| 题名 | 氧化锆相变的荧光分析方法 |
| 作者 | 惠宇 |
| 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 | 氧化锆 氧化铕 相变 荧光 |
| 中文摘要 | 为了提高燃气轮机的推重比和热效率，需要进一步提高燃气温度，涡轮叶片和其他热端部件的工作温度也相应地提高，因此热障涂层（TBCs）引起了人们的广泛关注。热障涂层是利用耐高温、抗腐蚀和低热导率的陶瓷材料，以沉积的方式与金属基底复合的表面防护涂层。目前，广泛使用的涂层顶层材料为6~8 wt.% Y2O3部分稳定化的ZrO2（8YSZ）。TBCs在长期使用过程中会发生脱落。导致涂层失效的因素很多，主要包括：陶瓷涂层与金属基底之间的热膨胀不匹配、陶瓷涂层发生相变、陶瓷涂层和粘结层之间发生反应、粘结层发生氧化和腐蚀、陶瓷涂层的烧结等。热障涂层失效机理的研究已经成为迫在眉睫的关键课题。其中，陶瓷涂层的相变是一个重要因素。目前，涂层相变的检测手段有X射线衍射（XRD）、中子衍射（ND）和Raman光谱等，这些测量方法不能完全满足涂层相变分析在探测深度、空间分辨率等方面的要求。因此，研发一种检测陶瓷涂层相变的无损检测技术有重要意义。稀土荧光离子可以在涂层任意位置实现掺杂而不影响涂层本身性质，本论文通过在8YSZ中掺杂稀土Eu3+离子，建立荧光性质和相组成之间的关系，研究新型相变检测手段。 采用高温固相合成法，通过控制Y3+的含量合成了单斜相、四方相和立方相的氧化锆粉末，研究了氧化锆相变对氧化铕荧光性质的影响。研究表明，当Eu3+处于低对称性无反演中心（单斜相）时，5D0→7F2电偶极子跃迁的强度最强，荧光寿命短；当Eu3+处于高对称性有反演中心（四方相和立方相）时，5D0→7F1磁偶极子跃迁的强度最强，荧光寿命长。可以利用Eu2O3的荧光性质来检测氧化锆的相变。不同摩尔浓度的Eu3+掺杂8YSZ的研究表明，当Eu3+的掺杂浓度为3 mol.%时，8YSZ:Eu3+具有四方相晶体结构，荧光发射强度强、荧光寿命长，是用于检测8YSZ涂层相变程度的理论最佳掺杂浓度。 采用水热合成法合成8YSZ:Eu3+ (1 mol.%)粉末，研究了该样品在高温长时间热暴露之后的相组成和荧光性质变化，并进一步探讨了两者之间的关系。在无单斜相存在时，可以利用荧光峰(I593/I608)的比值来初步评估相变的程度，荧光寿命也可以辅助说明相变的情况。采用共沉淀法合成8YSZ:Eu3+ (1 mol.%)粉末，在800℃处理6 h后，将样品置于150℃的水热釜中进行水热降解，考察其相组成和荧光性质的演化。结果表明，8YSZ:Eu3+粉末具有四方相晶体结构，在水热降解条件下，由于水的作用，发生了四方相到单斜相的相变，进一步的使粉末的荧光性质也发生改变。 采用水热合成法合成不同Eu3+掺杂浓度的ZrO2:Eu3+荧光粉，随后在不同温度下处理相同时间。研究表明，Eu3+的掺杂浓度和煅烧温度对于ZrO2:Eu3+荧光粉的晶体结构和荧光性质有重要影响。Eu3+作为三价稀土荧光离子，可以稳定四方相和立方相结构的ZrO2。四方相和立方相的ZrO2:Eu3+荧光粉是研究者关注的焦点，它们能够作为一种原材料去制备高效荧光性能的透明陶瓷。 |
| 英文摘要 | In order to meet the requirements of increasing propulsion and efficiency of gas–turbine engines, the using temperature of the turbine blade and the other parts of engine need to be further enhanced, thus thermal barrier coatings (TBCs) has attracted extensively attention. Thermal barrier coatings are protective coatings by depositing ceramic materials on a metal substrate, which have high temperature resistance, corrosion resistance and low thermal conductivity. Nowadays, the current state-of-the-art ceramic top coat material is 6~8 wt.% Y2O3 partially stabilized zirconia (8YSZ). Observations of coatings after service indicate that they can fail by cracking, delamination, and spallation, typically on cooling to room temperature. Many factors lead to the failure of thermal barrier coatings, including: the thermal expansion mismatch between ceramic top layer and metal substrate, phase transformation, chemical reaction between the ceramic top coat and bond coat, the formation and growth of a thermally grown oxide (TGO), porous coating sintering. Therefore, the research of TBCs failure mechanism is regarded as a key problem for the next generation turbine engines. Among these, the phase transformation of TBCs during service is a key factor in controlling the TBCs life. Though several techniques have been applied to assess the phase transformation of the TBCs, such as neutron diffraction, XRD and Raman spectroscopy, they still can not fully satisfy the special requirements needed in the TBCs, including the proper penetration depth and location, spatial resolution, and monitoring the evolvement. Therefore, it is necessary to develop a new non-destructive diagnostic tool to measure the phase transformation of TBCs. The rare earth elements can be doped into anywhere of the TBCs without affect the nature of the coatings, therefore, in the present work, we developed a new fluorescence measurement technique by using the materials of 8YSZ doped with Eu3+, furthermore the relationship between phase composition and fluorescence properties is established. A solid state reaction method at high temperature was used to synthesize monoclinic, tetragonal and cubic zirconia by controlling Y3+-doping concentration. The effects of phase transformation of zirconia on the fluorescence properties of Eu3+ were investigated. When the Eu3+ ions embedded in a low-symmetry site without an inversion center (monoclinic phase), the 5D0 - 7F2 electric dipole transition (EDT) around 617 nm is the strongest, and the decay lifetime is short; while in a high-symmetry site with an inversion center (tetragonal and cubic phase), the 5D0 - 7F1 magnetic dipole transition (MDT) is dominating with emission wavelength of about 593 nm, and the decay lifetime is long. So we can make use of the fluorescent properties of Eu3+ to detect the phase transformation of zirconia. In the case of different concentrations of Eu3+ doped 8YSZ, when doping concentration is 3 mol%, the nanophosphor has a pure tetragonal phase structure, the emission intensity is intense and decay lifetime is long, this concentration is the theory optimum doping concentration that can be used to indicate the extent of phase transformation. Nanocrystalline 8YSZ doped with 1 mol.% Eu3+ was synthesized via hydrothermal method. Fluorescence properties variation and phase composition variation of YSZ:Eu3+ powder were investigated after long-term, high temperature thermal exposure. The results show that when monoclinic phase is absent, the intensity ratio I593/I608 of fluorescence spectroscopy can be used to preliminary assess the extent of the phase transformation, the fluorescence lifetime can also assist in illustrating the extent of the phase transformation. Nanostructured 8YSZ doped with 1 mol.% Eu3+ was synthesized via chemical co-precipitation. The evolution of phase composition and fluorescence properties of 8YSZ:Eu3+ powder have been assessed after being subjected to hydrothermal degradati |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/64491]  |
| 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 | 惠宇. 氧化锆相变的荧光分析方法[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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