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Effect of Lead Oxide Vapor on the Strength of Alumina
Author(s) -
Elmadani Abdelaziz M.,
Green David J.,
Mei ZhiGang,
Liu ZiKui,
Dynan Steve
Publication year - 2011
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/j.1744-7402.2011.02619.x
Subject(s) - materials science , porosity , scanning electron microscope , composite material , sintering , flexural strength , phase (matter) , oxide , cracking , diffraction , metallurgy , chemistry , physics , organic chemistry , optics
This effect of PbO vapor on the strength of alumina was studied to determine the corrosion mechanism. Characterization of the corroded samples was carried out using X‐ray diffraction (XRD), scanning electron microscopy, strength and sound velocity measurements, weight and dimensional changes. The strength and sound velocity of alumina decreased when exposed to PbO but weight and volume increased. Thermodynamic modeling of the PbO–Al 2 O 3 system was carried out using the CALculation of PHAse Diagram method, which showed that three pseudo‐binary compounds, PbAl 2 O 4 , Pb 2 Al 2 O 5 , and PbAl 12 O 19 can be formed, in agreement with prior work. It was postulated that PbAl 12 O 19 is most likely to form when alumina is exposed to PbO at sintering temperatures and this was confirmed by XRD and energy‐dispersive analysis. The PbAl 12 O 19 phase does not form a surface layer but rather nucleates and grows as individual crystals embedded in the alumina surface, forming a more porous structure. This surface porosity then acts to concentrate applied stress, resulting in a lower strength. This strength degradation mechanism makes alumina kiln furniture more sensitive to thermal stresses with repeated use, explaining the observed cracking behavior.