Development and investigation of a high melting point binary sodium salt based composite phase change thermal energy storage material by an ultra-low sintering temperature with cold sintering technique

Wei, G. and Xiu, D. and Du, Y. and Li, C. and Qiao, G. and Li, Q. (2026) Development and investigation of a high melting point binary sodium salt based composite phase change thermal energy storage material by an ultra-low sintering temperature with cold sintering technique. Journal of Energy Storage, 168: 122680. ISSN 2352-152X

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Abstract

This work focuses on the development of a high melting point binary sodium salt phase change composite by an ultra-low sintering temperature for thermal energy storage. A so-called cold sintering approach is used for the composite fabrication in which a eutectic salt of Na₂SO₄/NaCl is adopted as phase change substance and diatomite is employed as skeleton material. By using sodium hydroxide solution as sintering agent, the effects of operation conditions and ingredient composition on the composite microstructural characteristics, mechanical and thermophysical properties as well as thermal stability are evaluated. The results indicate that the salt-diatomite composite could be successfully fabricated by a sintering temperature as low as 150 °C. A shape-stabilized framework containing a compact and dense microstructure could be obtained in the composite with the use of aqueous alkali as sintering liquid. Splendid chemical and physical compatibility have also been attained among the ingredients of sodium salt, diatomite and aqueous alkali. For a given uniaxial pressure, a mechanical strength as high as 253.84 MPa could be achieved in the composite. Over 60% of salt could be encapsulated by diatomite without the occurrence of liquid divulge. At such a composition, the composite presents a melting point of 623.9 °C and a latent heat of 148.2 kJ/kg. Moreover, the composite also exhibits excellent cycling performance and after experienced 300 heating-cooling cycles, a perfect macroscopic shape could be maintained and the latent heat of the composite only changes 4.9%, demonstrating the composite prepared through cold sintering technique in this work can be a competitive candidate used in medium and high temperature fields.