Preparation Of Graphene Oxide-silica Hybrid Aerogel And Studying On Properties Of Composite Phase Change Materials Based On Hybrid Aerogel

At present,most of the technical solutions for combining phase change materials(PCM)with solar energy are mainly aimed at improving the thermal conductivity of PCMs.However,the heat loss rate increases as the heat transfer rate increases.The PCMs with dual properties of light-to-thermal conversion and thermal insulation are needed in some application situations,such as some areas with long time illumination but large temperature differences between day and night,floor heating radiation system,and solar greenhouse.Therefore,it is very important to explore a PCM with dual properties of thermal insulation and photothermal conversion.In this paper,we choose silica aerogel with excellent thermal insulation properties as a matrix to adsorb octadecanol to prepare composite PCM.However,neither silica aerogel nor octadecanol possess light-to-thermal conversion performance.Therefore,in the preparation process of silica aerogel,graphene oxide with excellent photothermal conversion performance was added into the silica aerogel to obtain hybrid aerogel.Then the hybrid aerogel was used to adsorb octadecanol to obtain an original composite PCM with dual properties of light-to-thermal conversion and thermal insulation.The sol-gel method was adopted to prepare hybrid gel,then gel was immersed in organic solvent for solution replacement and hydrophobic modification.Finally,the wet gel was dried under atmospheric pressure to acquire hybrid aerogel.Moreover,the contact angle with water,density and porosity,specific surface areas and pore sizes,thermogravimetric analysis(TG),fourier transform infrared spectroscope(FTIR),raman spectroscopy and thermal conductivity of the hybrid aerogel were tested.The leakage experiments of composite PCMs were carried out.In addition,the latent heat and phase change temperature of composite PCMs were measured by differential scanning calorimeter(DSC).The thermal stability and cyclic stability of composite PCMs were characterized using thermogravimetric analysis(TG)and high and low temperature test chamber,respectively.Lastly,the simulated sunlight source was applied to explore the photothermal transformation properties of the composite PCMs.The main results show as following:(1)The graphene oxide/silica hybrid aerogel prepared under ambient pressure shows the advantages of high specific surface area,high porosity,and low thermal conductivity.As the content of graphene oxide increases,the density of the hybrid aerogel gradually decreases,the porosity gradually increases,the specific surface area and thermal conductivity of the hybrid aerogels increase first and then decrease.When the content of graphene oxide is 0.5%,the porosity of hybrid aerogel is 91.93%,its specific surface area and thermal conductivity reach the maximum values of 948 m~2/g and 0.0277 W/(m·K),respectively.The above results show that the hybrid aerogel is an excellent matrix to prepare heat-insulating phase change materials.(2)The composite PCM prepared by the hybrid aerogel with the highest specific surface area(GO content of 0.5%)has good heat storage capacity.The latent heat of PCM reaches optimal of 145.6 J/g,and its phase change temperature is 52.5oC,exhibiting its good energy storage capacity.The trend of the thermal conductivity of the composite PCM is similar to that of the hybrid aerogel.When the mass fraction of graphene oxide is 0.5%,the thermal conductivity of composite PCM reaches a maximum,the value of which is only 0.0808W/(m·K),indicating its excellent thermal insulation performance.Under simulated sunlight,the composite PCM is able to reach its melting point in 18 minutes,suggesting that the obtained composite PCM possess good photothermal conversion performance.The composite PCM we prepared has good heat storage capacity,thermal insulation performance and light-to-thermal conversion performance,which has achieved the experimental expectation.