Uranium nitride

Uranium nitrides are chemical compounds of uranium from the group of nitrides . In addition to the mononitride UN, two other uranium nitrides are known: the sesquinitride U ₂ N ₃ and the non-stoichiometric UN _x with x between 2.0 and 1.75 (usually referred to as urine nitride UN ₂ ).

presentation

Uranium mononitride can be obtained by reacting uranium with nitrogen, for example in an electric arc at 20 bar pressure. Uranium nitride can be obtained by ammonolysis of uranium (IV) fluoride , sesquinitride by thermal decomposition of uranium nitride at 700 ° C in a high-purity argon atmosphere .

properties

Uranium nitride
Surname	Uranium mononitride	Uranium sesquinitride
CAS number	25658-43-9	12033-83-9	12266-20-5
PubChem	117595
Molecular formula	U.N.	U 2 N 3	UN 2
Molar mass	252.04 g mol −1	518.08 g mol −1	266.04 g mol −1
Physical state	firmly
Brief description	dark gray solid
Melting point	2805 ° C	decomposition
density	14.3 g cm −3	11.3 g cm −3
solubility	insoluble in water
radioactivity	Radioactive

Uraninitrides are dark gray to gray, powdery substances that look metallic gray when compact. The higher nitrides decompose to uranium mononitride when heated, with the decomposition of uranium nitride starting at 675 ° C and uranium mononitride also being formed from 975 ° C.

${\displaystyle \mathrm {4\ UN_{2}\longrightarrow 2\ U_{2}N_{3}+N_{2}} }$

${\displaystyle \mathrm {2\ U_{2}N_{3}\longrightarrow 4\ UN+N_{2}} }$

Uranium nitride and uranium sesquinitride form solid solutions with variable mixing ratios, which are described in some sources as U ₃ N ₂ . Uranium mononitride has a face-centered cubic crystal structure of the sodium chloride type (a = 488.9 pm). Uranium nitride has a cubic crystal structure of the calcium fluoride type with the space group Fm 3 m (space group no. 225) , the α-form of sesquinitride has a cubic crystal structure of the manganese (III) oxide type with the space group  Ia 3 (no. 206 ) .

Individual evidence

1. ↑ ^{a b c d} Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1234.
2. ↑ ^{a b c d} G. W. Chinthaka Silva, Charles B. Yeamans, Alfred P. Sattelberger, Thomas Hartmann, Gary S. Cerefice, Kenneth R. Czerwinski: Reaction Sequence and Kinetics of Uranium Nitride Decomposition. In: Inorganic Chemistry. 48, 2009, pp. 10635-10642, doi : 10.1021 / ic901165j .
3. ↑ ^{a b c d e} William M. Haynes: CRC Handbook of Chemistry and Physics, 95th Edition . CRC Press, 2014, pp. 97 ( limited preview in Google Book search).