Fe-26Si-9B alloy as a Phase Change Material in Thermal Energy Storage System

Abstract

Fe-26Si-9B alloy was regarded as a potential phase change material (PCM), due to its high heat of fusion and moderate melting temperature. In order to use Fe-26Si-9B alloy in a thermal energy storage (TES) system successfully, the thermodynamic properties of Fe-26Si-9B alloy were investigated. Additionally, it is critical to select a compatible refractory material as a container for Fe-26Si-9B alloy. The interactions between Fe-26Si-9B alloy and three refractory materials were also studied in the long-term thermal cycle experiments. According to the experimental results, Fe-26Si-9B alloy had stable phases after long-term thermal cycles, minor volume shrinkage during solidification, and relatively high heat of fusion at a value of 3.53 kJ/cm3. When using Si3N4 and h-BN as crucibles for Fe-26Si-9B alloy, no nitrides and borides were introduced to the alloy. No reaction occurred at the interface between the alloys and Si3N4/h-BN. When it comes to graphite, a continuous SiC layer was formed at the interface between Fe-26Si-9B alloy and dense graphite. The amount of SiC particles was independent of thermal cycles and did not increase with increasing holding times. Hence, it is believed that Fe-26Si-9B alloy will be a good PCM. Graphite, Si3N4, and h-BN were suitable refractory materials for the Fe-26Si-9B PCM crucibles.

Keywords: PCM, TES, Fe-Si-B, thermal cycle, heat of fusion, ceramics