Modified Wagner model for the active-to-passive transition in the oxidation of Si(3)N(4)

作者：Wang Junjie^*; Zhang Litong; Zeng Qingfeng; Cheng Laifei; Xu Yongdong

来源：Journal of Physics D: Applied Physics , 2008, 41(11): 115412.

DOI：10.1088/0022-3727/41/11/115412

Si(3)N(4) is used as the coating material of space shuttle structures which receive very high thermal fluxes during the atmospheric re-entry phase. Two main regimes govern the oxidation of Si(3)N(4): the passive oxidation, with the formation of a protective silica layer leading generally to a mass gain, and the active oxidation, with vaporization of SiO leading to a mass loss of the sample. To ensure that silicon nitride will efficiently protect a material in given oxidizing environments, its own oxidation behaviour must be previously known. Therefore, the active-to-passive transition of Si(3)N(4) oxidation is a problem of deep scientific importance and of wide technological relevance. In this paper, a modified Wager model for the active-to-passive transition in the oxidation of Si(3)N(4) is presented, which includes the non-equilibrium effects caused by the mass transfer. The present theoretical calculations satisfactorily explained the reported experimental and theoretical data. The influence of flow rate on the active-to-passive transition boundary has been explained using our model. The rate controlling mechanism of the oxidation at the active-to-passive transition point is proposed.

• 出版日期2008-6-7
• 单位西北工业大学