| With the rapid development of modern industry,sustainability has become one of the most important principles meeting the objectives of human being's development.Phase change materials(PCMs)can absorb large amounts of energy as latent heat through physical phase transitions at a constant phase transition temperature and controllably release the latent heat afterwards with a very small variation in temperature on the basis of thermal energy demand.Thus,PCMs have attracted significant attention because of their low cost,high energy storage density,and small temperature difference between energy storage and releasing procedures.At present,a great deal of organic solid-liquid PCMs have some ubiquitous defects such as its seepage during phase change procedures,low thermal conductivity and poor thermal stability,which are the main factors that restrict their wide practical applications in thermal energy storage.In order to solve the above shortcomings,three kinds of composite PCMs were successfully designed and synthesized with different structures by adding thermal conductive fillers via physical impregnation and electrospinning.At the same time,the comprehensive properties of the prepared composite PCMs were systematically investigated.The specific research results are described as following:(1)The novel hollow carbon microspheres were prepared through a template-assisted method by using functionalized polystyrene(PS)nanoparticles as a template and low cost and abundant source of soluble starch as a carbon source.The novel hollow carbon microspheres were chosen as the promising supporting materials for n-octadecane to prepare novel composite PCMs with excellent comprehensive properties.The melting latent heat of the composite PCM can reach 170.5 J/g,and the thermal conductivity is improved up to0.631 W/(m·K).When the composite PCMs are heated above the phase change temperature,there are no n-octadecane leakage,which proves that the composite PCMs have excellent shaping effect.The results show that the prepared composite PCMs have higher latent heat and thermal stability,and its thermal conductivity is significantly improved compared with n-octadecane.(2)A series of graphene oxide/polyethylene glycol(PEG/GO)composite phase-change fibers(PCFs)with PEG content of 18 wt% had been successfully prepared by electrospinning.In the preparation,PEG was used as the PCM and GO with high thermal conductivity and excellent mechanical properties was used as reinforced material for thermal conductivity.When the amount of GO is 0.5 wt%,the melting latent heat of composite PCFs is 99.5 J/g.The results show that the addition of GO forms a good thermal conductivity network in the composite PCFs,which greatly increases storage/release rate of thermal energy.The thermal conductivity of the composite PCF was increased by 116% compared with PEG.The results indicate that composite PCFs showed excellent shape-stability and high thermal conductivity.(3)The three-dimensional hybrid graphene aerogel(GBA)was prepared via hydrothermal and freeze-drying by taking advantage of synergistic effects between GO and hexagonal boron nitride(h-BN).At the same time,the OD/GBA composite PCMs were successfully prepared through vacuum impregnation by using n-octadecane(OD)as the PCMs and GBA as the supporting materials with high thermal conductivity.It was found that the OD/GBA composite PCMs possess excellent shape-stability,and the melting latent heat can reach 208.3 J/g.Moreover,the thermal conductivity of the composite PCMs can be enhanced to 1.4442 W/(m·K),illustrating the thermal conductivities of the composite PCMs are improved significantly by the highly thermally conductive GBA.All results demonstrated that the composite PCMs possess excellent thermal properties. |
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