NOUAILHETAS Quentin

Characterization and comparison of new bulk superconductors Superconducting materials have already been used in many applications such as MRI, LHC or ITER. Their main feature, i.e. no resistivity, makes them essential elements to improve energy efficiency in the future. This project concerns the properties of bulk superconductors. Indeed, they have high critical currents and can be magnetized to very high magnetic flux densities of several Tesla. New types of bulk samples became recently available, and their possibilities will be explored in detail. Bulk superconductors have undergone phenomenal developments in recent years and they are very promising for several applications such as levitation, supermagnets, electrical motors and magnetic gears in the fields of transport and aeronautics. This PhD project has three main aims. Firstly, features of three kinds of materials, MgB2, FeSe and YBCO should be critically compared to each other with respect to respective applications. Secondly, superconducting foams, a new kind of bulk superconductors, should be studied and characterized. The characterization of all these bulks is a major work of this project. Several methods should be employed, e.g. electrical methods and magnetic methods at different temperatures in order to obtain a full picture.These measurements will be combined with a thorough characterization of the sample microstructure using advanced electron microscopy methods (SEM, TEM, EBSD, atom probe). This will enable to optimize the flux pinning properties by selectively tuning the microstructure. The candidate should also participate in the elaboration of the samples. Thirdly, the final aim is the measurement of the magnetization of the superconducting bulk in situ, i.e.,directly in the application. It is obvious that the ultimate purpose of this project is to identify which material is promising for the energetic efficiency of electrical engineering applications. This PhD position will be carried out jointly between Nancy and Saarbrücken, it will strengthen theFranco-German collaboration between two universities within the Greater Region. Strong links already exist with laboratories in Japan, so a short or long stay in Japan is to be considered.