Research On Synthesis Of Diamond-like Carbon Films By Electrodeposition Method At Low Voltage

Diamond-like carbon (DLC) films have low friction coefficient, high hardness, wear resistanceand many other excellent performance and show a good application in many fields. Vapor phasedeposition, the traditional method for the preparation of DLC films, which needs complex equipmentand high cost, limits the further application of DLC films to a certain extent. In recent years, theresearch of liquid phase electrochemical deposition has aroused widespread interest due to therelatively cheap equipment and mild deposition conditions and provides a new idea for the researchersengaging in the study of DLC films. In this paper, a low voltage electrochemical method to prepareDLC films is carried out, and the main contents and conclusions are as follows:(1) In methanol solution, the preparation of DLC film was carried out on ITO glass substrate.The study results shows that: with the adding of small amount of NaOH the current density wasincreased from several mA/cm2to about200mA/cm2and the films prepared contains diamond-likecomposition. On Si substrate, an approximately transparent film was got when pure methanol solutionadded with NaOH had been used as the electrolyte, under a certain experimental condition. Althoughthere is no diamond-like composition in the film, in pure methanol solution there is no deposition atall on the same conditions, indicating that the presence of NaOH has a tendency to low the filmdeposition voltages.(2) In methanol solution containing deionized water, DLC film was deposited on Cu substratewith a1~5mm distance between the electrodes. The study results of SEM, EDS and Raman spectrumshows that: lowering electrode distance is an effective way to drop DLC film deposition voltage andthere is a relatively high sp3carbon bonds in the film. In addition, there is a large amount of impuritiesof CaCO3crystals in the film and analysis result indicates it comes from the glass beaker. With theusing of electrolyte composed of ethanol and deionized water containing KCl the DLC film wasdeposited on a relatively low voltage. Besides, the growth of CaCO3was effectively suppressed due tothe generation of acidic environment during the electrolytic process. Meanwhile a large number ofcopper ions generated under the corrosion and deposited onto the substrate together with the carbonatoms, causing a loose-like morphology of the DLC film.(3) Cu doped DLC films were prepared under different voltages from methnal and ethanolsolutions containing K2CO3respectively. Electrode process study shows that the copper ions promote the electrode reaction. And the study results of SEM, EDS and Raman spectrum results show that: theDLC films were deposited under relatively lower voltage with K2CO3being used and K2CO3iscapable of inhibiting the growth of CaCO3. In addition, the copper ions increased the sp3carbonbonds in the film.（4）Fe、Ni doped DLC films were prepared under60V from a mixture of sucrose as carbonsource and deionized water containing K2CO3. Raman spectroscopy results show that: there is arelatively high content of graphite phase in the films and the adding of Fe promotes the formation ofgraphite phase.