目的 研究DLC薄膜、WC/a-C纳米复合薄膜及WC/a-C纳米多层薄膜的机械性能及在模拟质子交换膜燃料电池（PEMFC）阴极环境（70 ℃,1 mol/L H2SO4）下的耐腐蚀性能及导电性能,优选具有优异综合性能的薄膜。方法 通过闭合场非平衡磁控溅射（CFUBMS）技术在316L不锈钢基体表面分别制备了以上三种薄膜。通过划痕测试、纳米压痕测试和场发射扫描电镜（FESEM）测试研究了薄膜的机械性能和截面形貌。通过电化学阻抗、动电位极化、恒电位极化和界面接触电阻值分析了薄膜的耐腐蚀性和导电性。同时通过FESEM观察分析了薄膜的腐蚀形貌,使用能量色散光谱（EDS）和拉曼测试分析了薄膜的腐蚀产物。结果 WC/a-C纳米多层薄膜展现出独特的力学优化特征,纳米多层结构通过界面强化、位错钉扎效应实现了硬度与韧性的协同提升,从而显著提升了其机械性能。在电化学性能方面,相较于DLC薄膜与WC/a-C纳米复合薄膜,WC/a-C纳米多层薄膜具有最高的腐蚀电位（0.194 V）和最小的腐蚀电流密度（2.228×10-7 A/cm2）。在12 h恒电位极化测试前后,其界面接触电阻（ICR）值均为最低且变化最小,为8.84 mΩ·cm2（测试前）和9.95 mΩ·cm2（测试后）。结论 纳米多层界面能够有效抑制腐蚀性离子的渗入与扩散,显著提高了WC/a-C纳米多层薄膜的耐腐蚀性能。在1.4 MPa压力下,其导电性优于DLC薄膜及WC/a-C纳米复合薄膜。
Abstract
The service life and performance enhancement of proton exchange membrane fuel cells (PEMFC) critically depend on improving the corrosion resistance and electrical conductivity of their bipolar plates. This study systematically compares the mechanical properties of diamond-like carbon (DLC) film, WC/a-C nanocomposite film, and WC/a-C nanomultilayers and evaluated their corrosion resistance and electrical conductivity in a simulated PEMFC cathode environment (70 ℃, 1 mol/L H2SO4). The work aims to identify the film structure with superior overall performance, thereby providing a theoretical basis and practical guidance for the design of protective coatings on PEMFC bipolar plates. Three types of films are deposited on 316L stainless steel substrates by closed-field unbalanced magnetron sputtering. Adhesion strength, nanohardness, and elastic modulus are assessed through scratch testing and nanoindentation, respectively. Cross-sectional morphologies of the films are observed by field emission scanning electron microscopy (FESEM). For electrochemical characterization, the open circuit potentials (OCP) of the films are measured, and their corrosion resistances are evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The long-term durability and stability of the films are evaluated by potentiostatic polarization at a constant potential of +0.6 V. The interfacial contact resistance (ICR) values between the films and carbon paper are measured before and after the potentiostatic polarization testing under a pressure of 1.4 MPa. The conductivities of the film before and after corrosion and their variations are systematically evaluated. The corrosion morphologies are examined by FESEM, complemented by energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy to analyze the distribution of corrosion products. The results indicate that the WC/a-C nanomultilayers exhibits a hardness of 19 GPa, an elastic modulus of 287 GPa, a plasticity index (H3/E2) of 0.083 27 GPa, and an elastic index (H/E) of 0.066 20, demonstrating excellent mechanical properties. In terms of electrochemical performance, the WC/a-C nanomultilayers exhibits the highest open-circuit potential (329 mV) and the largest charge transfer resistance R2 (6.554 7×105 Ω·cm2). Its corrosion potential is 0.194 V, and its corrosion current density is 2.228×10-7 A/cm2, both superior to the DLC films (0.128 V, 2.960×10-7 A/cm2) and the WC/a-C nanocomposite film (0.174 V, 2.575×10-7 A/cm2), exhibiting the superior corrosion resistance among the three. The results of the potentiostatic polarization test further reveal that the WC/a-C nanomultilayers has the lowest stabilized corrosion current density (3.736 1×10-7 A/cm2) in the simulated PEMFC cathode environment, confirming its optimal long-term durability and stability. Furthermore, the WC/a-C nanomultilayers exhibits the lowest and most stable ICR values both before and after the potentiostatic polarization test, measuring 8.84 mΩ·cm2 (before) and 9.95 mΩ·cm2 (after), respectively, with a minimal change of only 1.11 mΩ·cm2. This indicates that it possesses not only excellent intrinsic conductivity but also outstanding corrosion resistance stability. Analysis by FESEM, EDS, and Raman spectroscopy confirms that the structure of the WC/a-C nanomultilayers effectively inhibits the penetration and diffusion of corrosive species and reduces the oxidative degradation of sp2-hybridized bonds, thereby mitigating corrosion damage of the film. In conclusion, the WC/a-C nanomultilayers exhibits outstanding corrosion resistance and electrical conductivity under the harsh operating conditions of PEMFC. It thus shows significant potential as a protective film for high-performance metallic bipolar plates.
关键词
DLC薄膜 /
WC/a-C纳米复合薄膜 /
WC/a-C纳米多层薄膜 /
双极板 /
腐蚀性能 /
导电性能
Key words
DLC film /
WC/a-C nanocomposite film /
WC/a-C nanomultilayers /
bipolar plates /
corrosion performance /
conductivity
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基金
国家自然科学基金（52365024）; 甘肃省自然科学基金（25JRRA084）; 甘肃省科技重大专项（24ZD13GA018）
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