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Effect of Water Vapor on Initial Sintering of Magnesia
Author(s) -
EASTMAN PAUL F.,
CUTLER IVAN B.
Publication year - 1966
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.1151-2916.1966.tb13156.x
Subject(s) - partial pressure , sintering , magnesium , activation energy , materials science , diffusion , vacancy defect , water vapor , vapor pressure , grain boundary diffusion coefficient , solubility , decomposition , analytical chemistry (journal) , grain boundary , mineralogy , metallurgy , chemistry , thermodynamics , microstructure , crystallography , oxygen , chromatography , physics , organic chemistry
The effects of water vapor on the initial sintering of magnesia powder compacts were studied from 800° to 1107°C. The magnesia was obtained by thermal decomposition of magnesium oxalate. Water vapor partial pressures from 8 × 10 –4 to 658 mm were used. Initial sintering occurred by a grain‐boundary vacancy‐diffusion mechanism with magnesium assumed to be the slow moving species. Increasing water vapor partial pressure increased sintering rates. A model based on the solubility of the hydroxide ion in MgO relates this increase to the increase in the cation vacancy concentration. The grain‐boundary diffusion coefficient, D G , varied with P H2O . For partial pressures up to about 5 mm, n was approximately ½ and for partial pressures above 5 mm it was between 1.0 and 1.5. The activation energy for densification was 80 kcal/mole for partial pressures up to about 5 mm and 48 kcal/mole above this partial pressure.