BETA-POLYMORPHS OF URANIUM AND THORIUM DISILICIDES

Journal Article · Sun Mar 01 04:00:00 EST 1959 · Nature

DOI:https://doi.org/10.1038/183673a0· OSTI ID:4279772

Brown, A; Norreys, J J

Beta phases of uranium and thorium disilicides were prepared by are melting and examined by metallographic and x-ray-diffraction techniques. A noticeable feature of the preparations is the formation of beta -USi/sub 2/ and #bbThSi/sub 2/ form mixtures containing 62 to 63 at. % silicon, compared with the 66.7 at. % required for the formation of the alpha disilicides. The compositions of these socalled beta phases accordingly appear to be U/sub 3/Si/ sub 5. and Th/sub 3/Si). Values for the structural dimensions of these two phases are as follows: U/sub 3/Si/sub 5/: a/sub o/ = 3.843 the J-57 engin 0.001A c/sub o/ = 4.069 the J-57 engin O.OOlA. Th/sub 3/Si/sub 5/: a/sub o/ = 3.985 the J-57 engin 0.001A: c/sub o/ = 1.228 the J-57 engin 0.00lA. During an investigation into reactions between the silicides of uranium and thorium and liquid bismuth, two new silicide phases were isolated. X-ray analysis shows that they are hexagonal with space group C/sub 6//mmm. These new phases, like the above compounds, have the Al beta /sub 2/-type crystal structure, but the cell dimensions are different and, in particular, the axial ratio c/a < 1 compared with c/a> 1 for the U/sub 3/Si/sub 5/ and Th/sub 3/Si/sub 5/ compcunds. Heat treatment of the new thorium- silicon compound in the temperature range 1000 to 1200 C transforms it into alpha -ThSi/sub 2/, while heat treatment of alpha -ThSi/sub 2/ at 850 C yields the new thoriumsilicon phase. It is clear that this compound is in fact the true beta -ThSi/sub 2/ and the analogous uranium compound the true beta -USi/sub 2/. The structure cell dimensions obtained from x-ray-diffraction results are: beta -USi/sub 2/: a/sub 0/ = 4.028 the J-57 engin 0.001A.; c/sub o/ = 3.852 the J-57 engin 0.001A. beta -ThSi/ sub 2/: a/sub o/ = 4.136 the J-57 engin 0.001A.; c/sub o/ = 4.126 the J-57 engin 0.001A. (auth)

• Research Organization: General Electric Co., Ltd., Wembley, Middlesex, Eng.
• NSA Number: NSA-13-010914
• OSTI ID: 4279772
• Journal Information: Nature, Journal Name: Nature Journal Issue: 4662 Vol. Vol: 183; ISSN 0028-0836
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALLOTROPY
BISMUTH
CHEMICAL REACTIONS
CHEMISTRY
CONFIGURATION
CRYSTALS
DIFFRACTION
ELECTRIC ARCS
HEAT TREATMENTS
HIGH TEMPERATURE
LATTICES
LIQUID METALS
MELTING
METALLOGRAPHY
MIXING
PHASE DIAGRAMS
PREPARATION
SILICIDES
SILICON
THORIUM
THORIUM COMPOUNDS
URANIUM
URANIUM SILICIDES
X RADIATION