基于气液混合层的吸附气体稳定性机理

doi:10.19596/j.cnki.1001-246x.8293

摘要/Abstract

摘要：

实验表明溶解在水中的气体会在疏水表面吸附和集聚，学界普遍认为其有"纳米气泡"和"微气饼"两种存在形式。对于这两种形式，经典理论无法解释其稳定存在。本文采用分子动力学方法对气体吸附和积聚过程进行模拟，结果显示吸附气体表层覆盖着气液混合层，对该混合层的形状和特性进行分析和研究，发现该气液混合层具有较高的粘度并且对气体的扩散有明显的抑制作用。

关键词: 气体吸附, 气液混合层, 疏水界面

Abstract:

Experimental results show that gas dissolved in water can be adsorbed and accumulated on hydrophobic surface. There are two formations of adsorbed gas, nanobubbles and micro pancakes. Classical theory can't explain their stable existence. In this paper, molecular dynamics simulation was used to study the adsorption and agglomeration of gas. It is found that there exist a gas-liquid mixed layer coated on the adsorbed gas. The shape and characteristics of the mixed layer were studied and analyzed. It was found that the viscosity of gas-liquid mixture was greater than that of water and it inhibits gas diffusion.

Key words: gas adsorption, gas-liquid mixing layer, hydrophobic interface

中图分类号:

O647.31

骆庆群, 李建素. 基于气液混合层的吸附气体稳定性机理[J]. 计算物理, 2021, 38(4): 465-469.

Qingqun LUO, Jiansu LI. Stability Mechanism of Adsorbed Gas in Gas-Liquid Mixed Layer[J]. Chinese Journal of Computational Physics, 2021, 38(4): 465-469.

图/表 9

图1 模拟模型

Fig.1 Model of simulation

表1 模拟过程中氮气和碳原子的力场参数

Table 1 Parameters in simulation

原子	b₀/nm	K_b/(kJ·mol^-1·nm^-2)	ε/(kJ·mol^-1)	σ/nm
N	0.112 0	1 280 025	0.711 280	0.325 000
C	0.142 0	334 720	0.359 824	0.339 967

图2 (a) 300 ns时水的等密度线分布；(b) 300 ns时气体的等密度线分布；(c) 300 ns时模拟单元上部的气体等密度线分布；(d) 从图(c)中提取出的气体数密度为20个/nm3的等密度线；(e) 圆弧拟合数密度为20个/nm3的等密度线

Fig.2 (a) Isoclines of water density at 300 ns; (b) Isoclines of gas density at 300 ns; (c) Isoclines of gas density at 300 ns obtained from a density matrix (The yellow line is the isocline with 20 gas molecules per nm3.); (d) The points with 20 gas molecules per nm3; (e) Best-fit circular arc of the isocline with 20 gas molecules per nm3

图3 40 ps时水、气体和系统的密度分布

Fig.3 Density distribution of water, gas and system at 40 ps

图4 不同模拟时刻的气体密度分布云图

Fig.4 Gas number density distribution at different simulation times

图5 气面的曲率随时间的变化

Fig.5 Curvature of gas surface as a function of time

图6 200 ns时整个系统水分子平均速度分布

Fig.6 Distribution of water molecular velocity at 200 ns

图7 200 ns时水的密度分布

Fig.7 Water density distribution at 200 ns

图8 一个氮原子在5.075 ns到5.095 ns模拟时间内每隔10步的坐标轨迹

Fig.8 Trajectory of a nitrogen atom in every ten steps from 5.075 ns to 5.095 ns

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