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Kinetics of NiCr 2 O 4 Formation and Diffusion of Cr 3+ Ions in NiO
Author(s) -
GRESKOVICH C.
Publication year - 1970
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.1151-2916.1970.tb15999.x
Subject(s) - non blocking i/o , nichrome , diffusion , activation energy , analytical chemistry (journal) , kinetics , ion , atmospheric temperature range , materials science , temperature coefficient , chemistry , metallurgy , thermodynamics , composite material , physics , biochemistry , organic chemistry , chromatography , quantum mechanics , catalysis
The reaction kinetics for NiCr 2 O 4 formation and the diffusion of Cr 3+ ions into single‐crystal NiO were studied between 1300° and 1600°C in air. The experimental activation energy for NiCr 2 O 4 formation was about 83 kcal/mol. After incubation, NiCr 2 O 4 formed by a diffusion‐controlled process. The origin of pores at the NiO/NiCr 2 O 4 interface is discussed. The concentration profiles of Cr 3+ in NiO were linear because the interdiffusion coefficient was directly proportional to the mol fraction Cr 3+ . Theoretical considerations indicate that the interdiffusion coefficient equals 3/2 the self‐diffusion coefficient of Cr 3+ , which is rate‐determining. The interdiffusion coefficient at 1 mol% Cr 2 O 3 can be expressed as D̄=4×10 −3 exp (−55,000/RT) cm 2 s −1 .