Compound Uranium
Formula U
Molecular Formula U
Molecular Weight 238.0289
CAS RN: 7440-61-1
Properties silvery white, lustrous; black powder, when obtained by reduction of UF4; three forms, α-form: ortho-rhomb; a=0.2854 nm, b=0.5869 nm, c=0.4956 nm; β: tetr, a=1.0763 nm, c=0.5652 nm; γ:bcc, a=0.3524 nm; resistivity 29 mohm·cm; enthalpy of fusion 9.14 kJ/mol; enthalpy of sublimation 1062.73 kJ/mol; flammable in air forming U3O8; t½ 238U is4.47 x 10+9 years, ionic radius of U++++0.0918 nm [MER89] [KIR78] [KIR83] [CRC93]
Density, g/cm3: α: 19.07; β: 18.11; γ: 18.06 [KIR83]
Melting point, C 1132 [KIR91]
Boiling point, C 3818 [ALD94]
Reactions: transition α to β at 667.7°C, β to γ at 774.8°C [MER89]
Thermal Conductivity, W/(m·K): 25.1 (36°C), 26.3 (100°C), 29.7 (200°C), 31.4 (300°C), 32.6 (400°C) [KIR83]



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