Pressure effect on long-term heat storage ceramics based on Mg-substituted λ-Ti3O5

Abstract

Waste heat energy could be effectively used if the accumulated thermal energy could be conserved. However, neither typical sensible heat-storage materials such as brick and concrete nor latent heat-storage materials such as water and polyethylene glycol can store energy for a prolonged period. Herein we report a heat-storage material, which is a ceramic that exhibits long-term storage of latent heat and release of the heat by applying pressure. This material is Mg-substituted lambda-trititanium-pentoxide (λ-Mg_xTi_3−xO₅ where 0 < x ≤ 0.053). λ-Mg_xTi_3−xO₅ shows a phase transition to Mg-substituted beta-trititanium-pentoxide (β-Mg_xTi_3−xO₅) by pressure application. Mg cation substitution can control the temperature of the heat storage originating from the β- to λ-phase transition from 196 °C (469 K) for x = 0 to 80 °C (353 K) for x = 0.053. This phase transition temperature range is suitable for heat storage from industrial waste and thermal power plants. The accumulated heat energy is maintained at a large value of 215–227 kJ L⁻¹ in the range of 0 < x ≤ 0.053. Such an eco-friendly and pressure-responsive heat-storage ceramic, which can preserve the latent heat energy for a prolonged period, is effective for the sustainable reuse of heat energy that has been wasted in industrial facilities and factories.