Preparation And Thermal Performance Of Carbon-based Composite Inorganic Hydrate Salt Phase Change Material

With the increase in energy consumption in recent years,problems such as the high cost of fossil fuels and environmental pollution have become more prominent.Researchers are committed to the development of renewable energy in order to achieve a sustainable future.Thermal energy and solar energy are the most abundant and ubiquitous renewable resources and have the potential to replace fossil fuels.Phase change material(PCM)is an advanced new energy material.The thermal energy can be stored in the form of phase change latent heat.Therefore,PCM has been applied in many fields,including energy-saving buildings,thermal management of electronic equipment,and solar energy collection.Inorganic hydrated salt materials have good thermodynamic properties and low prices.This type of material has a high phase change latent heat value and a moderate phase change temperature.They are widely sourced and easily available in nature.and are ideal energy storage materials that are most suitable for practical applications.However,as an inorganic phase change material,it also has many industrialization bottlenecks.For example,in the course of use,there will be more serious overcooling and phase separation.On the one hand,it will affect the quality and efficiency of its heat exchange,on the other hand,it will greatly reduce its actual life,which is not conducive to its industrial promotion.Carbon-based fillers and carriers include graphene oxide,reduced graphene oxide and expanded graphite,etc.,which have inherently good thermodynamic properties.Compounding with inorganic hydrated salt helps to suppress its supercooling phenomenon,improve its molding structure,and further enhance the overall performance of the composite material.Graphene oxide prepared by a modified Hummers method and reduced graphene oxide prepared by a chemical reduction method.In this work,we combine it with Na₂S₂O₃·5H₂O,Na₄P₂O₇·10H₂O,and sodium polyacrylate(PAAS)in a certain proportion.After ultrasonic,stirring,vacuum filtration and other steps,a carbon-based filler doped inorganic hydrated salt phase change composite material is obtained.Further,expanded graphite with different mass fraction ratios is used to vacuum load the two phase change composite systems.Characterization methods such as SEM,DSC analysis,Raman spectroscopy,XRD and TG analysis were used to test the morphology and performance of the product.It also reveals the influence of different proportions of fillers on the thermal properties and stability of composite materials.1.GO prepared by the modified Hummers method,Na₄P₂O₇·10H₂O and PAAS were used as filler additives to modify Na₂S₂O₃·5H₂O.The effect of the changes of different doping mass fractions on the thermodynamic properties of phase change composites was studied.Furthermore,the thermal stability of the phase change composite material and the performance degradation after multiple phase cycles were measured.The results show that when the mass fraction of GO,Na₄P₂O₇·10H₂O and PAAS are 0.03 wt%,2.0 wt%and 1.0 wt%,respectively,the composite has the best comprehensive performance.The overall undercooling degree of the material is reduced to 1.26?,with a decrease of more than 91%.The latent heat value of phase transition is about 188.24 J/g,which is not much different from that of pure Na₂S₂O₃·5H₂O.After 50 melt-solidification cycles,it still maintains good performance.2.RGO was prepared by chemical reduction method,and Na₄P₂O₇·10H₂O and Paa S were used as filler additives to modify Na₂S₂O₃·5H₂O.The optimal ratio was 0.05 wt%RGO+2.0 wt%Na₄P₂O₇·10H₂O+1.0 wt%PAAS.The comprehensive properties of phase change composites are the best at this ratio.The supercooling degree of the system is reduced to 1.32?,the latent heat value of phase change is about186.38 J/g,and the heat release platform is stable and uniform and lasts for a long time.3.Finally,based on the inorganic hydrated salt phase change core material compounded by GO or RGO,EG prepared by high temperature expansion method is vacuum-loaded.The effect of EG load on the properties of composites was investigated.It can be concluded that the phase change composites doped with carbon-based fillers can be well dispersed in the pores of EG without agglomeration.The composite material obtained after loading also has good properties.