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锆酸镧粉体与热障涂层的制备和性能研究
其他题名Study on the Properties and Preparation of La2Zr2O7 Powder and Derived TBCs
王学营
学位类型博士
导师张伟刚
2011-06-02
学位授予单位中国科学院研究生院
学位专业化学工程
关键词热障涂层 锆酸镧 等离子喷涂
摘要热障涂层兼有隔热和抗氧化功能,是目前最为先进的高温合金表面防护涂层技术,广泛应用在航空、航天、汽车和大型火力发电等行业。特别是随着燃气轮机/飞机发动机向着高温高效方向的发展,对陶瓷层材料的性能要求越来越高,传统的Y2O3稳定的ZrO2(YSZ)材料已经很难满足高性能需求,研究能替代YSZ用在更高温度下的热障涂层材料成为国内外研究的重点。锆酸镧(La2Zr2O7, LZ)由于具有熔点高、相结构稳定、导热系数低等特点而被认为是一种非常有潜力的新型高温热障涂层材料。本文采用不同方法制备了La2Zr2O7基粉体,利用大气等离子喷涂(APS)技术制备出新型锆酸镧基热障涂层。对涂层的热膨胀系数、抗热震、热导率、结合强度等性质进行了系统的研究。主要内容和结论如下:采用共沉淀喷雾造粒技术制备了化学整比的La2Zr2O7粉末,但是发现成分存在偏析;首次采用熔盐法,制备了存在烧绿石结构的纳米La2Zr2O7粉末。研究了反应时间、反应温度及盐料比对产物的物相、及粒径的影响。通过改变实验条件,成功实现了产量的适当放大。经过喷雾造粒后,粉体的流动性及松装密度均能满足等离子喷涂的要求。利用等离子喷涂制备了两种粉体的涂层,通过对两种涂层的性能进行对比发现,与传统微米级热障涂层相比,纳米陶瓷热障涂层有较高的热膨胀系数、更高的结合强度、较好的抗热冲击性能、较低的热扩散系数及更好的隔热性能。利用熔盐法制备了Dy, Gd离子掺杂La2Zr2O7粉体。研究了Dy, Gd离子掺杂对La2Zr2O7涂层性能的影响。结果表明, Dy, Gd掺杂可以明显改善La2Zr2O7涂层的结合强度、热震、热膨胀系数及热导率性能。研究了Ta离子在B位取代Zr离子对La2Zr2O7涂层性能的影响。随着Ta含量的增加,所制备粉体的松装密度逐渐增大;当x≤0.3随着Ta含量的增加,La2TaxZr2-xO7涂层的热膨胀系数整体上是增大的,涂层的结合强度逐渐增大;随着Ta含量的增加,涂层的抗热震性能先增强后下降;当x=0.3时,掺杂Ta可以明显降低涂层的热导率。
其他摘要Thermal barrier coatings (TBCs) are the most advanced high temperature protective coatings and widely used in aeronautic, astronautics, motor industry and heat power station, for their good performance at thermal barrier and oxidation resistance. With the improvement of working temperature and thermal efficiency of gas turbine, there is a growing demand for a better performance of the ceramic top-coat in the thermal barrier coatings (TBCs) whereas conventional yttria-stabilized zirconia (YSZ) ceramics can not meet the demand any more, and the search for new candidate materials that can work at even higher temperature has been intensified in the future. Among the interesting candidates for TBCs, lanthanum zirconate (La2Zr2O7, LZ) has been proposed as a promising TBCs material for its high melting point, more stable structure and lower thermal conductivity than YSZ. In this work, the La2Zr2O7-based powders were prepared by different methods, and the La2Zr2O7-based TBCs were fabricated by Air Plasma Spraying (APS). On this basis, the coefficient of thermal expansion, tensile strength, thermal shock resistance and thermal conductivities of TBCs were studied in detail. The obtained main results are summarized as follows: La2Zr2O7 powders were synthesized by co-precipitation spraying granultion method using ammonia as precipitating agent. Although the La2Zr2O7 powders in stoichiometric ratio have been prepared successfully, there has presented the ingredient segregation during the preparing process. The pyrochlore La2Zr2O7 nano-powders were prepared by Molten Salts method for the first time using Na2SO4-K2SO4 as molten salts and dispersants. A systematic investigation has been carried out to understand the factors, such as the molar ratio of the salts to the raw materials, the reaction time and the experimental temperature, influencing the particle size and bulk phase of the samples. The output has been enlarged successfully though changing the experimental conditions. After spraying granulation, the flowability and apparent density of La2Zr2O7 powders have satisfied the demand of APS. The coatings were prepared by APS using the powders synthesized by two methods. Through carrying on the contrast to two kind of coating's performance, we can see that the coating plasma-sprayed by nanostructured La2Zr2O7 powders have higher thermal expansion, higher tensile strength, better thermal shock resistance and lower thermal conductivities than microstructured La2Zr2O7 powders. La2Zr2O7 powders doped with Dy and Gd have been synthesized by Molten Salts method. The influences of dopted Gd and Dy on the performance of La2Zr2O7 coating were investigated. The results show that the addition of Gd and Dy into La2Zr2O7 can largely improve the performance of thermal expansion, tensile strength, thermal shock resistance and thermal conductivities of La2Zr2O7 coating. The influences of dopted Ta on the performance of La2Zr2O7 coating were also investigated. With increasing the content of Ta, the apparent density of La2TaxZr2-xO7 increased gradually; When x≤0.3, the thermal expansion coefficient and tensile strength of La2TaxZr2-xO7 coatings increased in whole, the performance of thermal shock resistance enhanced gradually; When x=0.3, dopted Ta can obviously reduce the thermal conductivities of La2Zr2O7 coating.
页数127
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/1677
专题研究所(批量导入)
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王学营. 锆酸镧粉体与热障涂层的制备和性能研究[D]. 中国科学院研究生院,2011.
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