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Carbon Thermal Diffusion in the UC 2 ‐C System
Author(s) -
GULDEN T. D.
Publication year - 1972
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.1151-2916.1972.tb13387.x
Subject(s) - pyrolytic carbon , graphite , carbon fibers , diffusion , activation energy , materials science , thermal diffusivity , analytical chemistry (journal) , thermodynamics , chemistry , mineralogy , pyrolysis , metallurgy , composite material , organic chemistry , physics , composite number
Alpha uranium dicarbide disks coated with pyrolytic carbon migrate, relative to the carbon, up a temperature gradient, leaving behind a layer of rejected graphite. A model for the migration process based on solution of carbon at the hot UC 2 ‐C interface, transport across the UC 2 phase by thermal diffusion, and rejection as graphite at the cool UC 2 ‐C interface was developed. The rate of migration may be described by:The apparent activation energy for migration is 76.5±9 kcal/mol, compared to a literature value for carbon self‐diffusion in α ‐UC 2 of 90.2 kcal/mol. This difference in temperature dependence may be considered preliminary evidence that the heat of transport decreases with increasing temperature. The average value of the heat of transport, calculated using literature values for carbon self‐diffusion in α ‐UC 2 , is 92±27 kcal/mol.