Oxidation of a silicon nitride ceramic densified with mixed magnesia/ neodymia additions

M. J. Pomeroy, S. Hampshire

Research output: Contribution to journalConference articlepeer-review

Abstract

Thermogravimetric studies demonstrate that the kinetics of oxidation follow a parabolic relationship. This suggests that the oxidation rate is controlled by the diffusion of reacting species across the oxide scale. Energy dispersive x-ray analyses show that there is a considerable enrichment of the oxide scale by magnesium and neodymium suggesting that cation diffusion from the intergranular amorphous phase occurs. Clearly, as the time of exposure increases, the concentration of additive cations in amorphous grain boundary phases decreases and a lower transport flux is expected giving rise to the observed deceleration in oxidation rate. A further effect which reduces the concentration of additive cations in the grain boundary phase is the time dependent devitrification of the amorphous Mg-Nd-Si-O-N glass.

Original languageEnglish
Pages (from-to)25-33
Number of pages9
JournalKey Engineering Materials
Volume32
Publication statusPublished - 1989
Externally publishedYes
EventDurability and Failure in Engineering Materials: Proceedings of the 5th Irish Durability and Fracture Conference - Cork, Irel
Duration: 1 Oct 19872 Oct 1987

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