Gas-atomized particles of giant magnetocaloric compound HoB2 for magnetic hydrogen liquefiers

TL;DR

This study successfully produced spherical HoB2 particles via gas atomization, demonstrating their potential as efficient magnetic refrigerants for hydrogen liquefaction due to their high magnetocaloric effect.

Contribution

First demonstration of gas atomization of HoB2 into spherical particles with high magnetocaloric performance for magnetic refrigeration applications.

Findings

Particles are spherical with no contamination.

Exhibit sharp magnetic transitions and large magnetic entropy change.

Suitable size distribution for magnetic refrigeration systems.

Abstract

The processing of promising magnetocaloric materials into spheres is one of the important issues on developing high-performance magnetic refrigeration systems. In the present study, we achieved in producing spherical particles of a giant magnetocaloric compound HoB2 by a crucible-free gas atomization process, despite its high melting point of 2350 C. The particle size distribution ranges from 100 to 710 micrometers centered at 212-355 micrometers with the highest yield of 14-20wt% of total melted electrode, which is suitable for magnetic refrigeration systems. The majority of the resulting particles are mostly spherical with no contamination during the processing, while unique microstructures are observed on the surface and inside. These spherical particles exhibit sharp magnetic transitions and huge magnetic entropy change of 0.34 J cm^{-3} K^{-1} for a magnetic field change of 5 T at 15.5 K. The high sphericality and the high magnetocaloric performance suggest that the HoB2 gas-atomized particles have good potential as magnetic refrigerants for use in magnetic refrigerators for hydrogen liquefaction.