The project "SupraMetall – innovative metal strips as a basis for high-temperature superconductors/energy-efficiency based on superconductors" was funded within the framework of the EU-NRW Objective 2 (EFRE) programme, which ran from 2010 to 2013, in the amount of a total of approximately € 1.5 million.
Along with our university, RWTH Aachen Technical University, Outokumpu VDM GmbH, Deutsche Nanoschicht GmbH and the University of Bonn were involved in the project. On our university’s part, Professor Dr Sabine Lepper and her colleagues Regina Böhm and Manuela Schebera from the Department of Electrical Engineering, Mechanical Engineering and Technical Journalism (EMT) collaborated to optimise the superconductors.
Superconductors include materials that virtually lose their electrical resistance if their temperature falls below a certain level. While the first superconductors had to be cooled down to a temperature of – 250 degrees Celsius for this purpose, the so-called “high-temperature superconductors (HTS)”, which were developed as early as in the 1980s, become superconductive as soon as they reach – 180 degrees. Corresponding applications, for instance in the area of renewable forms of energy, were thus made tangible. The problem with HTS is basically that they are made of ceramic materials. Hence, they cannot be formed into wires, as can metals; the HTS known as the “second generation” are turned into strips, with the superconductor applied to a special metal strip in the form of a thin layer.
Mass production made tangible
The SupraMetall project was aimed at developing production processes that not only operate in laboratory conditions, but also enable mass production in large-scale industrial plants. For this purpose, the metal substrate was decanted from an 18-ton molten mass and rolled in a mill in such a way that it was no more than 1/10 mm thick. The requirements for extremely low surface roughness and high texture (one-direction orientation of the crystals), which are essential for further processing, could thus be met. It was also possible to develop processes for laminating this metal strip that are suitable for large-scale production.
Supermetal topography under the atomic force microscope
The project partners from the Department of EMT were set the task to examine and collect data on the topography of the layers with the aid of an atomic force microscope. Atomic force microscopy enables the measurement of surface structures with a precision of one nanometre and even less (with one nanometre equalling one thousandth of a metre). The surfaces were tested for peculiarities, the degrees of roughness were measured, and the orientation of crystal growth could be observed in the superconductive layer. The illustration shows a superconductive layer in which the crystals have grown upwards like pillars, as is necessary for good superconductive behaviour.
Further information on the findings of the SupraMetall project can be found in the current May edition of the "Advanced Engineering Materials" periodical.
Prof. Dr Sabine Lepper
Department of Electrical Engineering, Mechanical Engineering and Technical Journalism (EMT) Grantham-Allee 20
D-53757 Sankt Augustin
Tel: +49 2241-865-316
Fax: +49 2241-865-8316