Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ICE-HT), Patras 265 04, Greece.
Nanotechnology. 2019 Jan 4;30(1):015704. doi: 10.1088/1361-6528/aae683. Epub 2018 Oct 26.
The mechanical integrity of composite materials depends primarily on the interface strength and the defect density of the reinforcement which is the provider of enhanced strength and stiffness. In the case of graphene/polymer nanocomposites which are characterized by an extremely large interface region, any defects in the inclusion (such as folds, cracks, holes, etc) will have a detrimental effect to the internal strain distribution and the resulting mechanical performance. This conventional wisdom, however, can be challenged if the defect size is reduced beyond the critical size for crack formation to the level of atomic vacancies. In that case, there should be no practical effect on crack propagation and depending on the nature of the vacancies the interface strength may in fact increase. In this work we employed argon ion (Ar) bombardment and subsequent exposure to hydrogen (H) to induce (as revealed by x-ray and ultraviolet photoelectron spectroscopy and Raman spectroscopy) passivated atomic single vacancies to CVD graphene. The modified graphene was subsequently transferred to PMMA bars and the morphology, wettability and the interface adhesion of the CVD graphene/PMMA system were investigated with atomic force microscopy technique and Raman analysis. The results obtained showed clearly an overall improved mechanical behavior of graphene/polymer interface, since an increase as well as a more uniform shift distribution with strain is observed. This paves the way for interface engineering in graphene/polymer systems which, in pristine condition, suffer from premature graphene slippage and subsequent failure.
复合材料的力学完整性主要取决于界面强度和增强材料的缺陷密度，增强材料是提高强度和刚度的提供者。在具有极大界面区域的石墨烯/聚合物纳米复合材料的情况下，包含物中的任何缺陷（例如褶皱、裂缝、孔等）都将对内部应变分布和由此产生的机械性能产生有害影响。然而，如果缺陷尺寸减小到超过形成裂纹的临界尺寸到原子空位的水平，则这种传统观点可能会受到挑战。在这种情况下，对裂纹扩展不应有实际影响，并且根据空位的性质，界面强度实际上可能会增加。在这项工作中，我们采用氩离子（Ar）轰击，随后暴露于氢（H）中，以诱导（如 X 射线和紫外光电子能谱以及拉曼光谱所揭示的）化学气相沉积石墨烯中的钝化原子单空位。随后将改性石墨烯转移到 PMMA 棒上，并通过原子力显微镜技术和拉曼分析研究 CVD 石墨烯/PMMA 系统的形态、润湿性和界面附着力。得到的结果清楚地表明了石墨烯/聚合物界面的整体机械性能得到了改善，因为观察到应变的增加以及更均匀的移位分布。这为在原始条件下遭受过早的石墨烯滑移和随后失效的石墨烯/聚合物系统的界面工程铺平了道路。
