Yang Lei, Guo Yanjie, Diao Dongfeng
Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Phys Chem Chem Phys. 2017 May 31;19(21):14048-14054. doi: 10.1039/c7cp01962a.
Recently, water flow confined in nanochannels has become an interesting topic due to its unique properties and potential applications in nanofluidic devices. The trapped water is predicted to experience high pressure in the gigapascal regime. Theoretical and experimental studies have reported various novel structures of the confined water under high pressure. However, the role of this high pressure on the dynamic properties of water has not been elucidated to date. In the present study, the structure evolution and interfacial friction behavior of water constrained in a graphene nanochannel were investigated via molecular dynamics simulations. Transitions of the confined water to different ice phases at room temperature were observed in the presence of lateral pressure at the gigapascal level. The friction coefficient at the water/graphene interface was found to be dependent on the lateral pressure and nanochannel height. Further theoretical analyses indicate that the pressure dependence of friction is related to the pressure-induced change in the structure of water and the confinement dependence results from the variation in the water/graphene interaction energy barrier. These findings provide a basic understanding of the dynamics of the nanoconfined water, which is crucial in both fundamental and applied science.
最近，由于纳米通道中受限水流具有独特性质及其在纳米流体装置中的潜在应用，它已成为一个有趣的研究课题。据预测，被困在纳米通道中的水会承受吉帕斯卡量级的高压。理论和实验研究已经报道了高压下受限水的各种新颖结构。然而，迄今为止，这种高压对水的动力学性质的作用尚未得到阐明。在本研究中，通过分子动力学模拟研究了石墨烯纳米通道中受限水的结构演化和界面摩擦行为。在吉帕斯卡量级的侧向压力作用下，观察到室温下受限水向不同冰相的转变。发现水/石墨烯界面处的摩擦系数取决于侧向压力和纳米通道高度。进一步的理论分析表明，摩擦对压力的依赖性与压力引起的水结构变化有关，而对受限情况的依赖性则源于水/石墨烯相互作用能垒的变化。这些发现为纳米受限水的动力学提供了基本认识，这在基础科学和应用科学中都至关重要。
