Construction Of Carbon-based Phase Change Materials And Their Thermal Performance

Phase change materials(PCMs)is the key factor for the development of energy storage technology.It plays a crucial role in exploring new energy and improving energy utilization.This study aims to prepare advanced shape stabilized PCMs.Usually,high thermal conductivity and large energy storage density can not be existed simultaneously for composite PCMs.Therefore,a new method of designing three-dimensional porous carbon support is proposed to solve this problem.High thermal conductive three-dimensional structural carbon provide heat conductive path,hierarchical structural porous materias encapsulate PCMs and the interfacial interaction between the support and the PCMs was controlled to decrease the interfacial thermal resistance and enance the thermal release efficiency.The detailed work and the main innovation are divided into the following parts:(1)SA/CNT@PC with large thermal conductivity and high energy storagecapabilitiesA core-sheath CNT@PC was prepared via carbonation of CNT@ZIF-8,simultaneouly 3D structural supports were obtained due to the porous carbon(PC)sheath stabilized the CNT@PC network structure.Porous carbon(PC),derived from carbonized metal organic frameworks(MOFs),exhibited high porosity and large specific surface area.PCMs,absorbed by capillary force of porous structure,was stabilized in the pores of PC sheath.Further,the interaction between PCMs and CNTs reduced the interfacial thermal resistance greatly.Carbon nano tubes(CNTs),acting as heat transfer pathways,provided continuous channels for phonons transfer and realized rapid heat transformation between ss-PCMs and external environment.The obtained SA/CNT@PC ss-PCMs exhibited excellent thermal conductivity(1.023 W/mK),large phase change enthepy(155.7 J g-1)and high thermal storage capabilities(99.9%).SA/CNT@PC with large energy storage density,and high thermal conductivity which shows great potential in waste heat utilization.(2)Novel SA/rGO@PC with large thermal conductivity and high energystorage capabilitiesA 3-D reduced graphene-porous carbon support PCMs has been successfully synthesized by carbonizing GO@MOFs.During the carbonization process,MOFs was converted to hierarchical porous carbon,while GO was reduced to high thermal performance rGO.3-D porous carbon structure with high porosity and large specific surface area stabilized the PCMs by capillary force and surface tension.The interaction between PCMs molecule and rGO significantly decreased the thermal resistance interface,and makes the composites to revealed high thermal conductivity.Furthermore,3-D network structure promoted the stretching and crystallization characteristics of SA molecule in the confined pore space,which used for enhanced heat release efficiency.SA/rGO@MOF-5-C revealed a thermal conductivity of 0.60 W m-1 K-1 and a large phase change latent heat to 168.7 J g-1 with a 90.0 wt.%loading percentage.Additionally,the obtained ss-PCMs showed a promising potential in electrothermal energy storage application.(3)Novel octadecane/ZIF-67@IRMOF-3-C with excellent electrothermalperformanceOrdered network structural CNTs penetrated CNTs@porous carbon support was obtained by carbonizing ZIF-67@IRMOF-3.3D network structure with decrease the electrical resistance of the composite which ensure a low operation voltage.Further,high electric/thermal conductive CNTs of each energy storage unites facilitate the interfacial interaction between the PCMs and heat transfer paths,then ensure a rapid heat transformation in the electrothermal system.Furthermore,low thermal conductive amorphous PC protector reduce the heat loss at the solid-air interface which reduce the convective heat dissipation.Thus,the obtained composite PCMs can be triggered by a low voltage of 1.1 V with a high electrical to thermal storage efficiency(94.5%)which is in advance in current nanocarbon-based materials for electrothermal application.This study provides insights into the optimized designation of advanced electrothermal materials.The significance of this research is that it expands the new method of the simultaneous conversion from MOFs-based precursor to conductive carbon@porous carbon,reveals the principle for heat storage and transfer integration,it leads the development of novel shape stabilized PCMs which integrate high energy storage,high thermal conductivity and high thermal storage efficiency as a whole.