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摘要
A one-step sintering process was developed to produce magnetocaloric La(Fe,Si)(13)/Ce-Co composites. The effects of Ce2Co7 content and sintering time on the relevant phase transformations were determined. Following sintering at 1373 K/30 MPa for 1-6 h, the NaZn13-type (La,Ce)(Fe,Co,Si)(13) phase formed, the mass fraction of alpha-Fe phase reduced and the CeFe7-type (La,Ce)(Fe,Co,Si)(7) phase appeared. The mass fraction of the (La,Ce)(Fe,Co,Si)(7) phase increased, and the alpha-Fe phase content decreased with increasing Ce2Co7 content. However, the mass fraction of the (La,Ce)(Fe,Co,Si)(7) phase reduced with increasing sintering time. The EDS results showed a difference in concentration between Co and Ce at the interphase boundary between the 1:13 phase and the 1:7 phase, indicating that the diffusion mode of Ce is reaction diffusion, while that of Co is the usual vacancy mechanism. Interestingly, almost 100 % single phase (La,Ce)(Fe,Co,Si)(13) was obtained by appropriate Ce2Co7 addition. After 6 h sintering at 1373 K, the Ce and Co content in the (La,Ce)(Fe,Co,Si)(13) phase increased for larger Ce2Co7 content. Therefore, the Curie temperature increased from 212 K (binder-free sample) to 331 K (15 wt.% Ce2Co7 sample). The maximum magnetic entropy change (-Delta S-M)(max) decreased from 8.8 (binder-free sample) to 6.0 J/kg center dot K (15 wt.% Ce2Co7 sample) under 5 T field. High values of compressive strength (sigma(bc))(max) of up to 450 MPa and high thermal conductivity (lambda) of up to 7.5 W/m center dot K were obtained. A feasible route to produce high quality La(Fe,Si)(13) based magnetocaloric composites with large MCE, good mechanical properties, attractive thermal conductivity and tunable T-C by a one-step sintering process has been demonstrated.
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单位南阳理工学院; 南昌航空大学; 北京科技大学
