Study On The Preparation And Properties Of Carbon-based Phase Change Materials Composites

Phase change materials（PCMs）,as excellent functional energy storage materials,can reversibly store thermal energy and release a large amount of latent heat during the phase transition from solid state to molten state.Due to its large energy storage capacity,high energy storage density,constant phase transition temperature,and high economic benefits,can well meet the requirements of energy supply and demand matching in time and space,it has shown great potential in the development and efficient utilization of renewable energy.The exploitation of phase change materials composite with high photothermal conversion efficiency and storage performance is of great significance for the development and efficient utilization of renewable energy.Solid-liquid organic phase change materialshave attracted more and more attention in the field of energy conversion and storage due to their high energy storage density,low supercooling and small volume variation during their phase transition.However,due to its shortcomings such as low thermal conductivity,easy leakage,and single application function in the practical applications which is greatly limited in energy conversion and storage.In view of the above problems,this paper proposed an idea for the construction of porous carbon materials to encapsulate solid-liquid organic phase change materials via different methods.The comprehensive properties of phase change materials have also been effectively improved,which provides experimental data and research ideas for the design and preparation of porous carbon-based phase change materials composite and their applications in thermal energy storage and solar energy conversion and storage.The main research contents of this paper are as follows:（1）Firstly,anodic aluminum oxide membranes（AAOM）was used as sacrifice templates,and polypyrrole（PPy）and asphalt were used as carbon sources.After high-temperature carbonization and acid washing,polypyrrole carbon membranes（C-PPM）and asphalt carbon membranes（C-AM）with rich ortho-aligned nanoporous network structure was obtained.The prepared carbon membranes have abundant porosity,excellent surface properties and strong light absorption capability.Then,hexadecylamine（HDA）and heptadecaamine（AHD）with high energy storage density are used as phase change materials,and they are impregnated into the ortho-aligned nanopores of C-PPM and C-AM by capillary effect and surface tension in the molten state,and the phase change materials were effectively encapsulated,and several carbon-based phase change materials composite were fabricated.The results show that the carbon-based phase change material composites have enhanced thermal conductivity of 0.525 W m^-1 K^-1,0.355 W m^-1 K^-1,0.408 W m^-1 K^-1 and 0.291 W m^-1K^-1,respectively.Compared with pure PCMs,the thermal conductivities of the phase change materials composite are 357.1%,241.5%,203.0%and 144.8%of their thermal conductivities,respectively.In addition,the phase change material composites also exhibit a photothermal conversion efficiency of up to 93.8%.The excellent comprehensive properties of carbon-based phase change materials composites make them great application potentials in solar energy harvesting,conversion and storage.（2）Then,conjugated microporous polymer/expanded graphene（EG）aerogels（CMPEs）were prepared by Sonogashira-Hagihara cross-coupling reaction,and the conjugated microporous polymer/expanded graphene carbon aerogels（CMPECAs）was obtained after high temperature carbonization treatment.Then,polypyrrole-coated conjugated microporous polymer/expanded graphene carbon aerogel（PCMPECAs）carrier materials were also obtained by uniformly spraying polypyrrole（PPy）on CMPECAs.Using 1-hexadecylamine（HDA）with high energy storage density as organic phase change material,HDA was loaded into the pores of PCMPECAs in vacuum atmosphere via melt-impregnated method to achieve efficient encapsulation of HDA,and three shape-stable phase change materials composites were prepared.The introduction of expanded graphene and polypyrrole is to further improve the photothermal properties and thermal conductivity of phase change materials composites.The results show that the thermal conductivity of PCMPECAs/HDA composites at 25℃is 0.342 W m^-1 K^-1,0.344 W m^-1 K^-1,0.327 W m^-1 K^-1,which are 232.7%,234.0%and 222.4%that of HDA,respectively.The phase change materials composites also possess remarkable shape stability,and no leakage occurs at 90°C.More importantly,the PCMPECAs/HDA composites also exhibit high photothermal conversion efficiency at 100 m W/cm²,where HDA/PCMPECA-1 is93.5%,HDA/PCMPECA-2 is 90.3%,HDA/PCMPECA-3 was 89.5%.And after 300heating and cooling cycles,PCMPECAs/HDA still have high latent heat.At the same time,the phase change materials composites also show excellent electro-thermal effect at low voltage.This research provides a rich theoretical basis for the application of PCMPECAs/HDA in high-efficiency solar energy conversion and storage.