论文标题
液体中流体的相位行为
Phase behaviour of fluids in undulated nanopores
论文作者
论文摘要
形成狭窄孔的壁的几何形状可能会在质量上影响受限流体的相位行为。具体而言，由正弦形墙（带有振幅$ a $ and $ p $）形成的纳米孔中的冷凝性质受墙平均分离$ l $的控制。对于$ l_t $，其中$ l_t $随着$ a $而增加，毛孔表现出标准的毛细管冷凝水，类似于平面缝隙。相比之下，对于$ l <l_t $，凝结以两个步骤发生，使得流体首先通过桥接过渡在全球凝结之前通过桥接过渡连接墙壁的相邻波峰。对于$ l = l_t $的边际值，所有三个阶段（类似于气体，桥和液体状）可能并存。我们表明，可以使用导致经过修改的开尔文方程的几何参数来描述相变的位置。但是，对于我们关注的完全潮湿的壁，由于存在润湿层，相边界会显着移动。为了考虑到这一点，提出了对宏观理论的介观校正。即使对于分子狭窄的孔，所产生的预测与密度功能理论也非常吻合。还详细讨论了由孔几何形状控制的桥相稳定性的限制。
The geometry of walls forming a narrow pore may qualitatively affect the phase behaviour of the confined fluid. Specifically, the nature of condensation in nanopores formed of sinusoidally-shaped walls (with amplitude $A$ and period $P$) is governed by the wall mean separation $L$ as follows. For $L>L_t$, where $L_t$ increases with $A$, the pores exhibit standard capillary condensation similar to planar slits. In contrast, for $L<L_t$, the condensation occurs in two steps, such that the fluid first condenses locally via bridging transition connecting adjacent crests of the walls, before it condenses globally. For the marginal value of $L=L_t$, all the three phases (gas-like, bridge and liquid-like) may coexist. We show that the locations of the phase transitions can be described using geometric arguments leading to modified Kelvin equations. However, for completely wet walls, to which we focus on, the phase boundaries are shifted significantly due to the presence of wetting layers. In order to take this into account, mesoscopic corrections to the macroscopic theory are proposed. The resulting predictions are shown to be in a very good agreement with a density functional theory even for molecularly narrow pores. The limits of stability of the bridge phase, controlled by the pore geometry, is also discussed in some detail.
