NIMSAWARD2025-abstracts

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P2-1281Development of magnetic refrigeration materials with superior hydrogen permeation barrier performanceMagnetic Refrigeration System Group, GREEN Ya XuE-mail：：XU.Ya@nims.go.jpKey Words: Hydrogen permeation barrier, magnetic refrigeration materialMagnetic refrigeration technology offers a more energy-efficient hydrogen liquefaction alternative to conventional gas compression/expansion refrigeration technology. However, exposure the magnetic refrigeration materials to a hydrogen atmosphere may lead to hydride formation, which weakens the magnetocaloric effect. It is imperative to develop magnetic refrigeration materials with superior hydrogen permeation barrier (HPB) performance.A uniform CuO film was formed on ErCo2by electroless Cu plating followed by oxidation treatment.The Cu-plated/oxidized ErCo2 particles exhibited excellent HPB performance and magnetocaloric effect.DFT calculations revealed that CuO possesses good HPB properties.Conclusion・CuO/CoOoxide layers were formed on ErCo2particles by electroless Cu plating and a subsequent oxidation treatment. ・SEM images and EDS analysis of cross-section of surface region of Cu-plated and Cu-plated/oxidized ErCo2particle, indicating the formation of oxide layers on the ErCo2particle surface.・TEM-SAED analysis of surface oxide layers formed on Cu-plated/oxidized ErCo2particle, indicating the formation of CuOand CoO. Forming oxide film on ErCo2surface Enhanced HPB performance of ErCo2Investigation of the HPB performance with electroless plating using other metallic elements.Implementation and application in magnetic refrigeration systems.Future Plan・The electroless Cu plating followed by oxidation treatment significantly improved the BPB performance of ErCo2particles.・DFT calculations reveal that large energy barriers (>27.7 kJ/mol) must be overcome for H₂ molecules to dissociate and adsorb as hydrogen atoms on CuO (111) surface, and for H atom diffusion into CuO, demonstrating that CuO possesses excellent HPB properties.・The Cu-plated/oxidized ErCo2particles maintained excellent magnetocaloric effect. IntroductionWe havedeveloped a novel technique combining electroless copper plating with oxidation treatment to enhancing the HPB properties. By forming a uniform oxide film on the surface, the HPB performance of magnetic refrigeration materials such as ErCo2have been enhanced. This low-cost, efficient method is also applicable to other materials requiring HPB properties near or below room temperature.Theme underDiscussionCu-plated/oxidized ErCo2Cu-plated/oxidized ErCo2Optimization0204060801001201400.00.20.40.60.81.01.21.41.61.8Adsorbed hydrogen (mass%)Exposure time (h)As-homogenizedCu plated/oxidized0123450.00.20.40.60.81.01.21.4Adsorbed hydrogen (mass%)Exposure time (h)Adsorbed hydrogen during H2exposure testOptimization of adsorbed H2on CuO(111) surfaceActivation barriers for H2dissociation to form two H-O bonds or one H-Cu and one H-O bond(a) Magnetic field dependence of magnetization at 2 K(b) Magnetic entropy change (∆SM) for μ0∆H= 5 TElectroless Cu plating at 348 K for 90 minOxidation treatment at 773 K for 30 min for 30 minAs-homogenized ErCo2particles(φ0.212~0.355mm)SurfaceCuOCoOCu-plated/oxidized ErCo2particlesCu-plated ErCo2particlesSurfaceCu-plated ErCo2SurfaceCu-plated/oxidized ErCo2