Qi Kai, P Fonte Cláudio, Stratford Kevin, Zhang Yuqing, Jiang Xiuyun, Pagonabarraga Ignacio
2020 X-Lab, Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences, Shanghai 200050, China.
College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China.
Langmuir. 2025 Aug 26;41(33):22067-22076. doi: 10.1021/acs.langmuir.5c02005. Epub 2025 Aug 11.
Liquid-phase exfoliation via shear flow is a widely adopted technique for the large-scale production of graphene. However, the underlying nano- and microscale exfoliation mechanisms remain poorly understood. In this work, we address this issue by performing hybrid nonequilibrium hydrodynamic simulations of coarse-grained defect-free graphite nanoplatelets immersed in a mesoscopic water fluid via the lattice Boltzmann method. This approach enables us to investigate graphene exfoliation up to 100 nm in length. Nonequilibrium effects, such as tumbling, alignment, and bending, are demonstrated. In particular, we reveal that due to the graphene-fluid hydrodynamic coupling, the graphite dynamics distorts the surrounding shear flow and reduces the local shear stress, thereby leading to an increase in the critical shear rate by a factor of 2 ∼ 4. This statement is fully supported by a theoretical analysis using a force-based criterion, i.e., overcoming the maximum interlayer van der Waals attraction, and hierarchical simulations: athermal and no coupling; athermal and hydrodynamic coupling; and thermal and hydrodynamic coupling. Our work unravels the paramount relevance of hydrodynamic coupling on graphene exfoliation and paves the way toward achieving large-scale nonequilibrium graphene simulations reminiscent of experiments.
通过剪切流进行的液相剥离是一种广泛采用的大规模生产石墨烯的技术。然而，其潜在的纳米和微观尺度的剥离机制仍知之甚少。在这项工作中，我们通过使用格子玻尔兹曼方法对浸没在介观水流体中的粗粒度无缺陷石墨纳米片进行混合非平衡流体动力学模拟来解决这个问题。这种方法使我们能够研究长度达100 nm的石墨烯剥离。展示了诸如翻滚、排列和弯曲等非平衡效应。特别地，我们揭示由于石墨烯 - 流体的流体动力学耦合，石墨动力学使周围的剪切流变形并降低局部剪切应力，从而导致临界剪切速率提高2至4倍。这一说法得到了基于力的准则（即克服最大层间范德华引力）的理论分析以及分层模拟的充分支持：无热且无耦合；无热且流体动力学耦合；以及有热且流体动力学耦合。我们的工作揭示了流体动力学耦合对石墨烯剥离的至关重要性，并为实现类似于实验的大规模非平衡石墨烯模拟铺平了道路。
