基于Ericsson磁制冷循环的宽温区大磁热效应材料的研究

Magnetic refrigerant materials based on magnetocaloric effect (MCE) are well known because of their characteristics of high energy-efficiency and environmental-friendly. It has been found that most magnetocaloric materials only exhibit a single phase transition. In order to further improve the MCE and refrigerant capacity, materials with large MCE over a wide temperature range based on Ericsson-cycle magnetic refrigeration will be extensively studied in this project. This project will focus on the RSi and RCuxGe2（R-Ho，Er）polycrystalline and NiCoMnIn film, and three methods are attempted to generate a “table-like” MCE: a) The in-situ multiphase RSi will be prepared by substituting the elementary rare earth with crude misch metal, which may induce multiple magnetic entropy change peaks. b) The “table-like” MCE will be fulfilled in multiphase materials with same structure but different phase transition, which could be fabricated by technology improvement. c) The “table-like” MCE is acquired from several transition temperatures that come from the different polarization of different regions. These three methods may also overcome the poor compatibility and controllability of mixed-refrigerants. The relationship among the magnetism, structure and magnetic entropy changes will be studied systematically by multiple characterizations, and would provide guidance for the materials design, technology update and practical application.

磁熵变材料因其高效节能和环境友好的特征而被广泛关注。大多数磁熵变材料表现为单一相变，为进一步提高磁制冷材料的磁热效应和制冷能力，本研究拟以Ericsson磁制冷循环的宽温区大磁热效应材料研究为主题，以RSi和RCuxGe2（R-Ho，Er）系列多晶材料以及NiCoMnIn薄膜为研究对象,尝试从三个方面尝试获得具有“平台”状熵变特征的磁热效应材料：a）使用混合稀土代替稀土单质，在多晶母体中原位直接制备多相组元RSi，进而在单一手段制备的材料中实现多个磁熵变峰共存；b）通过工艺调节在一种原始配比的材料中合成多种同结构、相变不一致的化合物，实现“平台”状磁热效应；c）将材料通过工艺进行分区，不同微区进行可控性调节，使得各个微区的相变温度不一致，实现“平台”状磁热效应。解决混合工质兼容性差、可控性低的问题。通过物性表征深入探讨磁性、结构和磁熵变的物理关联，为今后材料设计、工艺更新以及实际应用提供指

磁制冷技术因其高效节能和环境友好的特征而被广泛关注，而其核心课题之一是磁制冷材料的研发。本项目按计划设计并制备出混合稀土MMSi材料，材料呈现多个相变并实现了高性能“平台状”磁热效应，解决了磁热效应材料在宽温区具有大磁熵变的需求并大幅降低了材料成本。此外，还主导完成了具有反铁磁性及低温相变温度的TbFe2Al10以及DyNiGa合金的设计及制备，材料综合磁制冷效应优异；使用固相反应法制成了La2CoMnO6双钙钛矿样品，发现其相变温度处于近室温区，在150-240 K区间范围内呈现出“平台状”磁热效应。基于中子衍射实验重点研究了多相变磁制冷材料的相变类型和相变性质。.此外，还参与研究磁性纳米颗粒在交变磁场下的产热行为，探明了颗粒间偶极相互作用对磁热性能影响的物理机理，为磁热疗在临床中的有效应用提供了理论指导。在此基础上，发展出了具有高生物相容性和高磁热性能的新型纳米磁热介质，并有望在未来临床磁热疗中得以应用。