Hypothesis

Surface tension is a critical parameter in bubbles and foams, yet it is difficult to assess when microparticles are attached at the interface. By considering the interaction force between an air–liquid interface and microparticles, modified equations for sessile bubble tensiometry can be derived to determine the surface tension and shape of static microparticle-laden bubbles.

Experiments

A modified sessile bubble method, in which the forces between microparticles and the air–liquid interface are considered, was developed and used to analyse the surface tension of bubbles fully coated by a monolayer of silica microparticles of different sizes. The results are compared to those obtained using classical sessile bubble tensiometry. The new method is also used to investigate the contours of particle-laden bubbles of varying particle radius and contact angle.

Findings

While the classical sessile bubble method overestimates the surface tension, results obtained using the modified sessile bubble method show that the surface tension of static microparticle-laden bubbles remains the same as that of uncoated bubbles, with no dependency on the particle size. The discrepancy is due to the fact that microparticles attached to the air–liquid interface deform a bubble in a similar way that changes in surface tension do for uncoated bubbles.

中文翻译：

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微粒对静态气泡的形状和表面张力的作用

假设

表面张力是气泡和泡沫中的关键参数，但是很难评估何时微粒附着在界面上。通过考虑气液界面和微粒之间的相互作用力，可以得出固着气泡张力测定法的修正公式，以确定表面张力和载有静态微粒的气泡的形状。

实验

开发了一种改进的无泡方法，其中考虑了微粒与气液界面之间的作用力，并用于分析由不同尺寸的二氧化硅微粒单层完全覆盖的泡沫的表面张力。将结果与使用经典无柄气泡张力法获得的结果进行比较。该新方法还用于研究不同粒子半径和接触角的载有粒子的气泡的轮廓。

发现

虽然经典的无泡气泡方法高估了表面张力，但使用改良的无泡气泡方法获得的结果表明，载有静态微粒的气泡的表面张力与未涂覆的气泡的表面张力保持相同，而与粒度无关。差异是由于这样的事实，即附着在气液界面上的微粒使气泡变形，与未涂层气泡的表面张力变化类似。