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Graphene has a large specific surface area, high chemical inertness, and excellent barrier properties. It is considered to be the thinnest protective material known. The graphene film prepared by chemical vapor deposition (CVD) method can be directly used for metal corrosion protection , Has gradually become the main method of preparing graphene protective film. However, during the preparation process, graphene films will inevitably introduce structural defects such as vacancies and grain boundaries. Exposing them to the air for a long time, the corrosion medium will easily react with the base metal through these defects, and the highly conductive graphene film will promote the interface The electrochemical reaction at the site accelerates the corrosion of the base metal.
Recently, Wang Liping, a researcher at the Key Laboratory of Marine New Materials and Applied Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, successfully used CVD technology to prepare a series of nitrogen-doped graphene films on polycrystalline copper substrates. Nitrogen-doped graphene films with different nitrogen concentrations were obtained by gas flow. At the same time, the study found that nitrogen doping into the graphene lattice network will cause the conductivity of the thin film system to be lower than that of the original graphene. Under atmospheric long-term exposure test conditions, low conductivity nitrogen-doped graphene films can suppress electrons in the The transmission of the corrosion interface reduces the electrochemical corrosion rate at the interface of copper and nitrogen-doped graphene, effectively delays the diffusion of the corrosion area, and exhibits better long-term corrosion protection performance (Figure 1), but this method still cannot eradicate the film Structural defects formed during the growth process, as well as the resulting non-uniform corrosion spots on the surface. Relevant results have been published in Journal of Materials Chemistry A (2018, 6, 24136-24148), and have been reported as the highlight of the journal's Inside back cover.
On the other hand, hexagonal boron nitride (h-BN) nanosheets, as a graphene analog, also have good resistance to penetration. The team of Wang Liping grew different layers of h-BN films on the polycrystalline copper substrate by CVD method. Due to the insulating properties of h-BN, whether it is a single layer or multiple layers of h-BN film, it is wrapped in The surfaces of copper substrates all show excellent long-term atmospheric protection. Under high temperature heating conditions (200 ° C), the oxidation of single-layer h-BN film-coated copper foil mainly occurs at the grain boundaries and defects of the film, while the oxidation of multi-layer h-BN is mainly concentrated in the fold area of ​​the film; For a single-layer h-BN film, a multi-layer h-BN film can effectively hinder the lateral diffusion of oxygen, significantly improving the oxidation resistance of the underlying copper (Figure 2). Related results were published in ACS Applied Materials & Interfaces (2017, 9, 27152-27165).
The above research work was funded by the Key Research Project of Frontier Science of Chinese Academy of Sciences (QYZDY-SSW-JSC009), National Natural Science Foundation of China (41506098), Qingdao National Laboratory for Marine Science and Technology Open Fund (QNLM2016ORP0409), etc.
Fig.1 Long-term corrosion protection mechanism of nitrogen-doped graphene film
Fig. 2 Interface damage mechanism of single-layer and multi-layer hexagonal boron nitride-coated copper foil
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