Preparation Of Graphene-based Composite And Its Application In Thermal Management Materials

Increasing requirement for efficient thermal management in denser and faster next generation miniaturized electronics,aerospace and medical equipment demands the research on the efficient heat sink with low density and high thermal conductivity.Traditional heat removal systems,such as metal heat sink,cannot meet the requirements of portable equipment because of its heavy mass.Polymer-based composites can act as an alternative for a metal heat sink because they exert good thermal conductivity and light weight.Graphene with extraordinary thermal?⁵300 W/?m·K??conductivity,superior mechanical and low density,has driven research of graphene-based composites.However,the graphene has not embodied its super performance in the mostly existed polymer composite in terms of thermal conductivity.It is a challenged and meaningful research topic.In this paper,we have prepared the graphene-based composite with enhanced thermal conductivity.The main research contents and conclusions are as follows:In this paper,we prepared the pristine graphene by supercritical CO₂ and used AFM and TEM to characterize the structure and morphology of graphene.We found that the number and size of graphene layers was 3 layers and 0.5?m,respectively.Compared with vacuum-dry method,a facile vacuum dead-end micro-filtration method was presented to fabricate a pristine graphene-PVA composite film,the formation mechanism of the composite film was explored and the micro-sphere,structure and thermal properties of the as-prepared film were characterized.The graphene,made by a green technique of supercritical CO₂ exfoliation and kept original well crystallinity structure,was uniformly dispersed and well arranged in the graphene-PVA composite paper through the vacuum dead-end filtration.The thermal conductivity and heat dissipation of the as-prepared film were greatly influenced by the content,dispersion and arrangement of the graphene in the film.The film with 50 wt.%graphene has the highest thermal conductivity of 36.81 W/mK,and has excellent flexibility.Under heating power of 1.5W and heating period of 30 minutes,the temperature of the surface of the film was lower 8?than that of the heater which implies that it has excellent heat dissipation performance as well.The thermal stability of the composite film was determined by thermogravimetric analysis.The results showed that the thermal stability of the composite film was greatly increased under the effect of graphene.Compared with pure PVA,the initial decomposition temperature?the weight loss rate is 5%?of the composite membrane was increased by 60?,which greatly expands the temperature range of the composite film.When the content of graphene was 50wt.%,the initial decomposition temperature of the composite film was 287?.A modified graphene with stable dispersion in silicone oil was synthesized.The silane coupling agent?KH550?was grafted on graphene oxide,and the silicon oxygen bond was introduced into the graphene,which could be uniformly dispersed in the silicone oil.The modified graphene was characterized by FTIR.The dispersion and stability of different carbon materials and modified graphene in silicone oil were studied.The results showed that the dispersion of modified graphene in silicone oil was uniform and the stability was greatly enhanced.We also discussed that the content of modified graphene and graphite influenced on the thermal conductivity of thermal grease.When the content of graphite and modified graphene were 20wt.%and 15wt.%,respectively.The thermal conductivity of thermal grease achieved to 1.26W/mK.