Hydrogen defects in {alpha}-Al{sub 2}O{sub 3} and water weakening of sapphire and alumina ceramics between 600 and 1000 C -- 1. Infrared characterization of defects

Hydrogen impurities in materials influence their properties, including flow strength. {alpha}-Al{sub 2}O{sub 3} single crystals and polycrystalline ceramics were annealed in supercritical water between 850 and 1,025 C, under pressures in the range 1,500--2,000 MPa. A few specimens were further subje...

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Bibliographic Details
Published in:Acta materialia 2000-04, Vol.48 (7)
Main Authors: Kronenberg, A.K., Castaing, J., Mitchell, T.E., Kirby, S.H.
Format: Article
Language:English
Subjects:
ALUMINIUM OXIDES
ANNEALING
CRYSTAL DEFECTS
DIFFUSION
HYDROGEN
INFRARED SPECTRA
KINETICS
MATERIALS SCIENCE
SPECTROSCOPY
TEMPERATURE DEPENDENCE
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Summary:Hydrogen impurities in materials influence their properties, including flow strength. {alpha}-Al{sub 2}O{sub 3} single crystals and polycrystalline ceramics were annealed in supercritical water between 850 and 1,025 C, under pressures in the range 1,500--2,000 MPa. A few specimens were further subjected to plastic deformation. Hydrogen penetration was examined using infrared absorption measurements of O-H bond vibrations, which revealed two kinds of hydrogen defects. In single crystals, defects are characterized by sharp O-H absorption bands assigned to interstitial protons. Hydrogen impurities of hydrothermally annealed ceramics and of all hydrothermally deformed specimens are characterized by broad O-H bands assigned to molecular water. The grain boundaries of hydrothermally annealed ceramics are severely damaged. The kinetics of hydrogen penetration is consistent with diffusion data.
ISSN:1359-6454
1873-2453
DOI:10.1016/S1359-6454(99)00448-6