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| verifiedrevid = 377946909 |
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| Name = Uranium nitride<ref>{{cite journal |
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| title = Fabrication and testing of uranium nitride fuel for space power reactors |
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| Name = Uranium nitride<ref>{{cite journal |
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| title=Fabrication and testing of uranium nitride fuel for space power reactors |
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| author = R. B. Matthews, K. M. Chidester, C. W. Hoth, R. E. Mason, R. L. Petty |
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|author1=R. B. Matthews |author2=K. M. Chidester |author3=C. W. Hoth |author4=R. E. Mason |author5=R. L. Petty |journal=Journal of Nuclear Materials |volume=151 |issue=3 |year=1988 |
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| page=345 |doi=10.1016/0022-3115(88)90029-3|bibcode=1988JNuM..151..345M }}</ref> |
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| journal = Journal of Nuclear Materials | volume = 151 | issue = 3| year = 1988 |
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| IUPACName = Uranium nitride |
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| pages = 345| doi = 10.1016/0022-3115(88)90029-3}}</ref> |
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| ImageFile = La2O3structure.jpg |
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| IUPACName = Uranium nitride |
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|Section1={{Chembox Identifiers |
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| ImageFile=La2O3structure.jpg |
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| PubChem = 117595 |
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| Section1 = {{Chembox Identifiers |
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| index_label = UN |
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| CASNo = 12033-83-9 |
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| index1_label = UN<sub>2</sub> |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 25658-43-9 |
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| CASNo1 = 12033-83-9 |
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| ChemSpiderID = 105089 |
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| StdInChI=1S/N.U |
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| StdInChIKey = MVXWAZXVYXTENN-UHFFFAOYSA-N |
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| SMILES = U#N |
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| SMILES1 = N##N |
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| SMILES2 = N#=N(#N) |
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| SMILES2_Comment = U<sub>2</sub>N<sub>3</sub> |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = U<sub>2</sub>N<sub>3</sub> |
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| Formula = U<sub>2</sub>N<sub>3</sub> |
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| MolarMass = 518.078 g/mol |
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| MolarMass = 518.078 g/mol |
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| Appearance = crystalline solid |
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| Appearance = crystalline solid |
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| Density = 11300 kg m-3, Solid |
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| Density = 11300 kg·m<sup>−3</sup>, solid |
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| Solubility = 0.08 g/100 ml (20 °C) |
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| Solubility = 0.08 g/100 ml (20 °C) |
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| MeltingPt = 900°C (decomposes to UN) |
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| MeltingPtC = 900 to 1100 |
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| MeltingPt_notes = (decomposes to UN) |
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| BoilingPt = Decomposes |
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| BoilingPt = Decomposes |
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| Section3 = {{Chembox Structure |
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|Section3={{Chembox Structure |
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| CrystalStruct = Hexagonal, ] |
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| CrystalStruct = Hexagonal, ] |
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| SpaceGroup = P-3m1, No. 164 |
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| SpaceGroup = P-3m1, No. 164 |
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'''Uranium nitride''' refers to a family of several ceramic compounds: uranium mononitride (UN), uranium sesquinitride (U<sub>2</sub>N<sub>3</sub>), which exists in either an alpha or beta phase, and uranium dinitride (UN<sub>2</sub>). |
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'''Uranium nitrides''' is any of a family of several ] materials: ] mononitride (UN), uranium sesquinitride (U<sub>2</sub>N<sub>3</sub>) and uranium dinitride (UN<sub>2</sub>). The word ] refers to the −3 ] of the nitrogen bound to the ]. |
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Uranium nitride has been considered as a potential ] and will be used as such in the ] nuclear reactor currently under construction in Russia. It is said to be safer, stronger, denser, more thermally conductive and having a higher temperature tolerance. Challenges to implementation of the fuel include a complex conversion route from enriched UF<sub>6</sub>, the need to prevent oxidation during manufacturing and the need to define and license a final disposal route. The necessity to use expensive, highly isotopically enriched ] is a significant factor to overcome. This is necessary due to the (relatively) high neutron capture cross-section of the far-more-common <sup>14</sup>N, which affects the neutron economy of a reactor.<ref name="Chaudri2013">{{cite journal |last1=Chaudri |first1=Khurrum Saleem |title=Coupled analysis for new fuel design using UN and UC for SCWR |journal=Progress in Nuclear Energy |volume=63 |year=2013 |pages=57–65 |doi=10.1016/j.pnucene.2012.11.001}}</ref> |
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Uranium mononitride is used as ] in some ]s, because it has some properties similar to ] or ]. The property which makes uranium mononitride highly attractive as a nuclear fuel is its thermal conductivity, which is on the order of 4-8 times higher than that of uranium dioxide, the most commonly used nuclear fuel, at typical operating temperatures. Increased thermal conductivity results in lower thermal gradients between inner and outer sections of the fuel, potentially allowing for higher operating temperatures and reducing macroscopic restructuring of the fuel, which limits fuel lifetime. |
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==Synthesis== |
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Uranium nitride can be synthesized by the reaction of ] with ] at 700 K.<ref>Cotton, Simon (1991) Lanthanides and Actinides. New York: Oxford University Press, p. 126</ref> Uranium nitride may be formed as a minor product of uranium combustion in air; however, the more thermodynamically stable uranium dioxide will be the major product. |
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===Carbothermic reduction=== |
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According to an article in "Nuclear Engineering International", uranium nitride (enriched to less than 20% U-235) is the fuel chosen by ] to fuel their recently revised Hyperion Power Module.<ref name="HyperionUraniumNitride">{{cite news|url=http://www.neimagazine.com/story.asp?sectionCode=132&storyCode=2054804|title=Hyperion launches U2N3-fuelled, Pb-Bi-cooled fast reactor|last=Staff|date=2009-11-20|work=Nuclear Engineering International|publisher=Global Trade Media, a division of Progressive Media Group Ltd.|language=English|accessdate=29 November 2009}}</ref> This article, however, incorrectly states that uranium sesquinitride will be used, rather than uranium mononitride. The correct information is available at http://www.nrc.gov/reactors/advanced/hyperion.html |
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The common technique for generating UN is ] of ] (UO<sub>2</sub>) in a 2 step method illustrated below.<ref name="MinatoAkabori2003">{{cite journal |last1=Minato |first1=Kazuo |last2=Akabori |first2=Mitsuo |last3=Takano |first3=Masahide |last4=Arai |first4=Yasuo |last5=Nakajima |first5=Kunihisa |last6=Itoh |first6=Akinori |last7=Ogawa |first7=Toru |title=Fabrication of nitride fuels for transmutation of minor actinides |journal=Journal of Nuclear Materials |volume=320 |issue=1–2 |year=2003 |pages=18–24 |issn=0022-3115 |doi=10.1016/S0022-3115(03)00163-6|bibcode=2003JNuM..320...18M }}</ref><ref name="Carmack2004">{{cite journal |last1=Carmack |first1=W. J. |title=Internal Gelation as Applied to the Production of Uranium Nitride Space Nuclear Fuel |journal=AIP Conference Proceedings |volume=699 |year=2004 |pages=420–425 |issn=0094-243X |doi=10.1063/1.1649601|bibcode=2004AIPC..699..420C }}</ref> |
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:3UO<sub>2</sub> + 6C → 2UC + UO<sub>2</sub> + 4CO (in argon, > 1450 °C for 10 to 20 hours) |
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==References== |
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:4UC + 2UO<sub>2</sub> +3N<sub>2</sub> → 6UN + 4CO |
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{{reflist}} |
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===Sol-gel=== |
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] |
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] methods and arc melting of pure ] under ] can also be used.<ref name="Ganguly">Ganguly, C.; Hegde, P. ''J. Sol-Gel Sci. Technol.''. '''1997''', 9, 285.</ref> |
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] |
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===Ammonolysis=== |
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Another common technique for generating UN<sub>2</sub> is the ] of ]. Uranium tetrafluoride is exposed to ] gas under high pressure and temperature, which replaces the ] with nitrogen and generates ].<ref name=autogenerated2>Silva, G. W. C.; Yeamans, C. B.; Ma, L.; Cerefice, G. S.; Czerwinski, K. R.; Sarrelberger, A. P. Chem. Mater.''. '''2008''', 20, 3076.</ref> Hydrogen fluoride is a colourless gas at this temperature and mixes with the ammonia gas. |
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===Hydriding-nitriding=== |
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{{inorganic-compound-stub}} |
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An additional method of UN synthesis employs fabrication directly from metallic uranium. By exposing metallic uranium to hydrogen gas at temperatures in excess of 280 °C, UH<sub>3</sub> can be formed.<ref></ref> Furthermore, since UH<sub>3</sub> has a higher specific volume than the metallic phase, hydridation can be used to physically decompose otherwise solid uranium. Following hydridation, UH<sub>3</sub> can be exposed to a nitrogen atmosphere at temperatures around 500 °C, thereby forming U<sub>2</sub>N<sub>3</sub>. By additional heating to temperatures above 1150 °C, the sesquinitride can then be decomposed to UN. |
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:2U + 3H<sub>2</sub> → 2UH<sub>3</sub> |
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] |
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:2UH<sub>3</sub> + 1.5N<sub>2</sub> → U<sub>2</sub>N<sub>3</sub> |
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] |
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:U<sub>2</sub>N<sub>3</sub> → UN + 0.5N<sub>2</sub> |
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] |
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Use of the ] ] (which constitutes around 0.37% of natural nitrogen) is preferable because the predominant isotope, <sup>14</sup>N, has a significant ] ] which affects neutron economy and, in particular, it undergoes an (n,p) reaction which produces significant amounts of radioactive ] which would need to be carefully contained and sequestered during reprocessing or permanent storage.<ref name="Matthews">Matthews, R. B.; Chidester, K. M.; Hoth, C. W.; Mason, R. E.; Petty, R. L. ''Journal of Nuclear Materials''. '''1988'', 151(3), 345.</ref> |
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==Decomposition== |
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Each uranium dinitride complex is considered to have three distinct compounds present simultaneously because of decomposing of uranium dinitride (UN<sub>2</sub>) into uranium sesquinitride (U<sub>2</sub>N<sub>3</sub>), and then uranium mononitride (UN). Uranium dinitrides decompose to uranium mononitride by the following sequence of reactions:<ref name="SilvaYeamans2009">{{cite journal |last1=Silva |first1=G. W. Chinthaka |last2=Yeamans |first2=Charles B. |last3=Sattelberger |first3=Alfred P. |last4=Hartmann |first4=Thomas |last5=Cerefice |first5=Gary S. |last6=Czerwinski |first6=Kenneth R. |title=Reaction Sequence and Kinetics of Uranium Nitride Decomposition |journal=Inorganic Chemistry |volume=48 |issue=22 |year=2009 |pages=10635–10642 |issn=0020-1669 |doi=10.1021/ic901165j|pmid=19845318 }}</ref> |
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: 4UN<sub>2</sub> → 2U<sub>2</sub>N<sub>3</sub>+ N<sub>2</sub> |
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: 2U<sub>2</sub>N<sub>3</sub> → 4UN +N<sub>2</sub> |
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Decomposition of UN<sub>2</sub> is the most common method for isolating uranium sesquinitride (U<sub>2</sub>N<sub>3</sub>). |
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==Uses== |
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Uranium mononitride is being considered as a potential fuel for ] such as the ] reactor created by ].<ref name="HyperionUraniumNitride">{{cite news |url=https://www.neimagazine.com/news/newshyperion-launches-u2n3-fuelled-pb-bi-cooled-fast-reactor |title=Hyperion launches U2N3-fuelled, Pb-Bi-cooled fast reactor |last=Staff |date=2009-11-20 |work=Nuclear Engineering International |publisher=Global Trade Media, a division of Progressive Media Group Ltd.}}</ref> It has also been proposed as ] in some ] nuclear test reactors. UN is considered superior because of its higher fissionable density, ], and ] than the most common nuclear fuel, ] (UO<sub>2</sub>), while also demonstrating lower release of fission product gases and swelling, and decreased chemical reactivity with cladding materials.<ref>{{cite journal|title=Simple method for producing a stable form of uranium nitride|journal=Advanced Ceramics Report|date=August 1, 2012|publisher=International Newsletters|quote=esearcher ... ], says: '... it could help... extract and separate the 2-3% of the highly radioactive material in nuclear waste.'}}</ref> It also has a superior mechanical, thermal, and radiation stability compared to standard ]lic uranium fuel.<ref name="SilvaYeamans2009" /><ref name="Mizutani">Mizutani, A.; Sekimoto, H. ''Ann. Nucl. Energy''. '''2005''', 25(9), 623–638.</ref> The thermal conductivity is on the order of 4–8 times higher than that of uranium dioxide, the most commonly used nuclear fuel, at typical operating temperatures. Increased thermal conductivity results in a smaller ] between inner and outer sections of the fuel,<ref name="Matthews" /> potentially allowing for higher operating temperatures and reducing ] restructuring of the fuel, which limits fuel lifetime.<ref name="Carmack2004" /> |
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==Molecular and crystal structure== |
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The uranium dinitride (UN<sub>2</sub>) compound has a ] ] of the ] (CaF<sub>2</sub>) type with a ] of Fm{{overline|3}}m.<ref name="Rundle">Rundle, R. E.; Baenziger, N. C.; Wilson, A. S.; McDonald, R. A. ''J. Am. Chem Soc.''. '''1948''', 70, 99.</ref> |
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Nitrogen forms ]s on each side of uranium forming a ].<ref name="Weck">Weck P. F., Kim E., Balakrishnan N., Poineau F., Yeamans C. B., and Czerwinski K. R. ''Chem. Phys. Lett.''. '''2007''', 443, 82. |
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{{doi|10.1016/j.cplett.2007.06.047}}</ref><ref name="Wang">Wang, X.; Andrews, L.; Vlaisavljevich, B.; Gagliardi, L. ''Inorganic Chemistry''. '''2011''', 50(8), 3826–3831. doi:10.1021/ic2003244</ref> |
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α-(U<sub>2</sub>N<sub>3</sub>) has a ] ] of the (Mn<sub>2</sub>O<sub>3</sub>) type with a ] of Ia{{overline|3}} .<ref name="Rundle" /> |
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UN has a ] ] of the ] type.<ref name="Weck"/><ref name="Mueller">Mueller, M. H.; Knott, H. W.''Acta Crystallogr.''. '''1958''', 11, 751–752. doi:10.1107/S0365110X58002061</ref> |
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The ] component of the bond uses the 5] of the uranium but forms a relatively weak interaction but is important for the ]. The ] portion of the bonds forms from the overlap between the 6] and 7] on the uranium and the 2] on the nitrogen.<ref name="Weck"/><ref name="Évarestov ">Évarestov, R. A., Panin, A. I., & Losev, M. V. ''Journal of Structural Chemistry''. '''2008''', 48, 125–135.</ref> N forms a ] with uranium creating a linear structure.<ref name="Wang" /> |
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{{clear}} |
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<gallery class="center"> |
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Image:Fluorite-unit-cell-3D-ionic.png|Uranium dinitride |
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Image:Tl2O3structure.jpg|Uranium sesquinitride |
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Image:Sodium-chloride-3D-ionic.png|Uranium mononitride |
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</gallery> |
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==Uranium nitrido derivatives== |
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Recently, there have been many developments in the synthesis of complexes with terminal uranium nitride (–U≡N) bonds. In addition to radioactive concerns common to all uranium chemistry, production of uranium nitrido complexes has been slowed by harsh reaction conditions and solubility challenges. Nonetheless, syntheses of such complexes have been reported in the past few years, for example the three shown below among others.<ref>Nocton, G.; Pécaut, J.; Mazzanti, M. A Nitrido-Centered Uranium Azido Cluster Obtained from a Uranium |
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Azide. ''Angew. Chem. Int. Ed.'' '''2008,''' ''47'' (16), 3040–3042. {{doi|10.1002/anie.200705742}}</ref><ref>Thomson, R. K.; Cantat, T.; Scott, B. L.; Morris, D. E.; Batista, E. R.; Kiplinger, J. L. Uranium azide photolysis results in C–H bond activation and provides evidence for a terminal uranium nitride. ''Nature Chemistry'' '''2010,''' ''2'', 723–729. {{doi|10.1038/nchem.705}}</ref> Other U≡N compounds have also been synthesized or observed with various structural features, such as bridging nitride ligands in di-/polynuclear species, and various oxidation states.<ref>Fox, A. R.; Arnold, P. L.; Cummins, C. C. Uranium−Nitrogen Multiple Bonding: Isostructural Anionic, Neutral, and Cationic Uranium Nitride Complexes Featuring a Linear U═N═U Core. ''J. Am. Chem. Soc.'' '''2010,''' ''132'' (10), 3250–3251. {{doi|10.1021/ja910364u}}</ref><ref>Evans, W. J.; Kozimor, S. A.; Ziller, J. W. Molecular Octa-Uranium Rings with Alternating Nitride and Azide Bridges. ''Science'' '''2005,''' ''309'' (5742), 1835–1838. {{doi|10.1126/science.1116452}}</ref> |
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{| |
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| <ref>Fox, A.; Cummins, C. Uranium−Nitrogen Multiple Bonding: The Case of a Four-Coordinate Uranium(VI) Nitridoborate Complex. ''J. Am. Chem. Soc.'', '''2009,''' ''131'' (16), 5716–5717. {{doi|10.1021/ja8095812}}</ref>]] |
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| <ref>King, D.; Tuna, F.; McInnes, E.; McMaster, J.; Lewis, W.; Blake, A.; Liddle, S. T. Synthesis and Structure of a Terminal Uranium Nitride Complex. ''Science'' '''2012,''' ''337'' (6095)'','' 717–720. {{doi|10.1126/science.1223488}}</ref>]] |
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==See also== |
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* ] |
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* ] |
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* ] |
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* ] |
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* ] |
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==References== |
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{{Reflist}} |
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==External links== |
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* at '']'' (University of Nottingham) |
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* (Los Alamos National Laboratory) |
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{{Uranium compounds}} |
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{{Nitrides}} |
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] |
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] |