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{{Infobox element
[[File:UK Happisburgh c. 800000 BP EN.svg|thumb|right|250px|黑斯堡在[[更新世]]早期的地理位置,距今約80萬年。]]
|number=41
'''黑斯堡足跡'''是一組[[更新世]][[人族]]腳印化石,位於英國[[諾福克郡]][[黑斯堡]]一處沙灘新暴露出的沉積層,於2013年5月發現。這組足跡在發現後不久便已被潮水抹去。2014年2月7日,科學家公佈研究發現,指足跡距今約80萬年前形成,因此是人族在非洲大陸以外已知最早的腳印。<ref name="bbc-2014-02-07">{{cite web|last=Ghosh|first=Pallab|title=Earliest footprints outside Africa discovered in Norfolk|url=http://www.bbc.co.uk/news/science-environment-26025763|publisher=BBC News|accessdate=7 February 2014}}</ref><ref name="plos">Ashton N, Lewis SG, De Groote I, Duffy SM, Bates M, et al. (2014) [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0088329 Hominin Footprints from Early Pleistocene Deposits at Happisburgh, UK]. PLoS ONE 9(2): e88329. doi:10.1371/journal.pone.0088329</ref><ref name="ashton">{{Cite web | last=Ashton | first=Nicholas | title=The earliest human footprints outside Africa | url=http://blog.britishmuseum.org/2014/02/07/the-earliest-human-footprints-outside-africa-2/ | publisher=[[大英博物館|British Museum]] | date=7 February 2014 | accessdate=7 February 2014 }}</ref>黑斯堡足跡被發現之前,在英國已知最早的足跡位於南[[威爾士]]阿斯克茅斯(Uskmouth),形成時間根據[[碳定年法]]為公元前4600年的[[中石器時代]]。<ref>{{Cite web | title=Uskmouth | publisher=Severn Estuary Levels Research Committee | url=http://www.selrc.org.uk/maplocation.php?location_id=37 | accessdate=8 February 2014 }}</ref>
|symbol=Nb
|name=鈮
|left=[[鋯]]
|right=[[鉬]]
|above=[[釩]]
|below=[[鉭]]
|series = 過渡金屬
|group=5
|period=5
|block=d
|image name= Niobium_crystals_and_1cm3_cube.jpg
|appearance=灰色金屬質,氧化後呈藍色
|atomic mass=92.90637
|atomic mass 2=2
|electron configuration=&#91;[[氪]]&#93; 4d<sup>4</sup> 5s<sup>1</sup>
|electrons per shell= 2, 8, 18, 12, 1
|phase= solid
|density gpcm3nrt= 8.57
|melting point K=2750
|melting point C=2477
|melting point F=4491
|boiling point K=5017
|boiling point C=4744
|boiling point F=8571
|heat fusion= 30
|heat vaporization= 689.9
|heat capacity= 24.60
|vapor pressure 1= 2942
|vapor pressure 10= 3207
|vapor pressure 100= 3524
|vapor pressure 1 k= 3910
|vapor pressure 10 k= 4393
|vapor pressure 100 k= 5013
|vapor pressure comment=
|crystal structure= 體心立方
|oxidation states= '''5''', 4, 3, 2, -1<br />(弱[[酸性]]氧化物)
|electronegativity= 1.6
|number of ionization energies=3
|1st ionization energy= 652.1
|2nd ionization energy= 1380
|3rd ionization energy= 2416
|atomic radius= 146
|covalent radius= 164±6
|magnetic ordering= 順磁性
|electrical resistivity at 0= 152 n
|thermal conductivity= 53.7
|thermal expansion= 7.3
|speed of sound rod at 20= 3480
|Young's modulus= 105
|Shear modulus= 38
|Bulk modulus= 170
|Poisson ratio= 0.40
|Mohs hardness= 6.0
|Vickers hardness= 1320
|Brinell hardness= 736
|CAS number= 7440-03-1
|isotopes={{Elementbox_isotopes_decay | mn=91 | sym=Nb
| na=[[放射性同位素|人造]] | hl=6.8×10<sup>2</sup>年
| dm=[[電子捕獲|ε]] | de=- | link1=zirconium-91 | pn=91 | ps=Zr}}
{{Elementbox_isotopes_decay | mn=91[[同核異構體|m]] | sym=Nb
| na=人造 | hl=60.86天
| dm=[[同核異構體轉換|IT]] | de=0.104e | pn=91 | ps=Nb}}
{{Elementbox_isotopes_decay2 | mn=92 | sym=Nb
| na=人造 | hl=10.15天
| dm1=ε | de1=- | pn1=92 | ps1=Zr
| dm2=[[伽馬射線|γ]] | de2= 0.934 | pn2= | ps2=-}}
{{Elementbox_isotopes_decay2 | mn=92 | sym=Nb
| na=人造 | hl=3.47×10<sup>7</sup>年
| dm1=ε | de1=- | pn1=92 | ps1=Zr
| dm2=γ | de2=0.561, 0.934 | pn2= | ps2=-}}
{{Elementbox_isotopes_decay | mn=93 | sym=Nb | na=100% | hl=- | dm=([[自發裂變|SF]]) | de=<0.943 | pn= | ps= }}
{{Elementbox_isotopes_decay | mn=93m | sym=Nb
| na=人造 | hl=16.13年
| dm=IT | de=0.031e | pn=93 | ps=Nb}}
{{Elementbox_isotopes_decay2 | mn=94 | sym=Nb
| na=人造 | hl=2.03×10<sup>4</sup>年
| dm1=[[β衰變|β<sup>−</sup>]] | de1=0.471 | pn1=94 | ps1=Mo
| dm2=γ | de2=0.702, 0.871 | pn2= | ps2=-}}
{{Elementbox_isotopes_decay2 | mn=95 | sym=Nb
| na=人造 | hl=34.991天
| dm1=β<sup>−</sup> | de1=0.159 | pn1=95 | ps1=Mo
| dm2=γ | de2=0.765 | pn2= | ps2=- }}
{{Elementbox_isotopes_decay | mn=95m | sym=Nb
| na=人造 | hl=3.61天
| dm=IT | de=0.235 | pn=95 | ps=Nb}}
|isotopes comment=理論預測,但未有觀測證明的衰變方式以括號標示。
|discovered by=[[查理斯·哈契特]]
|discovery date=1801
|first isolation by=[[克利斯蒂安·威廉·布隆斯特蘭]]
|first isolation date=1864
|history comment label=證明為[[化學元素]]
|history comment=[[海因里希·羅澤]](1844年)
}}


'''Niobium''', formerly '''columbium''', is a [[chemical element]] with the symbol '''Nb''' (formerly '''Cb''') and [[atomic number]] 41. It is a soft, grey, [[ductile]] [[transition metal]], which is often found in the [[pyrochlore]] mineral, the main commercial source for niobium, and [[columbite]]. The name comes from [[Greek mythology]]: ''[[Niobe]]'', daughter of ''[[Tantalus]]''.
==發現==
[[File:Location of Happisburgh.png|thumb|250px|黑斯堡足跡遺址地圖,顯示暴露出的沙灘沉積層以及腳印表面的地點]]
[[大英博物館]]館長尼可拉斯·艾什頓(Nicholas Ashton)和[[威爾士三一聖大衛大學]]的馬丁·貝茨(Martin Bates)在進行英國古人族居住地研究的時候,在2013年5月發現了這一組足跡。足跡位於黑斯堡前灘的沉積層中,低潮時表面被沙部份遮掩。這裡曾是古河流的河口,河流消失後沉積層再被沙遮蓋,因此表面特徵得以保存。足跡位於山崖之下,其保護性沙層被暴風颳走,暴露出了沉積層。<ref name="ashton"/><ref name="CA288">{{cite journal | title=Colonising Britain: One million years of our human story | pages=14–21 | journal=Current Archaeology | issue=288 | date=March 2014}}</ref>不過,沉積層十分鬆軟,且位於最高潮水線以下,因此不到兩個星期,足跡已完全消失了。<ref name="bbc-2014-02-07"/>


Niobium has physical and chemical properties similar to those of the element [[tantalum]], and the two are therefore difficult to distinguish. The English chemist [[Charles Hatchett]] reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist [[William Hyde Wollaston]] wrongly concluded that tantalum and columbium were identical. The German chemist [[Heinrich Rose]] determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.
雖然考古團隊未能保存足跡,但是他們在有限時間內利用[[攝影測量法]]記錄了腳印的三維影像。[[利物浦約翰摩爾斯大學]]的伊莎貝爾·德·格魯特(Isabelle De Groote)分析了這組圖片,並確認沉積層上的印子確實是[[人族]]腳印。<ref name="bbc-2014-02-07"/><ref name="bm">{{Cite web | title=New discovery at Happisburgh: The earliest human footprints outside Africa | url=http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh/happisburgh_footprints.aspx | publisher=[[大英博物館|British Museum]] | accessdate=7 February 2014 }}</ref>


It was not until the early 20th century that niobium was first used commercially. [[Brazil]] is the leading producer of niobium and [[ferroniobium]], an [[alloy]] of niobium and iron. Niobium is used mostly in alloys, the largest part in special [[steel]] such as that used in gas [[Pipeline transport|pipelines]]. Although alloys contain only a maximum of 0.1%, that small percentage of niobium improves the strength of the steel. The temperature stability of niobium-containing [[superalloy]]s is important for its use in [[jet engine|jet]] and [[rocket engine]]s. Niobium is used in various [[Superconductivity|superconducting]] materials. These [[Type-II superconductor|superconducting alloys]], also containing [[titanium]] and [[tin]], are widely used in the [[superconducting magnet]]s of [[Magnetic resonance imaging|MRI scanners]]. Other applications of niobium include its use in welding, nuclear industries, electronics, optics, numismatics and jewelry. In the last two applications, niobium's low toxicity and ability to be colored by [[Anodizing|anodization]] are particular advantages.
2014年2月,艾什頓等人通過科學期刊《[[PLOS ONE]]》公佈了這項發現。<ref>{{cite web|url=http://www.archaeology.co.uk/articles/news/earliest-human-footprints-outside-africa-found-in-norfolk.htm|title=Earliest human footprints outside Africa found – in Norfolk|date=7 February 2014|publisher=Current Archaeology|accessdate=8 February 2014}}</ref>


==描述==
==History==
[[File:Charles Hatchett.jpg|thumb|left|Charles Hatchett was the discoverer of ''columbium''.|alt=Oval black and white painting of a man with a prominent shirt collar and necktie]]
[[File:Photographs of Area A at Happisburgh (2).png|thumb|250px|黑斯堡足跡遺址A區照片:上圖為朝北看足跡表面;下圖為朝南看足跡表面,其下方有橫向淤泥夾層]]
[[File:Sommer, Giorgio (1834-1914) - n. 2990 - Niobe madre - Firenze.jpg|left|thumb|110px|Picture of a Hellenistic sculpture representing ''Niobe'' by [[Giorgio Sommer]]|alt=Black and white image of a marmor sculpture of a bowing woman with a child nestling in her lap]]
在近40平方米的面積內,一共約有50個腳印。其中12個大體完整,2個甚至能看出腳趾。<ref name="independent-2014-02-08">{{Cite news | last=Keys | first=David | title=Meet the million-year-olds: Human footprints found in Britain are the oldest ever seen outside of Africa | url=http://www.independent.co.uk/news/science/archaeology/news/the-millionyearold-family-human-footprints-found-in-britain-are-oldest-ever-seen-outside-of-africa-9114151.html |newspaper=The Independent | date=8 February 2014}}</ref>這些腳印至少來自5個個體,包括成人和小孩。腳印長度為140至260毫米,即對應於0.9至1.7米高度。科學家認為這些足印屬於的物種是[[前人]](學名''Homo antecessor'')。<ref name="bm"/>


Niobium was [[Discovery of the chemical elements|discovered]] by the English chemist [[Charles Hatchett]] in 1801.<ref>See:
分析指出,辨認出的5個個體當時一同向南(向上游)沿著[[泰晤士河]]河口泥灘行走。當時的泰晤士河在此流入海洋,而如今則繼續流向北,且當時的[[大不列顛島]]東南部仍與歐洲大陸相連。<ref name="bm"/><ref>{{Cite news | last=Connor | first=Steve | title=Norfolk footprints: Just who were Homo antecessor and how did they arrive in Britain? | url=http://www.independent.co.uk/news/science/archaeology/news/norfolk-footprints-just-who-were-homo-antecessor-and-how-did-they-arrive-in-britain-9115354.html | newspaper=The Independent | date=7 February 2014 }}</ref>考古學家猜測,這一組前人正在泥灘上尋找食物,如[[貝類]]、[[螃蟹]]和[[海藻]]等。另一說法是,他們居住在河口的一個小島上,趁低潮的時候向河岸行走。<ref name="independent-2014-02-08"/>
* Charles Hatchett (1802) [http://books.google.com/books?id=c-Q_AAAAYAAJ&pg=PA49#v=onepage&q&f=false "An analysis of a mineral substance from North America, containing a metal hitherto unknown"], ''Philosophical Transactions of the Royal Society of London'', '''92''' : 49–66.
* {{cite journal|title = Eigenschaften und chemisches Verhalten des von Charles Hatchett entdeckten neuen Metalls, Columbium|trans_title = Properties and chemical behavior of the new metal, columbium, (that was) discovered by Charles Hatchett|first = Charles|last = Hatchett|authorlink = Charles Hatchett|language=German|journal = [[Annalen der Physik]]|volume = 11|issue = 5|pages =120–122|url = http://books.google.com/books?id=wSYwAAAAYAAJ&pg=PA120#v=onepage&q&f=false |doi = 10.1002/andp.18020110507|year = 1802|bibcode = 1802AnP....11..120H }}</ref> He found a new element in a mineral sample that had been sent to England from [[Massachusetts]], [[United States]] in 1734 by John Winthrop F.R.S. (grandson of [[John Winthrop the Younger]]) and named the mineral ''columbite'' and the new element ''columbium'' after ''[[Columbia (name)|Columbia]]'', the poetical name for the [[United States]].<ref name="Noyes" /><ref name="1853 Mining Journal">{{cite journal|last=Percival|first=James|title=Middletown Silver and Lead Mines|journal=Journal of Silver and Lead Mining Operations|date=July–December 1853|year=1853|month=January|volume=1|page=186|url=https://play.google.com/store/books/details?id=MFILAAAAYAAJ&rdid=book-MFILAAAAYAAJ&rdot=1|accessdate=2013-04-24}}</ref><ref>{{cite journal|title = Charles Hatchett FRS (1765–1847), Chemist and Discoverer of Niobium|first = William P.|last = Griffith|coauthors = Morris, Peter J. T.|journal = Notes and Records of the Royal Society of London|volume = 57|issue = 3|page = 299|year = 2003|jstor = 3557720|doi = 10.1098/rsnr.2003.0216}}</ref> The ''columbium'' discovered by Hatchett was probably a mixture of the new element with tantalum.<ref name="Noyes">{{cite book| last =Noyes| first = William Albert |title = A Textbook of Chemistry| publisher = H. Holt & Co| page = 523| url = http://books.google.com/?id=UupHAAAAIAAJ&pg=PA523&dq=columbium+discovered+by+Hatchett+was+a+mixture+of+two+elements| year =1918}}</ref>


Subsequently, there was considerable confusion<ref name="Wolla">{{cite journal|title = On the Identity of Columbium and Tantalum|pages = 246–252|journal = Philosophical Transactions of the Royal Society|first = William Hyde|last = Wollaston|authorlink = William Hyde Wollaston|doi = 10.1098/rstl.1809.0017| jstor = 107264|volume = 99|year = 1809}}</ref> over the difference between columbium (niobium) and the closely related tantalum. In 1809, the English chemist [[William Hyde Wollaston]] compared the oxides derived from both columbium—columbite, with a density 5.918&nbsp;g/cm<sup>3</sup>, and tantalum—[[tantalite]], with a density over 8&nbsp;g/cm<sup>3</sup>, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.<ref name="Wolla" /> This conclusion was disputed in 1846 by the German chemist [[Heinrich Rose]], who argued that there were two different elements in the tantalite sample, and named them after children of [[Tantalus]]: ''niobium'' (from [[Niobe]]), and ''[[pelopium]]'' (from [[Pelops]]).<ref name="Pelop">{{cite journal|title = Ueber die Zusammensetzung der Tantalite und ein im Tantalite von Baiern enthaltenes neues Metall|pages = 317–341|journal = Annalen der Physik|authorlink = Heinrich Rose|language=German|first = Heinrich|last = Rose|doi = 10.1002/andp.18441391006|url = http://gallica.bnf.fr/ark:/12148/bpt6k15148n/f327.table|volume = 139|issue = 10|year = 1844|bibcode = 1844AnP...139..317R }}</ref><ref>{{cite journal|title = Ueber die Säure im Columbit von Nordamérika|language=German|pages = 572–577|first = Heinrich|last = Rose|journal = Annalen der Physik|doi = 10.1002/andp.18471460410|url = http://gallica.bnf.fr/ark:/12148/bpt6k15155x/f586.table |year=1847| volume = 146|issue = 4|authorlink = Heinrich Rose|bibcode = 1847AnP...146..572R }}</ref> This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements ''pelopium'', ''[[ilmenium]]'' and ''dianium''<ref name="Dianium">{{cite journal|title = Ueber eine eigenthümliche Säure, Diansäure, in der Gruppe der Tantal- und Niob- verbindungen|first = V.|last = Kobell|journal =Journal für Praktische Chemie|volume = 79|issue = 1|pages = 291–303 |doi=10.1002/prac.18600790145|year = 1860}}</ref> were in fact identical to niobium or mixtures of niobium and tantalum.<ref name="Ilmen" />
==年代==
黑斯堡足跡由於年齡遠超過5萬年,所以超出了[[放射性碳定年法]]的有效年代區間。科學家需要利用[[地層學]]、[[古地磁學]]方法,以及沉積層存在的其他化石證據,來測定足跡的年代。綜合證據指出,沉積物是在距今78萬至100萬年之間的[[地磁逆轉]]晚期形成的。<ref>{{Cite web | title=Dating the site | url=http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh/dating_the_site.aspx | publisher=British Museum | accessdate=8 February 2014 }}</ref>


The differences between tantalum and niobium were unequivocally demonstrated in 1864 by [[Christian Wilhelm Blomstrand]],<ref name="Ilmen" /> and [[Henri Etienne Sainte-Claire Deville]], as well as [[Louis J. Troost]], who determined the formulas of some of the compounds in 1865<ref name="Ilmen">{{cite journal|title = Tantalsäure, Niobsäure, (Ilmensäure) und Titansäure|journal = Fresenius' Journal of Analytical Chemistry|volume = 5|issue = 1|year = 1866|doi = 10.1007/BF01302537|pages = 384–389|author= Marignac, Blomstrand, H. Deville, L. Troost und R. Hermann}}</ref><ref name="Gupta" /> and finally by the Swiss chemist [[Jean Charles Galissard de Marignac]]<ref>{{cite journal|journal = [[Annales de chimie et de physique]]|title = Recherches sur les combinaisons du niobium|pages = 7–75|authorlink = Jean Charles Galissard de Marignac|language=French| first = M. C.|last= Marignac|url = http://gallica.bnf.fr/ark:/12148/bpt6k34818t/f4.table|year= 1866|volume = 4|issue = 8}}</ref> in 1866, who all proved that there were only two elements. Articles on ''ilmenium'' continued to appear until 1871.<ref>{{cite journal|title = Fortgesetzte Untersuchungen über die Verbindungen von Ilmenium und Niobium, sowie über die Zusammensetzung der Niobmineralien (Further research about the compounds of ilmenium and niobium, as well as the composition of niobium minerals)|first = R.|last = Hermann|journal = Journal für Praktische Chemie|language=German|volume = 3|issue = 1|pages =373–427|doi = 10.1002/prac.18710030137|year = 1871}}</ref>
腳印所處的沉積物確切年代還沒有判斷出來。沉積層中的磁性特徵顯示,沉積物形成時正處於最近的兩次地磁逆轉事件之間——約78萬年前的[[布容尼斯-松山反轉|布容-松山逆轉]]和95萬至100萬年前的[[哈拉米略逆轉]]。鄰近動植物化石包括[[田鼠]]牙齒化石等,這些證據把年代定在至少84萬年前。目前的證據支持兩個可能的沉積物形成年代,即距今85萬或95萬年。然而要進行進一步研究才可判斷是兩者中的哪一個。<ref name="CA288" /><ref name="independent-2014-02-08"/>


De Marignac was the first to prepare the metal in 1864, when he [[redox|reduced]] niobium chloride by heating it in an atmosphere of [[hydrogen]].<ref name="nauti">{{cite web|url = http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e04100.html|title = Niobium|publisher = Universidade de Coimbra|accessdate = 2008-09-05}}</ref> Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was first used commercially, in [[incandescent lamp]] filaments.<ref name="Gupta" /> This use quickly became obsolete through the replacement of niobium with [[tungsten]], which has a higher melting point and thus is preferable for use in incandescent lamps. The discovery that niobium improves the [[Microalloyed steel|strength of steel]] was made in the 1920s, and this application remains its predominant use.<ref name="Gupta" /> In 1961 the American physicist [[Eugene Kunzler]] and coworkers at [[Bell Labs]] discovered that [[niobium-tin]] continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields,<ref>Geballe ''et al.'' (1993) gives a critical point at currents of 150&nbsp;[[ampere|kiloamperes]] and magnetic fields of 8.8&nbsp;[[tesla (unit)|tesla]].</ref> making it the first material to support the high currents and fields necessary for useful high-power magnets and electrically powered [[machinery]]. This discovery would allow — two decades later — the production of long multi-strand cables that could be wound into coils to create large, powerful [[electromagnet]]s for rotating machinery, particle accelerators, or particle detectors.<ref name="geballe">{{cite journal|last = Geballe|first = Theodore H.| title = Superconductivity: From Physics to Technology|journal = Physics Today|volume = 46|issue = 10|date=October 1993|pages=52–56|url =|doi=10.1063/1.881384}}</ref><ref>{{cite journal|volume = 95|pages = 1435–1435|year = 1954|title = Superconductivity of Nb<sub>3</sub>Sn|first = B. T.|last = Matthias|coauthors = Geballe, T. H.; Geller, S.; Corenzwit, E.|doi = 10.1103/PhysRev.95.1435|journal = Physical Review|bibcode = 1954PhRv...95.1435M|issue = 6 }}</ref>
==更新世時的地理環境==
人族在黑斯堡居住之時,大不列顛島和今法國一帶之間存在一條陸橋。今天的[[英吉利海峽]]要直到45萬年前才形成。[[泰晤士河]]流域比今天更趨向北,並與古拜坦河(Bytham River)匯合。<ref>{{Cite web | title = What do microfossils tell us about the first humans in Britain? Section 3. Happisburgh about 840,000-950,000 years ago | url = http://www.nhm.ac.uk/natureplus/blogs/micropalaeo/tags/foraminifera| date = November 14, 2012 |publisher = [[自然史博物館 (倫敦)|Natural History Museum, London]] | accessdate = February 10, 2014}}</ref>現在的[[諾福克郡]]和[[薩福克郡]]一帶的地形在當時由一系列泥脊和泥槽組成,稱為「東安格利亞峭岩盆地」(East Anglian Crag Basin)。<ref>{{Citation | title = Quaternary Glaciations - Extent and Chronology: A closer look | last1 = Ehlers | first1 = J. | last2 = Gibbard | first2 = P.L. | last3 = Hughes | first3 = P.D. | series = Developments in Quaternary Science | url = http://books.google.co.uk/books?id=pUjRgq7zyVcC&pg=PA61#v=onepage&q&f=false | year = 2011 | publisher = UK: Elsevier Science| isbn = 9780444535375}}</ref>黑斯堡當時離海岸大約{{convert|15|mi}},是拜坦河和泰晤士河匯合處的一片泥灘。兩河匯合後流入海灣。<ref name="CA288" />


===Naming of the element===
足跡形成時的泥灘附近是一片空曠的山谷,被松樹林環繞,氣候接近今天的[[斯堪的納維亞]]南部。居住在這片空曠草地上的動物包括:[[猛犸象]]、[[犀牛]]、[[河馬]]、[[鉅鹿]]和[[野牛]],獵食者有[[劍齒虎]]、[[獅子]]、[[狼]]和[[鬣狗]]等。此地動植物充裕,河中沙礫富含[[燧石]],對當時的早期人類來說是重要的資源。<ref name="CA288" />
''Columbium'' (symbol ''Cb''<ref>{{cite journal|title = Reaction of Tantalum, Columbium and Vanadium with Iodine|first = F.|last = Kòrösy|journal = Journal of the American Chemical Society|year = 1939|volume = 61|issue = 4|pages = 838–843|doi = 10.1021/ja01873a018}}</ref>) was the name originally given to this element by Hatchett, and this name remained in use in American journals—the last paper published by [[American Chemical Society]] with columbium in its title dates from 1953<ref>{{cite journal|title = Photometric Determination of Columbium, Tungsten, and Tantalum in Stainless Steels| first = Luther|last = Ikenberry|coauthors = Martin, J. L.; Boyer, W. J.|journal = Analytical Chemistry |year = 1953|volume = 25|issue =9|pages = 1340–1344|doi = 10.1021/ac60081a011}}</ref>—while ''niobium'' was used in Europe. To end this confusion, the name ''niobium'' was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949.<ref name="Contro">{{cite journal |first = Geoff|last = Rayner-Canham|coauthors = Zheng, Zheng|title = Naming elements after scientists: an account of a controversy|journal = Foundations of Chemistry|volume = 10|issue = 1|year = 2008|doi = 10.1007/s10698-007-9042-1|pages = 13–18}}</ref> A year later this name was officially adopted by the [[International Union of Pure and Applied Chemistry]] (IUPAC) after 100 years of controversy, despite the chronological precedence of the name Columbium.<ref name="Contro" /> The latter name is still sometimes used in US industry.<ref>{{cite journal|journal = Science|year = 1914|title = Columbium Versus Niobium|pages = 139–140|first = F. W.|last = Clarke|jstor = 1640945|volume = 39|issue = 995|doi = 10.1126/science.39.995.139|pmid = 17780662|bibcode = 1914Sci....39..139C }}</ref> This was a compromise of sorts;<ref name="Contro" /> the IUPAC accepted [[tungsten]] instead of wolfram, in deference to North American usage; and niobium instead of columbium, in deference to European usage. Not everyone agreed, and while many leading chemical societies and government organizations refer to it by the official IUPAC name, many leading metallurgists, metal societies, and the United States Geological Survey still refer to the metal by the original "''columbium''".<ref name="patel" /><ref name="Gree">{{cite journal|journal = Catalysis Today|year = 2003|title = Vanadium to dubnium: from confusion through clarity to complexity|pages = 5–11|last = Norman N.|first = Greenwood|doi = 10.1016/S0920-5861(02)00318-8 |volume = 78|issue = 1–4}}</ref>


==Characteristics==
黑斯堡足跡的發現首次證明早期人類曾在高緯度地區生活。古生物學家曾認為當時的人族需更暖的氣候,但在黑斯堡居住的早期人類已適應了寒冷天氣,證明他們已掌握狩獵、製衣、蔽匿和取暖等各種技巧,比人們所想的更早。<ref name="CA288" />


===Physical===
==其他古生物學發現==
Niobium is a [[Lustre (mineralogy)|lustrous]], grey, [[ductility|ductile]], [[paramagnetism|paramagnetic]] [[metal]] in [[Group 5 element|group 5]] of the [[periodic table]] (see table), although it has an atypical configuration in its outermost [[electron shell]]s compared to the rest of the members. (This can be observed in the neighborhood of [[ruthenium]] (44), [[rhodium]] (45), and [[palladium]] (46).)
[[File:Happisburgh handaxe.jpg|thumb|left|upright|在黑斯堡出土的[[舊石器時代]]手斧,2000年被人在沙灘上遛狗時發現]]
黑斯堡長期以來出土了許多重要的考古發現。由於海岸持續受到[[海岸侵蝕]],所以岩壁和沙灘上不斷有新暴露出來的物質。人們自1820年開始便在這一帶發現史前化石:當時的漁民在拖網捕捉牡蠣時,時常在網中發現大象、犀牛、鉅鹿等已滅絕物種的牙齒、骨頭和角。1825年2月的一次特高潮水沖走了表面沉積物,使這一地帶暴露出許多化石樹樁、動物骸骨和[[冷杉]]果子。1877年1月的一場大風暴把大塊鐵礦石從海床捲到黑斯堡海灘上。這些石板保存了數千年千[[橡木]]、[[榆木]]、[[櫸木]]和[[柳樹]]葉子所留下的印子。1999年,科學家在對1870年代出土的更新世野牛骸骨重新檢查時,發現骨頭表面留有切割的痕跡,這表明這頭野牛是被某種石造工具屠宰的。<ref name="CA288"/>


{| class="wikitable" style="margin:10px; float:right;"
2000年,有人在海灘散步時意外發現了具有60萬至80萬年歷史的黑色燧石手斧。在2012年播出的電視紀錄片《英國的神秘寶藏》(''Britain's Secret Treasures'')當中,來自大英博物館和英國考古學會(Council for British Archaeology)的一行專家在50件由公眾發現的考古物件中,把手斧評為最重要的一件。<ref>{{Cite web | title=Britain's Secret Treasures Episode Six | url=http://finds.org.uk/secrettreasures/episodesix | publisher=Portable Antiquities Scheme | accessdate=8 February 2014 }}</ref><ref>{{Cite web | title=NMS-ECAA52 | date=12 July 2012 | url=http://finds.org.uk/database/artefacts/record/id/512140 | publisher=[[Portable Antiquities Scheme]] | accessdate=10 February 2014 }}</ref>自從發現以來,黑斯堡的舊石器時代歷史成為了英國多項研究項目的對象。在2005至2010年間,海灘沉積物中共出土了80件燧石工具,年代可追溯至95萬年前,是北歐地區已知最早的人造物品。這些工具相信由前人所製,即腳印所屬的同一物種。<ref name="CA288" /><ref>{{Cite web | title=Excavation at Happisburgh | url=http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh/excavation_at_happisburgh.aspx | publisher=British Museum | accessdate=8 February 2014 }}</ref><ref>{{Cite web | title=Studying the finds | url=http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh/studying_the_finds.aspx | publisher=British Museum | accessdate=8 February 2014 }}</ref><ref>{{Cite web | title=Early humans in Europe and Asia | url=http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh/early_humans_in_europe__asia.aspx | publisher=British Museum | accessdate=8 February 2014 }}</ref>
|-
![[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]]
|-
| 23 || [[vanadium]] || 2, 8, 11, 2
|-
| 41 || niobium || 2, 8, 18, 12, 1
|-
| 73 || [[tantalum]] || 2, 8, 18, 32, 11, 2
|-
| 105 || [[dubnium]] || 2, 8, 18, 32, 32, 11, 2 (predicted)
|}
Niobium becomes a [[superconductor]] at [[cryogenics|cryogenic]] temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.2&nbsp;[[Kelvin|K]].<ref name="Pein">{{cite journal|title = A Superconducting Nb<sub>3</sub>Sn Coated Multicell Accelerating Cavity|first = M.|last = Peiniger|coauthors = Piel, H.|journal = Nuclear Science|year= 1985|volume= 32|issue = 5|doi = 10.1109/TNS.1985.4334443|page = 3610|bibcode = 1985ITNS...32.3610P }}</ref> Niobium has the largest [[superconductor#Meissner effect|magnetic penetration depth]] of any element.<ref name="Pein" /> In addition, it is one of the three elemental [[Type II superconductor]]s, along with [[vanadium]] and [[technetium]]. The superconductive properties are strongly dependent on the purity of the niobium metal.<ref name="Moura">{{cite journal|title=Melting And Purification Of Niobium|first=Hernane R.|last = Salles Moura|coauthor=Louremjo de Moura, Louremjo |journal=AIP Conference Proceedings|year=2007|issue=927(Single Crystal – Large Grain Niobium Technology)|pages=165–178|publisher=American Institute of Physics|issn=0094-243X|url=http://link.aip.org/link/?APCPCS/927/165/1}}</ref> When very pure, it is comparatively soft and ductile, but impurities make it harder.<!--awkward; this either contains redundancy or is leaving something out--><ref name="Nowak" />


The metal has a low [[Neutron capture#Capture cross section|capture cross-section]] for thermal [[neutron]]s;<ref>{{cite journal|title = Columbium Alloys Today| last = Jahnke| first = L.P.|coauthors = Frank, R.G.; Redden, T.K.|year = 1960|journal = Metal Progr.|volume = 77|issue = 6|pages = 69–74|osti = 4183692}}</ref> thus it is used in the nuclear industries.<ref>{{cite journal|first = A. V.|last = Nikulina|title = Zirconium-Niobium Alloys for Core Elements of Pressurized Water Reactors|journal = Metal Science and Heat Treatment|volume = 45|issue = 7–8|year = 2003|doi = 10.1023/A:1027388503837|pages = 287–292}}</ref>
考古學家希望透過分析當地的動植物化石,來了解黑斯堡足跡形成時的環境。目前已記錄了15個哺乳類物種、160個昆蟲物種以及至少100個植物物種。<ref name="independent-2014-02-08"/>


==Exhibition==
===Chemical===
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods.<ref name="Rubber">{{cite book|title = CRC Handbook of Chemistry and Physics|first = David R.|last = Lide|publisher = CRC Press|year = 2004 |isbn = 978-0-8493-0485-9| pages = '''4'''–21|edition = 85|chapter = The Elements}}</ref> Despite presenting a high melting point in elemental form (2,468&nbsp;°C), it has a low density in comparison to other refractory metals. Furthermore, it is corrosion resistant, exhibits superconductivity properties, and forms [[dielectric]] [[oxide]] layers.
The Happisburgh footprints will feature in an exhibition, "Britain: One Million Years of the Human Story", at the [[Natural History Museum, London|Natural History Museum]] in London from 13 February 2014.<ref>{{Cite web | title=Britain: One Million Years of the Human Story | url=http://www.nhm.ac.uk/visit-us/whats-on/temporary-exhibitions/britain-million-years/index.html | accessdate=10 February 2014 }}</ref>

Niobium is slightly less [[electropositive]] and more compact than its predecessor in the periodic table, [[zirconium]], whereas it is virtually identical in size to the heavier tantalum atoms, owing to the [[lanthanide contraction]].<ref name="Nowak" /> As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the [[periodic table]].<ref name="Gupta">{{cite book|title = Extractive Metallurgy of Niobium|first = C. K.|last = Gupta|coauthors = Suri, A. K.|publisher = CRC Press|year = 1994 |isbn = 0-8493-6071-4|pages = 1–16}}</ref> Although its corrosion resistance is not as outstanding as that of tantalum, its lower price and greater availability make niobium attractive for less demanding uses such as linings in chemical plants.<ref name="Nowak" />

===Isotopes===
{{main|Isotopes of niobium}}
Naturally occurring niobium is composed of one stable [[isotope]], <sup>93</sup>Nb.<ref name="NUBASE">{{cite journal| first = Audi| last = Georges|title = The NUBASE 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| bibcode=2003NuPhA.729....3A| last2 = Bersillon| first2 = O.| last3 = Blachot| first3 = J.| last4 = Wapstra| first4 = A.H.}}</ref> As of 2003, at least 32 [[radioisotope]]s have also been synthesized, ranging in [[atomic mass]] from 81 to 113. The most stable of these is <sup>92</sup>Nb with a [[half-life]] of 34.7&nbsp;million years. One of the least stable is <sup>113</sup>Nb, with an estimated half-life of 30&nbsp;milliseconds. Isotopes that are lighter than the stable <sup>93</sup>Nb tend to decay by [[beta decay|β<sup>+</sup> decay]], and those that are heavier tend to decay by [[beta decay|β<sup>-</sup> decay]], with some exceptions. <sup>81</sup>Nb, <sup>82</sup>Nb, and <sup>84</sup>Nb have minor β<sup>+</sup> delayed [[proton emission]] decay paths, <sup>91</sup>Nb decays by [[electron capture]] and [[positron emission]], and <sup>92</sup>Nb decays by both [[positron|β<sup>+</sup>]] and [[electron|β<sup>-</sup>]] decay.<ref name="NUBASE" />

At least 25 [[nuclear isomer]]s have been described, ranging in atomic mass from 84 to 104. Within this range, only <sup>96</sup>Nb, <sup>101</sup>Nb, and <sup>103</sup>Nb do not have isomers. The most stable of niobium's isomers is <sup>93m</sup>Nb with a half-life of 16.13&nbsp;years. The least stable isomer is <sup>84m</sup>Nb with a half-life of 103&nbsp;ns. All of niobium's isomers decay by [[isomeric transition]] or [[beta decay]] except <sup>92m1</sup>Nb, which has a minor [[electron capture]] [[decay chain]].<ref name="NUBASE" />

===Occurrence===
{{see also|Category:Niobium minerals}}
Niobium is estimated to be the 33rd [[Abundance of elements in Earth's crust|most common element in the Earth’s crust]], with 20&nbsp;[[Parts per million|ppm]].<ref>{{cite book|title = Nature's Building Blocks: An A-Z Guide to the Elements|last = Emsley|first=John|publisher = Oxford University Press|year = 2001|location = Oxford, England, UK|isbn = 0-19-850340-7|chapter = Niobium|pages = 283–286}}</ref> Some think that the abundance on Earth is much greater, but that the "missing" niobium may be located in the Earth’s core due to the metal's high density.<ref name="patel" /> The free element is not found in nature, but niobium occurs in combination with other elements in minerals.<ref name="Nowak">{{cite journal|title=Niobium Compounds: Preparation, Characterization, and Application in Heterogeneous Catalysis|author=Nowak, Izabela; Ziolek, Maria|journal=Chemical Reviews|year=1999|volume=99|issue=12|pages=3603–3624|doi=10.1021/cr9800208|pmid=11849031}}</ref>
Minerals that contain niobium often also contain tantalum. Examples include [[Ferrocolumbite|columbite]] ((Fe,Mn)(Nb,Ta)<sub>2</sub>O<sub>6</sub>) and [[coltan|columbite–tantalite]] (or ''coltan'', (Fe,Mn)(Ta,Nb)<sub>2</sub>O<sub>6</sub>).<ref name="ICE"/> Columbite–tantalite minerals are most usually found as accessory minerals in [[pegmatite]] intrusions, and in alkaline intrusive rocks. Less common are the niobates of [[calcium]], [[uranium]], [[thorium]] and the [[rare earth element]]s. Examples of such niobates are [[pyrochlore]] ((Na,Ca)<sub>2</sub>Nb<sub>2</sub>O<sub>6</sub>(OH,F)) and [[euxenite]] ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)<sub>2</sub>O<sub>6</sub>). These large deposits of niobium have been found associated with [[carbonatite]]s ([[carbonate minerals|carbonate]]-[[silicate]] [[igneous rocks]]) and as a constituent of pyrochlore.<ref name="Pyrochlore">{{cite journal|title = Geochemical alteration of pyrochlore group minerals: Pyrochlore subgroup|year = 1995|first = Gregory R.|last = Lumpkin|coauthor = Ewing, Rodney C.|journal = American Mineralogist|url = http://www.minsocam.org/msa/AmMin/TOC/Articles_Free/1995/Lumpkin_p732-743_95.pdf|volume = 80|pages = 732–743}}</ref> <!--http://minmag.geoscienceworld.org/cgi/content/abstract/64/4/683 -->

The two largest deposits of pyrochlore were found in the 1950s in Brazil and Canada, and both countries are still the major producers of niobium mineral concentrates.<ref name="Gupta" /> The largest deposit is hosted within a carbonatite intrusion at [[Araxá]], [[Minas Gerais]] Brazil, owned by CBMM ({{lang|pt|Companhia Brasileira de Metalurgia e Mineração}}); the other deposit is located in [[Goiás]] and owned by [[Anglo American plc]] (through its subsidiary Mineração Catalão), also hosted within a carbonatite intrusion.<ref name="tesla" /> Altogether these two Brazilian mines produce around 75% of world supply. The third largest producer of niobium is the carbonatite-hosted Niobec Mine, [[Saint-Honoré, Quebec|Saint-Honoré]] near [[Chicoutimi]], [[Quebec]] owned by [[Iamgold|Iamgold Corporation Ltd]], which produces around 7% of world supply.<ref name="tesla">{{cite web|url = http://tesla.desy.de/new_pages/TESLA_Reports/2001/pdf_files/tesla2001-27.pdf|title = Niob für TESLA|accessdate = 2008-09-02|first= J|last = Kouptsidis|coauthors =Peters, F.; Proch, D.; Singer, W.|publisher = Deutsches Elektronen-Synchrotron DESY|language = German}}</ref> [[Kenya]]'s deposits found in [[Kwale]] are ranked amongst the top six in the world.<ref>http://www.businessdailyafrica.com/Cortec-Mining-to-build-Sh12-8bn-factory-/-/539552/1882130/-/158j4v2z/-/index.html</ref>

==Production==
[[File:World Niobium Production 2006.svg|300px|thumb|Niobium producers in 2006|alt=Grey and white world map with Brazil colored red representing 90% of niobium world production and Canada colored in dark blue representing 5% of niobium world production]]

After the separation from the other minerals, the mixed oxides of tantalum [[tantalum pentoxide|Ta<sub>2</sub>O<sub>5</sub>]] and niobium [[Niobium pentoxide|Nb<sub>2</sub>O<sub>5</sub>]] are obtained. The first step in the processing is the reaction of the oxides with [[hydrofluoric acid]]:<ref name="ICE" />

:Ta<sub>2</sub>O<sub>5</sub> + 14 HF → 2 H<sub>2</sub><nowiki>[</nowiki>TaF<sub>7</sub><nowiki>]</nowiki> + 5 H<sub>2</sub>O
:Nb<sub>2</sub>O<sub>5</sub> + 10 HF → 2 H<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki> + 3 H<sub>2</sub>O

The first industrial scale separation, developed by [[Jean Charles Galissard de Marignac|de Marignac]], exploits the differing solubilities of the complex niobium and tantalum [[fluoride]]s, dipotassium oxypentafluoroniobate monohydrate (K<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki>·H<sub>2</sub>O) and dipotassium heptafluorotantalate (K<sub>2</sub><nowiki>[</nowiki>TaF<sub>7</sub><nowiki>]</nowiki>) in water. Newer processes use the liquid extraction of the fluorides from [[aqueous]] solution by [[organic solvents]] like [[cyclohexanone]].<ref name="ICE" /> The complex niobium and tantalum fluorides are extracted separately from the [[organic solvent]] with water and either precipitated by the addition of [[potassium fluoride]] to produce a potassium fluoride complex, or precipitated with [[ammonia]] as the pentoxide:<ref name="HollemanAF" />

:H<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki> + 2 KF → K<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki>↓ + 2 HF

Followed by:
:2 H<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki> + 10 NH<sub>4</sub>OH → Nb<sub>2</sub>O<sub>5</sub>↓ + 10 NH<sub>4</sub>F + 7 H<sub>2</sub>O

Several methods are used for the [[Reduction (chemistry)|reduction]] to metallic niobium. The [[electrolysis]] of a molten mixture of K<sub>2</sub><nowiki>[</nowiki>NbOF<sub>5</sub><nowiki>]</nowiki> and [[sodium chloride]] is one; the other is the reduction of the fluoride with [[sodium]]. With this method niobium with a relatively high purity can be obtained. In large scale production the reduction of Nb<sub>2</sub>O<sub>5</sub> with hydrogen or carbon<ref name="HollemanAF" /> is used. In the process involving the [[aluminothermic reaction]] a mixture of [[iron oxide]] and niobium oxide is reacted with [[aluminium]]:
:3 Nb<sub>2</sub>O<sub>5</sub> + Fe<sub>2</sub>O<sub>3</sub> + 12 Al → 6 Nb + 2 Fe + 6 Al<sub>2</sub>O<sub>3</sub>

To enhance the reaction, small amounts of oxidizers like [[sodium nitrate]] are added. The result is [[aluminium oxide]] and [[ferroniobium]], an alloy of iron and niobium used in the steel production.<ref>{{cite journal|title = Progress in Niobium Markets and Technology 1981–2001|author = Tither, Geoffrey|url = http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/images/pdfs/oppening.pdf|journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA)|year = 2001|isbn = 978-0-9712068-0-9 |publisher = Niobium 2001 Ltd, 2002|editor=Minerals, Metals and Materials Society, Metals and Materials Society Minerals|format = PDF}}</ref><ref>{{cite journal|title = The Production of Ferroniobium at the Niobec mine 1981–2001|first = Claude|last = Dufresne|coauthor = Goyette, Ghislain| url = http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_1/images/pdfs/start.pdf|accessdate =|journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA)|year = 2001|isbn = 978-0-9712068-0-9 |publisher = Niobium 2001 Ltd, 2002|editor=Minerals, Metals and Materials Society, Metals and Materials Society Minerals|format = PDF}}</ref> The ferroniobium contains between 60 and 70% of niobium.<ref name="tesla" /> Without addition of iron oxide, aluminothermic process is used for the production of niobium. Further purification is necessary to reach the grade for [[superconductive]] alloys. [[Electron beam melting]] under vacuum is the method used by the two major distributors of niobium.<ref name="Aguly" /><ref name="Chou">{{cite journal|journal = The Iron and Steel Institute of Japan International|volume = 32|year = 1992|issue = 5|doi = 10.2355/isijinternational.32.673|accessdate =|title = Electron Beam Melting and Refining of Metals and Alloys|first = Alok|last = Choudhury|coauthors = Hengsberger, Eckart|pages = 673–681}}</ref>

{{as of|2013}}, the Brazilian company Cia. Brasileira de {{not a typo|Metalurgia}} & Mineracao "controls 85 percent of the world's niobium production."<ref name=lucchesi2013>{{Citation
|last1=Lucchesi |first1=Cristane |last2=Cuadros|first2=Alex |date=April 2013 |title=Mineral Wealth |type=paper |magazine=[[Bloomberg Markets]] |page=14}}</ref> The [[United States Geological Survey]] estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.<ref name=USGSCS2006>{{cite web
|url=http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs06.pdf |title=Niobium (Columbium) |first=John F |last=Papp |publisher=USGS 2006 Commodity Summary |accessdate=2008-11-20 }}</ref><ref name=USGSCS2007>{{cite web
|url=http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs07.pdf |title=Niobium (Columbium) |first=John F |last=Papp |publisher=USGS 2007 Commodity Summary |accessdate=2008-11-20 }}</ref> The worldwide resources are estimated to be 4,400,000 tonnes.<ref name="USGSCS2007" /> During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.<ref name="USGSCS1997">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/niobium/230397.pdf|title = Niobium (Columbium)|first = John F |last=Papp|publisher = USGS 1997 Commodity Summary|accessdate = 2008-11-20}}</ref> Since 2009 production is stable at around 63,000 tonnes per year.<ref>[http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2011-niobi.pdf Niobium (Colombium)] U.S. Geological Survey, Mineral Commodity Summaries, January 2011</ref>

{| class="wikitable" style="text-align:right;"
|+ Mine production (t)<ref name="USGSNiobi">{{cite web|author=Larry D. Cunningham |url=http://minerals.usgs.gov/minerals/pubs/commodity/niobium/ |title=USGS Minerals Information: Niobium (Columbium) and Tantalum |publisher=Minerals.usgs.gov |date=2012-04-05 |accessdate=2012-08-17}}</ref> (USGS estimate)
|-
! scope="col" | Country
! scope="col" | 2000
! scope="col" | 2001
! scope="col" | 2002
! scope="col" | 2003
! scope="col" | 2004
! scope="col" | 2005
! scope="col" | 2006
! scope="col" | 2007
! scope="col" | 2008
! scope="col" | 2009
! scope="col" | 2010
! scope="col" | 2011
|-
| style="text-align:left;"| {{flag|Australia}} || 160 || 230 || 290 || 230 || 200 || 200 || 200 || ? || ? || ? || ? || ?
|-
| style="text-align:left;"| {{flag|Brazil}} || 30,000 || 22,000 || 26,000 || 29,000 || 29,900 || 35,000 || 40,000 || 57,300 || 58,000 || 58,000 || 58,000 || 58,000
|-
| style="text-align:left;"| {{flag|Canada}} || 2,290 || 3,200 || 3,410 || 3,280 || 3,400 || 3,310 || 4,167 || 3,020 || 4,380 || 4,330 || 4,420 || 4,400
|-
| style="text-align:left;"| {{flag|Democratic Republic of the Congo|name=Congo D.R.}} || ? || 50 || 50 || 13 || 52 || 25 || ? || ? || ? || ? || ? || ?
|-
| style="text-align:left;"| {{flag|Mozambique}} || ? || ? || 5 || 34 || 130 || 34 || 29 || ? || ? || ? || ? || ?
|-
| style="text-align:left;"| {{flag|Nigeria}} || 35 || 30 || 30 || 190 || 170 || 40 || 35 || ? || ? || ? || ? || ?
|-
| style="text-align:left;"| {{flag|Rwanda}} || 28 || 120 || 76 || 22 || 63 || 63 || 80 || ? || ? || ? || ? || ?
|-
| [[World]] || 32,600 || 25,600 || 29,900 || 32,800 || 34,000 || 38,700 || 44,500 || 60,400 || 62,900 || 62,900 || 62,900 || 63,000
|}

Lesser amounts are found in Malawi's [[Kanyika mine]].

==Compounds==
{{see also|Category:Niobium compounds}}
Niobium is in many ways similar to [[tantalum]] and [[zirconium]]. It reacts with most nonmetals at high temperatures: niobium reacts with [[fluorine]] at room temperature, with [[chlorine]] and [[hydrogen]] at 200&nbsp;°[[Celsius|C]], and with [[nitrogen]] at 400&nbsp;°C, giving products that are frequently interstitial and nonstoichiometric.<ref name="Nowak" /> The metal begins to [[oxidation|oxidize]] in air at 200&nbsp;°[[Celsius|C]],<ref name="HollemanAF">{{cite book|publisher = Walter de Gruyter|year = 1985|edition = 91–100|pages = 1075–1079|isbn = 3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first = Arnold F.|last = Holleman|coauthors = Wiberg, Egon; Wiberg, Nils;|chapter = Niob| language = German}}</ref> and is resistant to corrosion by fused [[alkali metal|alkalis]] and by acids, including [[aqua regia]], [[hydrochloric acid|hydrochloric]], [[sulfuric acid|sulfuric]], [[nitric acid|nitric]] and [[phosphoric acid]]s.<ref name="Nowak" /> Niobium is attacked by [[hydrofluoric acid]] and hydrofluoric/nitric acid mixtures.

Although niobium exhibits all of the formal oxidation states from +5 to −1, in most commonly encountered compounds, it is found in the +5 state.<ref name="Nowak" /> Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding.

===Oxides and sulfides===
Niobium forms [[oxide]]s with the [[oxidation state]]s +5 ([[Niobium pentoxide|Nb<sub>2</sub>O<sub>5</sub>]]), +4 ([[Niobium dioxide|NbO<sub>2</sub>]]), and +3 (Nb<sub>2</sub>O<sub>3</sub>),<ref name="HollemanAF" /> as well as with the rarer oxidation state +2 ([[niobium monoxide|NbO]]).<ref>{{Greenwood&Earnshaw}}</ref> Most commonly encountered is the pentoxide, precursor to almost all niobium compounds and alloys.<ref name="HollemanAF" /><ref name="Cardarelli">{{cite book|first = Francois|last = Cardarelli|year = 2008|title = Materials Handbook |publisher = Springer London|isbn = 978-1-84628-668-1}}</ref> Niobates are generated by dissolving the pentoxide in [[Base (chemistry)|basic]] [[hydroxide]] solutions or by melting it in alkali metal oxides. Examples are [[lithium niobate]] (LiNbO<sub>3</sub>) and lanthanum niobate (LaNbO<sub>4</sub>). In the lithium niobate is a trigonally distorted [[Perovskite (structure)|perovskite]]-like structure, whereas the lanthanum niobate contains lone {{chem|NbO|4|3-}} ions.<ref name="HollemanAF" /> The layered niobium sulfide (NbS<sub>2</sub>) is also known.<ref name="Nowak" />

Materials with a thin film coating of niobium(V) oxide can be produced by [[chemical vapor deposition]] or [[atomic layer deposition]] processes, in each case by the thermal decomposition of [[niobium(V) ethoxide]] above 350&nbsp;°C.<ref>{{cite thesis | title = Atomic Layer Deposition of High Permittivity Oxides: Film Growth and In Situ Studies | author = Rahtu, Antti | publisher = University of Helsinki | url = http://hdl.handle.net/10138/21065 | year = 2002 | isbn = 952-10-0646-3}}</ref><ref>{{cite journal | doi = 10.1149/1.2059247 | title = Electrochromic Properties of Niobium Oxide Thin Films Prepared by Chemical Vapor Deposition | year = 1994 | last1 = Maruyama | first1 = Toshiro | journal = Journal of the Electrochemical Society | volume = 141 | issue = 10 | pages = 2868}}</ref>

===Halides===
[[File:Niobium pentachloride.jpg|thumb|left|180px|A sample of niobium pentachloride (yellow portion) that has partially hydrolyzed (white material).|alt=Watch glass on a black surface with a small portion of yellow crystals]]
[[File:Niobium-pentachloride-from-xtal-3D-balls.png|thumb|left|180px|Ball-and-stick model of [[niobium pentachloride]], which exists as a [[Dimer (chemistry)|dimer]]]]

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse [[nonstoichiometric compound|substoichiometric compounds]].<ref name="HollemanAF" /><ref name="Aguly">{{cite book|first = Anatoly|last = Agulyansky|title = The Chemistry of Tantalum and Niobium Fluoride Compounds|pages = 1–11|publisher = Elsevier|year=2004| isbn = 978-0-444-51604-6}}</ref> The pentahalides ({{chem|NbX|5}}) feature octahedral Nb centres. Niobium pentafluoride (NbF<sub>5</sub>) is a white solid with a melting point of 79.0&nbsp;°C and [[niobium pentachloride]] (NbCl<sub>5</sub>) is yellow (see image at left) with a melting point of 203.4&nbsp;°C. Both are [[hydrolyzed]] to give oxides and oxyhalides, such as NbOCl<sub>3</sub>. The pentachloride is a versatile reagent being used to generate the [[organometallic]] compounds, such as [[niobocene dichloride]] ({{chem|(C|5|H|5|)|2|NbCl|2}}).<ref>{{cite journal|author = C. R. Lucas, J. A. Labinger, J. Schwartz|title = Dichlorobis(η5-Cyclopentadienyl)Niobium(IV)|editor = Robert J. Angelici|journal = [[Inorganic Syntheses]]|year = 1990|volume = 28|pages = 267–270|isbn = 0-471-52619-3|doi = 10.1002/9780470132593.ch68|publisher = J. Wiley & Sons|location = New York|series = Inorganic Syntheses}}</ref> The tetrahalides ({{chem|NbX|4}}) are dark-coloured polymers with Nb-Nb bonds, for example the black [[hygroscopic]] niobium tetrafluoride (NbF<sub>4</sub>) and brown niobium tetrachloride (NbCl<sub>4</sub>).

Anionic halide compounds of niobium are well known, owing in part to the [[Lewis acid]]ity of the pentahalides. The most important is [NbF<sub>7</sub>]<sup>2-</sup>, which is an intermediate in the separation of Nb and Ta from the ores.<ref name="ICE">{{cite journal|title = Staff-Industry Collaborative Report: Tantalum and Niobium|first = Donald J.|last = Soisson|coauthors = McLafferty, J. J.; Pierret, James A.| journal = Industrial and Engineering Chemistry|year = 1961|volume = 53|issue = 11|pages = 861–868|doi = 10.1021/ie50623a016}}</ref> This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound.Other halide complexes include octahedral [NbCl<sub>6</sub>]<sup>−</sup>:
:Nb<sub>2</sub>Cl<sub>10</sub> + 2 Cl<sup>−</sup> → 2 [NbCl<sub>6</sub>]<sup>−</sup>

As for other early metals, a variety of reduced halide clusters are known, the premier example being [Nb<sub>6</sub>Cl<sub>18</sub>]<sup>4−</sup>.<ref>{{Greenwood&Earnshaw2nd}}</ref>

===Nitrides and carbides===
Other [[binary compound]]s of niobium include the [[niobium nitride]] (NbN), which becomes a [[superconductor]] at low temperatures and is used in detectors for infrared light.<ref><!--highly specialized vanity paper, it appears:-->{{cite journal|doi = 10.1080/09500340410001670866|title = Ultrafast superconducting single-photon detectors for near-infrared-wavelength quantum communications|last = Verevkin|first = A.|coauthors = Pearlman, A.; Slstrokysz, W.; Zhang, J.; Currie, M.; Korneev, A.; Chulkova, G.; Okunev, O.; Kouminov, P.; Smirnov, K.; Voronov, B.; N. Gol'tsman, G.; Sobolewski, Roman|journal = Journal of Modern Optics|volume = 51|issue = 12|year = 2004|pages = 1447–1458}}</ref> The main [[niobium carbide]] is NbC, an extremely [[hardness|hard]], [[refraction (metallurgy)|refractory]], [[ceramic]] material, commercially used in [[tool bit]]s for cutting tools.

==Applications==
[[File:Niobium metal.jpg|thumb|A niobium foil|alt=Three pieces of metallic foil with yellow taint]]
It is estimated that out of 44,500 metric tons of niobium mined in 2006, 90% was used in the production of high-grade structural steel, followed by its use in [[superalloys]].<ref name="USGS2006">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/niobium/myb1-2006-niobi.pdf|title = Niobium (Columbium ) and Tantalum|first = John F |last=Papp|publisher = USGS 2006 Minerals Yearbook|accessdate = 2008-09-03}}</ref> The use of niobium alloys for superconductors and in electronic components account only for a small share of the production.<ref name="USGS2006" />

===Steel production===
Niobium is an effective [[Microalloyed steel|microalloying]] element for steel. Adding niobium to the steel causes the formation of [[niobium carbide]] and [[niobium nitride]] within the structure of the steel.<ref name="patel" /> These compounds improve the grain refining, retardation of recrystallization, and precipitation hardening of the steel. These effects in turn increase the toughness, strength, formability, and weldability of the microalloyed steel.<ref name="patel" /> Microalloyed [[stainless steel]]s have a niobium content of less than 0.1%.<ref name="heister">{{cite journal|title = Niobium: Future Possibilities – Technology and the Market Place|first = Friedrich|last= Heisterkamp|coauthors = Tadeu Carneiro|url = http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/images/pdfs/closing.pdf|accessdate =|journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA)|year = 2001|isbn = 978-0-9712068-0-9 |publisher = Niobium 2001 Ltd, 2002|editor=Minerals, Metals and Materials Society, Metals and Materials Society Minerals|format = PDF}}</ref> It is an important alloy addition to [[HSLA steel|high strength low alloy steels]] which are widely used as structural components in modern automobiles.<ref name="patel">{{cite journal|journal =Metallurgist|volume = 45|issue = 11–12|doi = 10.1023/A:1014897029026|pages = 477–480|year = 2001|title = Niobium for Steelmaking |first = Zh.|last = Patel|coauthors = Khul'ka K.|accessdate =}}</ref> These niobium-containing alloys are strong and are often used in pipeline construction.<ref name="eggert">{{cite journal|journal = Economic Bulletin|volume = 19|issue = 9|doi = 10.1007/BF02227064|pages = 8–11|year = 1982|title = Niobium: a steel additive with a future|first = Peter|last = Eggert|coauthors = Priem, Joachim; Wettig, Eberhard|accessdate =}}</ref><ref name="Hillenbrand">{{cite journal|url = http://www.europipe.com/files/ep_tp_43_01en.pdf|title = Development and Production of High Strength Pipeline Steels|first = Hans–Georg|last = Hillenbrand|coauthors = Gräf, Michael; Kalwa, Christoph| journal=Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |publisher = Europipe|accessdate =|date = 2001-05-02}}</ref>

===Superalloys===
[[File:Apollo CSM lunar orbit.jpg|thumb|Apollo 15 CSM in lunar orbit with the dark rocket nozzle made from [[niobium-titanium]] alloy |alt=Image of the Apollo Service Module with the moon in the background]]
Appreciable amounts of the element, either in its pure form or in the form of high-purity ferroniobium and [[nickel]] niobium, are used in nickel-, [[cobalt]]-, and [[iron]]-based [[superalloys]] for such applications as [[jet engine]] components, [[gas turbines]], rocket subassemblies, turbo charger systems, and heat resisting and combustion equipment. Niobium precipitates a hardening γ<nowiki>''</nowiki>-phase within the grain structure of the superalloy.<ref name="Donachie">{{cite book|publisher = ASM International|year = 2002|isbn = 978-0-87170-749-9|title = Superalloys: A Technical Guide|first = Matthew J.|last = Donachie|pages = 29–30}}</ref> The alloys contain up to 6.5% niobium.<ref name="heister" /> One example of a nickel-based niobium-containing superalloy is [[inconel|Inconel 718]], which consists of roughly 50% [[nickel]], 18.6% [[chromium]], 18.5% [[iron]], 5% niobium, 3.1% [[molybdenum]], 0.9% [[titanium]], and 0.4% [[aluminium]].<ref name="super">{{cite web|url = http://www.msm.cam.ac.uk/phase-trans/2003/Superalloys/superalloys.html|title = Nickel Based Superalloys| first = H. k. d. h|last = Bhadeshia|publisher = University of Cambridge|accessdate = 2008-09-04}}</ref><ref>{{cite journal|journal = Thermochimica Acta|volume = 382|year = 2002|pages= 55–267|doi = 10.1016/S0040-6031(01)00751-1|title = Thermophysikalische Eigenschaften von festem und flüssigem Inconel 718|language=German|first = G.|last = Pottlacher|coauthors = Hosaeus, H.; Wilthan, B.; Kaschnitz, E.; Seifter, A.|issue = 1––2}}</ref> These superalloys are used, for example, in advanced air frame systems such as those used in the [[Gemini program]].

An alloy used for [[liquid rocket]] thruster nozzles, such as in the main engine of the [[Apollo Lunar Module]]s, is the [[niobium alloy]] C-103, which consists of 89% niobium, 10% [[hafnium]] and 1% titanium.<ref name="hightemp">{{cite journal|url = http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_3/images/pdfs/016.pdf|title = Niobium alloys and high Temperature Applications| first = John|last = Hebda| journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |publisher = Companhia Brasileira de Metalurgia e Mineração|accessdate =|date = 2001-05-02|format = PDF}}</ref> Another niobium alloy was used for the nozzle of the [[Apollo service module|Apollo Service Module]]. As niobium is oxidized at temperatures above 400&nbsp;°C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.<ref name="hightemp" />

=== Niobium-base alloys===
'''C-103''' alloy was developed in the early 1960s jointly by the [[Wah Chang Corporation]] and [[Boeing]] Co. [[DuPont]], [[Union Carbide]] Corp., [[General Electric]] Co. and several other companies were developing [[Niobium alloy | Nb-base alloys]] simultaneously, largely driven by the [[Cold War]] and [[Space Race]]. The sensitivity of Nb to oxygen requires processing in [[Outgassing | vacuum]] or [[Inert gas | inert atmosphere]], which significantly increases the cost and difficulty of production. [[Vacuum arc remelting]] (VAR) and [[electron beam melting]] (EBM), novelty processes at the time, enabled the development of reactive metals such as Nb. The project that yielded C-103 began in 1959 with as many as 256 experimental Nb alloys in the "C-series" (possibly from '''c'''olumbium) that could be melted as buttons and rolled into [[Sheet metal | sheet]]. Wah Chang had an inventory of Hf, refined from nuclear-grade [[Zircaloy | Zr]], that it wanted to put to commercial use. The 103<sup>rd</sup> experimental composition of the C-series alloys, Nb-10Hf-1Ti, had the best combination of formability and high-temperature properties. Wah Chang fabricated the first 500-lb heat of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included [[turbine engine]] components and liquid metal [[heat exchangers]]. Competing Nb alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from Fansteel Metallurgical Corp., Cb129Y (Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr) from Union Carbide, and Nb1Zr from Superior Tube Co.<ref name="hightemp" />

===Superconducting magnets===
[[File:Modern 3T MRI.JPG|right|thumb|A 3 [[Tesla (unit)|tesla]] clinical [[MRI|magnetic resonance imaging]] scanner using niobium-superconducting alloy|alt=Room-high yellow-grey medical machine with a man-size hole in the middle and a stretcher directly in front of it]]
[[Niobium-germanium]] ({{chem|Nb|3|Ge}}), [[niobium-tin]] ({{chem|Nb|3|Sn}}), as well as the [[niobium-titanium]] [[alloy]]s are used as a [[type II superconductor]] wire for [[superconducting magnet]]s.<ref>{{cite journal|doi = 10.1109/77.828394|title = Powder-in-tube (PIT) Nb/sub 3/Sn conductors for high-field magnets|year = 2000|author = Lindenhovius, J.L.H.|journal=IEEE Transactions on Applied Superconductivity|volume = 10|pages = 975–978|last2 = Hornsveld|first2 = E.M.|last3 = Den Ouden|first3 = A.|last4 = Wessel|first4 = W.A.J.|last5 = Ten Kate|first5 = H.H.J.}}</ref><ref>{{cite web|url = http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/scmag.html|title = Superconducting Magnets|first = Carl R|last = Nave|publisher = Georgia State University, Department of Physics and Astronomy|accessdate = 2008-11-25}}</ref> These superconducting magnets are used in [[magnetic resonance imaging]] and [[nuclear magnetic resonance]] instruments as well as in [[particle accelerator]]s.<ref>{{cite journal|journal = Physica C: Superconductivity|volume= 372–376|issue = 3|year = 2002|pages = 1315–1320|doi = 10.1016/S0921-4534(02)01018-3|title = Niobium based intermetallics as a source of high-current/high magnetic field superconductors|first= B. A.|last = Glowacki|coauthors = Yan, X. -Y.; Fray, D.; Chen, G.; Majoros, M.; Shi, Y.|arxiv = cond-mat/0109088 |bibcode = 2002PhyC..372.1315G }}</ref> For example, the [[Large Hadron Collider]] uses 600 tons of superconducting strands, while the [[International Thermonuclear Experimental Reactor]] is estimated to use 600 tonnes of Nb<sub>3</sub>Sn strands and 250 tonnes of NbTi strands.<ref name="alstrom">{{cite journal|journal = Fusion Engineering and Design (Proceedings of the 23rd Symposium of Fusion Technology)|volume= 75–79|year = 2005|pages = 1–5|title = A success story: LHC cable production at ALSTOM-MSA|first = G.|last = Grunblatt|coauthor = Mocaer, P.; Verwaerde Ch.; Kohler, C.| doi = 10.1016/j.fusengdes.2005.06.216}}</ref> In 1992 alone, niobium-titanium wires were used to construct more than [[US$]]1&nbsp;billion worth of clinical magnetic resonance imaging systems.<ref name="geballe" />

====Superconducting, other====
The [[Superconducting Radio Frequency]] (RF) cavities used in the [[free electron laser]]s [[FLASH]] (result of the cancelled TESLA linear accelerator project) and [[European x-ray free electron laser|XFEL]] are made from pure niobium.<ref>{{cite journal|journal = Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume = 524|year = 2004|pages = 1–12|doi = 10.1016/j.nima.2004.01.045|title = Achievement of 35 MV/m in the superconducting nine-cell cavities for TESLA|first = L.|last = Lilje|coauthors = Kakob, E.; Kostina, D.; Matheisena, A.; Möllera, W. -D.; Procha, D.; Reschkea, D.; Saitob, K. Schmüserc, P.; Simrocka, S.; Suzukid T.; Twarowskia, K.|issue = 1–3|arxiv = physics/0401141 |bibcode = 2004NIMPA.524....1L }}</ref>

The high sensitivity of superconducting niobium nitride [[Microbolometer|bolometers]] make them an ideal detector for [[electromagnetic radiation]] in the THz frequency band. These detectors were tested at the [[Heinrich Hertz Submillimeter Telescope]], the [[South Pole Telescope]], the [[Receiver Lab Telescope]], and at [[Atacama Pathfinder Experiment|APEX]] and are now used in the HIFI instrument on board the [[Herschel Space Observatory]].<ref>{{cite journal|journal = Review of Scientific Instruments|volume = 79|year = 2008|pages = 0345011–03451010|doi = 10.1063/1.2890099|title = A Hot-electron bolometer terahertz mixers for the Herschel Space Observatory|first = Sergey|last = Cherednichenko|coauthors = Drakinskiy, Vladimir; Berg, Therese; Khosropanah, Pourya; Kollberg, Erik|pmid = 18377032|issue = 3|bibcode = 2008RScI...79c4501C }}</ref>

===Other uses===

====Electroceramics====
[[Lithium niobate]], which is a [[ferroelectric]], is used extensively in mobile telephones and [[optical modulators]], and for the manufacture of [[surface acoustic wave]] devices. It belongs to the [[Perovskite|ABO<sub>3</sub>]] structure ferroelectrics like [[lithium tantalate]] and [[barium titanate]].<ref>{{cite book|title = Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching|first = Tatyana|last = Volk|coauthors = Wohlecke, Manfred|publisher = Springer|year = 2008|isbn = 978-3-540-70765-3|pages = 1–9}}</ref> Niobium was evaluated as a cheaper alternative to tantalum in [[Tantalum capacitor|capacitors]],<ref>{{cite journal|journal = Quality and Reliability Engineering International|volume = 14|issue = 2|doi = 10.1002/(SICI)1099-1638(199803/04)14:2<79::AID-QRE163>3.0.CO;2-Y|pages = 79–82|year = 1991 |title = Reliability comparison of tantalum and niobium solid electrolytic capacitors|first = Y.|last = Pozdeev}}</ref> but tantalum capacitors are still predominant. Niobium is added to glass in order to attain a higher [[refractive index]], a property of use to the optical industry in making thinner [[glasses|corrective glasses]].

====Hypoallergenic applications: medicine and jewelry====
Niobium and some niobium alloys are physiologically inert and thus [[hypoallergenic]]. For this reason, niobium is found in many medical devices such as pacemakers.<ref>{{cite journal|last = Mallela| first = Venkateswara Sarma|coauthors = Ilankumaran, V.; Srinivasa Rao, N.| title = Trends in Cardiac Pacemaker Batteries|journal = Indian Pacing Electrophysiol J.|volume = 4|issue = 4|pages = 201–212|date=1 January 2004|pmid = 16943934|pmc = 1502062}}</ref> Niobium treated with [[sodium hydroxide]] forms a porous layer that aids [[osseointegration]].<ref>{{cite journal|last = Godley|first = Reut|coauthors = Starosvetsky, David; Gotman, Irena|year = 2004|title = Bonelike apatite formation on niobium metal treated in aqueous NaOH|journal = Journal of Materials Science: Materials in Medicine|volume = 15|pages = 1073–1077|doi = 10.1023/B:JMSM.0000046388.07961.81|url = http://www.springerlink.com/content/l5613670648017wp/|format = PDF|pmid = 15516867|issue = 10}}</ref>

Along with titanium, tantalum, and aluminium, niobium can also be electrically heated and [[anodize]]d, resulting in a wide array of colours using a process known as reactive metal [[anodizing]] which is useful in making jewelry.<ref>{{cite journal|journal = Journal of Applied Electrochemistry|volume = 21|issue = 11|doi = 10.1007/BF01077589|pages = 1023–1026 |year = 1991|title = Anodization of niobium in sulphuric acid media|first = M. A.|last = Biason Gomes|coauthors = Onofre, S.; Juanto, S.; Bulhões, L. O. de S.}}</ref><ref>{{cite journal|journal = Thin Solid Films|volume = 8|issue = 4|doi = 10.1016/0040-6090(71)90027-7|pages = R37–R39|year = 1971|title = A note on the thicknesses of anodized niobium oxide films|first = Y. L.|last = Chiou|bibcode = 1971TSF.....8R..37C }}</ref> The fact that niobium is hypoallergenic also benefits its use in jewelry.<ref>{{cite journal|doi = 10.1361/152981502770351860|last = Azevedo|first = C. R. F.|coauthors = Spera, G.; Silva, A. P.|title = Characterization of metallic piercings that caused adverse reactions during use|journal = Journal of Failure Analysis and Prevention|volume = 2|issue = 4|pages = 47–53|year =2002|url = http://www.springerlink.com/content/575x64408lnk560j/}}</ref>

====Numismatics====
[[File:2004 Austria 25 Euro 150 Years Semmering Alpine Railway front.jpg|thumb|A 150 Years [[Semmering railway|Semmering Alpine Railway]] Coin made of niobium and silver |alt=Coin with a dark green cener and a silvery outer rim. The rim reads: Republik Österreich 25 Euro. The centere shows electric and a steam driven locomotive]]
Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, [[Austria]] produced a series of silver niobium [[euro]] coins starting in 2003; the colour in these coins is created by the [[diffraction]] of light by a thin oxide layer produced by [[anodising]].<ref>{{cite journal|doi = 10.1016/j.ijrmhm.2005.10.008|journal = International Journal of Refractory Metals and Hard Materials|volume = 24|issue = 4|year = 2006|pages = 275–282|title = Niobium as mint metal: Production–properties–processing|first =Robert|last = Grill|coauthors = Gnadenberge, Alfred}}</ref> In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 [[Euro gold and silver commemorative coins (Austria)#2004 coinage|150 Years Semmering Alpine Railway commemorative coin]],<ref>{{cite web|url =http://austrian-mint.at/bimetallmuenzen?l=en&muenzeSubTypeId=113&muenzeId=217|archiveurl =http://web.archive.org/web/20110721053534/http://austrian-mint.at/bimetallmuenzen?l=en&muenzeSubTypeId=113&muenzeId=217|archivedate =2011-07-21|title = 25 Euro – 150 Years Semmering Alpine Railway (2004)|accessdate = 2008-11-04|publisher = [[Austrian Mint]]}}</ref>
and the 2006 Austrian €25 [[Euro gold and silver commemorative coins (Austria)#2006 coinage|European Satellite Navigation commemorative coin]].<ref>{{cite web|url =http://www.austrian-mint.at/cms/download.php?downloadId=131|archiveurl =http://web.archive.org/web/20110720002739/http://www.austrian-mint.at/cms/download.php?downloadId=131|archivedate =2011-07-20|title = 150 Jahre Semmeringbahn|accessdate = 2008-09-04| publisher = [[Austrian Mint]]| language=German}}</ref>
The Austrian mint produced for Latvia a similar series of coins starting in 2004,<ref>{{cite web|url =http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time/|archiveurl =http://web.archive.org/web/20080312222250/http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time/|archivedate =2008-03-12|title = Neraža – mēs nevarējām atrast meklēto lapu!|language=Latvian|accessdate = 2008-09-19|publisher = Bank of Latvia}}</ref>
with one following in 2007.<ref>{{cite web|url = http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time2/|archiveurl = http://web.archive.org/web/20090522101540/http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time2/|archivedate = 2009-05-22|title = Neraža – mēs nevarējām atrast meklēto lapu!|language=Latvian|accessdate = 2008-09-19|publisher = Bank of Latvia}}</ref>
In 2011, the Royal Canadian Mint started production of a $5 [[sterling silver]] and niobium coin named ''Hunter's Moon''<ref>{{Cite web|url=http://www.mint.ca/store/coin/5-sterling-silver-and-niobium-coin-hunters-moon-2011-prod1110013|title=$5 Sterling Silver and Niobium Coin – Hunter's Moon (2011)|publisher=Royal Canadian Mint|accessdate=1 February 2012|postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}</ref>
in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.

====Other====
The arc-tube seals of high pressure [[sodium vapor lamp]]s are made from niobium, or niobium with 1% of [[zirconium]], because niobium has a very similar coefficient of thermal expansion to the [[sintered]] [[alumina]] [[arc tube]] ceramic, a translucent material which resists chemical attack or [[redox|reduction]] by the hot liquid sodium and sodium vapour contained inside the operating lamp.<ref>{{cite book|title = Lamps and Lighting|first = Stanley Thomas|last = Henderson|coauthors = Marsden, Alfred Michael; Hewitt, Harry|publisher = Edward Arnold Press|year = 1972|isbn = 0-7131-3267-1|pages = 244–245}}</ref><ref>{{cite journal|title = Refractory metals: crucial components for light sources|last = Eichelbrönner|first = G.|year =1998|journal = International Journal of Refractory Metals and Hard Materials|volume = 16|issue = 1|pages = 5–11|doi = 10.1016/S0263-4368(98)00009-2|accessdate =}}</ref><ref>{{cite journal|title = Niobium and Niobium 1% Zirconium for High Pressure Sodium (HPS) Discharge Lamps|first = Christopher A.|last = Michaluk|coauthors = Huber, Louis E.; Ford, Robert B.| journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA)|year = 2001|isbn = 978-0-9712068-0-9 |publisher = Niobium 2001 Ltd, 2002|editor=Minerals, Metals and Materials Society, Metals and Materials Society Minerals}}</ref> The metal is also used in [[arc welding]] rods for some stabilized grades of stainless steel.<ref>{{US patent reference|number = 5254836|y = 1993|m = 10|d = 19|inventor = Okada, Yuuji; Kobayashi, Toshihiko; Sasabe, Hiroshi; Aoki, Yoshimitsu; Nishizawa, Makoto; Endo, Shunji|title = Method of arc welding with a ferrite stainless steel welding rod}}</ref><!--<ref>{{cite web|url=http://www.jxmetals.com/sdp/316680/4/cp-1271725.html|publisher=Shanghai Jiangxi Metals Co. Ltd|accessdate=2008-10-14|title=Niobium – Properties & Uses}}</ref>--> It is also used as a material in anodes for cathodic protection systems on some water tanks, which are then usually plated by platinum.<ref>{{cite book|author=Moavenzadeh, Fred |title=Concise Encyclopedia of Building and Construction Materials|url=http://books.google.com/books?id=YiJaEAUj258C&pg=PA157|accessdate=18 February 2012|date=14 March 1990|publisher=MIT Press|isbn=978-0-262-13248-0|pages=157–}}</ref><ref>{{cite book|author=Cardarelli, François |title=Materials handbook: a concise desktop reference|url=http://books.google.com/books?id=PvU-qbQJq7IC&pg=PA352|accessdate=18 February 2012|date=9 January 2008|publisher=Springer|isbn=978-1-84628-668-1|pages=352–}}</ref>

==Precautions==
Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is frequently used in jewelry and has been tested for use in some medical implants.<ref>{{cite journal|title = New trends in the use of metals in jewellery|first = J.|last = Vilaplana|coauthors = Romaguera, C.; Grimalt, F.; Cornellana, F.|journal = Contact Dermatitis|volume = 25|issue = 3 |pages = 145–148|year = 1990|doi = 10.1111/j.1600-0536.1991.tb01819.x|pmid = 1782765}}</ref><ref>{{cite journal|title = New developments in jewellery and dental materials|first = J.|last = Vilaplana|coauthors = Romaguera, C.| journal = Contact Dermatitis|volume = 39|issue = 2| pages = 55–57|year = 1998|doi = 10.1111/j.1600-0536.1998.tb05832.x|pmid = 9746182}}</ref>

Niobium-containing compounds are rarely encountered by most people, but some are toxic and should be treated with care. The short and long term exposure to niobates and niobium chloride, two chemicals that are water soluble, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a [[median lethal dose]] (LD<sub>50</sub>) between 10 and 100&nbsp;mg/kg.<ref name="Haley">{{cite journal|title = Pharmacology and toxicology of niobium chloride|first = Thomas J.|last = Haley|coauthor = Komesu, N.; Raymond, K.|journal = [[Toxicology and Applied Pharmacology]]|volume = 4|issue = 3|pages = 385–392|year = 1962|doi = 10.1016/0041-008X(62)90048-0|pmid=13903824}}</ref><ref>{{cite journal|title = The Toxicity of Niobium Salts |first = William L.|last = Downs|coauthors = Scott, James K.; Yuile, Charles L.; Caruso, Frank S.; Wong, Lawrence C. K.|journal = American Industrial Hygiene Association Journal|volume = 26|issue = 4|pages = 337–346|year = 1965|doi = 10.1080/00028896509342740|pmid = 5854670}}</ref><ref>{{cite journal|title = Zirconium, Niobium, Antimony, Vanadium and Lead in Rats: Life term studies|first= Henry A.|last = Schroeder|coauthors = Mitchener, Marian; Nason, Alexis P.|journal = Journal of Nutrition|volume = 100|issue = 1|pages = 59–68|year=1970|pmid =5412131|url=http://jn.nutrition.org/content/100/1/59.short}}</ref> For oral administration the toxicity is lower; a study with rats yielded a LD<sub>50</sub> after seven days of 940&nbsp;mg/kg.<ref name="Haley" />


==參考資料==
==參考資料==
{{reflist|2}}
{{Reflist|2}}


==外部鏈接==
==外部鏈接==
{{Commons category|Happisburgh footprints}}
{{Commons|Niobium}}
{{wiktionary|niobium}}
* {{en}}[http://www.youtube.com/watch?feature=player_embedded&v=tHFFMyBb1O8 The earliest human footprints outside Africa found in Norfolk]﹣[[自然史博物館 (倫敦)|倫敦自然史博物館]]有關黑斯堡足跡的影片
* [http://periodic.lanl.gov/41.shtml Los Alamos National Laboratory – Niobium]([[洛斯阿拉莫斯國家實驗室]]﹣鈮)
* {{en}}[http://www.britishmuseum.org/research/research_projects/all_current_projects/featured_project_happisburgh.aspx Happisburgh project]﹣[[大英博物館]]黑斯堡項目
* [http://www.tanb.org/ Tantalum-Niobium International Study Center](國際鉭鈮研究中心)
* [http://www.symmetrymag.org/cms/?pid=1000173 Niobium for particle accelerators eg ILC. 2005]用於粒子加速器的鈮,[[國際直線對撞機]],2005年
* {{Cite EB1911|wstitle=Columbium|short=x}}
* {{Cite NIE|wstitle=Columbium}}
* [http://www.periodicvideos.com/videos/041.htm Niobium] at ''The Periodic Table of Videos''(諾丁漢大學)
* 科學家經光譜學在高溫下發現NbCl,見:{{cite journal|doi = 10.1016/j.jms.2004.02.001|journal = Journal of Molecular Spectroscopy|volume = 228|year = 2004|pages = 544–553|url = http://bernath.uwaterloo.ca/media/270.pdf| title = Fourier transform emission spectroscopy and ab initio calculations on NbCl|accessdate =|first = R.S.|last = Ram|coauthors = Rinskopf, N.; Liévin, J.; Bernatha, P.F.|bibcode = 2004JMoSp.228..544R|issue = 2 }}

{{元素週期表}}
{{鈮化合物}}


[[Category:化学元素|5E]]
{{Coord|52.82542|1.53500|type:landmark_region:GB|format=dms|display=title}}
[[Category:过渡金属]]
[[Category:铌|*]]
[[Category:第5周期元素|5E]]


{{Link FA|el}}
[[Category:2013年英國]]
{{Link FA|en}}
[[Category:英国史前时期遗址]]
[[Category:早期人類]]

2014年2月19日 (三) 17:28的版本

鈮 41Nb
氫(非金屬) 氦(惰性氣體)
鋰(鹼金屬) 鈹(鹼土金屬) 硼(類金屬) 碳(非金屬) 氮(非金屬) 氧(非金屬) 氟(鹵素) 氖(惰性氣體)
鈉(鹼金屬) 鎂(鹼土金屬) 鋁(貧金屬) 矽(類金屬) 磷(非金屬) 硫(非金屬) 氯(鹵素) 氬(惰性氣體)
鉀(鹼金屬) 鈣(鹼土金屬) 鈧(過渡金屬) 鈦(過渡金屬) 釩(過渡金屬) 鉻(過渡金屬) 錳(過渡金屬) 鐵(過渡金屬) 鈷(過渡金屬) 鎳(過渡金屬) 銅(過渡金屬) 鋅(過渡金屬) 鎵(貧金屬) 鍺(類金屬) 砷(類金屬) 硒(非金屬) 溴(鹵素) 氪(惰性氣體)
銣(鹼金屬) 鍶(鹼土金屬) 釔(過渡金屬) 鋯(過渡金屬) 鈮(過渡金屬) 鉬(過渡金屬) 鎝(過渡金屬) 釕(過渡金屬) 銠(過渡金屬) 鈀(過渡金屬) 銀(過渡金屬) 鎘(過渡金屬) 銦(貧金屬) 錫(貧金屬) 銻(類金屬) 碲(類金屬) 碘(鹵素) 氙(惰性氣體)
銫(鹼金屬) 鋇(鹼土金屬) 鑭(鑭系元素) 鈰(鑭系元素) 鐠(鑭系元素) 釹(鑭系元素) 鉕(鑭系元素) 釤(鑭系元素) 銪(鑭系元素) 釓(鑭系元素) 鋱(鑭系元素) 鏑(鑭系元素) 鈥(鑭系元素) 鉺(鑭系元素) 銩(鑭系元素) 鐿(鑭系元素) 鎦(鑭系元素) 鉿(過渡金屬) 鉭(過渡金屬) 鎢(過渡金屬) 錸(過渡金屬) 鋨(過渡金屬) 銥(過渡金屬) 鉑(過渡金屬) 金(過渡金屬) 汞(過渡金屬) 鉈(貧金屬) 鉛(貧金屬) 鉍(貧金屬) 釙(貧金屬) 砈(類金屬) 氡(惰性氣體)
鍅(鹼金屬) 鐳(鹼土金屬) 錒(錒系元素) 釷(錒系元素) 鏷(錒系元素) 鈾(錒系元素) 錼(錒系元素) 鈽(錒系元素) 鋂(錒系元素) 鋦(錒系元素) 鉳(錒系元素) 鉲(錒系元素) 鑀(錒系元素) 鐨(錒系元素) 鍆(錒系元素) 鍩(錒系元素) 鐒(錒系元素) 鑪(過渡金屬) 𨧀(過渡金屬) 𨭎(過渡金屬) 𨨏(過渡金屬) 𨭆(過渡金屬) 䥑(預測為過渡金屬) 鐽(預測為過渡金屬) 錀(預測為過渡金屬) 鎶(過渡金屬) 鉨(預測為貧金屬) 鈇(貧金屬) 鏌(預測為貧金屬) 鉝(預測為貧金屬) 鿬(預測為鹵素) 鿫(預測為惰性氣體)




外觀
灰色金屬質,氧化後呈藍色
概況
名稱·符號·序數鈮({{{enname}}})·Nb·41
元素類別過渡金屬
·週期·5·5·d
標準原子質量92.90637(2)
电子排布[] 4d4 5s1
2, 8, 18, 12, 1
歷史
發現查理斯·哈契特(1801年)
分離克利斯蒂安·威廉·布隆斯特蘭(1864年)
證明為化學元素海因里希·羅澤(1844年)
物理性質
物態solid
密度(接近室温
8.57 g·cm−3
熔点2750 K,2477 °C,4491 °F
沸點5017 K,4744 °C,8571 °F
熔化热30 kJ·mol−1
汽化热689.9 kJ·mol−1
比熱容24.60 J·mol−1·K−1
蒸氣壓
壓/Pa 1 10 100 1 k 10 k 100 k
溫/K 2942 3207 3524 3910 4393 5013
原子性質
氧化态5, 4, 3, 2, -1
(弱酸性氧化物)
电负性1.6(鲍林标度)
电离能第一:652.1 kJ·mol−1

第二:1380 kJ·mol−1

第三:2416 kJ·mol−1
原子半径146 pm
共价半径164±6 pm
鈮的原子谱线
雜項
晶体结构體心立方
磁序順磁性
電阻率(0 °C)152 n Ω·m
熱導率53.7 W·m−1·K−1
热膨胀系数7.3 µm/(m·K)
聲速(細棒)(20 °C)3480 m·s−1
杨氏模量105 GPa
剪切模量38 GPa
体积模量170 GPa
泊松比0.40
莫氏硬度6.0
維氏硬度1320 MPa
布氏硬度736 MPa
CAS号7440-03-1
同位素
主条目:鈮的同位素
同位素 丰度 半衰期t1/2 衰變
方式 能量MeV 產物
91Nb 人造 6.8×102 ε - 91Zr
91mNb 人造 60.86天 IT 0.104e 91Nb

Template:Elementbox isotopes decay2 Template:Elementbox isotopes decay2

93Nb 100% - (SF) <0.943 X
93mNb 人造 16.13年 IT 0.031e 93Nb

Template:Elementbox isotopes decay2 Template:Elementbox isotopes decay2

95mNb 人造 3.61天 IT 0.235 95Nb
理論預測,但未有觀測證明的衰變方式以括號標示。

Niobium, formerly columbium, is a chemical element with the symbol Nb (formerly Cb) and atomic number 41. It is a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite. The name comes from Greek mythology: Niobe, daughter of Tantalus.

Niobium has physical and chemical properties similar to those of the element tantalum, and the two are therefore difficult to distinguish. The English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.

It was not until the early 20th century that niobium was first used commercially. Brazil is the leading producer of niobium and ferroniobium, an alloy of niobium and iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. Although alloys contain only a maximum of 0.1%, that small percentage of niobium improves the strength of the steel. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines. Niobium is used in various superconducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include its use in welding, nuclear industries, electronics, optics, numismatics and jewelry. In the last two applications, niobium's low toxicity and ability to be colored by anodization are particular advantages.

History

Oval black and white painting of a man with a prominent shirt collar and necktie
Charles Hatchett was the discoverer of columbium.
Black and white image of a marmor sculpture of a bowing woman with a child nestling in her lap
Picture of a Hellenistic sculpture representing Niobe by Giorgio Sommer

Niobium was discovered by the English chemist Charles Hatchett in 1801.[1] He found a new element in a mineral sample that had been sent to England from Massachusetts, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral columbite and the new element columbium after Columbia, the poetical name for the United States.[2][3][4] The columbium discovered by Hatchett was probably a mixture of the new element with tantalum.[2]

Subsequently, there was considerable confusion[5] over the difference between columbium (niobium) and the closely related tantalum. In 1809, the English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm3, and tantalum—tantalite, with a density over 8 g/cm3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.[5] This conclusion was disputed in 1846 by the German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: niobium (from Niobe), and pelopium (from Pelops).[6][7] This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium and dianium[8] were in fact identical to niobium or mixtures of niobium and tantalum.[9]

The differences between tantalum and niobium were unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand,[9] and Henri Etienne Sainte-Claire Deville, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865[9][10] and finally by the Swiss chemist Jean Charles Galissard de Marignac[11] in 1866, who all proved that there were only two elements. Articles on ilmenium continued to appear until 1871.[12]

De Marignac was the first to prepare the metal in 1864, when he reduced niobium chloride by heating it in an atmosphere of hydrogen.[13] Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was first used commercially, in incandescent lamp filaments.[10] This use quickly became obsolete through the replacement of niobium with tungsten, which has a higher melting point and thus is preferable for use in incandescent lamps. The discovery that niobium improves the strength of steel was made in the 1920s, and this application remains its predominant use.[10] In 1961 the American physicist Eugene Kunzler and coworkers at Bell Labs discovered that niobium-tin continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields,[14] making it the first material to support the high currents and fields necessary for useful high-power magnets and electrically powered machinery. This discovery would allow — two decades later — the production of long multi-strand cables that could be wound into coils to create large, powerful electromagnets for rotating machinery, particle accelerators, or particle detectors.[15][16]

Naming of the element

Columbium (symbol Cb[17]) was the name originally given to this element by Hatchett, and this name remained in use in American journals—the last paper published by American Chemical Society with columbium in its title dates from 1953[18]—while niobium was used in Europe. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949.[19] A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name Columbium.[19] The latter name is still sometimes used in US industry.[20] This was a compromise of sorts;[19] the IUPAC accepted tungsten instead of wolfram, in deference to North American usage; and niobium instead of columbium, in deference to European usage. Not everyone agreed, and while many leading chemical societies and government organizations refer to it by the official IUPAC name, many leading metallurgists, metal societies, and the United States Geological Survey still refer to the metal by the original "columbium".[21][22]

Characteristics

Physical

Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), although it has an atypical configuration in its outermost electron shells compared to the rest of the members. (This can be observed in the neighborhood of ruthenium (44), rhodium (45), and palladium (46).)

Z Element No. of electrons/shell
23 vanadium 2, 8, 11, 2
41 niobium 2, 8, 18, 12, 1
73 tantalum 2, 8, 18, 32, 11, 2
105 dubnium 2, 8, 18, 32, 32, 11, 2 (predicted)

Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.2 K.[23] Niobium has the largest magnetic penetration depth of any element.[23] In addition, it is one of the three elemental Type II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal.[24] When very pure, it is comparatively soft and ductile, but impurities make it harder.[25]

The metal has a low capture cross-section for thermal neutrons;[26] thus it is used in the nuclear industries.[27]

Chemical

The metal takes on a bluish tinge when exposed to air at room temperature for extended periods.[28] Despite presenting a high melting point in elemental form (2,468 °C), it has a low density in comparison to other refractory metals. Furthermore, it is corrosion resistant, exhibits superconductivity properties, and forms dielectric oxide layers.

Niobium is slightly less electropositive and more compact than its predecessor in the periodic table, zirconium, whereas it is virtually identical in size to the heavier tantalum atoms, owing to the lanthanide contraction.[25] As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the periodic table.[10] Although its corrosion resistance is not as outstanding as that of tantalum, its lower price and greater availability make niobium attractive for less demanding uses such as linings in chemical plants.[25]

Isotopes

Naturally occurring niobium is composed of one stable isotope, 93Nb.[29] As of 2003, at least 32 radioisotopes have also been synthesized, ranging in atomic mass from 81 to 113. The most stable of these is 92Nb with a half-life of 34.7 million years. One of the least stable is 113Nb, with an estimated half-life of 30 milliseconds. Isotopes that are lighter than the stable 93Nb tend to decay by β+ decay, and those that are heavier tend to decay by β- decay, with some exceptions. 81Nb, 82Nb, and 84Nb have minor β+ delayed proton emission decay paths, 91Nb decays by electron capture and positron emission, and 92Nb decays by both β+ and β- decay.[29]

At least 25 nuclear isomers have been described, ranging in atomic mass from 84 to 104. Within this range, only 96Nb, 101Nb, and 103Nb do not have isomers. The most stable of niobium's isomers is 93mNb with a half-life of 16.13 years. The least stable isomer is 84mNb with a half-life of 103 ns. All of niobium's isomers decay by isomeric transition or beta decay except 92m1Nb, which has a minor electron capture decay chain.[29]

Occurrence

Niobium is estimated to be the 33rd most common element in the Earth’s crust, with 20 ppm.[30] Some think that the abundance on Earth is much greater, but that the "missing" niobium may be located in the Earth’s core due to the metal's high density.[21] The free element is not found in nature, but niobium occurs in combination with other elements in minerals.[25] Minerals that contain niobium often also contain tantalum. Examples include columbite ((Fe,Mn)(Nb,Ta)2O6) and columbite–tantalite (or coltan, (Fe,Mn)(Ta,Nb)2O6).[31] Columbite–tantalite minerals are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements. Examples of such niobates are pyrochlore ((Na,Ca)2Nb2O6(OH,F)) and euxenite ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6). These large deposits of niobium have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a constituent of pyrochlore.[32]

The two largest deposits of pyrochlore were found in the 1950s in Brazil and Canada, and both countries are still the major producers of niobium mineral concentrates.[10] The largest deposit is hosted within a carbonatite intrusion at Araxá, Minas Gerais Brazil, owned by CBMM (Companhia Brasileira de Metalurgia e Mineração); the other deposit is located in Goiás and owned by Anglo American plc (through its subsidiary Mineração Catalão), also hosted within a carbonatite intrusion.[33] Altogether these two Brazilian mines produce around 75% of world supply. The third largest producer of niobium is the carbonatite-hosted Niobec Mine, Saint-Honoré near Chicoutimi, Quebec owned by Iamgold Corporation Ltd, which produces around 7% of world supply.[33] Kenya's deposits found in Kwale are ranked amongst the top six in the world.[34]

Production

Grey and white world map with Brazil colored red representing 90% of niobium world production and Canada colored in dark blue representing 5% of niobium world production
Niobium producers in 2006

After the separation from the other minerals, the mixed oxides of tantalum Ta2O5 and niobium Nb2O5 are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid:[31]

Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O
Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O

The first industrial scale separation, developed by de Marignac, exploits the differing solubilities of the complex niobium and tantalum fluorides, dipotassium oxypentafluoroniobate monohydrate (K2[NbOF5]·H2O) and dipotassium heptafluorotantalate (K2[TaF7]) in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like cyclohexanone.[31] The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water and either precipitated by the addition of potassium fluoride to produce a potassium fluoride complex, or precipitated with ammonia as the pentoxide:[35]

H2[NbOF5] + 2 KF → K2[NbOF5]↓ + 2 HF

Followed by:

2 H2[NbOF5] + 10 NH4OH → Nb2O5↓ + 10 NH4F + 7 H2O

Several methods are used for the reduction to metallic niobium. The electrolysis of a molten mixture of K2[NbOF5] and sodium chloride is one; the other is the reduction of the fluoride with sodium. With this method niobium with a relatively high purity can be obtained. In large scale production the reduction of Nb2O5 with hydrogen or carbon[35] is used. In the process involving the aluminothermic reaction a mixture of iron oxide and niobium oxide is reacted with aluminium:

3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3

To enhance the reaction, small amounts of oxidizers like sodium nitrate are added. The result is aluminium oxide and ferroniobium, an alloy of iron and niobium used in the steel production.[36][37] The ferroniobium contains between 60 and 70% of niobium.[33] Without addition of iron oxide, aluminothermic process is used for the production of niobium. Further purification is necessary to reach the grade for superconductive alloys. Electron beam melting under vacuum is the method used by the two major distributors of niobium.[38][39]

截至2013年 (2013-Missing required parameter 1=month!), the Brazilian company Cia. Brasileira de Metalurgia & Mineracao "controls 85 percent of the world's niobium production."[40] The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.[41][42] The worldwide resources are estimated to be 4,400,000 tonnes.[42] During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.[43] Since 2009 production is stable at around 63,000 tonnes per year.[44]

Mine production (t)[45] (USGS estimate)
Country 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
 澳大利亞 160 230 290 230 200 200 200 ? ? ? ? ?
 巴西 30,000 22,000 26,000 29,000 29,900 35,000 40,000 57,300 58,000 58,000 58,000 58,000
 加拿大 2,290 3,200 3,410 3,280 3,400 3,310 4,167 3,020 4,380 4,330 4,420 4,400
 Congo D.R. ? 50 50 13 52 25 ? ? ? ? ? ?
 莫桑比克 ? ? 5 34 130 34 29 ? ? ? ? ?
 奈及利亞 35 30 30 190 170 40 35 ? ? ? ? ?
 卢旺达 28 120 76 22 63 63 80 ? ? ? ? ?
World 32,600 25,600 29,900 32,800 34,000 38,700 44,500 60,400 62,900 62,900 62,900 63,000

Lesser amounts are found in Malawi's Kanyika mine.

Compounds

Niobium is in many ways similar to tantalum and zirconium. It reacts with most nonmetals at high temperatures: niobium reacts with fluorine at room temperature, with chlorine and hydrogen at 200 °C, and with nitrogen at 400 °C, giving products that are frequently interstitial and nonstoichiometric.[25] The metal begins to oxidize in air at 200 °C,[35] and is resistant to corrosion by fused alkalis and by acids, including aqua regia, hydrochloric, sulfuric, nitric and phosphoric acids.[25] Niobium is attacked by hydrofluoric acid and hydrofluoric/nitric acid mixtures.

Although niobium exhibits all of the formal oxidation states from +5 to −1, in most commonly encountered compounds, it is found in the +5 state.[25] Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding.

Oxides and sulfides

Niobium forms oxides with the oxidation states +5 (Nb2O5), +4 (NbO2), and +3 (Nb2O3),[35] as well as with the rarer oxidation state +2 (NbO).[46] Most commonly encountered is the pentoxide, precursor to almost all niobium compounds and alloys.[35][47] Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate (LiNbO3) and lanthanum niobate (LaNbO4). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone NbO3−
4
ions.[35] The layered niobium sulfide (NbS2) is also known.[25]

Materials with a thin film coating of niobium(V) oxide can be produced by chemical vapor deposition or atomic layer deposition processes, in each case by the thermal decomposition of niobium(V) ethoxide above 350 °C.[48][49]

Halides

Watch glass on a black surface with a small portion of yellow crystals
A sample of niobium pentachloride (yellow portion) that has partially hydrolyzed (white material).
Ball-and-stick model of niobium pentachloride, which exists as a dimer

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds.[35][38] The pentahalides (NbX
5
) feature octahedral Nb centres. Niobium pentafluoride (NbF5) is a white solid with a melting point of 79.0 °C and niobium pentachloride (NbCl5) is yellow (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as NbOCl3. The pentachloride is a versatile reagent being used to generate the organometallic compounds, such as niobocene dichloride ((C
5
H
5
)
2
NbCl
2
).[50] The tetrahalides (NbX
4
) are dark-coloured polymers with Nb-Nb bonds, for example the black hygroscopic niobium tetrafluoride (NbF4) and brown niobium tetrachloride (NbCl4).

Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is [NbF7]2-, which is an intermediate in the separation of Nb and Ta from the ores.[31] This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound.Other halide complexes include octahedral [NbCl6]:

Nb2Cl10 + 2 Cl → 2 [NbCl6]

As for other early metals, a variety of reduced halide clusters are known, the premier example being [Nb6Cl18]4−.[51]

Nitrides and carbides

Other binary compounds of niobium include the niobium nitride (NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light.[52] The main niobium carbide is NbC, an extremely hard, refractory, ceramic material, commercially used in tool bits for cutting tools.

Applications

Three pieces of metallic foil with yellow taint
A niobium foil

It is estimated that out of 44,500 metric tons of niobium mined in 2006, 90% was used in the production of high-grade structural steel, followed by its use in superalloys.[53] The use of niobium alloys for superconductors and in electronic components account only for a small share of the production.[53]

Steel production

Niobium is an effective microalloying element for steel. Adding niobium to the steel causes the formation of niobium carbide and niobium nitride within the structure of the steel.[21] These compounds improve the grain refining, retardation of recrystallization, and precipitation hardening of the steel. These effects in turn increase the toughness, strength, formability, and weldability of the microalloyed steel.[21] Microalloyed stainless steels have a niobium content of less than 0.1%.[54] It is an important alloy addition to high strength low alloy steels which are widely used as structural components in modern automobiles.[21] These niobium-containing alloys are strong and are often used in pipeline construction.[55][56]

Superalloys

Image of the Apollo Service Module with the moon in the background
Apollo 15 CSM in lunar orbit with the dark rocket nozzle made from niobium-titanium alloy

Appreciable amounts of the element, either in its pure form or in the form of high-purity ferroniobium and nickel niobium, are used in nickel-, cobalt-, and iron-based superalloys for such applications as jet engine components, gas turbines, rocket subassemblies, turbo charger systems, and heat resisting and combustion equipment. Niobium precipitates a hardening γ''-phase within the grain structure of the superalloy.[57] The alloys contain up to 6.5% niobium.[54] One example of a nickel-based niobium-containing superalloy is Inconel 718, which consists of roughly 50% nickel, 18.6% chromium, 18.5% iron, 5% niobium, 3.1% molybdenum, 0.9% titanium, and 0.4% aluminium.[58][59] These superalloys are used, for example, in advanced air frame systems such as those used in the Gemini program.

An alloy used for liquid rocket thruster nozzles, such as in the main engine of the Apollo Lunar Modules, is the niobium alloy C-103, which consists of 89% niobium, 10% hafnium and 1% titanium.[60] Another niobium alloy was used for the nozzle of the Apollo Service Module. As niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.[60]

Niobium-base alloys

C-103 alloy was developed in the early 1960s jointly by the Wah Chang Corporation and Boeing Co. DuPont, Union Carbide Corp., General Electric Co. and several other companies were developing Nb-base alloys simultaneously, largely driven by the Cold War and Space Race. The sensitivity of Nb to oxygen requires processing in vacuum or inert atmosphere, which significantly increases the cost and difficulty of production. Vacuum arc remelting (VAR) and electron beam melting (EBM), novelty processes at the time, enabled the development of reactive metals such as Nb. The project that yielded C-103 began in 1959 with as many as 256 experimental Nb alloys in the "C-series" (possibly from columbium) that could be melted as buttons and rolled into sheet. Wah Chang had an inventory of Hf, refined from nuclear-grade Zr, that it wanted to put to commercial use. The 103rd experimental composition of the C-series alloys, Nb-10Hf-1Ti, had the best combination of formability and high-temperature properties. Wah Chang fabricated the first 500-lb heat of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included turbine engine components and liquid metal heat exchangers. Competing Nb alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from Fansteel Metallurgical Corp., Cb129Y (Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr) from Union Carbide, and Nb1Zr from Superior Tube Co.[60]

Superconducting magnets

Room-high yellow-grey medical machine with a man-size hole in the middle and a stretcher directly in front of it
A 3 tesla clinical magnetic resonance imaging scanner using niobium-superconducting alloy

Niobium-germanium (Nb
3
Ge
), niobium-tin (Nb
3
Sn
), as well as the niobium-titanium alloys are used as a type II superconductor wire for superconducting magnets.[61][62] These superconducting magnets are used in magnetic resonance imaging and nuclear magnetic resonance instruments as well as in particle accelerators.[63] For example, the Large Hadron Collider uses 600 tons of superconducting strands, while the International Thermonuclear Experimental Reactor is estimated to use 600 tonnes of Nb3Sn strands and 250 tonnes of NbTi strands.[64] In 1992 alone, niobium-titanium wires were used to construct more than US$1 billion worth of clinical magnetic resonance imaging systems.[15]

Superconducting, other

The Superconducting Radio Frequency (RF) cavities used in the free electron lasers FLASH (result of the cancelled TESLA linear accelerator project) and XFEL are made from pure niobium.[65]

The high sensitivity of superconducting niobium nitride bolometers make them an ideal detector for electromagnetic radiation in the THz frequency band. These detectors were tested at the Heinrich Hertz Submillimeter Telescope, the South Pole Telescope, the Receiver Lab Telescope, and at APEX and are now used in the HIFI instrument on board the Herschel Space Observatory.[66]

Other uses

Electroceramics

Lithium niobate, which is a ferroelectric, is used extensively in mobile telephones and optical modulators, and for the manufacture of surface acoustic wave devices. It belongs to the ABO3 structure ferroelectrics like lithium tantalate and barium titanate.[67] Niobium was evaluated as a cheaper alternative to tantalum in capacitors,[68] but tantalum capacitors are still predominant. Niobium is added to glass in order to attain a higher refractive index, a property of use to the optical industry in making thinner corrective glasses.

Hypoallergenic applications: medicine and jewelry

Niobium and some niobium alloys are physiologically inert and thus hypoallergenic. For this reason, niobium is found in many medical devices such as pacemakers.[69] Niobium treated with sodium hydroxide forms a porous layer that aids osseointegration.[70]

Along with titanium, tantalum, and aluminium, niobium can also be electrically heated and anodized, resulting in a wide array of colours using a process known as reactive metal anodizing which is useful in making jewelry.[71][72] The fact that niobium is hypoallergenic also benefits its use in jewelry.[73]

Numismatics

Coin with a dark green cener and a silvery outer rim. The rim reads: Republik Österreich 25 Euro. The centere shows electric and a steam driven locomotive
A 150 Years Semmering Alpine Railway Coin made of niobium and silver

Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, Austria produced a series of silver niobium euro coins starting in 2003; the colour in these coins is created by the diffraction of light by a thin oxide layer produced by anodising.[74] In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 150 Years Semmering Alpine Railway commemorative coin,[75] and the 2006 Austrian €25 European Satellite Navigation commemorative coin.[76] The Austrian mint produced for Latvia a similar series of coins starting in 2004,[77] with one following in 2007.[78] In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named Hunter's Moon[79] in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.

Other

The arc-tube seals of high pressure sodium vapor lamps are made from niobium, or niobium with 1% of zirconium, because niobium has a very similar coefficient of thermal expansion to the sintered alumina arc tube ceramic, a translucent material which resists chemical attack or reduction by the hot liquid sodium and sodium vapour contained inside the operating lamp.[80][81][82] The metal is also used in arc welding rods for some stabilized grades of stainless steel.[83] It is also used as a material in anodes for cathodic protection systems on some water tanks, which are then usually plated by platinum.[84][85]

Precautions

Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is frequently used in jewelry and has been tested for use in some medical implants.[86][87]

Niobium-containing compounds are rarely encountered by most people, but some are toxic and should be treated with care. The short and long term exposure to niobates and niobium chloride, two chemicals that are water soluble, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD50) between 10 and 100 mg/kg.[88][89][90] For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg.[88]

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