Cold sintering of NaNO3/MgO heat-storage composite

Abstract Medium- and high-temperature phase change materials are important in the field of heat storage. They usually consist of inorganic salt/ceramic mixtures and require high temperatures for sintering. In this work, cold sintering was applied to fabricate heat storage composites using NaNO3/MgO as a model system. NaNO3 was successfully encapsulated in a MgO skeleton, which maintained stable after 500 melting−freezing cycles. The composites exhibited excellent chemical compatibility and good thermal stability. Moreover, the resultant composites achieved a compressive strength of higher than 100 MPa with relative density over 98% under 75 MPa at low temperatures (≤180 °C) in the presence of 6 wt% water. Compared with the conventional preparation processes that are implemented at high temperatures, this method is very simple, economical and environmentally friendly, and can be applied to the synthesis of other inorganic salt/ceramic phase change materials.