|
|
Line 20: |
Line 20: |
| {{Elementbox_density_gpcm3nrt | 13.31 }} | | {{Elementbox_density_gpcm3nrt | 13.31 }} |
| {{Elementbox_densityliq_gpcm3mp | 12 }} | | {{Elementbox_densityliq_gpcm3mp | 12 }} |
− | {{Elementbox_meltingpoint | k=2506 | c=2233 | f=4051 }}
| |
− | {{Elementbox_boilingpoint | k=4876 | c=4603 | f=8317 }}
| |
− | {{Elementbox_heatfusion_kjpmol | 27.2 }}
| |
− | {{Elementbox_heatvaporiz_kjpmol | 571 }}
| |
− | {{Elementbox_heatcapacity_jpmolkat25 | 25.73 }}
| |
− | {{Elementbox_vaporpressure_katpa | 2689 | 2954 | 3277 | 3679 | 4194 | 4876 | comment= }}
| |
− | {{Elementbox_section_atomicprop | color1=#ffc0c0 | color2=black }}
| |
− | {{Elementbox_crystalstruct | hexagonal }}
| |
− | {{Elementbox_oxistates | 4<br />([[amphoteric]] oxide) }}
| |
− | {{Elementbox_electroneg_pauling | 1.3 }}
| |
− | {{Elementbox_ionizationenergies4 | 658.5 | 1440 | 2250 }}
| |
− | {{Elementbox_atomicradius_pm | [[1 E-10 m|155]] }}
| |
− | {{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|208]] }}
| |
− | {{Elementbox_covalentradius_pm | [[1 E-10 m|150]] }}
| |
− | {{Elementbox_section_miscellaneous | color1=#ffc0c0 | color2=black }}
| |
− | {{Elementbox_magnetic | no data }}
| |
− | {{Elementbox_eresist_ohmmat20 | 331 n}}
| |
− | {{Elementbox_thermalcond_wpmkat300k | 23.0 }}
| |
− | {{Elementbox_thermalexpansion_umpmkat25 | 5.9 }}
| |
− | {{Elementbox_speedofsound_rodmpsat20 | 3010 }}
| |
− | {{Elementbox_youngsmodulus_gpa | 78 }}
| |
− | {{Elementbox_shearmodulus_gpa | 30 }}
| |
− | {{Elementbox_bulkmodulus_gpa | 110 }}
| |
− | {{Elementbox_poissonratio | 0.37 }}
| |
− | {{Elementbox_mohshardness | 5.5 }}
| |
− | {{Elementbox_vickershardness_mpa | 1760 }}
| |
− | {{Elementbox_brinellhardness_mpa | 1700 }}
| |
− | {{Elementbox_cas_number | 7440-58-6 }}
| |
− | {{Elementbox_isotopes_begin | color1=#ffc0c0 | color2=black }}
| |
− | {{Elementbox_isotopes_decay | mn=172 | sym=Hf
| |
− | | na=[[synthetic radioisotope|syn]] | hl=1.87 [[year|y]]
| |
− | | dm=[[electron capture|ε]] | de=0.350 | pn=172 | ps=[[lutetium|Lu]] }}
| |
− | {{Elementbox_isotopes_decay | mn=174 | sym=Hf
| |
− | | na=0.162% | hl=2×10<sup>15</sup> [[year|y]]
| |
− | | dm=[[alpha emission|α]] | de=2.495 | pn=170 | ps=[[ytterbium|Yb]] }}
| |
− | {{Elementbox_isotopes_stable | mn=176 | sym=Hf | na=5.206% | n=104 }}
| |
− | {{Elementbox_isotopes_stable | mn=177 | sym=Hf | na=18.606% | n=105 }}
| |
− | {{Elementbox_isotopes_stable | mn=178 | sym=Hf | na=27.297% | n=106 }}
| |
− | {{Elementbox_isotopes_decay | mn=178[[Nuclear isomer|m2]] | sym=Hf
| |
− | | na=[[synthetic radioisotope|syn]] | hl=31 [[year|y]]
| |
− | | dm=[[Gamma ray|IT]] | de=2.446 | pn=178 | ps=[[Hafnium|Hf]] }}
| |
− | {{Elementbox_isotopes_stable | mn=179 | sym=Hf | na=13.629% | n=107 }}
| |
− | {{Elementbox_isotopes_stable | mn=180 | sym=Hf | na=35.1% | n=108 }}
| |
− | {{Elementbox_isotopes_decay | mn=182 | sym=Hf
| |
− | | na=[[synthetic radioisotope|syn]] | hl=9×10<sup>6</sup> [[year|y]]
| |
− | | dm=[[beta emission|β]] | de=0.373 | pn=182 | ps=[[tantalum|Ta]] }}
| |
− | {{Elementbox_isotopes_end}}
| |
− | {{Elementbox_footer | color1=#ffc0c0 | color2=black }}
| |
− |
| |
− | '''Hafnium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/ˈhæfniəm/}}) is a [[chemical element]] in the [[periodic table]] that has the symbol '''Hf''' and [[atomic number]] 72. A lustrous, silvery gray tetravalent [[transition metal]], hafnium resembles [[zirconium]] chemically and is found in zirconium [[mineral]]s. Hafnium is used in [[tungsten]] [[alloy]]s in filaments and [[electrode]]s and also acts as a [[neutron]] absorber in [[control rod]]s in [[nuclear power plant]]s.
| |
− |
| |
− | == Notable characteristics ==
| |
− | [[Image:HafniumMetalUSGOV.jpg|thumb|left|Hafnium metal]]
| |
− | Hafnium is a shiny silvery, ductile [[metal]] that is [[corrosion]] resistant and chemically similar to [[zirconium]]. The properties of hafnium are markedly affected by zirconium impurities and these two elements are amongst the most difficult to separate. The only notable difference between them is their density (zirconium is about half as dense as hafnium).
| |
− |
| |
− | [[Hafnium carbide]] is the most [[Refraction (metallurgy)|refractory]] [[binary compound]] known and [[hafnium nitride]] is the most refractory of all known metal nitrides with a [[melting point]] of 3310 [[Celsius|°C]]. This metal is resistant to concentrated [[alkali]]s, but [[halogen]]s react with it to form hafnium tetrahalides. At higher temperatures hafnium reacts with [[oxygen]], [[nitrogen]], [[carbon]], [[boron]], [[sulfur]], and [[silicon]].
| |
− | The [[nuclear isomer]] Hf-178-m2 is also a source of cascades of [[gamma rays]] whose energies total to 2.45 [[Electronvolt|MeV]] per decay. It is notable because it has the highest excitation energy of any comparably long-lived isomer of any element. One gram of pure Hf-178-m2 would contain approximately 1330 megajoules of energy, the equivalent of exploding about 317 kilograms (700 pounds) of [[Trinitrotoluene|TNT]]. Possible applications requiring such highly concentrated energy storage are of interest. For example, it has been studied as a possible power source for gamma ray [[laser]]s.
| |
− |
| |
− | ==Applications==
| |
− | Hafnium is used to make control rods for [[nuclear reactor]]s because of its ability to absorb [[neutron]]s (its thermal neutron absorption cross section is nearly 600 times that of zirconium), excellent mechanical properties and exceptional corrosion-resistance properties.
| |
− |
| |
− | Other uses:
| |
− |
| |
− | *In gas-filled and [[incandescent lamp]]s, for scavenging oxygen and nitrogen,
| |
− | *As the electrode in [[plasma cutting]] because of its ability to shed electrons into air,
| |
− | *and in [[iron]], [[titanium]], [[niobium]], [[tantalum]], and other metal [[alloy]]s.
| |
− | *[[Hafnium dioxide]] is a candidate for [[High-K]] gate insulators in future generations of [[integrated circuits]].
| |
− | *[[DARPA]] has been intermittently funding programs in the US to determine the possibility of using a [[nuclear isomer]] of hafnium (the above mentioned Hf-178-m2) to construct small, high yield weapons with simple x-ray triggering mechanisms—an application of ''[[induced gamma emission]]''. That work follows over two decades of basic research by an international community <ref>[http://www.utdallas.edu/research/quantum/isomer/03IsomerHistory_files/frame.htm Historical reference]</ref> into the means for releasing the stored energy upon demand. There is considerable opposition to this program, both because the idea may not work<ref>[http://www.aip.org/pt/vol-57/iss-5/p21.html Review of the underlying physics in 1994 Physics Today article]</ref> and because uninvolved countries might perceive an imagined "isomer weapon gap" that would justify their further development and stockpiling of conventional nuclear weapons. A related proposal is to use the same isomer to power [[Unmanned Aerial Vehicles]],<ref>http://www.informationclearinghouse.info/article1534.htm</ref> which could remain airborne for weeks at a time.
| |
− |
| |
− | == History ==
| |
− | [[Image:Sigilum Facultatis Naturalis.JPG|left|thumb|150px|The hafnium seal of the [[University of Copenhagen Faculty of Science|Faculty of Science of the University of Copenhagen]]]]
| |
− | Hafnium ([[Latin]] ''Hafnia'' for "[[Copenhagen]]", the home town of [[Niels Bohr]]) was discovered by [[Dirk Coster]] and [[Georg von Hevesy]] in [[1923]] in Copenhagen, [[Denmark]]. Soon after, the new element was predicted to be associated with [[zirconium]] by using the Bohr theory and was finally found in zircon through [[X-ray]] [[spectroscope]] analysis in [[Norway]].
| |
− |
| |
− | It was separated from zirconium through repeated recrystallization of double [[ammonium]] or [[potassium]] fluorides by Jantzen and von Hevesey. Metallic hafnium was first prepared by [[Anton Eduard van Arkel]] and [[Jan Hendrik de Boer]] by passing tetraiodide vapor over a heated [[tungsten]] filament.
| |
− |
| |
− | The [[University of Copenhagen Faculty of Science|Faculty of Science]] of the [[University of Copenhagen]] uses in its [[Seal (device)|seal]] a stylized image of hafnium.
| |
− |
| |
− | == Occurrence ==
| |
− | Hafnium is found combined in natural [[zirconium]] compounds but it does not exist as a free element in nature. [[Mineral]]s that contain zirconium, such as alvite [(Hf, [[thorium|Th]], [[zirconium|Zr]])[[silicon|Si]][[oxygen|O]]<sub>4</sub> [[water|H<sub>2</sub>O]], [[thortveitite]] and [[zircon]] (ZrSiO<sub>4</sub>), usually contain between 1 and 5% hafnium. Hafnium and zirconium have nearly identical chemistry, which makes the two difficult to separate. About half of all hafnium metal manufactured is produced by a by-product of zirconium refinement. This is done through reducing [[hafnium(IV) chloride]] with [[magnesium]] or [[sodium]] in the [[Kroll process]].
| |
− |
| |
− | == Precautions ==
| |
− | Care needs to be taken when machining hafnium because when it is divided into fine particles, it is [[pyrophoric]] and can ignite spontaneously in air. Compounds that contain this metal are rarely encountered by most people and the pure metal is not normally toxic but all its compounds should be handled as if they are toxic (although there appears to be limited danger to exposed individuals).
| |
− |
| |
− | ==See also==
| |
− | * [[:Category:Hafnium compounds|Hafnium compounds]].''
| |
− | * [[:Nuclear isomer|Nuclear isomer]].''
| |
− | * [[Induced gamma emission]]
| |
− |
| |
− | ==References==
| |
− | <references/>
| |
− | *[http://periodic.lanl.gov/elements/72.html Los Alamos National Laboratory - Hafnium]
| |
− | *van Arkel, A.E., and de Boer, J.H., 1925, Preparation of pure titanium, zirconium, hafnium, and thorium metal: Zeitschrift für Anorganische und Allgemeine Chemie, v. 148, p. 345-350.
| |
− |
| |
− | == External links ==
| |
− | *[http://www.webelements.com/webelements/elements/text/Hf/index.html WebElements.com - Hafnium]
| |
− | {{Commons|Hafnium}}
| |
− | {{wiktionary|hafnium}}
| |
− |
| |
− | [[Category:Chemical elements]]
| |
− | [[Category:Transition metals]]
| |
− |
| |
− | <!-- interwiki —>
| |
− |
| |
− | [[bs:Hafnijum]]
| |
− | [[ca:Hafni]]
| |
− | [[cs:Hafnium]]
| |
− | [[co:Afniu]]
| |
− | [[da:Hafnium]]
| |
− | [[de:Hafnium]]
| |
− | [[et:Hafnium]]
| |
− | [[es:Hafnio]]
| |
− | [[eo:Hafnio]]
| |
− | [[fr:Hafnium]]
| |
− | [[ko:하프늄]]
| |
− | [[hr:Hafnij]]
| |
− | [[io:Hafnio]]
| |
− | [[id:Hafnium]]
| |
− | [[is:Hafnín]]
| |
− | [[it:Afnio]]
| |
− | [[he:הפניום]]
| |
− | [[ku:Hafniyûm]]
| |
− | [[la:Hafnium]]
| |
− | [[lv:Hafnijs]]
| |
− | [[lb:Hafnium]]
| |
− | [[lt:Hafnis]]
| |
− | [[hu:Hafnium]]
| |
− | [[nl:Hafnium]]
| |
− | [[ja:ハフニウム]]
| |
− | [[no:Hafnium]]
| |
− | [[nn:Hafnium]]
| |
− | [[pl:Hafn]]
| |
− | [[pt:Háfnio]]
| |
− | [[ru:Гафний]]
| |
− | [[simple:Hafnium]]
| |
− | [[sl:Hafnij]]
| |
− | [[sr:Хафнијум]]
| |
− | [[sh:Hafnijum]]
| |
− | [[fi:Hafnium]]
| |
− | [[sv:Hafnium]]
| |
− | [[th:แฮฟเนียม]]
| |
− | [[uk:Гафній]]
| |
− | [[zh:铪]]
| |
− |
| |
| {{Elementbox_meltingpoint | k=2506 | c=2233 | f=4051 }} | | {{Elementbox_meltingpoint | k=2506 | c=2233 | f=4051 }} |
| {{Elementbox_boilingpoint | k=4876 | c=4603 | f=8317 }} | | {{Elementbox_boilingpoint | k=4876 | c=4603 | f=8317 }} |