The Research On Construction Of Three-dimensional Metallized Thermal Network And Its Functionalization For Phase Change Composites

With the development of miniaturization and integration,a large amount of heat is generated during the operation of electronic devices.The accumulated heat affects the operating speed and service life of electronic devices,so thermal management for electronic devices is essential to conduct.Phase change materials(PCMs)capable of absorbing or releasing heat at a constant temperature have received extensive attention.The application of PCMs in the thermal management field of electronic devices has been intensively studied by utilizing the efficient heat storage capacity of PCMs to absorb the heat generated by electronic devices during operation to maintain the normal operation of electronic devices.However,the inherent defects of traditional PCMs,such as low thermal conductivity,easy leakage,and high rigidity,limit their further applications in the thermal management field of advanced electronic devices.Therefore,the construction of PCMs with good encapsulation properties,high thermal conductivity and high flexibility is of great research significance for improving the thermal management efficiency of PCMs.Based on this,in this paper,flexible melamine foam(MF)with a three-dimensional(3D)porous structure was selected as the template to prepare a 3D flexible thermal-conductive skeleton based on MF by electroless plating,and the obtained flexible thermal-conductive skeleton was used to encapsulate polyethylene glycol(PEG)to prepare the composite PCMs,thereby achieving the advantages of high encapsulation performance,high thermal conductivity and high flexibility compatibility of PCMs.The MF-based 3D flexible metallized thermal-conductive skeleton can serve as a support carrier to efficiently adsorb and encapsulate PEG,and the 3D metal network can act as a thermal pathway to facilitate rapid heat transfer.Besides,the elasticity of the metallized MF combined with the crystallization-melting transition of PEG can also endow the composite PCMs with flexibility.Not only that,3D metal networks can also impart other functional properties to composite PCMs,such as solar/electro-to-thermal conversion and storage,electromagnetic interference(EMI)shielding performance et al.The main research contents and results of this paper are as follows:(1)3D porous flexible thermal conductive/conductive copper(Cu)-covered MF(MF@Cu)foams were prepared by chemical reduction using MF as a template,and the foams were used to encapsulate PEG by vacuum impregnation to prepare MF@Cu/PEG PCMs.Owing to the successful construction of the 3D continuous porous Cu skeleton,the MF@Cu foams can not only enhance the mechanical carrying capacity and encapsulation performance of the MF@Cu/PEG PCMs,endowing them with excellent dimension retention ratios(95%)and high enthalpy value(152.5 J/g);but also endow them with excellent thermal/electrical conductivity,which make them have excellent electro-to-thermal conversion and storage performance(the electro-to-thermal conversion and storage efficiency at a low voltage of 2 V can even reach 85.6%).Compared with Cu foam-based composite PCMs without and deformability,due to the interaction between the flexibility of MF@Cu foams and the phase change process of PEG,the MF@Cu/PEG PCMs also exhibit excellent thermal-induced shape memory behavior.In addition,MF@Cu/PEG PCMs with high enthalpy value and electro-to-thermal conversion and storage ability can also be applied to the thermal management of electronic devices in cold/hot environments,which can play a dual thermal management role of high-temperature control and low-temperature heating.Therefore,this kind of flexible MF@Cu/PEG PCMs with electro-to-thermal conversion and storage capacity and shape memory behavior are expected to be deeply applied in the field of thermal management of electronic devices.(2)In order to enhance the stability of the thermal-conductive network constructed by metal nanoparticles and endow composite PCMs with more functionality,the 3D porous flexible thermal-conductive MF@PDA@Ag NPs(MPA)foams loaded with polydopamine(PDA)and silver nanoparticles(Ag NPs)were obtained by in-situ deposition and chemical reduction using MF as a template,and the foams were subsequently used to encapsulate PEG to prepare MPA-PEG PCMs by vacuum-impregnated.The bonding between MF and Ag NPs is enhanced by the adhesion of PDA,and the solar-to-thermal conversion effect of MPA-PEG PCMs is endowed due to the synergistic effect of solar-to-thermal filler PDA and plasma Ag NPs.The continuous Ag NPs covering the MF skeleton form a 3D thermal-conductive porous network,which not only endow the MPA foams with better encapsulation ability for PEG,but also enable the MPA-PEG PCMs with a high phase change enthalpy(148.9 J/g);They also make MPA-PEG PCMs have a thermal conductivity that is nearly 1400%higher than that of pure PEG.In addition,thanks to the successful constrcution of internal 3D conductive network,the MPA-PEG PCMs also have excellent EMI shielding performance(their average SE_Tcan reach 82.02 d B)and electro-to-thermal conversion and storage capacity at low voltage(the electro-to-thermal conversion efficiency can reach 86.3%at 1.2 V).The combination of the solar-to-thermal effect of PDA with Ag NPs,the elasticity of MPA foams,and the phase transition process of PEG also endow the MPA-PEG PCMs with good solar-induced shape memory behavior.What’s more,the flexible MPA-PEG PCMs with high enthalpy value and thermal conductivity can also prevent the temperature of the smartphone from rising sharply when they are applied to the thermal management of smartphone.Therefore,those flexible MPA-PEG PCMs,which can realize the conversion and storage of various energy sources,thermal management behavior,and EMI shielding function,have a good application prospect in the field of electronic devices protection.