Gd基非晶与Gd纳米晶复合结构的磁制冷效应

The magnetocaloric effect of the Gd-based amorphous composite with Gd nanocrystals

通过调控冷却速率和成分配比,制备出了Gd基非晶与Gd纳米晶的复合材料.采用X射线衍射、热分析、原子力和磁力显微镜对其微结构进行表征,从多个角度证实了非晶/纳米晶的复合结构.磁性测试结果表明:内生的纳米晶颗粒能有效改善非晶基体的磁熵效应,相对于Gd基块体纯非晶和Gd单质,复合体系的磁制冷效率大幅提高达到了10~3 J·kg^(-1);磁熵变化峰△Sm的半高宽超过纯Gd的5倍;最大磁熵变区出现平台区,但△Sm峰值有待于进一步提高.理论分析表明,复合结构中超顺磁纳米团簇的形成有效提高了磁制冷温区和效率.结合磁滞小和电阻大等优点,Gd基非晶/Gd纳米晶复合材料具有一定的发展潜力.

The Gd-based amorphous/nanocrystal composite is prepared by controlling the cooling rate and the element ratio. The X-ray diffraction, differential scanning calorimeter and atomic force microscope/magnetic force microscope are used to confirm the composite microstructures from different perspectives. The magnetic test shows the great enhancement of magnetocaloric effect in the metallic glassy composite. The large magnetic refrigerant capacity （RC） up to 103 J. kg-1 is more than double the RC values of the Gd-based bulk metallic glass and pure Gd. The full width at half maximum of the magnetic entropy change （ASm） peak almost spreads over the whole low-temperature range, which is five times wider than that of the pure Gd. The maximum ASm approaches a nearly constant value in a wide temperature span （over 80 K）. The super paramagnetic nanoclusters of the composite increase the magnetic refrigerant capacity greatly. In combination with the low magnetic hysteresis and large resistance, the metallic glass composite may be a potential candidate for the ideal Ericsson-cycle magnetic refrigeration.