| Titanium and its alloys are widely used in antibacterial and anticorrosive packaging due to their light weight,high specific strength,biocompatibility and good corrosion resistance.The dense and stable oxide film on the surface of titanium is easily generated in air and aqueous solutions,and its passivation ability is strong and self-healing,which can be repaired in time when it is damaged.However,the oxide film is of nanometer scale,and in an oxygen-free.oxygen-deficient or water-free environment,the titanium alloy passivation film will be corroded once it is damaged.Then its anti-corrosion and wear resistance will not meet the practical application.Therefore,anodic oxidation technology is usually used to surface treat titanium and its alloys.A new environmentally friendly reduced graphene oxide(RGO)/citric acid(C6H8O7)system electrolyte was investigated and the corrosion resistance of the films obtained at an oxidation potential of 10-90 V and an oxidation time of 1h was analyzed.The results showed that the best corrosion resistance was obtained at 50 V potential,and the spark discharge phenomenon started to appear at 90 V.Therefore,in order to further investigate the preparation of highly corrosion-resistant titanium oxide films and to analyze the film formation mechanism.In this paper,the chemical composition of RGO/C6H8O7 electrolyte was firstly analyzed,and then the effects of oxidation potential and oxidation time on the growth crystallization,hardness and corrosion resistance of titanium oxide film were investigated,and the film formation mechanism of titanium oxide film was further explored.The details of the study and the main conclusions are as follows:(1)By chemical reduction method,the C-O,C=O and O-C-O oxygen-containing functional groups content in graphene oxide(GO)was effectively reduced by the reducing agent C6H8O7.On the one hand high conductivity RGO/C6H8O7 electrolyte was obtained,and on the other hand a new solution for green reduction of GO was provided.(2)Titanium oxide films with different oxidation times at 50 V low potential were prepared in RGO/C6H8O7 electrolyte,all doped with RGO nanosheets.The thickness of the oxide films decreased to a minimum of 5.92 μm during the dissolution phase(2-9 min),and increased gradually with further oxidation time,reaching 7.42 μm at 60 min.The crystallinity of anatase TiO2 in the film was also gradually increased,but its crystallization type remained unchanged.The hardness of the film increased to a maximum of 6.32 Gpa at 9 min,but it gradually decreased to 4.38 Gpa with the increase of crystallinity.The jcorr of the film decreased to 50.34 nA cm-2 at 5 min,and then reached 76.53 nA cm-2 at 60 min.The corrosion resistance of oxide film tends to increase gradually.Therefore,the corrosion resistance of the titanium oxide film is synergized by its film formation,thickness,crystallinity and doping of RGO nanosheets.(3)Preparation of titanium oxide films with different oxidation times at high potentials of 85-150 V was investigated in RGO/C6H8O7 electrolyte.The potential was oxidized at 97 V into the microarc oxidation stage.At 100 V potential,oxidation for 30 s could have a crystallinity of 50/60M.With the increase of oxidation potential as well as oxidation time,the crystallinity and crystallinity type of anatase type of the film layer were stable.However,the denseness and film formation of the film decreased,and large dissolution and breakdown structures appeared,and the doping amount of RGO nanosheets gradually decreased to near zero.The hardness and corrosion resistance of the titanium oxide film at high potential decreased significantly compared with the low voltage of 50 V,but still had some protection. |
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