稀土钽酸盐低热导陶瓷制备与热学及力学性质的研究

发布时间：2018-02-12 20:12

  本文关键词： 稀土钽酸盐陶瓷块体 稀土钽酸盐涂层 热扩散系数 热导率 硬度　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：热障陶瓷涂层材料在航空航天、交通和大型火力发电等领域有广泛而重要的应用,对热障陶瓷涂层在高温下的使用提出了更高的要求,为了解决热障陶瓷涂层热导率低,相稳定性差等问题,本实验采用钽酸钇,镧系稀土钽酸盐作为新的候选材料,以期在降低热导率的同时还具有较好的高温力学性能。采用固相法制备镧系稀土钽酸盐陶瓷块体,粒径在2～14μm,气孔率在4%～9%之间,其中 NdTaO4,EuTaO4,DyTaO4,GdTaO4 和 ErTaO4 属于 m 相,YbTaO4和LuTaO4属于m'相。由于热效应导致的体积膨胀和声子散射,稀土钽酸盐陶瓷块体的热容(0.3J/k.mol～0.46J/k.mol)低于7-8YSZ。热扩散系数(0.38mm2/s～1.3mm2/s)和热导率(0.3J/k·mol～0.46W·m-1·k-1)在低温下呈线性下降,高温下由于热辐射的作用光子的热导不容忽视,热导率下降平缓并趋于一个较小值,当温度为800℃时,DyTaO4有最低的热导率1．38W·m-1·K-1 NdTaO4的热导率(1.41W·m-1·K-1)和DyTaO4是比较接近的,同时,稀土钽酸盐陶瓷块体的热扩散系数和热导率随着气孔率的升高而降低。在低温时,单斜m相有最低的能量,因而是低温稳定结构;当温度升高到1430℃以上时,四方相t有最低的能量,最为稳定。实验测得稀土钽酸盐陶瓷块体的显微硬度值在504HV～641HV之间,结合扫描电镜(SEM)图谱发现,在气孔和晶界处可能隐藏着局部的变形有助于提高材料的硬度值。选择较好化学稳定性和热稳定性的钽酸钇(YTaO4)粉体造粒后,采用大气等离子喷涂技术,在45钢基体上喷涂制备厚度为1.2mm左右的YTaO4热障涂层。当温度升高到700℃以后,由于光子的传热机制作用增大,气孔的烧结和缩聚,使涂层热扩散系数和热导率上升。钽酸钇热障陶瓷涂层的平均显微硬度值为498HV,低于钽酸钇陶瓷块体(520HV)的硬度值,与钽酸钇陶瓷块体相比,涂层比较粗糙,涂层间颗粒间距较大,孔隙率较高,导致涂层材料低于钽酸钇陶瓷块体的显微硬度值。
[Abstract]:Thermal barrier ceramic coating materials have been widely used in aerospace, transportation and large scale thermal power generation fields. The application of thermal barrier ceramic coatings at high temperature has put forward higher requirements, in order to solve the problem of low thermal conductivity of thermal barrier ceramic coatings. The phase stability is poor. In this experiment, yttrium tantalate and lanthanide rare earth tantalate are used as new candidate materials, in order to reduce thermal conductivity and have better mechanical properties at high temperature, lanthanide rare-earth tantalate ceramic blocks were prepared by solid phase method. The particle size is 2 ~ 14 渭 m and the porosity is between 4% and 9%. Among them, NdTaO4, EuTaO4DyTaO4Dy TaO4DTAO4 and ErTaO4 belong to m phase YbTaO4 and LuTaO4 belong to m phase. Volume expansion and phonon scattering due to thermal effect, The thermal capacity of rare-earth tantalate ceramic blocks is 0.3J / k.mol0.46J / k.mol. the thermal diffusivity is lower than 7-8YSZ. the thermal diffusivity is 0.38mm2s1.3mm2s) and the thermal conductivity is 0.3J / k 路mol~0.46W 路m-1 路k-1). At low temperature, the thermal conductivity of photons due to thermal radiation can not be ignored, and the thermal conductivity decreases slowly and tends to a smaller value. When the temperature is 800 鈩，

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