Stability assessment of alumina and SiC based refractories in a high temperature steam environment as potential thermal energy storage materials

Abstract

Solar energy can be utilized not only for electricity generation but also for synthetic fuel production, making it a versatile option in the transition to a low-carbon and sustainable energy system. However, to enable economically viable solar fuel production, the development of efficient thermal energy storage (TES) materials is crucial. Ceramic materials have been identified as a potential solution for high-temperature TES applications. In this study, two commercially available refractories, alumina coated recrystallized silicon carbide and alumina-based refractory were investigated for their stability under long-term steam corrosion tests to evaluate their suitability as TES materials for a potential TES unit. X-ray diffraction (XRD) revealed that recrystallized silicon carbide is composed of two different SiC polytypes (moissanite 6H and moissanite 4H) while alumina-based refractory contained corundum and mullite. Upon being exposed to steam, both materials exhibited distinct characteristics. SiC experienced significant mass gain, a subtle lightning of its surface color and erosion of a porous alumina coating on the SiC. Amorphous silica phases were detected as an indication of oxidation of SiC from X-ray diffractrograms. These remarkable changes clearly indicate that SiC is unsuitable for use in a potential thermal energy storage (TES) unit. On the other hand, there was no significant visual changes in the alumina-based refractory and the weight change was only marginal after corrosion tests. However, XRD indicated mullite completely disappeared after steam corrosion tests possibly due to its decomposition into Al2O3 and Si(OH)4.