CONTRIBUTION TO THE STUDY OF THE STABILITY OF URANIUM DICARBIDE AND THE CARBON-STABLE REGIONS IN THE PARTIAL SYSTEMS OF UC WITH ZrC, HfC, NbC AND TaC (in German)
At temperatures below 1800 deg C UC/sub 2/ gradually decomposes into UC and C. Under the selected conditions, the phase U/sub 2/C/sub 3/ cannot be detected in the decomposition products. The C-stable regions in the series UC -- Zr(Hf, Nb, Ta)C extend at 1600 deg C almost over the whole mixed crystal region and become smaller at higher temperatures. ln contrast with previous measurements it was found that the formation of the dicarbide from monocarbide and C proceeds endothermically. The free enthalpies of reaction for the reaction UC + C yields UC/sub 1+x/ (x = 0.80 to 0.90), calculated from the phase field distribution, amount to DELTA G/sub R/(cal) == of the values, taking into account the transformation of the dicarbide of 1820 deg C, gives the equations DELTA G/sub R/ (cal) = 10350 5.57 x T (2100 to 2300 deg K) and DELTA G/sub R/(cal) = 7710 -4.31 x T (1900 to 2100 deg K). Both the phase field distributions in the individual systems calculated from the mean values and the decomposition temperature of about 1550 deg C for UC, extrapolated using the temperature dependence of DELTA G/sub R/, agree well with the experimental results. Further possibilities for calculating thermochemical data still outstanding for high-melting U and Th compounds are discussed. (tr-auth)
- Research Organization:
- Metallwerk Plansee AG, Reutte/Tirol, Austria
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-032617
- OSTI ID:
- 4669396
- Journal Information:
- Monatshefte fuer Chemie (Austria), Journal Name: Monatshefte fuer Chemie (Austria) Vol. Vol: 94; ISSN MOCHA
- Country of Publication:
- Country unknown/Code not available
- Language:
- German
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