| Graphene has been applied in flexible sensors,transparent displays and radio frequency antennas because of its high thermal conductivity,high transmittance,high mechanical strength and superior conductivity.Inkjet printing is a technology with simple operations,low cost and high precisions.In recent years,more and more attentions have been paid to how to make graphene-based flexible functional electronic devices by inkjet printing.In this dissertation,graphene oxide(GO)was prepared by modified Hummers method and used as raw material for the further study of the preparation of ink.Research was conducted to understand the effects of the concentration of ink and the composition and content of solvents on the viscosity,surface tension and the stability.It is demonstrated that the ink with maximum concention of 4 mg/m L was prepared by adjusting the concentration of the ink,the composition and content of solvents.GO ink with mixed solvents of deionized water,ethanol and ethylene glycol was more suitable for inkjet printing when the volume ratio of solvents is 1:1:1.The ink exhibited the viscosity of 9.0 m Pa?s,the surface tension of 56.3 m N/m and the calculated Z of 3.9.Study was also performed to determinate the effects of different treatments on the improvement of PET hydrophilicity.The contact angle of water on the treated PET substrate decreased from 84.6 ° to 40.0 ° after the oxygen plasma etching with the etching power of 45 W and the etching time of 1 min.And the surface energy of the treated PET substrate was 56.7 m J/m2.GO-based thin films were fabricated by inkjet printing of the as-obtained inks.The ejection behavior and spreading behavior of ink on the treated PET substrate were studied.Research was conducted to understand the effects of printing passes on the film morphology and the electrical conductivity.It is indicated that the ink could be ejected stably from the nozzle and formed high-resolution patterns without coffee rings.As printing passes increased from 5 to 30,abundant network-connection ridges were formed and distances between adjacent ridges and the thickness of films were increased.The conductivity of GO films increased at first and then decreased with the increasing of printing passes,and the highest electrical conductivity of 0.5 S/m had been obtained with 20 printing passes.Flexible reduced GO films were obtained by placing printed films under IPL,100 ? annealing and HI solution immersing,respectively.Compared with another two treatments,reduced GO(r GO)films with the best conductivity could be obtained by IPL without damaging the substrate.Furthermore,the electrical conductivity of r GO films increased with the decreasing of distance between the films and light and the increasing of the duration time of pulsed light.As the printing passes increased from 5 to 30,there were more and more cracks occurred on the films surface and the electrical conductivity increased at first and then decreased,achieving the lowest sheet resistance of 760.4 ? with 20-pass films when the distance was 5 cm and the duration time of single pulse was 1.5 cm.It provides the new possibilities for fabricating GO-based flexible electronic circuits or functional devices. |
PDF Full Text Request