2-21.High-throughput synthesis and characterization of rare earth-based magnetocaloric materials

Jian Liu
Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences

Abstract:Refrigeration plays an important role in our daily life. Magnetic cooling based on the magnetocaloric effect is an efficient and environmental-friendly refrigeration technique. The synthesis and processing of rare earth-based magnetocaloric compounds by traditional methods are difficult, due to their complex chemical compositions and solidification paths, intrinsic brittleness and processing-sensitive Curie temperatures. Initiated from the materials genome, extensively efforts have been made in the development of new high-throughput synthesis and characterization methods for screening high performance rare earth-based magnetocaloric compounds. A combinatorial masking strategy had been used to produce compositionally diverse intermetallic films. The gradient element distribution, structure and performance of the films were acquired by scanning or combinatorial characterizations. However, such methods are not applicable for rare earth-based magnetocaloric compounds because their functional phases could not be directly formed, and volatilization and oxidation of rare earth elements are unavoidable. The development of bulk combinatorial synthesis approach has become essential for the investigation of different compositions, structures and performances under different solidification conditions of rare earth-based functional materials.

         The present work is initiated from the concept of materials genome. The bulk high-throughput synthesis system which is capable of automatic powder delivery, multi-crucible combinatorial melting and inverse suction casting has been developed and used for producing magnetocaloric compounds. A high resolution infrared thermal imaging device has been used for the non-contact, visualized and localized measurement of adiabatic temperature changes of these compounds. In addition, magnetocaloric composites are produced and the interfacial interaction and microstructures are investigated. The thermal conductivity could be predicted by using a thermal transport model regarding the intrinsic thermal conductivity of constituent phases, phase fractions, particle sizes and interface thermal resistances of the composites.

Keyword : Magnetocaloric alloys; rare earth-based compounds; high-throughput synthesis; high-throughput characterization

           稀土磁制冷材料的高通量制备与表征

            刘剑
             中国科学院宁波材料技术与工程研究所

摘要:制冷和我们的日常生活息息相关。以磁热效应为基础的磁制冷技术具有绿色环保、高效 节能的特点。多元稀土磁制冷合金大都表现出化学成分和居里温度控制难度大、凝固路径复杂 和加工成型困难等特点，传统的研发途径不易高效合成稀土磁制冷材料。从材料基因技术出发， 发展基于高通量的制备和表征的新型研究方法是当前高性能稀土磁制冷材料的研究热点。传统 高通量组合式金属材料的制备主要是以掩膜方法为基础，通过自动扫描或者并行快速表征的方法获得成分梯度材料的成分、结构和性能等关键信息，建立多元材料体系的成分与性能关联关 系。但对于稀土磁制冷合金，由于稀土元素具有高挥发和易氧化性，以及稀土化合物通常成相 困难和凝固路径复杂，所以薄膜方法并不适合稀土化合物的高通量制备。开发基于块体材料的 高通量制备方法，并研究不同凝固条件下块体材料的成分、组织和性能是稀土功能材料的关键技术。

      本工作以材料基因方法为研究理念，研发出基于粉末自动配料、多仓并行熔炼和顶吸式成 型技术的高通量块体材料制备系统，高效制备了多组元磁制冷材料;用高精度红外成像设备， 非接触、可视化、局域化表征，实现磁制冷材料绝热温变的高通量表征。并在磁制冷复合材料 成型的理论和实验研究方面，构建了复合热导模型，研究磁制冷材料复合成型中的界面反应和 界面微结构，实现对不同颗粒尺寸和界面热阻的复合材料导热性能的有效预测。 关键词:磁制冷合金;稀土化合物;高通量制备;高通量表征