Tunable Magnetocaloric Effect in Ni-Mn-Ga Microwires.
Tunable Magnetocaloric Effect in Ni-Mn-Ga Microwires.
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Ni-Mn-Ga 微线中的可调谐磁热效应
DOI：
10.1038/s41598-018-35028-9
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发表时间：
2018-11-08
影响因子：
4.6
通讯作者：
Peng HX
中科院分区：
文献类型：
--
作者：
Qian M;Zhang X;Wei L;Martin P;Sun J;Geng L;Scott TB;Peng HX
磁制冷因其高能效、环保和低成本而引起人们的极大兴趣。然而，不希望的磁滞损耗，集中的工作温度区间（WTI）和机械稳定性差是阻碍其实际应用的重要缺点。非化学计量比Ni-Mn-Ga Heusler合金具有巨磁热效应和可调相变温度。在这里，通过使用熔体提取技术产生直径为35-80 μm的Ni-Mn-Ga微丝，由于降低相邻晶粒之间的不相容性的高比表面积（SSA），发现可忽略的滞后和相对良好的机械稳定性。高SSA还有利于在高温下的元素蒸发，使得可以可行地调节转变温度。由于不同的磁-结构耦合状态而产生的可调磁热效应通过（i）成分设计和随后的调谐来实现，其调节马氏体转变（MT）和磁转变之间的温度差，以及（ii）梯度成分分布状态的产生，其操纵MT范围。磁熵变ΔSm~−18.5 J kg− 1 K − 1，相对集中的WTI和WTI高达~60 K，净制冷量~240 J kg− 1，在50 kOe的当前Ni-Mn-Ga微丝被证明。该标准也适用于其他小尺寸材料。
Magnetic refrigeration is of great interest due to its high energy efficiency, environmental friendliness and low cost. However, undesired hysteresis losses, concentrated working temperature interval (WTI) and poor mechanical stability are vital drawbacks that hinder its practical application. Off-stoichiometric Ni-Mn-Ga Heusler alloys are capable of giant magnetocaloric effect (MCE) and tunable transformation temperatures. Here, by creating Ni-Mn-Ga microwires with diameter of 35–80 μm using a melt-extraction technique, negligible hysteresis and relatively good mechanical stability are found due to the high specific surface area (SSA) that reduces incompatibility between neighboring grains. The high SSA also favors the element evaporation at high temperatures so that the transformation temperatures can be feasibly adjusted. Tunable magnetocaloric effect owing to different magneto-structural coupling states is realized by (i) composition design and subsequent tuning, which adjusts the temperature difference between the martensite transformation (MT) and the magnetic transition, and (ii) creation of gradient composition distribution state, which manipulates the MT range. Magnetic entropy changeΔSm~−18.5 J kg−1K−1with relatively concentratedWTIandWTIup to ~60 K with net refrigeration capacity ~240 J kg−1at 50 kOe are demonstrated in the present Ni-Mn-Ga microwires. This criterion is also applicable for other small-sized materials.
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影响因子：
4
作者：
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通讯作者：
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作者：
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