原子氧环境下SiC基防热材料主/被动氧化在线识别及演化

On-line identification and evolution of active and passive oxidation for SiC-based thermal protection materials in atomic oxygen environment

当前,高超声速飞行器主流SiC基防热材料在1200~1700℃内的防热机制主要依靠SiC被动氧化生成的SiO_(2)保护层,但高超声速飞行带来的高温气体效应使得防热材料遭受高温、低压、原子氧载荷,原子氧的高活性将改变SiC氧化反应类型,导致材料丧失防护能力。因此,判别不同飞行工况下材料主/被动氧化类型将直接决定材料的使用阈值,对于高超声速飞行器防热设计和新型防热材料研制极为重要。基于此,本文打破通过分析氧化反应后材料微观成分辨别主/被动氧化反应的传统方法,基于光谱诊断、射频等离子放电及高功率激光技术,建立高温、低压、原子氧环境下SiC基防热材料主/被动氧化反应在线识别方法与系统,实现了SiC基防热材料主/被动氧化反应快速在线识别,经过SEM、EDS和XRD等材料分析,验证了在线识别方法的准确性和可靠性,进一步探究了原子氧环境下SiC材料主动氧化的演化规律,并建立了氧化动力学方程,为SiC基防热材料防护阈值及材料性能改进提供了重要支撑。

At present,the thermal protection mechanism of SiC-based materials for hypersonic vehicles mainly depends on the SiO_(2)protective layer formed by SiC passive oxidation at 1200-1700℃.However,the high-temperature gas effect caused by hypersonic flight makes the thermal protection materials subjected to high temperature,low pressure and atomic oxygen loadings.The high activity of atomic oxygen will change the type of SiC oxidation reaction,resulting in the loss of protective ability.Therefore,the identification of active and passive oxidation types of materials under different flight conditions will directly determine the use threshold of materials,which is very important for the thermal protection systems(TPS)design of hypersonic vehicles and the development of new thermal protection materials.Based on it,this paper breaks the traditional method of analyzing the micro-composition of materials after oxidation,and establishes an on-line identification method and system of active and passive oxidation reaction for SiC-based thermal protection materials under high temperature,low pressure and atomic oxygen environment based on spectral diagnosis radio frequency(RF)plasma discharge and high power laser technology.The rapid on-line identification of active and passive oxidation reaction for SiC-based thermal protection materials is realized.After material analysis by SEM,EDS and XRD,the accuracy and reliability of this method were verified,and the evolution law for active oxidation of SiC materials in atomic oxygen environment was further explored,which provides an important support for the protection threshold of SiC-based thermal protection materials and the improvement of material properties.