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Kinetics of Precipitation and Measurements of Strain in the System MgO‐Al 2 O 3 ‐Cr 2 O 3
Author(s) -
STUBICAN V. S.,
GRESKOVICH C.,
McKINSTRY H. A.
Publication year - 1969
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.1151-2916.1969.tb13359.x
Subject(s) - corundum , precipitation , spinel , isothermal process , materials science , monoclinic crystal system , activation energy , phase (matter) , metastability , analytical chemistry (journal) , strain (injury) , solid solution , mineralogy , oxide , kinetics , diffusion , crystallography , thermodynamics , metallurgy , chemistry , crystal structure , medicine , physics , organic chemistry , chromatography , quantum mechanics , meteorology
A quantitative X‐ray technique for measuring precipitation strains has not been previously applied in metallic or oxide systems. The Warren‐Averbach analysis of strain was used to determine the buildup of elastic strain energy in the spinel crystalline solution matrix (gross composition = 60 mol% MgAl 2 O 2 + 40 mol% Cr 2 O 3 ) during the isothermal (1135°C) precipitation of a metastable (coherent) monoclinic phase. The elastic strain energy of the spinel crystalline solution matrix increased to a maximum of about 3.1 × 10 7 ergs/cm 3 for a reaction time of 8 h. There was a marked decrease in the elastic strain energy during the initial precipitation of the equilibrium corundum crystalline solution with the composition (Al 3+ 0.72 Cr 3+ 0.25 )O 3 . An overall diffusion activation energy for precipitation of the mono‐clinic phase was approximately 86 kcal/mol.