirconium production is approximately 900,000 metric tons.Citation|first=John|last=Peterson|first2=Margaret|last2=MacDonell| contribution=Zirconium|title=Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas|year=2007|pages=64–65|publisher=Argonne National Laboratory|format=PDF |url=http://www.evs.anl.gov/pub/doc/ANL_ContaminantFactSheets_All_070418.pdf|accessdate=2008-02-26]Zircon is a by-product of the mining and processing of the
titanium mineralsilmenite andrutile , as well astin mining. [cite web|last=Callaghan|first=R.|title=Zirconium and Hafnium Statistics and Information|publisher=US Geological Survey|date=2008-02-21|url=http://minerals.usgs.gov/minerals/pubs/commodity/zirconium/|accessdate=2008-02-24] From 2003 to 2007, zircon prices have steadily increased from $360 to $840 per metric ton. Zirconium also occurs in more than 140 other recognized mineral species includingbaddeleyite andkosnarite . [cite web|last=Ralph|first=Jolyon|coauthors=Ida Ralph|title=Minerals that include Zr|publisher=Mindat.org| year=2008|url=http://www.mindat.org/chemsearch.php?inc=Zr%2C&exc=&sub=Search+for+Minerals|accessdate=2008-02-23] This metal is commercially produced mostly by the reduction of the zirconium(IV)chloride withmagnesium metal in theKroll process . Commercial-quality zirconium for most uses still has a content of 1% to 3% hafnium.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."See also ."
Biological
Zirconium has no known biological role, though zirconium salts are of low toxicity. The human body contains, on average, only 1 milligram of zirconium, and daily intake is approximately 50 μg per day. Zirconium content in human blood is as low as 10 parts per billion. Aquatic plants readily take up soluble zirconium, but it is rare in land plants. 70% of plants have no zirconium content at all, and those that do have as little as 5 parts per billion.
Compounds
As a
transition metal , zirconium forms various inorganic compounds, such aszirconium dioxide (ZrO2). This compound, also referred to as "zirconia", has exceptionalfracture toughness and chemical resistance, especially in its cubic form.cite web|title=Zirconia| publisher = AZoM.com| year = 2008| url = http://www.azom.com/details.asp?ArticleID=133#_Key_Properties| accessdate=2008-03-17] These properties make zirconia useful as a thermal barrier coating, [cite journal|last=Gauthier| first=V.| last2=Dettenwanger|first2=F.|last3=Schütze|first3=M.|title=Oxidation behavior of γ-TiAl coated with zirconia thermal barriers| journal=Intermetallics| volume=10| issue=7|pages=667–674|publisher=Karl Winnacker Institut der Dechema|location= Frankfurt, Germany|date=2002-04-10| doi=10.1016/S0966-9795(02)00036-5] though it is also a commondiamond substitute.Zirconium tungstate is an unusual substance in that it shrinks in all directions when heated, whereas other elements expand when heated. ZrZn2 is one of only two substances to exhibitsuperconductivity andferromagnetism simultaneously, with the other being UGe2. [cite journal|last=Day|first=Charles|title=Second Material Found that Superconducts in a Ferromagnetic State|journal=Physics Today|volume=54|issue=9|pages=16| publisher=American Institute of Physics |month=September | year=2001| issn=0031-9228|doi=10.1063/1.1420499] Other inorganic zirconium compounds include zirconium(II) hydride, zirconium nitride, andzirconium tetrachloride (ZrCl4), which is used in theFriedel-Crafts reaction . [cite journal | author= Bora U.|title=Zirconium Tetrachloride|journal=Synlett |year=2003|pages=1073–1074|doi=10.1055/s-2003-39323]Organozirconium chemistry is the study of compounds containing acarbon -zirconium bond. These organozirconium compounds are often employed as polymerization catalysts. The first such compound was zirconocene dibromide, prepared in 1952 byJohn M. Birmingham at Harvard University. [cite journal|last=Rouhi|first=A. Maureen|title=Organozirconium Chemistry Arrives|journal=Science & Technology| volume=82|issue=16|pages=36–39|publisher=Chemical & Engineering News|date=2004-04-19|url=http://pubs.acs.org/cen/nlw/8216sci1.html|issn=0009-2347| accessdate=2008-03-17] Schwartz's reagent, prepared in 1970 by P. C. Wailes and H. Weigold, [cite journal|author=P. C. Wailes and H. Weigold|title=Hydrido complexes of zirconium I. Preparation|journal=Journal of Organometallic Chemistry |year=1970|volume=24|pages=405–411|doi=10.1016/S0022-328X(00)80281-8] is ametallocene used inorganic synthesis for transformations ofalkenes andalkynes .cite journal | author=D. W. Hart and J. Schwartz| title=Hydrozirconation. Organic Synthesis via Organozirconium Intermediates. Synthesis and Rearrangement of Alkylzirconium(IV) Complexes and Their Reaction with Electrophiles| journal=J. Am. Chem. Soc. |volume=96 |issue=26|year=1974|pages=8115–8116|doi=10.1021/ja00833a048]Isotopes
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.cite journal|title=Nubase2003 Evaluation of Nuclear and Decay Properties|journal=Nuclear Physics A|volume=729|pages=3–128|publisher=Atomic Mass Data Center|year=2003|doi=10.1016/j.nuclphysa.2003.11.001|author=Audi, G]
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.
Zirconium also has six metastable isomers, 83mZr, 85mZr, 89mZr, 90m1Zr, 90m2Zr, and 91mZr. Of these, 90m2Zr has the shortest halflife at 131 nanoseconds. 89mZr is the longest lived with a half-life of 4.161 minutes.
Toxicity
Ingestion or inhalation of 93Zr, a radioactive isotope, causes a slight increase in the likelihood of developing cancer. Short-term exposure to zirconium powder can cause irritation, but only contact with the eyes requires medical attention. [Citation| contribution=Zirconium|title=International Chemical Safety Cards|date=October 2004|publisher=International Labour Organization|url=http://www.oit.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc14/icsc1405.htm|accessdate=2008-03-30] Inhalation of zirconium compounds can cause skin and lung
granuloma s. Zirconium aerosols can causepulmonary 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. [cite web|title=Zirconium Compounds|publisher=National Institute for Occupational Health and Safety|date=2007-12-17|url=http://www.cdc.gov/niosh/pel88/7440-67.html|accessdate=2008-02-17]ee also
*
Notes
External links
* [http://webelements.com/zirconium/ WebElements.com: Zirconium]
* [http://periodic.lanl.gov/elements/40.html Los Alamos National Laboratory: Zirconium]
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