Preparation And Characterization Of Composite Phase Change Material Based On Graphene Oxide Framework

Phase change materials(PCMs)can store and release thermal energy according to different environmental temperature,which can effectively overcome the limitations of space and time between energy supply and demand.Due to high thermal conductivity,low density,high stability and good compatibility with PCMs of carbon materials,composite PCMs are prepared by the framework of carbon materials,which can be hopeful to effectively solve the shortcomings of the single PCMs such as low thermal conductivity,supercooling degree and leakage,and enhance practical application value.In this paper,two shape-stabilized phase change materials were prepared by using graphene oxide(GO)as matrix material,hexadecanol(HD)and erythritol(ET)as PCMs,respectively.The chemical and thermal characterization of the composites were investigated using fourier transform infrared(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectrometer(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM),differential scanning calorimeter(DSC),thermogravimetry(TG)and thermal conductivity analysis.The influence of the chemical grafting on the leakage and the thickening agent in improvement of the supercooling degree were studied.Aiming to improve the shape stability,recycled reliability and thermal conductivity of HD,GO grafted HD(GO-g-HD)shape-stabilized phase change material was prepared by oxidizing graphite powders to GO,converting to acyl chloride and finally grafting with HD.And then,its structure and performance were characterized.The results show that HD embedded in the composite with the maximum mass fraction of 62.7 wt.% through physical adsorption and covalent bonding ways.The grafted percentage and density of HD on the ultra-thin GO sheets is 36.5 wt.% and 1.51 mmol/g,respectively.The GO-g-HD SSPCM melt at 49.7 ℃ with the latent heats of 152.3 J/g and freeze at 45.4 ℃ with the phase change enthalpy of 129.9 J/g.The thermal conductivity of GO-g-HD is measured as 0.519 W/m·K,improved 41.8% compared with neat HD.Moreover,the as-prepared composite also presents superexcellent chemical and thermal stability,excellent thermal durability,no changed behavior in phase change temperatures and the reduction of only 0.5 percent in latent heats due to the strong covalent bonds and interactions between the matrix and HD.GO-g-HD is a promising candidate for thermal energy storage in future.ET/GO shape-stabilized phase change material was prepared by sol-gel method,using ET as PCMs and GO as framework material.The influence of GO and thickening agent of carboxyl methyl cellulose(CMC)on the supercooling degree of ET were studied.Three-dimensional network structure of GO thin-film uniformly encapsulate ET,which prevent leakage in phase transformation.The melting latent heat,freezing latent heat,supercooling and exothermicity of ET are 349.9 J/g,224.2 J/g,90.3 ℃ and 64.1%,respectively.The mass fraction of nucleating agent of GO was 3.0%,1.5% and 1.0% was added.The composite of mass fraction of GO is 3.0%(ET/GO30),which has high thermal storage property.The melting latent heat,freezing latent heat,supercooling and exothermicity of ET/GO30 are 346.6 J/g,236.2 J/g,90.3 ℃ and 68.1%,respectively.For further solving supercooling problem,the mass fraction of CMC was 0.2%,0.5% and 0.7% was added.The results show that the composite of mass fraction of CMC is 0.7%(ET/GO30-7C),which has minimum supercooling(17.9 ℃).The melting latent heat,freezing latent heat and exothermicity of ET/GO30-7C are 316.8 J/g,295.1 J/g and 93.2%,respectively.Moreover,the thermal conductivity of ET/GO30-7C(0.563 W/m·K)improve 80.4% compared with neat ET,which has good chemical structure,thermal and thermal storage stability.