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

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 degrees C and include solid-solid phase change (48.85 J/g, 686 degrees C) and solid-liquid phase change (128 J/g, 1136 degrees 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.