Research On Graphene Thermal Conductive Materials And Its Application Based On Supercritical Carbon Dioxide Method

The improvement of the processing accuracy of semiconductor devices has led to the rapid replacement of electronic products.The increasingly prominent problems of energy consumption and heat dissipation put forwards higher requirements on the thermal conductivity of materials.Graphene prepared by supercritical CO2 method combined with mechanical peeling possess high quality and large size,may be quiet suitable used as thermally conductive materials.However,due to its inherent property of thermal conductivity anisotropy,it cannot achieve high heat flux applications in three-dimension.Here,we propose a new sight to weaken its anisotropy by introducing copper nanoparticle between graphene layers.After systematical studied the effect of copper particles on the thermal properties of graphene composites,the optimal operating conditions were determined.With the help of quantities of characterization methods,the mechanism of its heat conduction enhancement was analyzed,and its heat dissipation effect was tested in actual cooling cases.The thermal conductivity of graphene products was improved effectively.Firstly,nano-copper particles were prepared in a mixed dispersion of graphene and copper precursor,vacuum-assisted filtration combined with applied pressure was used to orient the graphene sheets.The morphology of the composite materials was characterized by SEM,and the results showed that copper particles were introduced between the graphene layers successfully.The LFA results showed that when the content of copper approach to 20 wt.%,lateral and longitudinal thermal conductivity of the composites were 139.42 W/(m·K)and 5.22 W/(m·K),respectively,and the value of anisotropy decreased from 247 to 45.Finite element heat dissipation simulation of graphene materials before and after modification was performed with the help of ANSYS.The simulation results revealed that weakening anisotropy of material could improve its heat dissipation performance.Subsequently,graphene oxide was added to optimize the spatial distribution of copper nanoparticles between graphene layers,and it was reduced to graphene by thermal reduction method.Ascorbic acid and ethylene glycol were applied as reductant to prepare coppers nanoparticles with different sizes.SEM pictures showed that the particle size and spatial distribution of nano-copper particles were optimized.The results of LFA indicated that the lateral thermal conductivity of graphene composite materials was eventually elevated to 211.25 W/(m·K).XRD,Raman and XPS characterization methods were used to monitor the defect degree of the composites and the results showed that after thermal reduction treatment,the ID/IG value of the composite materials was at a low level and uniformly distributed,with a carbon-tooxygen ratio of 96.51:3.06.Finally,several prepared graphene composites thermal conductive materials were used for the heat dissipation evaluation of 3W LED.The results showed that graphene composites thermal conductive materials can reduce the temperature of the central heat source by 25.7℃,whose heat dissipation effect is much better than graphene and aluminum with heat dissipation structure,which means a great potential for lightweight and strong heat dissipation application prospects.