Preparation And Characterization Of Three-dimensional Thermally Conductive Elastic Composites

With the rapid development of high power,high integration electronic devices,aerospace,energy and chemical industry,the requirement of thermal management system is getting higher.Thermal interface materials with light weight,high thermal conductivity,high stability and elasticity,are the key materials of thermal management system.Elastic heat conductor can effectively reduce the contact thermal resistance between the heating body and the radiator,and prevent the structure damage or interface separation when it is subjected to thermal expansion,contraction and stress impact.However,the contradiction between elasticity and heat conduction makes it difficult to prepare elastic thermal conductive composites.It is an effective way to prepare highperformance composites by constructing three-dimensional network as thermal conductive filler and adjusting its microstructures according to different polymers.The three-dimensional continuous network is significance to improve the uniformity of composites and reduce the phonon scattering at interfaces.In the traditional three-dimensional structure,the lack of connection between individual elements results in poor mechanical and thermal performance.It can effectively reduce the internal thermal resistance of the interface and improve the mechanical stability and integrity by enhancing the continuity of the three-dimensional structure through the welding of the junctions.In this paper,three-dimensional carbon nanotube(CNT)sponge were grown via chemical vapor deposition(CVD),which was used as the basic framework for constructing three-dimensional conductive network.The continuity of sponge was improved by cross-linking welding of graphene and graphite structures.Then different composite strategies were implemented for different polymers to prepare elastic high thermal conductive composites.In this work,the effects of process control(atmosphere,carbon source,time,catalyst,etc.)and structural strengthening(graphene bridging,graphite welding)on thermal conductivity and elasticity of CNT-based network were studied.According to different polymer matrix(thermoplastic elastomer and high modulus polymer),the control mechanism of thermal conductivity and elastic properties of composites was studied,and a series of composites with different thermal conductivity and elasticity were prepared.The results show that the structural strengthening of CNT sponge is important to improve the thermal conductivity,elasticity and structural stability.The introduction of graphite/graphene structure can effectively enhance the connection between the tube and tube in the sponge,which improves the stress transfer at interfaces and reduces interfacial scattering of phonons.For thermoplastic elastomers(polydimethylsiloxane,PDMS),elastic polymer composites can be prepared by constructing three-dimensional heat conductive network in polymer matrix,the matrix provides elasticity and network for high-speed heat transfer.For high strength and high modulus polymer(polyimide,PI),three-dimensional carbon skeleton is used as the basic thermal conductive skeleton and elastic template,by controlling the micro-pore structure via adjusting the amount of polymer coating,to achieve both elasticity and thermal conductivity.