Interfacial Thermal Resistance in Magnetocaloric Epoxy-Bonded La-Fe-Co-Si Composites
Magnetocaloric composites made from La−Fe−Co−Si particles and an epoxy binder matrix exhibit mechanical stability and good magnetocaloric properties, but also a large characteristic time for thermal transport. Here, the origin of this large time constant is examined by comparing two measurement techniques, direct and contactless, to finite-element simulations based on a tomographic dataset of the sample. The combination of the low thermal conductivity of the epoxy matrix and a thermal resistance at the interface between epoxy and La−Fe−Co−Si is shown to be in good agreement in simulations and experiments. The findings help to disentangle the role of the thermal conductivity and the interfacial thermal resistance for the heat flow in magnetocaloric composites. It is shown that the low thermal conductivity of the epoxy alone cannot explain the large time constant and possibilities for using the interfacial thermal resistance to tailor anisotropic thermal conductivity for directional heat transfer in magnetocaloric composites are presented.
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K.S. and A.W. would like to gratefully acknowledge funding from the DFG SPP “Ferroic Cooling” under grant number WA3294/3-2. M.K. was financially supported by the Germany Federal Ministry for Economic Affairs and Energy under the project number 03ET1374B (SOMAK). L.H. and A.H. gratefully acknowledge funding by the Deutsche Forschungsgemeinschaft through SPP 1599 “Ferroic Cooling” (Project No. HU 857/8-1).