采用热压和热轧方法制备了三维石墨烯纳米片网络/Cu复合材料(3D-GLNN/Cu),组织表征结果表明,在块体复合材料中石墨烯网络结构保持完整,有效限制了Cu基体晶粒长大,热压态和热轧态3D-GLNN/Cu的硬度分别较纯Cu提高了8%和46%。采用电化学方法和空蚀失重分析研究了其在模拟海洋环境中的腐蚀和空蚀行为。极化曲线测试结果表明,3D-GLNN/Cu的阳极溶解电流与热压态纯Cu相比显著降低,热轧处理对复合材料的耐蚀性影响不大。腐蚀电位下的电化学阻抗谱(EIS)及电化学等效电路拟合分析结果表明,3D-GLNN/Cu的电极过程动力学较为复杂,主要受电荷转移和扩散过程共同控制。欧姆电阻校正后的Bode图结果表明,高频区的相位角大于-90°而阻抗模斜率约为-0.9,Cu及2种3D-GLNN/Cu复合材料在模拟海水中均存在常相位角元件(CPE)特征,这主要是因为电极表面材料结构和成分不均一性导致的局部界面电容和电荷转移电阻存在差异。随着浸泡时间延长(从1 h到9 d),EIS高频区容抗弧均是先增加后减小,主要是因为腐蚀生成的CuCl盐膜在表面的覆盖与局部脱落有关,EIS低频区出现扩散阻抗特征,且低频区相位角为18 °~23 °,说明电极过程不是单一反应物的Warburg扩散阻抗特征,而是受阴阳极传质过程共同控制。空蚀失重结果表明,热轧后的3D-GLNN/Cu与热压态的材料相比,耐空蚀性能显著下降,这主要是因为石墨烯与Cu基体的弹性模量的差异,在空蚀机械冲击力作用下形变不协调,易产生凹坑。

Herein, three-dimensional graphene-like nanosheet network (3D-GLNN)/copper (Cu) materials were synthesized using hop-pressing (HP) and hot-rolling (HR) methods and their corrosion resistance and mechanism were investigated using polarization curves, electrochemical impedance spectroscopy (EIS), and weight loss data after a cavitation corrosion test. Microstructural characterization results revealed that the 3D-GLNN structure was intact in the bulk composites, thereby restricting the effective grain growth of the Cu matrix. Compared with pure Cu, the Vickers hardness of 3D-GLNN/Cu fabricated using the HP and HR methods improved by 8% and 46%, respectively. Polarization curve results indicated that the anodic dissolution current of 3D-GLNN/Cu was considerably lower than that of pure Cu, indicating that 3D-GLNN/Cu exhibited better corrosion resistance. EIS measurements under a corrosion potential revealed that the electrode process kinetics was complex, with both charge and mass transfer controlling it. By extending the immersion time from 1 h to 9 d, the corrosion potential first became positive and then became negative. The capacitance arc at a high-frequency EIS range first increased and then decreased, attributed to the formation and detachment of a CuCl salt film. Diffusion impedance was observed in the low-frequency EIS range, with a phase angle of 18°-23°, indicating that the mass transfer process was not attributed to a single species but controlled by anodic and cathodic reactants. The constant phase angle element (CPE) behavior of the electrochemical system was further evaluated using the ohm-corrected phase angle and impedance modulus. The high-frequency phase angle was greater than -90 °, while the slope of impedance modulus was approximately -0.9; thus, the CPE was used to model the EIS data. The CPE behavior was attributed to the surface distribution of the charge transfer resistance and interface capacitance, implying a time-constant dispersion on the surface. Weight loss data after the cavitation corrosion test indicated that pure Cu showed better cavitation resistance than 3D-GLNN/Cu fabricated using the HR and HP methods. This is because of the difference in the elastic modulus between the graphene and Cu matrix that caused deformation dissonance during cavitation erosion.