应用陶瓷纤维增强陶瓷基复合材料(Ceramic matrix composites, CMCs)作为热端部件，是未来航空涡轮发动机进一步提升推重比，提高热效率的重要发展方向。燃气涡轮发动机内高压、高速的燃气会对直接暴露的CMCs产生严重侵蚀。环境障涂层(Environment barrier coating, EBC)是确保SiCf/SiC CMCs在高压燃气环境下长期服役的重要技术。EBC材料所需的性能要求涉及多个方面，很难通过一两种材料满足所有的性能要求，因此当前EBC的设计思路为多组元多层体系。通过不同材料的复合，使材料兼具多方面的优异性能，满足不同功能层对性能的要求。因此，采用多种材料的复合，制备兼具多方面优异性能的新型环境障涂层材料是本文核心的研究思路。首先针对EBC粘接层材料，现有Si的低熔点和表面氧化形成TGO层的反应速率是限制EBC使用温度和耐久性的短板。采用SPS（Spark Plasma Sintering）烧结的方式制备HfO2-Si复相EBC粘接层材料，研究了不同的两相体积分数材料的力学性能、热学性能，发现HfO2-Si体系具有显著的增韧效果，当Si比例为20vol.%断裂韧性为5.4MPam1/2，且具有同CMCs匹配的热膨胀系数。其次研究了HfO2-Si材料的抗氧化性能，在空气气氛下1250℃恒温进行了氧化测试。根据氧化增重情况分析了HfO2-Si材料高温氧化动力学特点。相比传统Si粘接层材料，复相HfO2-Si材料被更均匀的氧化。HfO2-Si材料氧化增重符合抛物线规律，从材料抗氧化性考虑适宜的Si复合含量应为28~37%。针对EBC涂层制备方法，本文提出以采用浆料浸渍提拉的方法制备EBC涂层，以Yb2SiO5/Yb2Si2O7混合不同体积分数的纳米SiC，制备了Yb2SiO5 /Yb2Si2O7/SiC复相涂层，其中纳米SiC在涂层热处理过程中会发生氧化生成SiO2而后与Yb2SiO5反应生成Yb2Si2O7，产生体积膨胀，使涂层具备自愈合性能，并有利于涂层的致密化。当复合SiC含量为30%时，涂层具有最高的粘接强度，约为21.9MPa。最后通过将莫来石按照不同体积分数复合到Yb2Si2O7中，制备Yb2Si2O7/莫来石复相陶瓷。当莫来石含量为50%时，Yb2Si2O7/莫来石复相材料的硬度为8.6GPa，杨氏模量为204GPa，断裂韧性为2.4MPa·m1/2，热膨胀系数为5.4×10-6℃-1，是理想的EBC中间层候选材料。
The application of ceramic fiber reinforced ceramic matrix composites as hot section is an important development field for further improve the thrust weight ratio and thermal efficiency of aviation turbine engines in the future. But high pressure and high-speed gases in turbine engine will seriously erode directly exposed CMCs. Environmental barrier coating is an important technology to ensure the long-term service of SiCf/SiC CMCs in high pressure gas environment. The performance requirements of EBC materials involve many aspects, and it is difficult to meet all the performance requirements by one or two materials. Therefore, the current design of EBC is a multi-component and multi-layer system. Through the composite of different materials, the materials have many excellent properties and meet the performance requirements of different functional layers. Therefore, the core research idea of this paper is to use a variety of composite materials to prepare a new type of environmental barrier coating material with many excellent properties.Firstly, for the EBC bond coating material, the low melting point of Si and the reaction rate of surface oxidation to form TGO layer are short board that limit the service temperature and durability of EBC. HfO2-Si multiphase EBC bond coating was prepared by SPS sintering. The mechanical properties of materials with different Si content were studied. It was found that composite played a significant role in toughening. When the ratio of mixed Si was 20vol.% and the fracture toughness was 5.4MPa·m1/2, and with matched the thermal expansion coefficient with CMCs.Secondly, the oxidation resistance of HfO2-Si material was studied, and the oxidation was measured at 1250 ℃ in air environment. According to the oxidation weight gain, the high temperature oxidation kinetics of HfO2-Si material was analyzed. Compared with the traditional Si bond coating material, the multiphase HfO2-Si material is oxidized more uniformly. The oxidation weight gain of HfO2-Si material conforms to the parabolic law. Considering the oxidation resistance of the material, the appropriate Si composite content should be 28% ~ 37%.For the preparation method of EBC coating, this paper proposes to prepare EBC coating by slurry impregnation and pulling film, the Yb2SiO5/Yb2Si2O7/SiC composite coating is prepared by mixing nano SiC with different volume fractions. Nano SiC will oxidize to form SiO2 during coating heat treatment, and then react with Yb2SiO5 to form Yb2Si2O7, resulting in volume expansion, which could densified the coating. When the content of composite SiC is 30%, the coating has the highest bonding strength, about 21.9 MPa.Finally, Yb2Si2O7/mullite multiphase ceramics were prepared by composite mullite into Yb2Si2O7 by different volume fraction. When the content of mullite is 50%, the hardness of Yb2Si2O7/mullite composite is 8.6 GPA, the Young's modulus is 204 GPA, the fracture toughness is 2.4MPa·m1/2 and the coefficient of thermal expansion is 5.4 × 10-6℃-1, it is an ideal EBC middle layer material.
