MESA+ University of Twente
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Chung-Yul Yoo (promotion date: 12 September 2012)

Phase stability and oxygen transport properties of mixed ionic-electronic conducting oxides.

Promotion date: 12. September 2012

Promotor: Arian Nijmeijer

Assistant promotor: Dr. Henny J. M. Bouwmeester

Mixed ionic-electronic conductors (MIECs) have a potential for use as an oxygen separation membrane, which possesses oxide ionic conductivity in conjunction with electronic conductivity at elevated temperatures, typically 500 – 1000 °C.

Application of MIECs offers significant advantages over conventional cryogenic distillation, in the sense that membrane separation is simpler and more energy efficient. Also it provides a continuous delivery of oxygen with infinite selectivity.

Here, a focus has been on the examination of the crystal structure and phase stability of selected MIECs and elucidation of the oxygen transport kinetics, with emphasis on the oxygen surface exchange properties, exhibited by these solids.

What do you hope to contribute in your research?

Using membranes for oxygen separation from air, has significant advantages over conventional cryogenic distillations, which need huge distillation towers. The aim of my research within the MEM-BRAIN project is to develop membrane materials and integrate these into coal power plants. The membranes must be stable at high temperatures, continuously showing excellent oxygen transport properties. In my PhD-study, I have developed membrane materials and investigated their oxygen surface exchange kinetics, using the pulse-response 18O-16O isotope exchange technique.

Did you collaborate with other scientists and institutes?

The MEM-BRAIN project has been funded by the German government, via the Helmholtz Association. At the University of Twente, we have performed some fundamental research on the materials, and investigated their stability and performance. Good collaborations have taken place with Jülich Research Centre, Fraunhofer Institute, Universidad Politécnica de Valencia and University of Science and Technology of China.

What skills did you learn during the project?

I have learned that communication and presentation are very important for a scientist. I have improved greatly on that, talking to other experts and performing on talks at symposia and conferences.

Also, I possess far more knowledge now and experimental skills like: preparing samples, testing and characterizing materials, and interpretation of measurements.

In the Netherlands I have learned that having meetings and being open-minded, contribute to speeding up scientific research and coming to better results. I hope to bring these skills into research groups in my home country South Korea one day.

Can you mention some publications?

I have published in: Physical Chemistry and Chemical Physics (PCCP), Applied Physics Letters, Journal of Solid State Electrochemistry and Solid State Ionics. Also I was a speaker on the EMRS meeting 2010/2012 in Strasbourg, and at the Electroceramics twelfth and thirteenth International Conference on Inorganic Membranes, here in Enschede.

What are your future plans?

I am applying for a research job at an institute and company in South Korea. I guess materials technology and cost-efficient materials for energy-efficient systems, will be the main focus there. I would like to perform practical research together with fundamental aspects, closer to the final products sold by companies.

What in your opinion is important for Mesa+ to stay successful in future?

Many people I owe a lot. Mark Smithers always carves out his time to help me on the scanning electron microsope (SEM) experiments. Also, my colleagues were always open to discuss the line of research I was striving for. My colleagues from spin-off company Solmates have helped me to use prepared thin films, using pulse laser deposition for my experiments. All different disciplines are present at Mesa+. They understand each other’s disciplines and are open minded.