Study On Preparation And Properties Of Reduced Graphene Oxide@Carbon Nitride/Epoxy Resin Composites

With the development of electronics towards to miniaturization,integration and multifunction,there is a main focus on heat transferring of great integrated circuit for packing electronics.However,polymer composites are more widely used in the field of electronic packaging.Therefore,seeking for highly thermal conductive polymer-based materials becomes one of the main topics.In our work,we mainly study novel two-dimensional nano materials as thermal conductive fillers.These materials refer to the compound of graphite-like carbon nitride?B-g-C₃N₄?and reduced graphene oxide?RGO?,which is marked as RGO@g-C₃N₄.Then we prepare highly thermal conductive epoxy-based composites.Our studies focus mainly on the preparation of g-C₃N₄ and combination with RGO.In addition,we also study the effects of thermal conductive fillers towards to thermal conductivity,electric insulation,thermal stability and machinability of epoxy composites.B-g-C₃N₄ is prepared through pyrolysis polycondensation.We use XRD,FTIR,TGA and SEM to characterize the structure and morphology of it.The main focus is to study the thermal stability and insulating property of the compound of B-g-C₃N₄and epoxy.The results show that heat conductivity coefficient of B-g-C₃N₄/EP composite reaches to 0.63 W/?m*K?when adding 70 wt%of B-g-C₃N₄,which is three times higher than pure epoxy.The breakdown voltage is 3.8 kV,which is available for the demands of electronics.In comparison with the same amount thermal conductive Al₂O₃ filler,B-g-C₃N₄?70 wt%?/EP has lower density?1.57 g/cm³?than Al₂O₃?70 wt%?/EP?1.88 g/cm³?.Therefore,the former is much more suitable as sealing and thermal insulating materials for electronics.Moreover,the limiting oxygen index of 70 wt%B-g-C₃N₄/EP comes up to 29.3%,which is 1.5 times higher than pure epoxy.With the increase of the filler mass fraction,the tensile strength,thermal decomposition temperature and glass transition temperature of the composites increase first and then decrease,reaching the highest at the mass fraction of 50 wt%,the tensile strength of epoxy composite has improved to 65.8 MPa?pure epoxy?61.3 MPa??.And the thermal decomposition temperature has enhanced to347.3°C comparing with pure epoxy?323.0°C?.Besides,the glass-transition temperature has improved from 64°C to 88°C.B-g-C₃N₄ can be exfoliated to negative charged nano sheet in NaOH solution.The RGO is modified by PDDA.Then,the g-C₃N₄ can combine with modified RGO throughelectrostaticselfassembly,obtainingtwo-dimensionallaminated heterojunctive thermal conductive filler?RGO@g-C₃N₄?.The filler is formed through the face-to-face method.And the Zeta potential shows that the self assembly is mainly controlled by charge neutralization of these two-dimensional laminated materials.Therefore,we can choose proper amount of each components through adjusting the surface Zeta potential.The FTIR,Raman and XPS indicate that g-C₃N₄and RGO present the structure of them.In addition,SEM and TEM can further explain the compound still has laminated structure.They combine with each other via face-to-face method in vertical direction.RGO@g-C₃N₄ with fixed ratio(m_RGO:m_g-C3N4=1:5),as thermal conductive fillers,combine with EP to prepare RGO@g-C₃N₄/EP composites.In addition,we also choose simple physical mixing method to obtain the RGO+g-C₃N₄ filler.Then we add these physical mixed fillers to EP.By comparison,with 70 wt%filler,the RGO@g-C₃N₄/EP composite obtains 5.5 times higher thermal conductive coefficient?1.11 W/?m*K??than the EP composite adding physical mixed filler?0.75 W/?m*K??.Furthermore,the breakdown voltage of RGO@g-C₃N₄/EP is 3.5 kV,while the EP composite adding physical mixed filler is 2.1 kV.The storage modulus of RGO@g-C₃N₄/EP achieves 3910 MPa,which has improved 44%higher than pure epoxy.Meanwhile,the glass-transition temperature and thermal stability of RGO@g-C₃N₄/EP composite have also improved.