Improving the corrosion resistance of a-C:H film by a top a-C:H:Si:O layer |
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Affiliation: | 1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China;2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China |
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Abstract: | During the deposition of a-C:H film, defects (pinholes or discontinuities) caused by excessive stress will inevitably appear, which will reduce the corrosion resistance of the a-C:H film. In this study, top a-C:H:Si:O layers (thickness of approximately 0.3 μm) on the surface of a-C:H films were deposited on a large scale by PACVD technology using acetylene (C2H2) and/or hexamethyldisiloxane (HMDSO) as reactants, to improve the corrosion resistance of a-C:H films while ensuring the appropriate overall hardness of the films. The corrosion behaviors of the films were studied by electrochemical impedance spectroscopy (EIS) and Tafel polarization. We found that the a-C:H/a-C:H:Si:O films possess a lower electrolyte penetration rate due to their stronger capacitance characteristics. In addition, the corrosion current density of the a-C:H/a-C:H:Si:O films (10?10 A cm?2) were reduced by 2 orders of magnitude compared to the a-C:H film (10?8 A cm?2), and by 3 orders of magnitude compared to 316 stainless steel (10?7 A cm?2). The impedance results obtained by EIS were simulated using appropriate equivalent circuits, and the corresponding electrical parameters were used to further verify the electrochemical protection behavior of the top a-C:H:Si:O layer. |
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Keywords: | a-C:H:Si:O a-C:H Corrosion resistance EIS Tafel polarization |
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