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Effects of Thin Mullite Coating on the Environmental Stability of Sintered Si 3 N 4
Author(s) -
Tsarenko Irina,
Du Henry H.,
Lee Woo Y.
Publication year - 2004
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.1551-2916.2004.00417.x
Subject(s) - mullite , materials science , coating , ceramic , isothermal process , oxide , chemical engineering , composite material , mineralogy , metallurgy , chemistry , physics , engineering , thermodynamics
We investigated the effects of a chemically‐vapor‐deposited mullite coating (∼100 nm) on the oxidation resistance of sintered Si 3 N 4 in air and steam environments. The coating was sacrificially incorporated into the thermally grown oxide (TGO) on Si 3 N 4 during isothermal oxidation in air at 1400°C, leading to significantly reduced TGO growth as well as markedly improved TGO morphology. This improvement can be attributed to the refractory and viscous nature of the SiO 2 ‐Al 2 O 3 system, compared with SiO 2 , when under the influence of alkali and/or alkaline‐earth fluxing elements. However, the mullite coating had little effect on the stability of the ceramic in the steam environment at 1200°C, due likely to high activity of SiO 2 in mullite.