Interfacial Design And Multi-Functional Properties Of Graphene/Polymer Compsites Based On Morphology Regulation Of Graphene

Graphene possess unique two-dimensional structure,high mechanical strength,and excellent electrical and thermal performance.Graphene can significantly improve mechanical and multi-functional properties of polymeric composites,opening a door for designing and fabricating high-performance composites combining integrated structure with multi-functional performance.For graphene/polymer nanocomposites,their ultimate performance strongly depends on intrinsic properties of graphene,dispersion throughout matrix,construction of graphene network,and graphene-polymer interactions.In order to obtain high-performance composites with structure/multi-function integration,it is essential to regulate graphene morphology,design suitable interfaces,and construct transport networks.The aim of this thesis is to develop high-performance graphene/polymer nanocomposites with highly structural and functional integration,solving key problems existing in mechanical reinforcement,vibration damping,heat transport,and lubricating friction.Some studies on morphology regulation,microstructure design,network construction,and interface interaction,were carried out in this work.We fabricated high-performance nanocomposites with high mechanical strength,high vibration damping(energy dissipation),high thermal conductivity(heat transport),and high-efficiency lubrication.Potential applications of these above graphene-based composites in some industrial fields were also explored.In order to fabricate advanced composites with both high strength and damping property,we presented a new idea of construction of graphene-based microcells with constrained-damping structures.ZnO nanowire was grown onto graphene surface,and epoxy resin was used as polymeric matrix to prepared ZnO/GNS/EP hybrid composites.The presence of ZnO nannowires can greatly enrich interfaces for much interfacial slipping and energy dissipation,and also enhance interface bonding between graphene and epoxy.On the other hand,a constrained-damping microstructure of ZnO/GNS plays an important role in constraining motivation of resin,resulting in a significant strength and damping reinforcement.The ZnO/GNS/EP hybrid composites exhibited much higher storage modulus,loss modulus,and damping ratio,increasing by 62%,20%and 24%in comparison with epoxy.Such remarkable mechanical and damping reinforcement is mainly attributed to enriched interfaces,much interfacial slipping-slide,and constrained-damping microstructures of the ZnO/GNS/EP composites.With rapid development of aerospace industry,high-performance composites with high mechanical strength and quick heat transport is urgently required.It is rather difficult for conventional composites to possess both high strength and high thermal conductivity.Here,we proposed a new laminated structure by embedding CVD graphene foams as heat transport units into carbon fabric layers,effectively bridging carbon fabric layers each other through graphene foams for high-efficiency heat transport in off-plane direction of composites.In addition,we use annealed pyrolytic graphite(APG)as functional layers to imprive the in-plane thermal conductivity of composites.The obtained APG/CF/GF/EP laminated composites exhibited significant enhancement in thermal conductivity,its in-plane and off-plane conductivity is up to 175 W/m·K and 1.5 W/m·K,meeting the technical requirement for highly-thermal conductive composites in aerospace industry.In addition,the presence of graphene foam can also greatly improve interlaminar shearing strength of composites.In that case,the APG/GF/CF/EP laminated composites exhibited both high mechanical strength and high thermal conductivity,showing great potential to be used as high-performance composites in aerospace industry.Graphene have been regarded extraordinary lubricating additives for enhancing tribological properties of lubricating oils,but there still exist unsatisfactory dispersion stability in a long period and urgent requirement for high-efficiency lubricating performance.We have developed a high-performance lubricating additive based on hollow graphene ball with smooth surfaces.The hollow graphene balls(HGB)were prepared using a modified spray-drying technique,and we investigated its microstructure,dispersion stability in lubricating oil,friction coefficient,and wear rate in detail.We found that the HGB exhibited satisfactory dispersion stability in lubricating oil(up to 30 days)due to its hollow structure,good compatibility,and weak interaction between HGBs.We further measured friction coefficient and wear scar diameter of the HGB-based lubricating oils in comparison with that of conventional graphene additives.We found that the HGB/oil exhibited the low friction coefficient,and small wear scar diameter,and low wear volume,decreasing by 66%,36%,and 88%respectively in comparison with that of base oil.It indicates that the HGB as a high-performance lubricating additive can greatly improve tribological performance of lubricating oil.Such enhanced performance is mainly attributed to the satisfactory dispersion stability,good graphene-oil compatibility,self-lubricating characteristics of grapheme,and rolling friction mechanism.This HGB shows great potential to be used as novel additives for high-performance lubricants.