Novel approach in fabricating microchannel-structured La(Fe,Si)(13)H-y magnetic refrigerant via low-contamination route using dissolutive mold

Herein, as the fabrication of the microchannels for fluid flow using La(Fe,Si)(13) magnetic refrigerant material is required while maintaining its superior magnetocaloric performance, sinter molding of the microchannel-designed La(Fe,Si)(13) was investigated using a dissolutive mold comprised of NaCl to develop a molding process without contamination by carbon and other light elements. In addition, to avoid the thermal decomposition of fine particles of La(Fe,Si)(13), a solid-state reaction was conducted during sintering using a mixture of alpha-Fe and La-rich compounds as the initial powder. After sintering, the sample shape exhibited channel widths and depths of 200 mu m and pillar widths of 300 mu m, which were originally designed for the NaCl dissolutive mold. The metallographic microstructure mostly comprised the La(Fe,Si)(13) phase, and the volume fractions of the extra phases, such as alpha-Fe and La2O3, were suppressed to 1.1 % and 3.2 %, respectively. The maximum of the magnetic entropy change in a single pillar reached-19 J/kg K. Direct observation of magnetic nucleation/growth confirmed the smooth emergence of the first-order transitions in multiple pillars. Consequently, this fabrication approach promoted micro channel-designed La(Fe,Si)(13)H-y while maintaining a large magnetocaloric effect via low carbon contamination. (C) 2022 The Authors. Published by Elsevier Ltd.