Enhanced comprehensive magnetic refrigeration performance in La0.8Ce0.2Fe11.7Si1.3H by incorporation of graphene

Thus far, metal-bonding has presented high efficacy in improving the mechanical, thermal conductive, and anti-corrosion properties of La(Fe,Si)13-based hydrides. However, to ensure high performance, the proportion of metal bonders has to be as high as 20 wt%, thereby significantly weakening the magnetocaloric effect (MCE). In this work, small amounts of graphene nanosheets (up to 2 wt%) with high thermal conductivity and specific surface area were incorporated into the La0.8Ce0.2Fe11.7Si1.3Hy matrix through a cold-pressing and sintering process. X-ray diffraction analysis indicates that carbon from graphene can easily diffuse into the lattice of La(Fe,Si)13 main phase as an interstitial atom, resulting in a significant increase of the lattice constant accompanied by a significant decrease of the Curie temperature and H content of the composites. While 0.3 wt% graphene doping only has minor improvements in the thermal conductivity λ and corrosion resistance of the parent La0.8Ce0.2Fe11.7Si1.3Hy, further increase of graphene content to 1 wt% causes a significant increase of λ from 1.4 W/(m·K) for the parent material to ∼2 W/(m·K) and a decrease of corrosion current density from 1.43×10‒5 to 9.63×10‒6 A/cm2. When the graphene content is lower than 0.3 wt%, the large MCE does not significantly deteriorate. In 0–1.5 T, the maximal magnetic-entropy change ΔSm of 11.5 J/(kg·K) at 336 K for the parent material decreases to 8.2 J/(kg·K) at 306 K for the 2 wt% graphene-doped composite.