铌合金表面Nb5Si3/NbSi2/Nb2O5-SiO2/硅化物多层涂层构建与辐射热防护强化机制

针对铌合金高温抗氧化性差、辐射热防护性差而制约其在高超声速飞行器应用的瓶颈问题，提出采用高温渗硅与微弧氧化-纳米粒子同步沉积烧结复合技术构建Nb5Si3/NbSi2/Nb2O5-SiO2/SiC-MoSi2-ZrC-Yb2O3全新结构多层涂层，实现高温抗氧化/耐烧蚀/高发射率辐射热防护多重功能。通过铌合金高温渗Si形成Nb5Si3/NbSi2底层，进而构建微弧氧化-纳米粒子同步沉积烧结特殊条件，通过电解液中SiC-MoSi2-ZrC-Yb2O3功能性纳米粒子匹配掺杂，研究纳米粒子分散特性及微弧参数对Nb2O5-SiO2/SiC-MoSi2-ZrC-Yb2O3外层生长的影响机制；揭示多层涂层结构及纳米粒子分布状态对发射率、氧化、热震、烧蚀行为的影响规律与辐射热防护强化机制，最终优选出高发射率涂层与工艺。这对于探索辐射热防护涂层制备新方法、丰富抗氧化/辐射散热理论具有重要学术与工程应用价值。

To solve the key problems of poor high temperature oxidation resistance and poor radiative thermal protection due to low surface emissivity of niobium alloy for hypersonic vehicles applications, a novel Nb5Si3/NbSi2/Nb2O5-SiO2/SiC-MoSi2-ZrC-Yb2O3 multi-layer thermal protection coating is constructed on niobium alloy by using high temperature pack cementation Si followed by microarc oxidation-synchronous nanoparticle deposition sintering technology, for the purpose to achieve the multiple functions of high temperature oxidation resistance, ablation resistance, high emissivity radiative thermal protection. Firstly, the Nb5Si3/NbSi2 bottom layer is prepared by high temperature pack cementation Si. Further, the unique process parameters of microarc oxidation-synchronous nanoparticle deposition sintering are experimentally constructed to design the multi-layer coating. The effects of various nanoparticles dispersion characteristics and microarc process parameters on the growth and microstructure of Nb2O5-SiO2/SiC-MoSi2-ZrC-Yb2O3 composite layers are determined by matching doping of SiC-MoSi2-ZrC-Yb2O3 nanoparticle in the special electrolyte. The effects of nano particles distribution in the outer layer and multi-layer coating microstructure on high temperature emissivity, oxidation resistance, transient thermal shock and ablation resistance are revealed. Finally, the optimal high emissivity multi-layer coating system and corresponding fabrication process are presented. This proposed project is of broader societal impact on scientific disciplines and engineering applications. Not only will it explore and find the novel way for preparing radiative thermal protective coatings for hypersonic vehicles, but will also enrich the theory of oxidation resistance and radiative heat dissipation.