| With the rapid development of science and technology and the rapid development of electronic and electric industry,electronic products are developing towards miniaturization,high performance and portable direction.Single material is difficult to meet the requirements of all kinds of high performance,will be two or more than one component of composite materials,can produce the effect of 1+1>2,taking advantage of the various components was prepared and characteristics of the components of the performance even more is better than that of raw materials.New elements or a single new material is hard to find or took breakthrough,the new material widely various packing filling matrix,superior performance,the complex can the stiffness,strength,quality of light,or have an advantage in terms of energy storage.For example,the high dielectric flexible energy storage complex can be used in the development of large scale integrated circuits for embedded integrated circuits,which has a wide application prospect and is used to make laminated capacitors.However,due to the improvement of the dielectric constant of the composite materials,the dielectric materials with high dielectric constant have a prospective and far-reaching significance.In this work,polyvinylidene(PVDF)flexible polymer was used as the matrix,and the dielectric properties of the composite was studied by using solution method with inorganic fillers such as carbon nanotubes(CNT)and graphene(GNs).Using scanning electron microscopy(SEM),X-ray diffraction(XRD)to analysis composite materials characterization.The effects of different volume fractions on dielectric properties of composite materials were studied in order to obtain CNT/GNs/PVDF composites with high dielectric properties and energy storage density.It can be seen from the dielectric properties of composite materials that CNT/GNs/PVDF composites within a certain range will decrease with the increase of packing volume fraction.The percolation threshold and the dielectric constant of composite materials are also different with different properties of conductive fillers.Carbon nanotubes and graphene with poly(vinylidene fluoride compound respectively to study the dielectric properties,found at room temperature,10~0 Hz and GNs volume fraction of 1.50 vol%,the dielectric constant of 27.00.At room temperature,10~0 Hz and CNT volume fraction of 2.00vol%,the dielectric constant is 53.00,and the overall dielectric loss is 0.35.In order to further improve the dispersion of carbon nanotubes in PVDF,use the sodium hydroxide(NaOH)aqueous solution mechanical ball grinding way of surface modification of carbon nanotubes for hydroxylation of carbon nanotubes(MWNT-OHs),then with PVDF composite,the preparation of MWNT-OHs/PVDF composites.The results showed that the surface of carbon nanotubes treated with NaOH did contain hydroxyl group,and SEM clearly showed that MWNT-OHs were distributed uniformly in PVDF,and the dielectric performance was also improved.When MWNT-OHs volume fraction was 2.00 vol%,the dielectric constant at 10~0 Hz reaches 540,the dielectric constant of 100 Hz reached 540.In order to further improve the dielectric of the composite material,the three-phase CNT/GNs/PVDF composite was made on the basis of the two phase combination of CNT/PVDF and GNs/PVDF.The results showed that the volume ratio of CNT/GNs/PVDF composites(CNT+GNs)and PVDF was fixed at 46.4:100,and when the volume ratio of GNs to CNT was 1:9,the dielectric constant was 550 at room temperature and 100 Hz,and the dielectric loss was 0.55.When the volume ratio of GNs and CNT is fixed at 1:9 in the composite material,(CNT+GNs)will form a seepage mass when the volume fraction of the composite material is 8 vol%,forming a conductive pathway.At room temperature and 100Hz,the dielectric constant is as high as 530.00,and the dielectric loss is more than 26.00.while in GNs and CNT volume ratio of 1:9,volume fraction(CNT+GNs)composites for 9vol%when the dielectric constant is close to 560.00,dielectric loss was 0.35.The results show that adding graphene and carbon nanotubes to PVDF matrix can obtain good dielectric properties. |
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