Uranium dicarbide

Crystal structure
U 2+ : __   / C 2 2− : __
General
Surname	Uranium dicarbide
other names	Uranium acetylide
Ratio formula	UC 2
Brief description	light gray solid
External identifiers / databases
CAS number 12071-33-9 PubChem 518487 Wikidata Q77351048
properties
Molar mass	262.05 g mol −1
Physical state	firmly
density	11.68 g cm −3
Melting point	2375 ± 25 ° C
boiling point	4370 ° C
Hazard and safety information
Radioactive
GHS labeling of hazardous substances danger H and P phrases H: 330-300-373-411 P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Urandicarbide is a chemical compound from the group of uranium carbides .

Extraction and presentation

Uranium dicarbide can be obtained by reacting the purest uranium (IV) oxide or uranium (V, VI) oxide with the purest graphite in a vacuum at temperatures between 1800 ° C and 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 . The stoichiometry UC ₂ is not achieved.

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

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 .

properties

Uranium dicarbide is in the form of a light gray, metallic luster crystalline mass. At temperatures below 1600 ° C, it gradually breaks down into uranium monocarbide and carbon. Urandicarbide reacts with hot water to form hydrogen , methane , higher paraffinic hydrocarbons and traces of ethyne , carbon monoxide and carbon dioxide . However, the reaction also takes place at room temperature. Similar reactions can also be observed when reacting with hydrochloric and sulfuric acid . No hydrocarbon compounds are formed when reacting with nitric acid . Instead, much of the carbon is converted into carbon dioxide. Urandicarbide is sparingly soluble in ethanol . In air or oxygen, the compound ignites at around 400 ° C. From 1100 ° C it reacts with nitrogen . Urandicarbide 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. Above 1800 ° C it changes into a cubic form (a = 548.8 pm) with the space group Fm 3 m (space group no. 225) . The formation of mirror twins was observed in tetragonal uranium dicarbide crystals and the {112} plane was found as a twin plane.

use

Uranium carbides are used in high temperature and breeder reactors. Uranium dicarbide was used as the reactor fuel in Unit 1 of the Peach Bottom Nuclear Power Plant . A mixture of uranium dicarbide and thorium dicarbide can also be used as fuel at the THTR-300 nuclear power plant .

Individual evidence

1. ↑ ^{a b c d e f g} 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} Joseph Jacob Katz, Eugene Rabinowitch: Chemistry of Uranium - Collected Papers . United States Atomic Energy Commission, Technical Information Service Extension, 1958, p. 71 ( limited preview in Google Book search).
3. ^ ^{A b} Dale L. Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2016, ISBN 978-1-4398-1462-8 , pp. 488 ( limited preview in Google Book search).
4. ↑ Entry on uranium compounds in the GESTIS substance database of the IFA , accessed on December 4, 2019(JavaScript required) .
5. ↑ The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling.
6. ↑ ^{a b} Dissertation Rocky-Pitua Sutanto: The behavior of uranium carbides and uranium oxicarbides in repository-relevant aquatic phases .
7. ↑ E. Rudy, F. Benesovsky: To the knowledge of the stability of uranium dicarbide and the carbon-stable areas in the partial systems of UC with ZrC, HfC, NbC and TaC. In: Monthly magazine for chemistry . 94, 1963, p. 204, doi: 10.1007 / BF00900240 .
8. ↑ H. Holleck, H. Kleykamp: U Uranium Uranium Carbides . Springer Science & Business Media, 2013, ISBN 978-3-662-10716-4 , pp. 135 ( limited preview in Google Book search).
9. ^ JJ Katz, Eugene Rabinowitch: The Chemistry of Uranium . 1961, ISBN 5-88135-966-6 , pp. 224 ( limited preview in Google Book search).
10. ↑ EM Hörl: Formation of twins in uranium dicarbide crystals. In: Journal of Nuclear Materials . 12, 1964, p. 193, doi: 10.1016 / 0022-3115 (64) 90140-0 .
11. ↑ 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).
12. ↑ 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).
13. ↑ 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. 
14. ↑ Manfred Grathwohl: Energy supply: resources, technologies, perspectives . Walter de Gruyter, 1983, p. 206 ( limited preview in Google Book search).