| Scientific research had showed that PVDF has good physical and chemical stability,and it has high dielectric constant compared with most other polymer materials,so it is widely used in the research of flexible dielectric materials.However,the dielectric constant of pure poly(vinylidene fluoride)is still not good enough,which can not meet the requirements of high dielectric materials.Therefore,researchers have been prepared prepare multiphase dielectric materials by using of one or more conductive materials added to the polymer matrix as filler(s).This method can give full play to the advantages of each material to meet the demand for high dielectric properties,light and flexible materials.Due to its excellent mechanical properties,high electron transfer ability and relatively low production cost,Graphene have attracted more and more attention,it can be directly dispersed in polymers to improve the dielectric properties of polymer matrices.However,owing to the high specific surface energy of graphene,it is easy to agglomerate and can not be uniformly dispersed in polymer matrices.So,we assume to take advantage of the interaction between hydroxyl on polyvinyl alcohol and oxygen-containing groups of graphene oxide,forming graphene oxide coated with polyvinyl alcohol,improving its dispersibility in the PVDF matrix after reduction.Finally,the composites with excellent dielectric properties are obtained.The main contents of this thesis are as follows:(1)The graphene oxide was prepared by Hummers method,the structure and morphology of the graphene oxide were characterized and analyzed.The XRD diffraction spectrum,infrared spectrum and ultraviolet spectrum all shows that the graphene oxide could be reduced laigely under the condition of 120?;(2)We had used two dimethyl sulfoxide(DMSO)as solvent,and had studied the relationship between PVDF crystal structure and film forming temperature.XRD diffraction and FT-IR spectra indicates that the film formed under 120? can get more ?-crystal structure;(3)We had prepared non-covalent modified graphene oxide by polyvinyl alcohol;then,the RGO/PVA/PVDF composites were prepared by solution casting and low temperature heat treatment.The results of XRD,SEM and fluorescence microscopy suggested that the PVA modified RGO has better dispersibility?Finally,the dielectric properties and conductivity of the composites were measured by LCR digital bridge,which showed that The percolation threshold(f*vol)of RGO/PVA/PVDF film is estimated to be 8.45 vol.%,and the dielectric constant of the film is 238 times as large as that of the pure PVDF films at 102 Hz.In conclusion,in this work,a flexible composite dielectric material with low cost,simple preparation method and excellent dielectric properties is obtained,which has a high potential application value in the field of electronic science and technology. |
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