表面疏水性对气-液界面颗粒运动行为的影响

Influence of Surface Hydrophobicity on the Motion Behavior of Particles at Gas-Liquid Interface

利用改进的L-B水槽,借助高速动态显微试验装置,基于颗粒间相互作用力计算、界面聚团微观结构分析、聚团重组过程解析以及颗粒所受平衡作用力计算,系统研究了气泡与气-液界面单颗粒层兼并后不同疏水性颗粒的震荡运动行为。结果表明,在界面颗粒吸附密度相同的情况下,低疏水性颗粒(接触角43°)更容易形成密实的聚团,而高疏水性颗粒(接触角75°)形成的聚团则较为松散。气泡与单颗粒层兼并可诱导界面产生震荡,在此影响下,位于界面上的聚团受表面压力梯度和震荡波的影响不断发生重组,并最终使界面颗粒的分散变得更加均匀,其原理和起泡剂分子稳定液膜的Gibbs-Marangoni效应非常类似。在界面聚团重组的过程中,水平曳力和惯性力以及颗粒间的相互作用力起着关键作用。相同试验条件下,低疏水性颗粒由于额外受到垂直向上毛细力的作用,其瞬时速度和均方位移(MSD)均明显大于高疏水性颗粒,这意味着低疏水性颗粒的震荡运动强度更加剧烈,振幅更大,脱附概率也更高。

Based on the calculation of interaction force between particles,the analysis of interfacial agglomeration microstructure,the analysis of agglomeration reorganization process and the calculation of equilibrium force acting on particles,the oscillation behavior of particles with different hydrophobicity after the coalescence of bubble and particle monolayer at gas-liquid interface was systematically studied by using a modified L-B trough and a high-speed dynamic microscopic test device.The results showed that,with the same adsorption density of interfacial particles,dense aggregates were formed more easily for the particles with low hydrophobicity(contact angle=43°),while the aggregates formed by the particles with high hydrophobicity(contact angle=75°)were looser.The interface oscillation can be induced by the coalescence of bubble and particle monolayer.Under this effect,the agglomerates on the interface were continuously reorganized under the influence of the surface pressure gradient and the oscillation wave,and finally the dispersion of the interface particles became more uniform,which was very similar to the Gibbs-Marangoni effect of stabilizing the liquid film by foaming agent molecules.The horizontal drag force,inertia force and the interaction force between particles played a key role in the process of interfacial agglomeration reorganization.Under the same test conditions,the instantaneous velocity and the mean square displacement(MSD)of the particles with low hydrophobicity were significantly larger than those of the particles with high hydrophobicity due to the additional vertical upward capillary force,which means that the oscillation intensity of particles with low hydrophobicity was more intense,the amplitude was larger,and the desorption probability was higher.