NANOMAGMA · Nanocomposite magnetocaloric materials

Worldwide a large part of produced electrical energy is used in inefficient vapour-compression cooling systems. Magnetic refrigeration near room-temperature has great potential to establish itself as a 21st century cooling technology and become an energy-efficient, environmentally friendly, cost-saving approach to replace the conventional technology. For successful operation of the magnetic refrigerator, the magnitude of the entropy change associated with the change of magnetic state of the active magnetic coolant is crucial and some materials including La(Fe,Si)13 are very attractive. Previous work has focused on optimising materials to enhance the magnetic properties of the parent compound, but it is clear that the operating field and the ability to create suitable thermal pathways are critical factors limiting industrial use. In this project we propose to use simple low-cost, scalable processing routes to develop novel nano-architectures to tackle thermal management and low operating fields. The magnetocaloric material La(Fe,Si)13 will be integrated into a percolating network of high thermal conductivity material e.g. Cu, alumina or carbon nanotubes. A number of approaches will be explored: solution, vapour phase and conventional powder processing. We will examine 1D, 2D and 3D nanocomposite structures to probe key issues such as effects of grain and particle size, strain, orientation and volume fraction of active material. Exploring intergrain exchange coupling of the La(Fe,Si)13 with a soft magnetic material of high moment such as -Fe will address the issue of lowering the operating field. The project will provide ample training opportunities for the IEF fellow in a range of complementary areas. We will establish structure-property relationships and develop fundamental physical models for single-phase and composite devices. This will allow rational design of magnetic refrigerant systems and be a major step towards industrial application of this technology.