Uranium carbides

Uranium carbides are chemical compounds between uranium and carbon , of which three compounds are known: UC ₂ , U ₂ C ₃ and UC.

properties

Uranium carbides
Surname	Uranium dicarbide	Diurantricarbide	Uranium monocarbide
other names	Uranium acetylide	Uranium sesquicarbide	Uranium (IV) carbide
Molecular formula	UC 2	U 2 C 3	UC
CAS number	12071-33-9	12076-62-9	12070-09-6
PubChem	518487		166603
Molar mass	262.05 g mol −1	512.09 g mol −1	250.04 g mol −1
Physical state	firmly	firmly	firmly
Brief description	light gray solid	black solid	gray-black solid
Melting point	2375 ° C	~ 1700 ° C (decomposition)	~ 2400 ° C
boiling point	4370 ° C
density	11.68 g cm −3	12.7 g cm −3	13.6 g cm −3
GHS labeling	danger
H and P phrases	330-300-373-411
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Although uranium carbides still have a metallic character, their properties differ markedly from the carbides of IV., V and VI. Subgroup. Their hardness is significantly lower, they are pyrophoric and are easily hydrolyzed by water or weak acids.

Uranium dicarbide is in the form of a light gray, metallic luster crystalline mass. It has a tetragonal crystal structure with the space group I 4 / mmm (space group no. 139) and the lattice parameters a = 352.7 pm and c = 600.2 pm. This form exists from room temperature to 1800 ° C. It changes into a cubic form (a = 548.8 pm) above 1800 ° C.

Diurantricarbide is a black, shiny metal solid with a cubic crystal structure and the space group  I 4 3 d (No. 220) and the lattice parameter a = 808.8 pm.

Uranium monocarbide is in the form of a gray-black, crystalline mass with shiny metallic surfaces. This has a crystal structure of the sodium chloride type with a homogeneity area (a = 495.9 to 496.1 pm). The compound reacts with oxygen and molten beryllium , nickel , zirconium and silicon .

presentation

Uranium dicarbide can be obtained by reacting uranium (IV) oxide or uranium (V, VI) oxide with graphite in a vacuum at 2400 ° C. To produce ceramic moldings (e.g. reactor pellets), the starting materials are pressed and sintered at 2250 ° C. The stoichiometric composition is usually not quite achieved in the syntheses. Preparations with the composition UC _1.85 to UC _{1.9 are} normally obtained .

${\displaystyle {\ce {UO2 + 4 C -> UC2 + 2 CO}}}$

${\displaystyle {\ce {U3O8 + 14 C -> 3 UC2 + 8 CO}}}$

The reaction of a stoichiometric mixture of uranium and carbon at 2400 ° C only gives a reaction product with the composition UC _1.85 to UC _1.94 .

${\displaystyle {\ce {U + 2 C -> UC2}}}$

Diurantricarbide can be obtained by reacting a stoichiometric mixture of uranium (IV) oxide or uranium and carbon at 2400 ° C.

${\displaystyle {\ce {2 UO2 + 7 C -> U2C3 + 4 CO}}}$

${\displaystyle {\ce {2 U + 3 C -> U2C3}}}$

It is also possible to display it by reacting uranium monocarbide with uranium dicarbide.

${\displaystyle {\ce {UC + UC2 -> U2C3}}}$

Uranium monocarbide can be obtained by reacting a stoichiometric mixture of uranium and graphite.

${\displaystyle {\ce {U + C -> UC}}}$

It is also possible to show this by reacting uranium with methane at 625 ° C to 900 ° C.

${\displaystyle {\ce {U + CH4 -> UC + 2 H2}}}$

During production, it should be noted that uranium carbides are often contaminated with oxygen, resulting in uranium oxide carbide mixed crystals UC _{1 − x} O _x .

use

Uranium carbides are used in high temperature and breeder reactors. Uranium monocarbide was used as reactor fuel in the Hallam Nuclear Power Plant and uranium dicarbide in Unit 1 of the Peach Bottom Nuclear Power Plant . They were also tested as fuels for nuclear spacecraft propulsion in the 1960s. The use of mixed compounds with niobium carbide , tantalum carbide , zirconium carbide and others for nuclear reactors is also being investigated. For example, a mixture of uranium dicarbide and thorium dicarbide can be used as fuel in the THTR-300 nuclear power plant .

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n o} Georg Brauer (Hrsg.): Handbook of Preparative Inorganic Chemistry . 3., reworked. Edition. tape II . Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1240 .
2. ^ ^{A b} William M. Haynes: CRC Handbook of Chemistry and Physics, 93rd Edition . CRC Press, 2012, p. 97 ( limited preview in Google Book search).
3. ^ Dale L. Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2011, pp. 488 ( limited preview in Google Book search).
4. ↑ Entry on uranium compounds in the GESTIS substance database of the IFA , accessed on July 17, 2014(JavaScript required) .
5. ↑ ^{a b} Martin Bertau, Armin Müller, Peter Fröhlich, Michael Katzberg, Karl Heinz Büchel, Hans-Heinrich Moretto, Dietmar Werner: Industrial Inorganic Chemistry - Martin Bertau, Armin Müller, Peter Fröhlich, Michael Katzberg, Karl Heinz Büchel, Hans-Heinrich Moretto, Dietmar Werner . John Wiley & Sons, 2013, ISBN 978-3-527-64959-4 , pp. 616 ( limited preview in Google Book search).
6. ↑ Werner Martienssen, Hans Warlimont: Springer Handbook of Condensed Matter and Materials Data . Springer Science & Business Media, 2006, p. 464 ( limited preview in Google Book search).
7. ↑ Dr. BK Sharma: Nuclear and Radiation Chemistry . GOEL Publishing, 2001, ISBN 81-85842-63-9 , pp. 165 ( limited preview in Google Book search).
8. ↑ Dissertation Rocky-Pitua Sutanto: The behavior of uranium carbides and uranium oxicarbides in repository-relevant aquatic phases
9. ↑ United States. Office of Saline Water: Proceedings . US Dept. of the Interior, Office of Saline Water; for sale by the Supt. of Docs., US Govt. Print. Off., 1965, p. 91 ( limited preview in Google Book search).
10. ↑ LM Ferris; MJ Bradley; US Atomic Energy Commission .; Oak Ridge National Laboratory; 1964. Off-gases from the reactions of uranium carbides with nitric acid at 90 ° C ( Memento of the original from July 26, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed July 19, 2014. 
11. ↑ bernd-leitenberger.de: Nukleare Antriebe , accessed on July 19, 2014.
12. ↑ FP7829.PDF: Ternary Carbide Uranium Fuels for Advanced Reactor Design Applications - FP7829.PDF ( Memento of the original from July 29, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , April 1999, accessed July 19, 2014. 
13. ↑ Manfred Grathwohl: Energy supply: resources, technologies, perspectives . Walter de Gruyter, 1983, p. 206 ( limited preview in Google Book search).