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Dissolution Kinetics of β‐Si 3 N 4 in an Mg‐Si‐O‐N Glass
Author(s) -
TSAI R. L.,
RAJ R.
Publication year - 1982
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.1151-2916.1982.tb10431.x
Subject(s) - dissolution , activation energy , enthalpy , phase (matter) , ternary operation , crystal (programming language) , kinetics , materials science , analytical chemistry (journal) , mineralogy , crystallography , thermodynamics , chemistry , chromatography , physics , organic chemistry , quantum mechanics , computer science , programming language
The rate of dissolution of β‐Si 3 N 4 into an Mg‐Si‐O‐N glass was measured by working with a composition in the ternary system Si 3 N 4 ‐SiO 2 ‐MgO such that Si 2 N 2 O rather than β‐Si 3 N 4 was the equilibrium phase. Dissolution was driven by the chemical reaction Si 3 N 4 (c)+SiO 2 ( l )→Si 2 N 2 O(c). Analysis of the kinetic data, in view of the morphology of the dissolving phase (Si 3 N 4 ) and the precipitating phase (Si 2 N 2 O), led to the conclusion that the dissolution rate was controlled by reaction at the crystal/glass interface of the Si 3 N 4 , crystals. The process appears to have a fairly constant activation energy, equal to 621 ±40 kJ‐mol −1 , at T=1573 to 1723 K. This large activation energy is believed to reflect the sum of two quantities: the heat of solution of β‐Si 3 N 4 hi the glass and the activation enthalpy for jumps of the slower‐moving species across the crystal/glass interface. The data reported should be useful for interpreting creep and densification experiments with MgO‐fluxed Si 3 N 4 .