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High-Temperature Modifications of Thorium Dicarbide

Published online by Cambridge University Press:  06 March 2019

P. K. Gantzel ,
S. Langer ,
N. L. Baldwin  and
F. L. Kester
P. K. Gantzel
Affiliation:
General Atomic Division of General Dynamics Corporation San Diego, California
S. Langer
Affiliation:
General Atomic Division of General Dynamics Corporation San Diego, California
N. L. Baldwin
Affiliation:
General Atomic Division of General Dynamics Corporation San Diego, California
F. L. Kester
Affiliation:
General Atomic Division of General Dynamics Corporation San Diego, California
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Abstract

Thermal analyses of samples of thorium dicarbide in equilibrium with graphite show arrests which indicate phase transitions at 1427 ± 21°C arid 1481 ± 28°C. These thermal effects have been observed on heating and cooling both in standard thermal analysis and in differential thermal analysis using graphite as a reference material. The microstructure of thorium dicarbide samples shows the characteristic “herringbone” pattern of a material which has undergone a martensitic-type transition.

A high-temperature X-ray investigation has revealed that the observed thermal arrests correspond to erystallographic transformations. The monodinic modification found at room temperature is stable to 1427°C, at which temperature a tetragonal modification with a0 = 4.235 ± 0.002Å and c0 = 5.408 ± 0.002Å is formed. At 1481°C, the tetragonal is transformed to cubic with a0 = 5.809 ± 0.002 Å. The best agreement between observed and calculated intensities has been obtained with C-C units of 1.5-Å assumed bond length in space groups P42/mmc and Pa3 for the tetragonal and cubic modifications, respectively.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 8: Thirteenth Annual Conference on Applications of X-ray Analysis, August 12-14, 1964 , 1964 , pp. 78 - 85
Copyright
Copyright © International Centre for Diffraction Data 1964

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