High-Temperature Modifications of Thorium Dicarbide
| Autor: | P. K. Gantzel, S. Langer, N. L. Baldwin, F. L. Kester |
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| Rok vydání: | 1964 |
| Předmět: | |
| Zdroj: | Advances in X-ray Analysis. 8:78-85 |
| ISSN: | 2631-3626 0376-0308 |
| DOI: | 10.1154/s0376030800002998 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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