掺杂对氧化锆基热障涂层材料热物理性能的影响

发布时间：2018-02-25 08:12

本文关键词： 热障涂层氧化锆热物理性能热导率晶格缺陷　出处：《清华大学》2016年博士论文　论文类型：学位论文

【摘要】：随着工业的发展,燃气轮机和飞机发动机的工作温度不断提高,这对高温合金部件的热防护提出了越来越严苛的要求。具有极低热导率的热障涂层可以有效的降低合金部件表面的温度,从而延长其使用寿命,提高热机工作效率。目前,应用最为广泛的热障涂层材料是具有t′相结构的6-8%氧化钇稳定氧化锆(YSZ)。本文以YSZ等稀土氧化物和氧化锆组成的二元固溶体为基础,通过掺杂构造多元固溶体材料体系,系统研究了缺陷对材料晶格结构以及热物理性能的影响,并对氧化锆基多元氧化物固溶体作为热障涂层新材料的潜力进行了初步的评估。具体研究内容包括:首先,我们分别采用Ti~（4+）、Sn~（4+）和Th~（4+）取代8YSZ中的Zr~(4+),构造三元固溶体材料体系,研究了四价离子半径对8YSZ晶格结构以及t′相稳定性的影响。此外,我们还测试了材料的硬度、弹性模量、断裂韧性、热导率以及热膨胀系数这些对热障涂层性能有重要影响的热物理性能,并深入研究了晶格缺陷与晶格畸变对材料热导率的影响。基于晶格结构的稳定性以及热物理性能,我们对四价离子掺杂8YSZ固溶体作为热障涂层新材料的潜力进行了初步的评估。其次,我们在8YSZ中增加稀土元素含量,以Ln_2Zr_2O_7型稀土锆酸盐为基础,在晶格Ln位和Zr位同时引入掺杂,构造(Ca_2Nb_2O_7)_x(Gd_2Zr_2O_7)_(1-x)、(Nd_2Sn_2O_7)_x(Yb_2Zr_2O_7)_(1-x)和(Sm_2Sn_2O_7)_x(Yb_2Zr_2O_7)_(1-x)三个四元固溶体材料体系。我们研究了掺杂对焦绿石结构和萤石结构之间有序无序相变的影响,并在相变临界点附近观察到材料硬度、弹性模量和断裂韧性的特殊变化。此外,我们还分别讨论了晶格结构对材料声子热导和辐射热导的影响,提出了在整个温度范围内获得低热导率材料的设计原则。最后,我们在Ln_2Zr_2O_7型稀土锆酸盐中进一步增加稀土元素含量,构造Zr_3Ln_4O_(12)型固溶体(Ln=Gd、Y、Er、Yb),研究了稀土离子半径对材料晶格结构以及显微形貌的影响。同时,我们还测试了材料的硬度、弹性模量、断裂韧性以及热导率和热膨胀系数,并对Zr_3Ln_4O_(12)型固溶体与8YSZ构造多层或梯度热障涂层的潜力进行了初步的评估。
[Abstract]:With the development of industry, the working temperature of gas turbine and aircraft engine is increasing. The thermal barrier coating with extremely low thermal conductivity can effectively reduce the surface temperature of alloy parts, thus prolong its service life and improve the efficiency of heat engine. The most widely used thermal barrier coating material is 6-8% yttrium oxide stabilized zirconia with t 'phase structure. Based on the binary solid solution composed of rare earth oxides and zirconia such as YSZ, the multicomponent solid solution system is constructed by doping. The effects of defects on the lattice structure and thermal physical properties of the materials are systematically studied, and the potential of zirconia based polyoxide solid solution as a new material for thermal barrier coating is preliminarily evaluated. The ternary solid solution material system was constructed by replacing the Zr~(4 in 8YSZ with Ti~(4 / Sno _ 4) and Th~(4), respectively. The effects of tetravalent ion radius on the lattice structure and t'phase stability of 8YSZ were studied. In addition, the hardness and elastic modulus of the material were measured. Fracture toughness, thermal conductivity and thermal expansion coefficient are the thermal physical properties which have important influence on the properties of thermal barrier coatings. The effects of lattice defects and lattice distortion on the thermal conductivity of materials are studied. The potential of tetravalent ion doped 8YSZ solid solution as a new material for thermal barrier coating is preliminarily evaluated. Secondly, we increase the content of rare earth elements in 8YSZ based on Ln_2Zr_2O_7 rare earth zirconate. At both the Ln and Zr sites of the crystal lattice, the addition of dopants to the structure of the structure of the Quaternary solid solution material system has been constructed. We have studied the effect of doping on the orderly phase transition between the pyrochlore structure and the structure of the fluorite structure. We have studied the effect of doping on the orderly phase transition between the pyrochlore structure and the structure of the fluorite structure, and the structure of the ternary solid solution material system, we have studied the effect of the doping on the orderly phase transition between the pyrochlore structure and the fluorite structure, and the structure of the Nd2Sn2O7xYb2Zr2O7 and the Nd2Sn2O2Zr2O7 structure, we have studied the effect of doping on the ordered phase transition between the pyrochlore structure and the structure of the pyrochlore. Special changes in hardness, elastic modulus and fracture toughness are observed near the critical point of phase transition. In addition, the effects of lattice structure on phonon thermal conductivity and radiation thermal conductivity are discussed, respectively. The design principles for obtaining low thermal conductivity materials in the whole temperature range are proposed. Finally, we further increase the content of rare earth elements in Ln_2Zr_2O_7 rare earth zirconate. In this paper, the effect of the radius of rare earth ions on the lattice structure and the microstructure of the material has been studied. At the same time, the hardness, elastic modulus, fracture toughness, thermal conductivity and thermal expansion coefficient of the material have also been tested. The potential of the structure of multilayer or gradient thermal barrier coatings with the structure of Tix _ 3Ln _ 4O _ 2O _ (12) type solid solution and 8YSZ has been preliminarily evaluated.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG174.4

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