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(A*STAR) A rare earth aluminate thermal barrier coating for prolonged lifetime


   Department of Materials

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  Dr Y Chen, Dr David Hall  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

Modern gas turbines, either aircraft engines for jet propulsion or industrial gas turbines for electricity generation, operate at extremely high temperatures (>1500°C) for high efficiency and low emission. Such aggressive operating conditions have brought unprecedented challenges to ceramic thermal barrier coatings (TBCs), which are applied to the critical engine components for insulating them from hot gases and extending their lifetime. The materials being used for TBCs, such as yttria stabilised zirconia (YSZ) or gadolinium zirconate (Gd2Zr2O7), were introduced decades ago and cannot meet the current performance requirements. For example, YSZ is thermodynamically unstable above 1200°C and has little resistance to molten silicate attack. While Gd2Zr2O7 is stable up to 1500°C, it is brittle and susceptible to delamination and erosion. As a result, there has been a strong demand for a new TBC to achieve safer and more cost-effective flights. While many efforts have been made to modify the compositions of YSZ and Gd2Zr2O7 for overcoming their fundamental weaknesses, very few successes have been achieved so far.

In this project, we will develop a new TBC with higher temperature capability and durability. Instead of carrying on incremental research to modify current TBC materials, we will explore a new material based on gadolinium aluminate, which is a member of the perovskite rare earth aluminate family with high melting temperatures of up to 2500°C. We will first fabricate bulk ceramics and measure a number of thermal and mechanical properties to evaluate the suitability of gadolinium aluminate for TBC applications, including phase stability, coefficient of thermal expansion, fracture toughness, thermal conductivity and resistance to molten silicate attack. We will then manufacture gadolinium aluminate TBCs by air plasma spray and test their performance in simulated engine operating conditions. Failure analysis will be performed to identify failure mechanisms and quantify damage evolution. The thermal and mechanical properties of the coatings will be measured and compared to bulk ceramics to study the effect of microstructure on the properties. We will perform detailed characterisations to develop fundamental understanding of their structure-property relationships. The understanding will provide scientific guidance for optimising the coating design.

 The duration of the PhD programme is 4 years, split between the University of Manchester and A*STAR. You will use the world-leading capabilities in both institutes to manufacture, test and characterise the gadolinium aluminate ceramics and TBCs. The two institutes will work together for achieving a new robust TBC.

Entry Requirements:

Applicants must have obtained or be about to obtain a First or Upper Second class UK honours degree, or the equivalent qualifications gained outside the UK, in a related subject area.

Many of our students have also undertaken a master's degree, although this is not compulsory.

International applicant eligibility requirements: Some restrictions apply to applicants from certain Asian countries. In general, students from Europe, the Americas, Africa, Australia, New Zealand, Korea and Japan are eligible to apply for the programme. Unfortunately, we cannot accept applications from south-east Asian countries such as Singapore, China and Malaysia.

International applicants must ensure they meet the academic eligibility criteria (including English language) as outlined before contacting potential supervisors to express an interest in their project.

How to Apply

To be considered for this project you MUST submit a formal online application form - full details on how to apply can be found on the A*STAR PhD website https://www.bmh.manchester.ac.uk/study/research/astar/

Equality, Diversity and Inclusion

Equality, diversity and inclusion is fundamental to the success of The University of Manchester, and is at the heart of all of our activities. The full Equality, diversity and inclusion statement can be found on the website https://www.bmh.manchester.ac.uk/study/research/apply/equality-diversity-inclusion/


Funding Notes

Funding will cover tuition fees and stipend only. This scheme is open to both UK and international applicants. However, we are only able to offer a limited number of studentships to applicants outside the UK. Therefore, full studentships will only be awarded to exceptional quality candidates, due to the competitive nature of this scheme. Candidates will be required to split their time between Manchester and Singapore, as outlined on www.manchester.ac.uk/singaporeastar.

References

1. J.P. Martins, Y. Chen, G. Brewster, et al., Investigation of the bond coat interface topography effect on lifetime, microstructure and mechanical properties of air-plasma sprayed thermal barrier coatings. Journal of the European Ceramic Society, 2020. 40(15): 5719-5730.
2. Y. Chen, X. Zhang, X. Zhao, et al., Measurements of elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating using micro-cantilever bending. Surface and Coatings Technology, 2019. 374: 12-20.
3. C. Li, X. Zhang, Y. Chen, et al., Understanding the residual stress distribution through the thickness of atmosphere plasma sprayed (APS) thermal barrier coatings (TBCs) by high energy synchrotron XRD; digital image correlation (DIC) and image based modelling. Acta Materialia, 2017. 132: 1-12.
4. S. H. Lim, C. S. Chua, Brian T. M. Ong, Coryl Jing Jun Lee, Dennis Cheng Cheh Tan, L. T. Koh, W. K. Na, Shijie Wang, In Situ High Temperature XRD Studies of Molten Natural CMAS Corrosion on Thermal Barrier Coatings, Proceedings of the 2nd International Conference on Advanced Surface Enhancement (INCASE 2021), Springer
5. N. Khansur, U. Eckstein, Y. Li, D.A. Hall, J. Kaschta, and K.G. Webber, “Revealing the effects of aerosol deposition on the substrate-film interface using NaCl coating”, J. Am. Ceram. Soc. 2019;102:5763-5771.
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