Ni-Mn-Sn磁性形状记忆合金多层膜的宽温区磁热效应研究

The narrow working temperature span is the crucial problem limiting the application and development of Ni-Mn-Sn magnetic shape memory alloys thin films in micro-scale magnetic refrigeration. In this project, the new idea for increasing the working temperature span and refrigerant capacity is proposed by fabricating Ni-Mn-Sn multilayer thin films based on the tunable transition temperature and magnetic entropy change by the variation of composition. The design of Ni-Mn-Sn multilayer thin films is investigated. Then the Ni-Mn-Sn multilayer thin films are fabricated by the magnetron sputtering technique. Moreover, the microstructure and interface structure between phases and layers of multilayer thin films are studied. The magnetic field-induced martensitic transformation and motion characteristics of parent phase-martensite interface are clarified. The effects of multilayer films structure, fabrication technique, crystallization treatment on magnetic entropy change and working temperature span are systematically investigated. In addition, the internal relationship between the magnetic transition and magnetic entropy change is illustrated. The origin of magnetic entropy change of Ni-Mn-Sn multilayer thin films is revealed. The internal relationships between the multilayer films structure and fabrication technique, motion characteristics of parent phase-martensite interface and magnetic entropy change are built. Furthermore, the principle for design of Ni-Mn-Sn multilayer thin films which exhibit wide working temperature span and large magnetic entropy change is presented. The researches mentioned above provide guidance for developing novel magnetocaloric thin films applied in micro-scale magnetic refrigeration with wide working temperature span and large refrigerant capacity.

制冷工作温区窄是限制Ni-Mn-Sn磁性形状记忆合金薄膜在微型磁制冷中应用和发展的关键问题。本项目提出利用Ni-Mn-Sn合金相变温度和磁熵变随成分可调的特点，制备Ni-Mn-Sn合金多层膜，以实现拓宽制冷温区与提高磁制冷能力的目的。本项目拟从设计Ni-Mn-Sn合金多层膜入手，采用磁控溅射方法制备Ni-Mn-Sn合金多层膜；研究多层膜的微观组织结构、相界面结构与层间界面结构，阐明磁场驱动马氏体相变行为以及母相-马氏体界面运动特点及规律；系统研究膜层结构、制备工艺、晶化处理对多层膜磁熵变及制冷工作温区的影响，阐明磁相变与磁熵变的内在联系，揭示多层膜磁熵变的物理本质；建立膜层结构及制备工艺、相界面结构及其可动性与磁熵变之间的内在联系，确定获得宽制冷温区、大磁熵变Ni-Mn-Sn合金多层膜的设计准则及制备工艺，为发展兼具宽工作温区、大磁制冷能力的新型微磁制冷用薄膜材料奠定基础。

制冷工作温区窄是限制Ni-Mn-Sn磁性形状记忆合金薄膜在微型磁制冷中应用和发展 的关键问题。利用Ni-Mn-Sn 合金相变温度和磁熵变随成分可调的特点，本项目制备出Ni-Mn-Sn 合金多层膜，实现了拓宽制冷温区与提高磁制冷能力的目的。本项目从设计Ni-Mn-Sn 合金多层膜入手，采用磁控溅射方法制备Ni-Mn-Sn 合金多层膜，系统研究了制备工艺对薄膜化学成分、膜厚及表面形貌的影响规律，掌握了Ni-Mn-Sn合金多层膜的制备技术，揭示了薄膜生长动力学；同时针对Ni-Mn-Sn合金靶材脆性大的问题，进行了一系列系统性的研究；揭示了稀土元素以及Co、Fe、Cu等元素对合金靶材力性改善的微观机制；系统研究了膜层结构、制备工艺、晶化处理对多层膜磁熵变及制冷工作温区的影响，阐明磁相变与磁熵变的内在联系，揭示了多层膜磁熵变的物理本质；建立了膜层结构及制备工艺、相界面结构及其可动性与磁熵变之间的内在联系，确定了获得宽制冷温区、大磁熵变Ni-Mn-Sn 合金多层膜的设计准则及制备工艺，为发展兼具宽工作温区、大磁制冷能力的新型微磁制冷用薄膜材料奠定基础。