NANOMAGMA · Nanocomposite magnetocaloric materials

Nanocomposite magnetocaloric materials

Energy usage for cooling and refrigeration is estimated to be approximately 15 % of current consumption, and is increasing steadily. Magnetic refrigeration is an emerging technology that promises a doubling of energy efficiency compared to conventional vapour-compression cycle devices. The future of this technology relies heavily on the availability and ease of processing of high-performance magnetic refrigerant materials. Compounds that undergo a first order magnetic phase transition resulting in a giant magnetocaloric effect are attractive for applications, but the material properties need to be tunable and the material should be easily processable. The materials must also be made up of elements that are cheap, abundant and accessible. One of the front runner magnetic refrigerant materials is the family of La(Fe,Si)13-based alloys. The main objective of the project was to develop novel magnetocaloric material architectures based on the La(Fe,Si)13 compound through the use of nanofabrication techniques and in particular to provide magnetic refrigerant materials with improved thermal transport properties. A related objective was to develop novel materials synthesis routes that would be attractive for large-scale manufacturing and thus, contribute to lowering the economic barrier for the entry of the magnetic refrigeration as energy efficient technology in various industries (household, automobile, computer, food industry etc.). Environmentally-friendly, solution-based processing routes were used to develop novel magnetocaloric material composites with desired thermal and magnetic properties comprising the magnetocaloric phase La(Fe,Si)13 and high thermal conductivity Cu. In particular, electroless plating proved to be a successful technique. The optimisation of electroless deposition with respect to structure and magnetic properties resulted in obtaining magnetocaloric composites with improved thermal transport properties and excellent magnetic properties. The influence of such factors as the particle size, Cu fraction and wettability on the thermal transport and magnetic properties was studied. The plating process was developed that allows the production of composite materials in a highly reproducible and controllable manner. Fundamental understanding of the dependence of the thermal transport properties on the microstructure allowed the design of various approaches to control thermal transport in these materials. The success of the electrochemical processing provided the ground-work for a further development in the area that resulted in the invention of a cost-effective, simple, low-temperature method for hydriding the La(Fe,Si)13-type compounds by an electrolytic hydriding process. Hydriding is an attractive way to adjust the Curie temperature, and thus the operating temperature range, of the La(Fe,Si)13-type alloys. The work focused on the optimisation of electrolytic hydriding conditions. As a result, an electrochemical processing route was developed that allows obtaining materials with the same high-level magnetic properties as in gas-phase hydrided alloys. A patent application has been filed. Apart from the technological importance, new materials physics related to the interplay between hydrogen absorption phenomena and magnetism has been revealed, which is of general interest for the broader scientific community. The solution-based processing techniques explored and successfully applied in this project are very attractive for large-scale manufacturing and may bring about a much needed breakthrough in the practical application of magnetic refrigeration. The obtained results present a significant step forward in the development of magnetic refrigerant materials and will benefit researchers and industries aiming to advance the magnetic cooling technology.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз