防热涂层材料La2Ce2O7@La2Zr2O7的核壳结构调控及对热物理性能的影响机制

coating materials are critical to the progress of thermal protection coatings. To solve the serious problems in thermal physical properties of A2B2O7 rare earth composites as thermal barrier coatings, this project suggest a new research idea that La2Ce2O7 with high thermal explosion and low thermal conduction is synthetized as core and La2Zr2O7 with high thermal stability in high temperature and excellent sintering resistance is synthetized as shell, to form a core-shell particle La2Ce2O7@La2Zr2O7, which can be used as thermal protective coating material. First, La2Ce2O7@La2Zr2O7 nanoparticles with core-shell structure are synthetized by hydrothermal method. The mechanism of formation is revealed to control the microstructure. Then, the core-shell particles are pre-compacted and sintered at high temperature. The influences of the core-shell structure to the thermophysical properties are studied with special emphasis to reveal the mechanism of insulation. Finally, the core-shell particles are prepared as thermal protective coating and the mechanism of thermal shock resistance of the coating is revealed under thermo-mechanical coupling effect. The core-shell particles prepared in this project have important applications at thermal protection for superalloys in high temperature. The achievement of this project can provide theoretical and thecnological support for the application research of new thermal protective coating materials.

涂层材料是防热涂层发展的关键。针对A2B2O7型稀土复合氧化物热障涂层材料在热物理性能方面存在的突出问题，本项目提出以具有高膨胀、低热导率的La2Ce2O7为核芯，以高温稳定性好且抗烧结的La2Zr2O7为壳层，形成核壳结构La2Ce2O7@La2Zr2O7粉体用作涂层材料的研究思路。首先采用水热法合成具有核壳结构的La2Ce2O7@La2Zr2O7粉体，揭示其形成机理，实现可控制备。然后将核壳结构粉体预压并高温烧结成形，重点研究粉体的核壳结构对其烧结体热物理性能的影响机制，揭示其隔热机理。最后将核壳结构粉体制备成防热涂层并进行抗热震性能测试，揭示在热力耦合作用下，涂层的抗热震机制。本项目所制备的核壳结构粉体在高温合金表面热防护领域有重要的应用前景。项目的研究成果可为新型防热涂层材料的应用提供理论与技术支持。

热障涂层是航空发动机、燃气轮机等热端部件热防护的关键技术。La2Ce2O7和La2Zr2O7因其优异的性能有望成为比8%氧化钇稳定氧化锆（YSZ）耐热性能更好的新型热障涂层材料。然而La2Ce2O7抗烧结性能较差，La2Zr2O7的热膨胀系数较低。在本项目的支持下，项目组成员针对二者的性能特点，采用水热法合成了La2Ce2O7内核，然后通过共沉淀法成功制备La2Ce2O7@La2Zr2O7核壳结构纳米粉体。将粉体预压成块，在1100 ℃、1300℃和1500℃下进行了不同时间的烧结测试及在1100~1500 ℃烧结6 h以考察温度对其抗烧结性能的影响。采用扫描电镜、透射电镜、能谱仪分析了材料的形貌和成分，并测试了试样的密度和显微硬度。结果表明，La2Ce2O7内核宜采用低浓度的磷酸三钠作为沉淀剂，以水热法合成具有立方结构或八面体结构外形，粒径约200 nm。La2Zr2O7壳层宜采用十二烷基苯磺酸钠为表面活性剂，并调节pH值至10，采用共沉淀法制备。形成了包覆效果良好的La2Ce2O7@La2Zr2O7核壳结构。1100℃等温烧结时，核壳结构的密度变化率保持在2.1%以内，远低于La2Ce2O7和La2Zr2O7，孔隙和晶粒尺寸分布均匀，无裂纹和烧结现象出现。当烧结温度在1300 ℃以内时，核壳结构组织均匀，多孔，密度变化率稳定在10.6%以内，晶粒尺寸约维持在450 nm，晶粒长大速率与La2Zr2O7接近，抗烧结性能良好；烧结温度高于1300 ℃时，核壳结构孔隙增大且晶粒迅速长大，致密化加快，晶粒长大速率也变快，与La2Ce2O7接近，出现明显烧结现象；其显微硬度稍高于La2Ce2O7，而远低于La2Zr2O7。