Construction And Thermal-energy Storage Properties Of Micro-nanometer Co-reinforced Composite Phase Change Materials

With the global ebergy crisis becoming more and more severe,it is urgent to seek new renewable energy sources and improve the existing energy efficiency.Since phase chage materials(PCMs)have the characteristics of high heat storage density and suitable working temperature,which can effectively improve the energy efficiency,they have been widely concerned in energy storage fields.However,PCMs possess the defects of easy leakage and low thermal conductivity in working process and the traditional composite PCMs has single function with unstable structure,which seriously limit their applications.Therefore,with the help of structural design,series of novel composite phase change materials with high performance and stable structure were constructed through micro/nano-scale encapsulation and multi-porous structure encapsulation method.Specific research contents are described as following:(1)Since PCMs single function and MnO₂has excellent electrochemical properties and optical properties,this research innovatively constructed a MnO₂reinforced microencapsulated PCMs with double shell materials using electro-chemical adsorption and redox methods.And a layer of dense MnO₂nanowires was coated on the initial polymer shell of the microcapsules.The encapsulation rate and energy storage efficiency of the microcapsules are both higher than 56%.Their particle size of the microcapsules is between 3 and 8?m,and their phase change enthalpy is between 133.56 J/g and 152.71 J/g.In addition,the MnO₂shell material provides the microcapsule with excellent electrochemical performance and photothermal conversion performance.When the MnO₂ shell content is 7 wt%,the specific capacity of the microcapsules reaches 364 F/g and the photo-thermal conversion efficiency is as high as 93%.(2)CdS-reinforced bivalve microcapsule were constructed with a layer of CdS nanoparticles coated on the surface of the first polymer shell of the microcapsules through interactions of functional groups,and CdS can supply the microcapsules with good optical properties.The encapsulation rate and energy storage efficiency of the microcapsules is as high as 65.52%and 65.32%,respectively.The particle size distribution of the microcapsules is between 3 and 10?m,and the enthalpy value is between 113.4 J/g and154.94 J/g.In addition,CdS endows the bivalve microcapsules with up to 85%visible light absorption performance and excellent photo-thermal conversion performance.(3)In order to improve the thermal conductivity of PCMs,this study used high thermal conductivity silver nanowires(AgNW)and graphene oxide(GO)to construct a novel composite three-dimensional graphene aerogel,so that AgNW were intersected into the graphene sheets forming a continuously thermal conductivity network.And the AgNW-GA composite PCMs were prepared by using the graphene aerogel to encapsulate PEG6000.Enthalpy value of the AgNW-GA composite PCMs is between 170.31J/g?180.89 J/g,and the energy storage efficiency is higher than 90%.In addition,the AgNW-GA composite PCMs have excellent photo-thermal conversion performance and their thermal conductivity is up to 0.724 W/m·K,which is improved by 173% compared with PEG6000.