Preparation And Thermal Storage Properties Of Hexadecaminebased Composite Phase Change Materials

In recent years,the exploitation and utilization of industrial waste heat is regarded as one of the important means to solve the energy problem.Phase change materials(PCMs)can be used to recover industrial waste heat because of their high energy storage density and stable temperature during the phase change process.Compared with other PCMs,organic PCMs have the advantages of high latent heat,low undercooling,stable physical and chemical properties,non-corrosive and good cold and heat cycle stability.However,at present,organic PCMs still have the disadvantages of low thermal conductivity and easy leakage when phase transition occurs.Therefore,it is urgent to develop a phase change material with high thermal conductivity,high latent heat and low leakage rate.In this paper,hexadecylamine(HDA)was selected as PCMs.Firstly,threedimensional graphene aerogel(GA)was prepared by hydrothermal method,and then hexadecylamine/three-dimensional graphene composite phase change material(HDA/GA CPCMs)was prepared by melt impregnation method.In order to further improve the thermal properties of composite phase transition materials,polystyrene/calcium carbonate/cetylamine microcapsule phase change materials(PS/CaCO3/HDA MEPCMs)were prepared by ultrasonic emulsification using styrene(C8H8),calcium chloride(CaCl2)and sodium carbonate(NaCO3)as raw materials.Then,scanning electron microscopy(SEM),X-ray diffraction analyzer(XRD),X-ray photoelectron spectroscopy(XPS),Raman spectrometer(Raman),Fourier infrared spectrometer(FT-IR),thermogravimeter(TG),differential scanning calorimetry(DSC)and other characterization methods were used to characterize and test the properties of the prepared materials.The results are as follows:(1)GA was successfully prepared by hydrothermal method,and HDA/GA CPCMs were prepared by melt impregnation method.The results showed that GA had a large number of pores inside,and the appearance was nearly ellipsoidal,and the large number of pores provided storage space for HDA,which filled most of the pores in GA.However,there is still a small part of pores not completely filled,and HDA covers the surface of GA.the latent heat of HDA/GA CPCMs reaches up to 284.5 kJ/kg,and it can still maintain high latent heat after several cycles.the thermal conductivity of HDA/GA CPCMs is 0.238 W/(m·K),which is 1.62 times of the thermal conductivity of HDA,and the subcooling degree is less than 10℃.HDA/GA CPCMs have good thermal storage properties at low temperatures,and the presence of GA inhibits the leakage of HDA during the occurrence of phase transition and has good cycling stability.(2)PS/CaCO3/HDA MEPCMs were prepared by ultrasonic emulsification.Then the prepared phase change materials were characterized and their properties were tested using TEM,SEM,XRD,XPS,FT-IR,TG,DSC and other characterization methods.The results showed that PS/CaCO3/HDA MEPCMs with microcapsule structure were successfully prepared with diameters ranging from 1 μm to 10 μm.the thermal conductivity of PS/CaCO3/HDA MEPCMs was 0.491 W/(m·K),which was 3.41 times of the thermal conductivity of pure HDA.the latent heat of PS/CaCO3/HDA MEPCMs was up to 120.6 kJ/kg,and the subcooling degree is less than 10℃,and no leakage problem occurs in use,which indicates that PS/CaCO3/HDA MEPCMs have good stability and high thermal conductivity,and have good thermal storage performance at low temperatures.