ZrB_2+SiC陶瓷在高温氧化过程中会形成一层多孔的SiC耗尽层.本文首先计算了在高温氧化过程中的主要氧化产物.通过对氧化过程中相变机制的分析,利用质量守恒、固体区域体积守恒并结合反应速率方程,研究了SiC耗尽层的形成与演化过程,给出了孔隙率随温度的变化规律.结果表明:氧化过程中生成相的体积膨胀及SiC的初始体积含量是影响SiC耗尽层孔隙率的主要因素.对计算结果的分析解释了试验中发现的在低SiC含量下不出现耗尽层,以及氧化层破坏的现象.
The SiC depletion layer will be formed during high temperature oxidation of ZrB_2+SiC. The minimum free energy method was used to investigate the main oxide products. By the analyses of phase transformation characteristics, combining the principle of mass conservation, volume conservation of solid phase and the equation of chemical reaction rate, cavity nucleation and evolution was investigated. The results show that the volume expansion of resultant phase and the volume fraction of SiC are the major factors leading to the cavity nucleation and evolution. The phenomena of the lack of SiC depletion layer and the failure of oxide layer are well explained by the low SiC content.
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