Charakterisierung und Vergleich von neuen Bulk-Supraleitern
Zusammenfassung der Projektergebnisse
The project had originally three main aims. Firstly, features of two kinds of materials, MgB2 and YBCO were to be compared to each other with respect to applications. Secondly, superconducting foams, a new kind of bulk superconductors, should be studied and characterized. Thirdly, the measurement of the magnetization of the bulk, in situ, in superconducting electrical machines was planned. In the project runtime, a fourth topic was investigated: We have explored the possibilities of the simplest iron-based HTSc, FeSe, which offers a combination of the advatages of MgB2 with the properties of the true HTSc materials, even though the Tc of this material is only about 8-9 K. The first part was done in collaboration with P. Badica (Magurele, Romania), enabling the magnetic characterization and trapped field measurements of MgB2 samples prepared by spark-plasma sintering (SPS). Trapped-field (TF) magnets were constructed using up to 6 MgB2 pellets, and a maximum TF field of 6.78 T (center, 12 K) was recorded. Furthermore, we attempted to perform 3D X-ray measurements on MgB2 and YBCO pellets, resulting in a 3D mapping of the residual pores of the samples. Thus, worthy information about the internal microstructure of the samples could be obtained. The YBCO system was further investigated by high-field cantilever magnetometry (HFML Nijmegen), enabling the recording of magnetic data up to 33 T applied magnetic field. These measurements enabled a determination of the irreversibility fields and the current density down to 40 K, filling an important void in the literature. For the second part, the YBCO foam samples, a variety of characterization measurements of the magnetic properties and the respective microstructure was performed in this project. All the data collected enable a modelling of the superconducting foams. Although the obtained TF values of the foam material are quite low at 77 K, it is clear that the foams can act as TF magnets, and lowering the temperature by means of a cryocooler will improve the field trapping capability considerably. The first results of this modelling already provided valuable information about the limits of such samples, suggesting that a more regular structure would be beneficial. Such structures could be e.g., realized by means of 3D printing. Based on the experimental practice with the foam samples, we could come up with possible applications of TF-magnets in space – the so-called FPDI interfaces of small satellites (cube sats). We have developed a new scheme for this situation, and deduced a novel design of a compact TF-magnet energized by pulsed fields, dubbed PFM. For the use in satellites, the win by reducing the sample weight of the superconductor will bring a larger payload as well as a much more flexible use of these systems, as the TF magnets can be energized in space. The fabrication/characterization of FeSe bulk sample provided insight to a quite complicated material system having several competing phases. Also in this case, the SPS-technique enabled the fabrication of highly dense samples. A remaining task is now the design of additional flux pinning sites in these samples to improve the achievable critical current densities by minimizing the FeSe grain size. This will be a task for future work. Overall, the present project enabled a deeper understanding of all the investigated materials, resulted in 24 publications in refereed journals, and created several new topics and directions for both experiments and modelling in future work.
Projektbezogene Publikationen (Auswahl)
- Superconducting YBCO Foams as Trapped Field Magnets. Materials, 12(6):853, March 2019
Michael Koblischka, Sugali Naik, Anjela Koblischka-Veneva, Masato Murakami, Denis Gokhfeld, Eddula Reddy, and Georg Schmitz
(Siehe online unter https://doi.org/10.3390/ma12060853) - Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag. Materials, 13(21):5018, November 2020
Michael Rudolf Koblischka, Yassine Slimani, Anjela Koblischka-Veneva, Thomas Karwoth, XianLin Zeng, Essia Hannachi, and Masato Murakami
(Siehe online unter https://doi.org/10.3390/ma13215018) - Flux creep after field trapping in YBa2Cu3Ox foams. Superconductor Science and Technology, 33 (4):044008, April 2020
M Koblischka, S Pavan Kumar Naik, A Koblischka-Veneva, D Gokhfeld, and M Murakami
(Siehe online unter https://doi.org/10.1088/1361-6668/ab72c3) - Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5 T. Scientific Reports, June 2020
Petre Badica, Gheorghe Aldica, Mihai Alexandru Grigoroscuta, Mihail Burdusel, Iuliana Pasuk, Dan Batalu, Kévin Berger, Anjela Koblischka-Veneva, and Michael Rudolph Koblischka
(Siehe online unter https://doi.org/10.1038/s41598-020-67463-y) - Secondary phase particles in bulk, infltration-growth processed YBCO investigated by transmission Kikuchi diffraction and TEM. Superconductor Science and Technology, 33(3):034010, March 2020
A Koblischka-Veneva, M Koblischka, J Schmauch, and M Murakami
(Siehe online unter https://doi.org/10.1088/1361-6668/ab6ebf) - (RE)Ba2Cu3O7-d and the Roeser-Huber Formula. Materials 2021, 14, 6068
Anjela Koblischka-Veneva and Michael Rudolf Koblischka
(Siehe online unter https://doi.org/10.3390/ma14206068) - Magnetic phases in superconducting, polycrystalline bulk FeSe samples. AIP Advances, 1(1):015230, January 2021
Quentin Nouailhetas, Anjela Koblischka-Veneva, Michael Rudolf Koblischka, S. Pavan Kumar Naik, Florian Schäfer, Hiraku Ogino, Christian Motz, Kévin Berger, Bruno Douine, Yassine Slimani, and Essia Hannachi
(Siehe online unter https://doi.org/10.1063/9.0000167) - Paramagnetic Meissner Effect and Current Flow in YBCO Nanofiber Mats. IEEE Transactions on Applied Superconductivity, 31(5):1-5, August 2021
Alexsander Pessoa, Anjela Koblischka-Veneva, Claudio Carvalho, Rafael Zadorosny, and Michael Koblischka
(Siehe online unter https://doi.org/10.1109/TASC.2021.3058596) - Review on the Use of Superconducting Bulks for Magnetic Screening in Electrical Machines for Aircraft Applications. Materials, 14(11):2847, May 2021
Remi Dorget, Quentin Nouailhetas, Alexandre Colle, Kévin Berger, Kimiaki Sudo, Sabrina Ayat, Jean Leveque, Michael Rudolf Koblischka, Naomichi Sakai, Tetsuo Oka, and Bruno Douine
(Siehe online unter https://doi.org/10.3390/ma14112847) - Microstructural Parameters for Modelling of Superconducting Foams. Materials 2022, 15, 2303
Michael Rudolf Koblischka, Anjela Koblischka-Veneva , Quentin Nouailhetas , Ghazi Hajiri, Kévin Berger, Bruno Douine and Denis Gokhfeld
(Siehe online unter https://doi.org/10.3390/ma15062303)
