Topic: Efficient energy-conversion near room-temperature with transition metal based magnetic materials
Speaker: Professor Ekkes Brück, Delft University of Technology, Holand
Time: 9:00, December 5, 2017
Venue: Room 205, Building 14, Wushan Campus
Abstract: Magneto-caloric power conversion can be used to convert heat into electricity that up to now was considered as waste. This new technology therefore has the potential to significantly contribute to the energy transition on a global scale.
With the advent of giant magneto-caloric effects (MCE) that occur in conjunction with magneto-elastic or magneto-structural phase transition of first order (FOT), room temperature heat-pump applications became feasible. In this context the MnFe(P,X) system is of particular interest as it contains earth abundant ingredients that are not toxic. This material family derives from the Fe2P compound, a prototypical example known since a long time to exhibit a sharp but weak FOT at 210 K (-63°C).
Magneto-caloric power-conversion calls for a somewhat different combination of properties, in particular a large latent heat that is favourable for a heat-pump, is detrimental for power conversion as a lot of heat is needed to change the temperature. Yet a large change of magnetization is required, which suggests one should either employ materials exhibiting exchange inversion or second order materials. Magnetically highly responsive materials in combination with the field generated by a permanent magnet open the way to new technology for magnetic refrigeration, heat pumps and power generation. Employing the highly efficient coupling between the degrees of freedom of magnetic spins and lattice vibrations in a solid, will render energy conversion and energy generation technologies that get close to the theoretical limits.