Preparation， Energy Storage， and Supercooling Characteristics of Carbonized Melamine Sponge/Sodium Chloride Aqueous Solution Composite Phase Change Cold Energy Storage Materials

This study prepared composite phase-change cold storage materials using carbonized melamine sponge （CMS） and NaCl aqueous solution to address the problems of low energy storage density and large supercooling degree of traditional sodium chloride （NaCl） aqueous solution， and broaden their application in cold thermal energy storage. Fifteen CMS samples were prepared by sintering melamine sponge （MS） at different temperatures and durations in air. The microstructures， thermal conductivities， mechanical properties， and surface wettability of the CMS were systematically characterized. The phase-change characteristics of NaCl aqueous solutions with different concentrations were further explored， and the CMS prepared by the optimal process was compounded with an NaCl aqueous solution to analyze the variation rules of the energy storage density and supercooling degree of the composite materials. The experimental results showed that the CMS sintered at 400 ℃ for 150 minutes exhibited a uniform porous structure and a thermal conductivity of 0.039 41 W/（m·K）， which was 36.7% higher than that of the original MS. Additionally， the CMS exhibited good hydrophilicity， which enabled effective adsorption of the NaCl aqueous solution. Although the high porosity resulted in a slight decrease in its mechanical properties， the material could still satisfy the application requirements of composite cold storage materials. The phase change characteristics test showed that the latent heat of phase change of the NaCl aqueous solution decreased with increasing concentration， while the degree of supercooling initially increased and subsequently stabilized. Compared with pure NaCl aqueous solution， the composite material prepared by CMS sintered at 400 oC for 150 minutes， and NaCl aqueous solution exhibited an energy storage density increase of 6.3%~15.3%， and a significant reduction in supercooling degree of 8.2%~70.1%. The results indicate that CMS can effectively enhance the phase-change energy-storage performance of NaCl aqueous solutions and inhibit supercooling. The prepared composite phase-change cold-storage material demonstrates good application potential， which provides a theoretical basis as well as technical reference for the design and preparation of high-efficiency cold-storage materials.