二水合硫酸钙多孔复合热化学储热材料的制备及热性能研究OA

Calcium sulfate dihydrate(CaSO4·2H2O),the main component of phosphogypsum,exhibits significant potential for medium-temperature thermal energy storage because of its high heat storage density,low cost,and wide availability.Its reversible dehydration-hydration reaction enables efficient thermal energy storage and release,making it suitable for applications such as medium-temperature solar heat collection and industrial waste heat recovery.However,inherent limitations,including low thermal conductivity and severe agglomeration during cycling,restrict heat and mass transfer efficiency and long-term operational stability,thereby hindering engineering applications.To address these challenges,this study focuses on the preparation and performance optimization of thermochemical heat storage materials through synergistic modification using functional additives and a composite porous structure.High-purity CaSO4·2H2O powder was synthesized via a solution method.Subsequently,3%expanded graphite was introduced as a thermal conductivity enhancer and 5%nano-silica(SiO2)as an agglomeration inhibitor,followed by ball milling to obtain a CaSO4·2 H2O/3EG/5SiO2 heat storage matrix.A porous composite thermochemical heat storage material was then fabricated by vacuum impregnation of the matrix into porous copper foam.The microstructure,crystal structure,chemical compatibility,thermal performance,and cyclic stability were systematically characterized using scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,differential scanning calorimetry,and a laser thermal conductivity tester.The results show that the incorporation of expanded graphite increases the thermal conductivity of CaSO4·2H2O from 0.577 W/(m·K)to 0.797 W/(m·K),corresponding to an improvement of 27.6%.Nano-SiO2 effectively suppresses particle agglomeration after cycling by enhancing particle dispersion and inhibiting grain boundary migration.The porous structure and high thermal conductivity of copper foam further improve heat and mass transfer pathways,resulting in a thermal conductivity of 1.509 W/(m·K),which is 161.5%higher than that of pure CaSO4·2H2O.The composite material exhibits a reaction enthalpy of 359 J/g,a packaging efficiency of 70.4%,and an operating temperature range of 120-160℃,which is well matched with medium-temperature solar thermal systems.After 80 hydration-dehydration cycles,the heat storage density remains at 92.3%,with no significant changes in crystal structure or chemical compatibility,demonstrating excellent cyclic stability.Through the synergistic design of porous support and functional modification,this study effectively addresses the key challenges of low thermal conductivity and agglomeration in hydrated salt thermochemical heat storage systems,providing a practical strategy for performance enhancement and high-value utilization of phosphogypsum resources.