Surface oxidation of zirconium above room temperature
1989; Elsevier BV; Volume: 222; Issue: 1 Linguagem: Inglês
10.1016/0039-6028(89)90336-1
ISSN1879-2758
Autores Tópico(s)Ion-surface interactions and analysis
ResumoIn order to investigate the initial oxidation mechanism of Zr, the temperature dependence of surface oxidation of Zr has been examined by in situ AES surface analysis and subsequent depth profiling with Ar ion sputtering for the first time. Below 600 K surface oxidation proceeds through three stages, that is, oxygen solution in α-Zr(O) up to around 30 at%, precipitation and development of ZrO2 on the surface, and growth of the ZrO2 thickness. Depth profiling of the oxidized specimen shows that the oxidized surface is completely covered by a ZrO2 layer followed by a mixed layer of ZrO2 and α-Zr(O) and a single phase of α-Zr(O) beneath the mixed layer. Above 700 K no precipitation or layer formation of the oxide is observed, and the oxygen concentration, which is determined by the balance between the oxygen uptake rate on the top surface from the gas phase and the diffusion flux into the bulk, is changed depending on the pressure of exposed oxygen. Supposing that growth of the oxide layer obeys the parabolic rate law, oxygen diffusion coefficients in the ZrO2 and the α-Zr(O) are estimated. The determined values are consistent with the extrapolated values from high temperature literature data, which confirms the oxidation kinetics described here.
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