Gd-(Co,Fe)非晶合金基复合材料的制备及其近室温平台型高磁熵变的研究

Research of near room temperature magnetocaloric materials attracted much attention, due to their potential in commercial application. There is few single material could meet the requirement for magnetocaloric properties from ideal Ericsson magnetic refrigeration cycle. Be aimed at this problem, in this project we plan to prepare Gd-(Co, Fe) amorphous alloy matrix composite by in-situ crystallization method, and develop a novel magnetocaloric refrigerant with table-like high magnetic entropy change at near room temperature. Influence of composition, preparation parameters and annealing process on phase structure, component, crystalline size and distribution as well as magnetic crystalline anisotropy of the composite will be studied. Then the effect of microstructural characterization on magnetocaloric properties will be analyzed. Meanwhile, we will investigate the correlations among synthesis, microstructure and magnetocaloric properties in this alloy system, and accordingly optimize the magnetocaloric properties of Gd-(Co, Fe) amorphous alloy matrix composite. Achievements of this project will provide a theoretical foundation of regulating microstructure and improving magnetocaloric properties through fabrication process, which is significant for promoting and applying magnetic refrigeration in commercial field.

与民用领域密切相关的近室温磁制冷材料的研究，是国内外关注的热点。针对大多数单相材料无法满足理想的Ericsson磁制冷循环对磁热性能的要求，本项目拟采用内生晶化法制备Gd-(Co, Fe)非晶合金基复合材料，研发在近室温区具有平台型、高磁熵变的磁致冷工质，研究合金成分、制备条件、退火工艺与相组成、成分组成、晶粒尺寸与分布、磁晶各向异性的关系；分析微观结构对磁热性能的影响；建立该体系中材料合成、微观结构、磁热性能之间的关联，实现对Gd-(Co, Fe)非晶合金基复合材料磁热性能的优化。课题研究将为通过合成工艺调控显微结构，改良材料磁热性能奠定理论基础，对近室温磁致冷技术的推进和广泛应用具有重要意义。

本项目旨在揭示不同成分、冷却速率和退火工艺对Gd-(Co, Fe)合金的微观结构和磁热性能的影响，构建Gd-(Co, Fe)非晶合金基复合材料的合成、结构、磁热性能三者之间的关联，优化设计近室温平台型磁热效应。研究表明在一定成分范围内，可以利用Fe取代Co对Gd-(Co, Fe)系非晶合金的磁热性能进行调控，并且能得到具有平台型磁热效应的材料；复合材料中的相组成和相含量配比是获得平台型磁热效应的重要影响因素，选择磁转变温度相近（如温度差≤50 K）的析出相以及优化的相含量，是本项目总结出的得到具有平台型磁熵变的设计思路，为进一步改进材料磁热性能提供了理论依据。研究还有如下发现：过量Fe添加会导致磁交换作用积分的变化，并显著影响磁热效应的表现，类金属的引入可以在一定程度上改进此不良影响。通过这些研究工作，负责人以第一及通讯作者共发表论文4篇，其中SCI论文3篇，EI论文1篇，基本完成了课题计划任务和预计的成果。