Thermal and Chemical Stability of Ceramic Heat Storage Media Under High-Temperature Steam Environments

This study investigates the key material properties governing the long-term stability of ceramic heat-storage media exposed to severe high-temperature and high-humidity conditions (up to 950 °C under high-steam partial pressure). Candidate ceramics, including high-purity alumina, mullite, and cordierite compositions, were evaluated through physical property measurements, chemical composition analysis, SEM–EDX microstructural characterization, and hydrothermal corrosion simulations. Ceramics containing significant SiO2 exhibited chemical weakening due to steam-induced silica dissolution and the formation of hydroxyl-rich surface layers. However, the overall mechanical integrity was predominantly limited by thermal shock failure occurring during rapid heating–cooling cycles and repeated steam condensation and evaporation. The results demonstrate that ceramics with a low coefficient of thermal expansion (CTE ≈ 2–4 × 10−6/K) show markedly enhanced resistance to thermal shock, leading to improved operational durability. In addition, low open porosity (<10 vol%) effectively restricted internal steam penetration and reduced the rate of hydrothermal degradation, particularly in SiO2-based systems where pore-connected pathways accelerate corrosion. These findings indicate that thermal shock resistance, enabled by intrinsically low CTE, together with reduced porosity, constitutes the primary design criterion for ensuring the structural reliability of ceramic heat-storage components operating in high-humidity thermal environments.