Weiß Nico P, Rocabert Ulysse, Hoppe Cornelia, Zwick Jens-Peter, Loewe Konrad, Fries Maximilian, Karttunen Antti J, Gutfleisch Oliver, Muench Falk
Magnotherm Solutions GmbH, Pfungstädter Straße 102, 64297 Darmstadt, Germany.
Inorganic Materials Modelling Group, Department of Chemistry and Material Science, Aalto University, FI-00076 Aalto, Finland.
ACS Appl Eng Mater. 2025 Jan 13;3(1):256-265. doi: 10.1021/acsaenm.4c00747. eCollection 2025 Jan 24.
Magnetic refrigeration leads the current commercialization efforts of ambient caloric cooling technologies, is considered among its peers most promising in terms of anticipated energy efficiency gain, and allows for complete elimination of harmful coolants. By now, functional magnetocaloric components (so-called regenerators) based on Mn-substituted and hydrogenated LaFeSi alloys are commercially available. However, this alloy system exhibits magnetostriction, is susceptible to fracture, oxidation, and does not passivate well, rendering it prone to failure and corrosion, particularly when using water as favorable heat exchange medium. Demonstrating stable and extended operation of LaFeSi-based regenerators under realistic conditions with cost-sensitive measures thus constitutes a key milestone for derisking the materials system, paving a path toward reliable and maintenance-friendly magnetic cooling devices. Building upon a fundamental analysis of materials properties, process, and target specifications, we outline a 2-fold protection strategy, encompassing a highly conformal copper coating working in tandem with a tailored inhibitor system. The former is applied using an optimized electroless plating procedure, allowing us to evenly envelop complex regenerator architectures in a dense, nondefective, homogeneous, and ductile copper film of excellent interfacial quality. The latter addresses the corrosion characteristics of both coating and substrate in the application environment. In-device aging experiments prove the effectiveness of our multifaceted approach in maintaining the chemical, mechanical, and functional integrity of LaFeSi regenerators under continuous use.
磁制冷引领着当前环境热冷却技术的商业化进程，在预期的能源效率提升方面被同行认为是最有前途的，并且可以完全消除有害冷却剂。目前，基于锰取代和氢化的LaFeSi合金的功能性磁热组件（所谓的回热器）已可商业化获得。然而，这种合金体系表现出磁致伸缩，易断裂、氧化，且钝化性能不佳，容易导致失效和腐蚀，特别是在使用水作为良好的热交换介质时。因此，在成本敏感的措施下，证明基于LaFeSi的回热器在实际条件下的稳定和长期运行，是降低材料体系风险的一个关键里程碑，为通往可靠且易于维护的磁制冷设备铺平了道路。基于对材料性能、工艺和目标规格的基础分析，我们概述了一种双重保护策略，包括与定制的缓蚀剂系统协同工作的高度保形铜涂层。前者采用优化的化学镀工艺进行应用，使我们能够在具有优异界面质量的致密、无缺陷、均匀且有延展性的铜膜中均匀包裹复杂的回热器结构。后者则针对应用环境中涂层和基材的腐蚀特性。器件内老化实验证明了我们多方面方法在持续使用下维持LaFeSi回热器的化学、机械和功能完整性方面的有效性。
