Preparation, Structure And Properties Of Graphene Oxide Foams And Composite Phase Change Materials

Phase change materials(PCMs) are one of the most promising heat storage materials.But many PCMs have some problems such as low thermal conductivity and poor shape stability.Graphene foams or aerogels can solve these problems to some extent,but there is still a lack of batch,efficient and low-cost preparation technology,and most of them have low mechanical strength or overall fragility,which limits their practical application.In order to solve these problems,a cyclic deposition method based on melamine foam(MF) template was developed,and the preparation,structure,properties and applications of GO matrix composite foam and composite phase change materials were studied.Firstly,MF@GO composite foam was prepared by circulating impregnation deposition method.Composite foam has the advantages of low density(0.12g/cm~3),high compressive strength(>400KPa),high compressive modulus(up to 95.3 MPa)and high specific modulus(up to 1560 MPa/cm~3/g).A low melting point metal(LMA,a tin-bismuth alloy) is loaded into a composite foam by vacuum-assist method.The composite foam has excellent mechanical properties and can withstand the high pressure formed when the metal melts at low melting point without breaking.The prepared composite has the advantages of high thermal conductivity(～10W/mK),large volume phase change enthalpy(150-250MJ/m~3) and stable shape during phase change.The thermal management application of composite phase change materials is studied.The results show that composite phase change materials can effectively reduce the heat source temperature.However,we also found that the thermal conductivity of GO itself has no advantage over the low-melting metal,and the GO layer leads to cracks or pores in the low-melting metal,so the thermal conductivity of composite phase change materials is somewhat lower than that of low-melting metal(～14 W/mK),which fails to give full play to the feature of high thermal conductivity of GO.In order to give full play to the high thermal conductivity of GO,GO and carbon nanotube(CNT) were deposited into melamine foam by cyclic impregnation deposition method,and MF@GO/CNT composite foam with high thermal conductivity and strong compressive property was prepared.Paraffin is loaded into the composite foam by vacuum-assist method.Because the thermal conductivity of GO and CNT is much higher than that of paraffin,the thermal conductivity of the prepared composite phase change material increases from 0.31W/mK of pure paraffin to 1.22W/mK.In addition,the composite phase change material has good shape stability and can be poured or mixed with other materials to form the composite heat storage material.Composite heat storage materials have the characteristics of fast heat transfer,large heat storage capacity and flexible application,and have a good development prospect.In this paper,a cyclic impregnation deposition method was developed for the preparation of GO-based foam with high strength and high modulus.The prepared composite foam and composite phase change materials have good application effect in the field of heat storage and thermal management.