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Knudsen Cell Studies of the Vaporization of Gadolinium and Gadolinium Dicarbide
Author(s) -
HOENIG CLARENCE L.,
STOUT NORMAN D.,
NORDINE PAUL C.
Publication year - 1967
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1967.tb15140.x
Subject(s) - vaporization , gadolinium , knudsen number , chemistry , analytical chemistry (journal) , vapor pressure , enthalpy , body orifice , thermodynamics , ecology , physics , organic chemistry , biology , chromatography
Vapor pressure of gadolinium metal and carbon‐rich gadolinium dicarbide was measured by the Knudsen effusion technique using an automatic recording balance. Knudsen pressures calculated on the basis that Gd( g ) is the major gaseous species did not vary significantly as a function of orifice diameter or sample surface area. Corrections were made for a minor gaseous species, GdC 2 ( g ). The entropy and heat content of GdC 2 were estimated. For the reaction Gd( l ) = Gd( g ) the third‐law Δ H ° 298 of 95.2 ± 0.3 kcal/g‐atom was in agreement with the second‐law value of 97.3 ± 0.8 kcal/g‐atom. Third‐ and second‐law Δ H ° 298 were combined to give a value of 125 ± 9 kcal/mole for the reaction GdC 2 ( s ) = Gd( g ) + 2C( s ). From these values the enthalpy of formation of carbon‐rich GdC 2 was calculated to be — 30 ± 9 kcal/mole. Studies of rare earth dicarbide vaporization behavior are briefly reviewed and discussed, and their possible application to a self‐purifying, high‐temperature nuclear reactor is considered.