School of Materials Science and Engineering & Low-Dimensional Carbon Material Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.
School of Mechanical, Aerospace, and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.
Adv Mater. 2018 Jul;30(30):e1800022. doi: 10.1002/adma.201800022. Epub 2018 Jun 11.
Graphene has recently attracted particular interest as a flexible barrier film preventing permeation of gases and moistures. However, it has been proved to be exceptionally challenging to develop large-scale graphene films with little oxygen and moisture permeation suitable for industrial uses, mainly due to the presence of nanometer-sized defects of obscure origins. Here, the origins of water permeable routes on graphene-coated Cu foils are investigated by observing the micrometer-sized rusts in the underlying Cu substrates, and a site-selective passivation method of the nanometer-sized routes is devised. It is revealed that nanometer-sized holes or cracks are primarily concentrated on graphene wrinkles rather than on other structural imperfections, resulting in severe degradation of its water impermeability. They are found to be predominantly induced by the delamination of graphene bound to Cu as a release of thermal stress during the cooling stage after graphene growth, especially at the intersection of the Cu step edges and wrinkles owing to their higher adhesion energy. Furthermore, the investigated routes are site-selectively passivated by an electron-beam-induced amorphous carbon layer, thus a substantial improvement in water impermeability is achieved. This approach is likely to be extended for offering novel barrier properties in flexible films based on graphene and on other atomic crystals.
石墨烯作为一种防止气体和湿气渗透的柔性阻隔膜，最近引起了特别的关注。然而，开发出适合工业用途的、氧气和水分渗透率低的大规模石墨烯薄膜极具挑战性，这主要是因为存在来源不明的纳米级缺陷。在这里，通过观察底层 Cu 基底中的微米级铁锈，研究了石墨烯涂层 Cu 箔上水渗透途径的起源，并设计了一种纳米级途径的选择性钝化方法。结果表明，纳米级孔或裂缝主要集中在石墨烯褶皱上，而不是其他结构缺陷上，这导致其水不渗透性严重下降。研究发现，这些缺陷主要是由在石墨烯生长后的冷却阶段，由于热应力的释放，与 Cu 结合的石墨烯分层引起的，特别是在 Cu 阶边缘和褶皱的交叉处，因为它们的粘附能更高。此外，通过电子束诱导非晶碳层对调查途径进行了选择性钝化，从而显著提高了水的不渗透性。这种方法很可能会扩展到基于石墨烯和其他原子晶体的柔性薄膜中，以提供新的阻隔性能。
