文献类型：期刊文献

英文题名：In-situ evaluation of porosity in thermal barrier coatings based on the broadening of terahertz time-domain pulses: simulation and experimental investigations

作者：Ye, Dongdong[1];Wang, Weize[1];Zhou, Haiting[2];Huang, Jibo[1];Wu, Wenchao[1];Gong, Hanhong[3,4];Li, Zhen[3,4]

机构：[1]East China Univ Sci & Technol, Sch Mech & Power Engn, Minist Educ, Key Lab Safety Sci Pressurized Syst, Shanghai 200237, Peoples R China;[2]China Jiliang Univ, Dept Qual & Safety Engn, Hangzhou 310018, Zhejiang, Peoples R China;[3]Univ Shanghai Sci & Technol, Minist Educ, Shanghai Key Lab Modern Opt Syst, Shanghai 200093, Peoples R China;[4]Univ Shanghai Sci & Technol, Minist Educ, Engn Res Ctr Opt Instrument & Syst, Shanghai 200093, Peoples R China

年份：2019

卷号：27

期号：20

起止页码：28150

外文期刊名：OPTICS EXPRESS

收录：;EI(收录号：20194007486949);WOS:【SCI-EXPANDED(收录号:WOS:000488282800086)】；

基金：National Natural Science Foundation of China (51775189).

语种：英文

外文关键词：Dielectric properties - Monte Carlo methods - Refractive index - Turbomachine blades - Ceramic materials - Terahertz waves - Intelligent systems - Time domain analysis - Ceramic coatings - Thermal barrier coatings

摘要：Porosity is one of the most important indicators for the characterization of the comprehensive performance of thermal barrier coatings (TBCs). Herein, we explored a fast, nondestructive porosity evaluation method based on the terahertz time-domain broadening effect. Different preparation process parameters were used to deposit the ceramic coatings, and the porosity ranged from 9.09% to 21.68%. Monte Carlo simulations were conducted to reveal the transitive relation between porosity and the terahertz time-domain broadening at different extinction coefficients and transmission distances. A transmission mode with an incidence angle of 0 degrees was used to estimate the terahertz dielectric properties of ceramic coatings and the relative broadening ratio of terahertz pulses at different porosities. As a result, the Monte Carlo simulations showed that the time-domain broadening effect was enhanced when the extinction coefficient and transmission distances increased. As the porosity increased, the refractive index decreased and the extinction coefficient increased. The latter was more sensitive to minor porosity changes as demonstrated by linear fitting comparisons. Meanwhile, the relative broadening ratio increased when the porosity increased, and reserved the sensitivity of the extinction coefficient to porosity changes. The effect was more obvious on the relative broadening ratio which experienced multiple transmissions and reflections. Moreover, the relative broadening ratio could be obtained faster and in an easier manner compared to the dielectric parameters in both the transmission and reflection modes, based on single-step tests with the use of actual terahertz wave inspection. Finally, this study proposed a novel, convenient, online, nondestructive, and noncontact porosity evaluation method that could be potentially utilized to evaluate the integrity of TBCs in gas turbine blades. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement