Ultra-high temperature performance of h-BN based composite in contact with molten silicon

Silicon has been recently proposed as a very promising phase change material for applications inlatent heat thermal energy storage (LHTES) and conversion systems working at ultra-hightemperatures. However, in order to successfully develop such kind of devices, suitable refractoriesshowing low reactivity and non-wetting behavior upon the melting and storing of moltensilicon at temperatures much higher than its melting point have to be selected. In our previouswork, we have documented that the non-wetting behavior in Si/h-BN system is preserved attemperatures up to 1650 C, with the absence of new reaction products formed at the interface.These findings make hexagonal boron nitride (h-BN) a reasonable first candidate for Si-basedLHTES applications. Nevertheless, the rather poor mechanical strength of ''pure'' h-BN oughtto be improved in order to enhance the reliability under thermocycling operational conditionsand to increase the life period of the device. Therefore, in the present paper, we examine for thefirst time the interactions at ultra-high temperatures between a high strength commercialh-BN-based composite and molten Si. At temperatures up to 1750 C, the wettability of theh-BN-based composite (h-BN+SiC+ZrO2) with molten Si is much lower if compared to thepure h-BN counterpart. Additionally, the role of reinforcements (SiC+ZrO2) and occuredmicrostructural evolution is discussed based on the results obtained by SEM and XRD analyses.