Preparation And Characterization Of The Modified Graphene Oxide Materials

The application of graphene and graphene-based materials has been extensively studied in various fields due to the advantages of the unique two-dimensional structure,high thermal conductivity and electron mobility,and excellent mechanical properties,etc.However,a variety of scientific and technical challenges are remainingfor the large-scale practical application of graphene-based materials.One problem is that graphene is a zero bangap semiconductor,its electrical conductivity can not be controlled as the conventional semiconductor,leading to the limited usage of graphene-based materials in the photoelectrical devices.The second problem is that strong Van der Waals forcesexist between the graphene layers,causing the self-agglomeration and poor dispersivity of graphene materials in the solvents.At the same time,it is difficult to obtain the uniform dispersion of graphene in the polymer matrix,thus prepare graphene-polymer composite materials.With the aim to solve those problems and broaden the application of graphene oxide materials,the works of this dissertation include:1.The doping of nitrogen into the reduced graphene oxide can change the electronic distribution adjacent to the carbon atoms,improving its electrical-chemical properties.By using a DBD plasma treatment method,which has the advantages of low energy and time consumption,mild operating conditions,and promising industrial application,the nitrogen-doped reduced graphene oxide?N-rGO?was prepared from the the GO precursor and ammonium bicarbonate.The electrochemical evaluation demonstrated that the obtained N-rGO materials exhibit excellent performance as a capacitor,processing higher capacity and better charge/discharge properties than rGO.2.By using the improved Hummers'method,we successfully prepared graphene oxide materials,and then by chemically grafting HCCP on the surface of graphene oxide,the functionlized HCCP-FGO matrials were synthesized and evaluated.SEM images show that the surface of HCCP-FGO is more smoother than that of GO,indicating the layer interation in FGO is weaker.The apparance of a chatacteristic peak corresponding to the C-O-P bonds in the XPS spectrum of HCCP-FGO verified the successful grafting of HCCP on GO surface.Subsquently,the FGO/PS composite material was prepared bythe in-situ polymerization method and its performance of fire-resistance was evaluated and compared with that of GO/PS.All the results of total heat release?THR?,heat release rate?HRR?and the CO₂ emission verified that HCCP-FGO is a better fire-retardant than GO due to its better dispersivity in PS.3.The functionlized APTS-FGO matrials was prepared by covalent-grafting HCCP on the surface of graphene oxide,then the APTS-FGO/PVC composite matrials were prepared by using the solution blending method.The evluation verified that the APTS-FGO/PVC matrials exhibit better fire-resistance performancethan GO/PVC.The addition of GO or APTS-GO can both increrase the oxygen index of the materials with APTS-GO showing a better performance.When the content of APTS-GO exceeds 1.5wt%,the oxygen index of the APTS-FGO/PVC materials would be higher than 35.The addition of GO or APTS-GO will not affect the calorific value of the materials,which keeps around 21MJ/Kg.SEM images of carbon residue after materials burning demonstrates that the distribution and compatibility of APTS-FGOin PVC is better than that of GO,whose stacking in PVC is very obvious.Thermogravimetric analysis proved that the thermal stability of PVC materials can be enhanced by adding GO or APTS-GO,when their content is 2.5 wt%,the initial degradation temperature of composite materials increased by 7.5%compared with that of pure PVC and the carbon yield also increased significantly.