基于氧原子浓度的防热材料表面催化特性诊断方法探索

Scientific evaluation and characterization method of surface catalytic properties is vital for a precise prediction of aerodynamic heating environment and an accurate design of thermal protection system (TPS). According to the limitations of the ground based facilities and the differences of the test methods of surface catalytic properties, a laser spectral diagnosis technology based on tunable diode laser absorption spectroscopy (TDLAS) is proposed for evaluation and characterization the thermal protection materials. TDLAS is widely used for gas parameters of high-temperature flow field because it is robustness, relatively simple implementation, and just simple instruments constitute. In our studies, TDLAS is used to determine the atomic oxygen concentration on the surface of the thermal protection material at the high-enthalpy flow field environment simulated by an inductively coupled plasma wind tunnel and an arc-heated wind tunnel. Based on the mechanism of surface catalytic reaction, the on-line measurement of atomic oxygen concentration is helpful to explore the following critical scientific issues of catalytic behavior of thermal protection materials, it contains the relationship between the oxygen atomic concentration and surface catalytic properties, the relationship between the evolution of the surface properties of the thermal protection materials and the surface catalytic properties under long-time aerothermal heating environment, and the effect of the non-equilibrium phenomena on the surface catalytic properties. In addition, the super-catalytic material Cu and non-catalytic material SiO2 are chosen to calibrate and verify this characterization method.

材料表面催化特性的科学测试与评价已成为准确预测飞行器热载荷、热防护材料选择与结构设计的关键。针对当前实验平台和测试手段的局限性和差异性，将光谱学领域中蓬勃发展的可调节二极管激光吸收光谱技术引入材料表面催化特性研究，发展基于高频感应风洞、电弧风洞等地面气动热试验平台的氧原子浓度定量测量的吸收光谱技术，实现防热材料表面氧原子浓度的在线定量测量，探索真实气动热环境下防热材料表面催化特性测试所涉及的基础问题，为高超声速飞行器热环境预测、防热设计提供科学依据。选用近似完全催化材料铜和完全非催化材料二氧化硅对该表征方法进行标定和验证，研究高焓离解气体环境下材料表面原子浓度与材料表面催化特性的依赖关系。探索长时间、多状态气动热环境下，防热材料表面特性演化与材料表面催化特性的相互关系。针对高频感应风洞和电弧风洞的流场差异，分析流场非平衡性对材料表面催化特性的影响。

高焓非平衡环境下防热材料表面催化特性的科学测试与评价是准确预测飞行器热载荷、热防护材料选择与结构设计的关键。材料表面离解原子数密度与其催化特性密切相关，由于在高焓非平衡流场中实现防热材料表面原子浓度定量测量难度极大，且有效测量手段异常匮乏，高焓非平衡流场与防热材料特性耦合作用机制仍缺乏清晰认知。本项目针对高焓非平衡流场，发展了一种融合吸收光谱和发射光谱的测量方法，并与中国航天空气动力技术研究院合作，基于其1MW高频感应等离子风洞开展实验研究。该研究以考虑材料表面高时、空分辨的氧原子数密度动态变化为主，结合表面物理化学反应特征组分及自由基的辐射光谱动态特征，明确了高焓非平衡环境下典型防热材料表面的物理化学反应路径，深入微观原子尺度开展催化反应的机理研究，揭示了防热材料与高焓非平衡流场的多物理化学场耦合机制。本项目的研究成果丰富了对高焓非平衡流场与材料特性耦合作用机制的认知，同时也为新型防热材料的设计与优化提供参考