It is important to enhance their performance of supercooling and low thermal conductivity in hydrate salt phase change materials. A hydrophilic silicon carbide (nano-SiC) was prepared via treating SiC nanoparticles in HF/HNO₃ with Na₂SO₄·10H₂O-Na₂HPO₄·12H₂O eutectic hydrated salt as basic materials, and the phase change nanofluids materials (nano-SiC EHS PCMs) with Na₂SiO₃·9H₂O and nano-SiC were composited. The results show that the modified nano-SiC can be dispersed in EHS PCMs. The synergistic effect of Na₂SiO₃·9H₂O and nano-SiC can reduce the supercooling degree to 0.3 ℃ without the phase separation. The thermal conductivity of nano-SiC EHS PCMs enhances both in solid and liquid. The energy storage time of EHS PCMS with 0.2% (in mass) nano-SiC is decreased by 21.8%. The enthalpy of melting and crystallization of EHS PCMs with 0.15% nano-SiC is 267.3 J/g and 231.4 J/g, respectively. The enthalpy of nano-SiC EHS PCMs is stable after 1000 heating and cooling cycles, indicating that nano-SiC EHS PCMs have a great thermal cyclic stability.

To solve the problem of the shortened cycle life of phase-change latent heat storage due to the large subcooling degree and serious phase stratification of mirabilite phase-change materials, a graphene oxide/mirabilite composite phase-change material (GO–MCPCM) was prepared with Na₂SO₄·10H₂Na₂CO₃·10H₂–NaCl phase-change composite as a matrix and graphene oxide (GO) as additives. The microstructure and properties of GO and GO–MCPCMs were characterized by scanning electron microscopy, transmission electron microscopy Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry-Differential scanning calorimetry, respectively. The results show that the O/C ratio in oxidized graphene oxide is increased by 65.75%, the structural defect level is increased from 0.224 to 1.088, indicating that the oxidation–treated graphene has no agglomeration phenomenon and has good hydrophilicity and compatibility. The crystalline phase transition temperature of GO–MCPCMs is 23 ℃, the degree of subcooling reduces to 0 ℃, only sodium sulfate decahydrate releases heat, and the crystalline hydrate is Na₂SO₄·10H₂O with a grain length of approximately 2 cm. The maximum latent heat of GO–MCPCMs crystallization at a mass fraction of 0.075% is 156.7 J/g, and the attenuation rate of the latent heat of GO–MCPCMs crystallization at a mass fraction of 0.075% is 4.3% after 500 solid–liquid cycles. Therefore, the addition of GO can improve the thermal stability of the mirabilite composite phase-change material, and graphene oxide/mirabilite composite phase-change material prepared has a good thermal cycle stability and a long service life.

Carbon sponge can be used as a carrier for phase-change materials due to its advantages of low density, large pore volume, and high thermal conductivity. A carbon sponge with certain graphitization characteristics and a porosity of 96.30% was synthesized as a carrier with absorbent cotton and MgO as raw materials, and a composite phase-change material encapsulated by a porous carbon sponge was prepared with Na₂SO₄·10H₂O/Na₂HPO₄·12H₂O as a phase-change medium. The results show that the adsorption amount of carbon sponges prepared at 700, 800 ℃ and 900 ℃ to the phase-change materials is 60, 75 and 102 times greater than their weights, respectively. Also, the solid-liquid phase-change cycle performance of the carbon sponge-encapsulated materials prepared at different temperatures was discussed at 5–60 ℃. After 5 000 cycles, the latent heat of the phase-change material is still > 200 J·g^–1, which is reduced by 13%, and the thermal conductivity increasing rate is > 50%. The composite phase-change material encapsulated by porous carbon sponge has promising application prospects in the field of solar energy storage.