Graphene Oxide Directed Interlayer Confinement Orientation Of Pyrolyzed Polymers

Recently,with the high-speed development of flexible electron device,5G technology and aerospace industry,the demand for high thermal conductive cooling element is increasing.The electronic equipment can be maintained reliability and stability,or even increase of service life by rapid heat dissipation of cooling element.Graphene oxide（GO）-based films have high thermal conductivity and flexibility.Especialy,the GO-based thermal conductive film with thickness more than 80μm shows obvious advantages in thermal properties.These make them widely studied and applied in industry.However,the high price of GO is the disadvantage in commercial competition,it is necessary to lower the cost of GO film.GO-polymer composite film becomes a now choice.However,the polymer only as cross-linking agent to connect GO sheets with contents less than 10%,which not really lowers the cost of films.We delved the preparation route of GO-polymer composite film,in which the polymer as the mainly raw materials.The design of the subject is focused on three questions listed as following:First,the influence of GO size on thermal conductivity.Second,the intrinsic connection between polymer structure and graphitization.Third,the influence of thermal conductivity when adding polymer.Meanwhile,this dissertation proposes a solution for treating waste thermal conductive film by establishing a carbon waste cycle model.A series of topics are shown:1.The pyrolysis process of polyimide（PI）is investigated in detail,obtaining the three stages of structural evolution.The PI are prepared to be size-tunable graphene,which range from 3 nm to tens of micrometers.The carbon waste cycle model is established according to this method,cycling the carbon wastes to be high-value carbon products.The PI with a bicontinuous structure（comprising sp² and sp³）was efficiently cut into GQDs with a high yield of 98%.Moreover,we demonstrated that the GQDs performed well as dispersants to disperse hydrophobic carbon nanotubes(0.6 mg m L^-1)in water and improved the gravimetric capacitance of graphene-based supercapacitors by 79.4%with 3%GQDs added as nano-fillers.2.The effect of“GO directed interlayer confinement orientation of pyrolyzed polymers”is discovered by us.Through confinement of GO interlayer,the molecular chain of polyacrylonitrile（PAN）is reoriented.Then,the reorientation PAN forms high orientation and crystallinity afther high temperature annealing.The defects of PAN are eliminated and AB stacking of the film is increased.3.The graphited film derived by GO and PAN with high thermal conductivity and flexibility is prepared according to the effect.The 50%mass fraction of PAN can be induced to sp² carbon by adding 50%mass fraction of GO,realizing the layered graphite film using polymer as main materials.The thermal conductivity and conductivity of film is 1282 W m^-1 k^-1 and 9.94×10⁵ S m^-1.The sample,cheap method can extend to biomass polymer,providing a new direction for high thermal conductive and flexible film.Moreover,the phase separation phemomemon in the preparation of composite film is investigated,which is contributed for development of GO-PAN derived graphited film in industry.In summary,this dissertation explored the preparation methods of GO-PAN-derived graphite film and discovered the effect of“graphene oxide directed interlayer confined orientation of pyrolyzed polymers”,promoting the development of low-cost,thermal conductive and flexible film,as well as structure design of GO and PAN composites.Furthermore,carbon waste cycle model and structure relationship between carbon materials and products contribute for recycle of carbon wastes.