Encapsulation of metal-based phase change materials using ceramic shells prepared by spouted bed CVD method

•SB-CVD was applied to encapsulate metal PCMs for the first time with high performance pyrolytic carbon (PyC) and SiC layers.•The capsules have high thermal conductivity, high energy density, excellent oxidation resistance and good cycling performance.•Multi-phase changes are achieved at 686 °C(48.85 J/g) and 1136 °C (128 J/g) for solid-solid and solid-liquid phase change.

Metals are promising high-temperature phase change materials (PCMs) with high heat storage density and high heat exchange rate for high high-temperature heat storage. However, encapsulation of metallic PCMs is essential for its practical application owing to its highly corrosive to encapsulation materials and its volume expansion during the phase change. The present study applied spouted bed chemical vapor deposition (CVD) method to encapsulate metallic PCMs. A novel heat storage capsule was developed using iron core encapsulated with porous pyrolytic carbon (PyC) layer, dense PyC layer and dense silicon carbide (SiC) layer in turn from inside to outside. The inner porous PyC layer is used to accommodate the volume expansion of the iron core and the outer dense SiC layer act as package layer and the oxidation resistance layer. The SiC/C-shells/Fe-core capsules could work at a temperature up to 1100 °C and include solid-solid phase change (48.85 J/g, 686 °C) and solid-liquid phase change (128 J/g，1136 °C). It is demonstrated that the SiC/C-shells/Fe-core capsules have several desired characteristics, such as high thermal conductivity and high thermal density, excellent oxidation resistance and good thermal cycling performance.