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Zirconium carbide oxidation: Kinetics and oxygen diffusion through the intermediate layer
Author(s) -
Gasparrini Claudia,
Chater Richard J.,
Horlait Denis,
Vandeperre Luc,
Lee William E.
Publication year - 2018
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/jace.15479
Subject(s) - oxide , amorphous solid , kinetics , zirconium , materials science , cubic zirconia , carbide , diffusion , zirconium carbide , oxygen , layer (electronics) , carbon fibers , analytical chemistry (journal) , chemistry , metallurgy , crystallography , composite material , composite number , ceramic , physics , organic chemistry , chromatography , quantum mechanics , thermodynamics
Oxidation of hot‐pressed ZrC was investigated in air in the 1073‐1373 K range. The kinetics were linear at 1073 K, whereas at higher temperature samples initially followed linear kinetics before undergoing rapid oxidation leading to a Maltese cross shape of the oxide. The linear kinetics at 1073 K was governed by inward oxygen diffusion through an intermediate layer of constant thickness between ZrC and ZrO 2 which was comprised of amorphous carbon and ZrO 2 nanocrystals. Diffusion of oxygen through the intermediate layer was measured to be 9 × 10 −10 cm 2 s −1 using 18 O as a tracer in a double oxidation experiment in 16 O/ 18 O. Oxidation at 1073 and 1173 K produced samples made of m‐ZrO 2 and either t‐ or c‐ZrO 2 with an adherent intermediate layer made of amorphous carbon and ZrO 2 , whereas oxidation at 1273 and 1373 K produced samples with a voluminous oxide made of m‐ZrO 2 showing a gap between ZrC and the oxide. A substoichiometric zirconia layer was found at the gap at 1273 K and no carbon uptake was detected in this layer when compared with the top oxide layer. The loss of the intermediate layer and the slowdown of the linear rate constant (g m −2 s −1 ) at 1273 K compared to 1173 K was correlated with the preferential oxidation of carbon at the intermediate layer which would leave as CO and/or CO 2 leaving a gap between ZrC and substoichiometric zirconia.