| 题名 | 稀土荧光性质在热障涂层失效机理研究中的应用-博士论文 |
| 作者 | 赵素梅 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 中国科学院长春应用化学研究所 |
| 导师 | 曹学强 |
| 关键词 | 热障涂层 无损检测 Eu3+压力荧光探针 大气等离子喷涂 |
| 中文摘要 | 热障涂层被用来保护金属基底免受高温氧化和腐蚀，提高发动机热效率并延长其寿命，在航空、航天、汽车和大型火力发电等方面都有重要应用。目前广泛使用的涂层材料是6-8wt%Y2O3部分稳定的ZrO2（8YSZ）。由于8YSZ的长期使用温度低于1473K，高温易发生相变和烧结导致涂层失效，已难满足涡轮发动机进口温度进一步提高的需求。为了提高涂层的使用温度，延长涂层的使用寿命，使用新的涂层材料和优化涂层结构成为两个主要研究方向。 应力检测对于涂层失效机理的研究有重要意义。传统的无损应力检测方法有X射线衍射（XRD）、中子衍射（ND）和红宝石荧光光谱法，但是以上方法无法满足热障涂层热循环过程中应力测试的要求。采用掺Eu3+荧光亚层来指示涂层的脱落位置和脱落模式，用Eu3+离子荧光探针来指示涂层体系中内层的应力分布情况。Eu3+是常用的荧光离子，能发射单色性好和量子效率高的红色荧光。掺Eu3+的8YSZ荧光层在254nm紫外线照射下有发射峰在592nm和606nm的红色荧光产生，将荧光亚层的这一特性用于指示双陶瓷层热障涂层的脱落位置和脱落程度。Eu3+离子的5D0→7F2跃迁峰峰位与离子所处应力环境有线性关系。根据此关系，测得涂层5D0→7F2跃迁峰峰位从而求得涂层的应力分布情况。 研究稀土的荧光性质在热障涂层失效机理中的应用。采用大气等离子喷涂（APS）制备了8YSZ:Eu单陶瓷层涂层、La2(Zr0.7Ce0.3)2O7/8YSZ:Eu （LZ7C3/8YSZ:Eu）双陶瓷层涂层、LaMgAl11O19/8YSZ:Eu（LaMA/8YSZ:Eu）双陶瓷层涂层和LZ7C3/8YSZ功能梯度涂层，并且研究了Eu3+离子掺杂对于8YSZ高温相变稳定性的影响。 对LZ7C3/8YSZ:Eu涂层在1250±50℃条件下进行热循环实验，7370次后失效。在热循环过程中，随着LZ7C3外层的逐渐脱落，内层8YSZ:Eu荧光亚层逐渐暴露于空气中，在紫外灯照射下可以看到有明显的红色荧光。荧光亚层可以用来简单有效的指示LZ7C3/8YSZ:Eu双陶瓷层热障涂层体系的脱落和失效程度。LZ7C3/8YSZ:Eu双陶瓷层热障涂层的寿命远远大于传统8YSZ涂层和其他双陶瓷层涂层，这主要是因为LZ7C3和8YSZ相似的热膨胀系数。LZ7C3/8YSZ涂层失效的主要原因是热生长氧化物的生成，LZ7C3外层材料的烧结和相变以及8YSZ的老化。 在LZ7C3/8YSZ:Eu双陶瓷层热障涂层的基础上发展了LZ7C3/8YSZ功能梯度热障涂层，涂层从内到外依次为100%8YSZ, 75%8YSZ+25%LZ7C3，50%8YSZ+50%LZ7C3，25%8YSZ+75%LZ7C3，100%8YSZ。相应块材料的热膨胀系数依次为10.97×10-6K-1、10.92×10-6K-1、10.77×10-6K-1、10.64×10-6K-1和10.10×10-6K-1。LZ7C3/8YSZ梯度热障涂层在1250±50℃热循环寿命是880次，小于LZ7C3/8YSZ:Eu双层。粘结层的反常氧化、LZ7C3的重结晶和烧结是涂层点状脱落的主要原因。 将Eu3+压力荧光探针技术应用到LaMA/8YSZ:Eu双陶瓷层热障涂层中，激发波长为532nm。测得涂层荧光发射曲线5D0→7F2跃迁峰峰位，根据Eu3+离子的5D0→7F2跃迁峰峰位与离子所处应力环境有线性关系，计算得相应荧光测试点的应力情况。喷涂后LaMA/8YSZ:Eu涂层中8YSZ:Eu层既有压缩应力又有拉伸应力，总体平均值为55MPa的拉伸应力。随着热循环的进行，压缩应力逐渐消失拉伸应力逐渐增大。另外，8YSZ:Eu荧光亚层在依然可以用来指示LaMA/8YSZ:Eu热障涂层的脱落和失效。 使用高温固相法合成了8YSZ:Eu粉末，并通过大气等离子方法制备了8YSZ:Eu涂层，对涂层的相变、荧光性质进行分析，在8YSZ中添加Eu3+可以提高8YSZ的高温相稳定性。在氧化锆晶格中掺杂不同价态的离子，可以将氧空穴引入到晶格中。而氧空穴可以提高四方相在高温煅烧过程中的相稳定性。发射光谱中5D0→7F2能级跃迁发射峰随着粉末和涂层高温老化的进行，除了刚开始的不规律变化之外，变化情况为：峰位值发生红移；半峰宽度呈现增大的趋势；发射峰强度不断降低。 |
| 英文摘要 | Thermal barrier coatings (TBCs), which are applied to protect substrate materials against thermal corrosion and oxidation, have been widely used in the hot section of gas turbine engines to improve the fuel efficiency and prolong the lifetime of components. The state-of-art topcoat material typically used is yttria partially stabilized zirconia (YSZ), especially 8YSZ. 8YSZ performs well up to about 1200oC, but it cannot be used above 1200oC for long term due to sintering and phase transformation, which will result in failure of TBCs. In order to increase the operation temperature and lifetime of TBCs, new TBCs structures were designed and new materials were developed. Non-destructive diagnostic tools could assess the damage of TBCs, which would alleviate the risk of TBC premature failure by prompting its replacement before the level of TBC damage threatens performance of safety. It is necessary and important to evaluate and predict the development of the residual stress for the study of failure mechanism of TBCs. Several non-destructive techniques such as X-ray diffraction (XRD) techniques, neutron diffraction (ND), ruby fluorescence spectroscopy (RFS) have been applied to investigate the coating stresses. However, all of them have some limitations. It is highly demanded to develop a new method to overcome the limitation of these techniques in order to monitor the residual stress in the ceramic layer of the TBCs. Eu3+ is one of the most typical luminescent rare-earth ions, which provides a very intense and sharp luminescence spectrum when doped into the host material. 8YSZ:Eu coating has intense emission peak at 592 nm and 606 nm for excitation at 254 nm. 8YSZ:Eu luminescence sublayer is applied to indicate the spallation and damage degree of double-ceramic-layer coatings. Eu3+ photoluminescence piezo-spectroscopy based on the relationship between the stress and peak position of 5D0→7F2 transition of Eu3+ ions in 8YSZ is used to detect the residual stress of the inner ceramic layer of the TBCs. The property of rare-earth photoluminescence is applied in the study of TBC failure mechanism. 8YSZ:Eu coating, La2(Zr0.7Ce0.3)2O7/8YSZ:Eu (LZ7C3/8YSZ:Eu) double-ceramic-layer coating, LaMgAl11O19/8YSZ:Eu (LaMA/8YSZ:Eu) double-ceramic-layer coating, and LZ7C3/8YSZ:Eu five-layer ceramic-ceramic functionally graded TBCs (FG-TBCs) have been prepared by atmospheric plasma srpraying (APS). Furthermore, the effect of Eu3+ ions addition on the phase stability of 8YSZ has been studied. Thermal cycling test has been carried out on the LZ7C3/8YSZ:Eu coating, and the coating failed after 7370 cycles. As thermal cycling test going on, LZ7C3 top layer spalled bit by bit and the inner 8YSZ:Eu luminescence layer exposed. Red luminescence can be observed from the exposed 8YSZ:Eu layer under 254 nm UV illumination. The application of Eu3+-doped luminescence sublayer can be a useful non-destructive technique to indicate the spallation and damage degree of DCL coatings. LZ7C3/8YSZ:Eu coating has a much longer lifetime than that of dual layer LZ/8YSZ, LC/8YSZ coating and single layer LZ7C3, 8YSZ coating. It can be concluded that LZ7C3/8YSZ:Eu TBCs showed a promising thermal cycling performance at 1250±50oC. This could be due to the thermal expansion coefficient (TEC) of LZ7C3, which is about 10.66×10-6 K-1 and similar to that of 8YSZ. The similar TEC of LZ7C3 and 8YSZ can reduce the thermal residual stress during thermal cycling and prolong the lifetime of LZ7C3/8YSZ:Eu coating. The phase transition and sintering of LZ7C3, formation of thermally grown oxides (TGO), and the sintering of 8YSZ:Eu, are the primary factors for the spallation of DCL coating. LZ7C3/8YSZ FG-TBC consists of 100%8YSZ, 75%8YSZ+25%LZ7C3, 50%8YSZ+50%LZ7C3, 25%8YSZ+75%LZ7C3 as the interlayer, 100%LZ7C3 as the top coat. The average TEC values of bulk samples of each layer are 10.97×10-6，10.92×10-6，10.77×10-6，10.64×10-6，10.10×10-6K-1. The graded coating failed after 880 thermal cycles |
| 语种 | 中文 |
| 公开日期 | 2016-05-25 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/65051]  |
| 专题 | 长春应用化学研究所_长春应用化学研究所知识产出_学位论文 |
| 推荐引用方式 GB/T 7714 | 赵素梅. 稀土荧光性质在热障涂层失效机理研究中的应用-博士论文[D]. 中国科学院长春应用化学研究所. 中国科学院研究生院. 2015. |
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