Construction And Thermal Storage Structure-properties Relationship Of Porous Carbon Synergistic Reinforced Composite Phase Change Materials

With the rapid consumption of fossil fuels and rapid industrial development,it is urgent to develop new techniques and materials to efficiently convert and storage energy.Phase change materials(PCMs)are considered as important and attractive material for energy storage and conversion,which have the potential to solve the problem of mismatch between energy supply and demand.Among the PCMs studied at present,organic PCMs represented by polyethylene glycol(PEG)show great potential due to stable physicochemical properties,negligible supercooling,no phase separation and no corrosion.However,organic PCMs also have some defects that limit their practical applications,such as solid-liquid leakage,low thermal conductivity,and poor light-to-thermal conversion capability.Therefore,in this paper,a series of new porous carbon synergistic reinforced compsite PCMs with stable structure were prepared by structural design using porous matrices encapsulation and chemical grafting,and their comprehensive properties were analyzed.(1)In order to develop a composite PCMs with excellent light-to-thermal conversion performance,a new porous aerogel with a regular structure was prepared using graphitized carbon nitride with excellent photo-catalytic performance and graphene oxide,which was used as a supporting matrix for encapsulating PEG to prepare the composite PCMs.The obtained composite PCMs have good leakage resistance and thermal stability,showing high phase change enthalpy of 165 J/g-173 J/g and light-to-thermal conversion efficiency of 90.33%.(2)Low-cost and abundant pea flour was used as porous carbon source,and modified two-dimensional nanosheet boron nitride was added to synergistically enhance the thermal conductivity of PCMs.The pea flour/h-BN dual thermally conductive carbon aerogel was prepared using a green process,and was used as a supporting matrix for the encapsulation of PEG.The composite PCMs was able to adsorb 98.61 wt%of PEG,showing excellent heat storage performance.Its enthalpy was up to 174.04 J/g and thermal conductivity improved to 0.58 W/(m·K).It also shown excellent shape stability and temperature control ability.(3)In order to develop flame retardant and highly thermally conductive composite PCMs,a new composite PCMs was prepared in this study by chemical grafting and physical blending using graphene oxide(GO)with high thermal conductivity and decabromodiphenyl ethane with high flame retardant efficiency in a synergistic manner.The phase change enthalpy was in the range of 131.21 J/g-162.18 J/g,and the thermal conductivity was up to 0.453 W/(m·K).The peak heat release rate of the composite PCMs was 84.88 kW/cm~2,and the fire performance was significantly improved compared with that of pure PEG(388.31 kW/cm~2).The enthalpy retention rate of composite PCMs was as high as 98.99%after 400 thermal cycles,showing excellent thermal cycle stability.