Steinhorst Maximilian, Giorgio Maurizio, Roch Teja, Leyens Christoph
Project Group at the Dortmunder OberflächenCentrum DOC, Fraunhofer Institute for Material and Beam Technology IWS, Eberhardstr. 12, 44145 Dortmund, Germany.
Institute for Materials Science, TUD Dresden University of Technology, Helmholtzstraße 7, 01069 Dresden, Germany.
ACS Appl Mater Interfaces. 2023 Nov 8;15(44):51704-51712. doi: 10.1021/acsami.3c10719. Epub 2023 Oct 27.
Carbon-based coatings composed of a chromium interlayer and a carbon top layer were deposited on stainless steel substrates via cathodic arc evaporation. During the carbon deposition, the bias voltage was varied between 900 and 1 V to investigate the influence on the structural, electrical, and electrochemical properties. Raman spectroscopy indicated a dependency of the intensity ratio and G peak position on the bias voltage, which can be attributed to an alteration of the structure. Transmission electron microscopy (TEM) cross-section investigations revealed a graphite-like structure for most carbon top layers but with an increasing amount of disordered fractions, eventually resulting in an amorphous structure at 1 V. To further examine the structure, electron energy loss spectroscopy (EELS) was used. In the high-loss region, distinct π* and σ* peaks could be observed, which agree well with the TEM results. Additionally, analysis of the low-loss region showed that the 1 V carbon top layer exhibits a shifted σ plasmon peak at 20 eV corresponding to an amorphous structure. The carbon-based coatings are highly conductive with low interfacial contact resistance values between 4 and 1.5 mΩ cm at 150 N cm. From a bias voltage of 200 V, the resistance increases. To evaluate the corrosion resistance, we conducted potentiodynamic polarization tests. At first, with decreasing bias voltage, the corrosion resistance increases and then decreases for both the 100 and 1 V samples. Considering the low thickness, the coating with a carbon top layer deposited at 600 V had the best corrosion resistance. In combination with the excellent contact resistance, the 600 V sample is a highly suitable coating for metallic bipolar plates.
通过阴极电弧蒸发法在不锈钢基底上沉积了由铬中间层和碳顶层组成的碳基涂层。在碳沉积过程中，偏压在900 V和1 V之间变化，以研究其对结构、电学和电化学性能的影响。拉曼光谱表明强度比和G峰位置与偏压有关，这可归因于结构的改变。透射电子显微镜（TEM）截面研究表明，大多数碳顶层具有类石墨结构，但无序部分的数量不断增加，最终在1 V时形成非晶结构。为了进一步研究结构，使用了电子能量损失谱（EELS）。在高损失区域，可以观察到明显的π和σ峰，这与TEM结果非常吻合。此外，对低损失区域的分析表明，1 V的碳顶层在20 eV处表现出σ等离子体峰的位移，这对应于非晶结构。碳基涂层具有高导电性，在150 N cm的压力下，界面接触电阻值较低，介于4和1.5 mΩ cm之间。从200 V的偏压开始，电阻增加。为了评估耐腐蚀性，我们进行了动电位极化测试。首先，对于100 V和1 V的样品，随着偏压降低，耐腐蚀性先增加后降低。考虑到涂层厚度较低，在600 V下沉积的具有碳顶层的涂层具有最佳的耐腐蚀性。结合优异的接触电阻，600 V的样品是金属双极板非常合适的涂层。
