Department of Chemical and Materials Engineering, University of Auckland, 20 Symonds Street, Auckland 1142, New Zealand.
J Colloid Interface Sci. 2010 Dec 1;352(1):114-20. doi: 10.1016/j.jcis.2010.08.018. Epub 2010 Aug 10.
Pulsed-field gradient nuclear magnetic resonance, previously used for measuring droplet size distributions in emulsions, has been used to measure bubble size distributions in a non-overflowing pneumatic gas-liquid foam that has been created by sparging propane into an aqueous solution of 1.5g/l (5.20mM) SDS. The bubble size distributions measured were reproducible and approximated a Weibull distribution. However, the bubble size distributions did not materially change with position at which they were measured within the froth. An analysis of foam coarsening due to Ostwald ripening in a non-overflowing foam indicates that, for the experimental conditions employed, one would not expect this to be a significant effect. It is therefore apparent that the eventual collapse of the foam is due to bubble bursting (or surface coalescence) rather than Ostwald ripening. This surface coalescence occurs because of evaporation from the free surface of the foam. An analytical solution for the liquid fraction profile for a certain class of non-overflowing pneumatic foam is given, and a mean bubble size that is appropriate for drainage calculations is suggested.
脉冲梯度磁场核磁共振以前用于测量乳液中的液滴尺寸分布，现在已被用于测量在非溢流充气气液泡沫中的气泡尺寸分布，该泡沫是通过将丙烷鼓泡到 1.5g/l（5.20mM）SDS 的水溶液中产生的。测量得到的气泡尺寸分布具有可重复性，并且近似符合威布尔分布。然而，在泡沫中测量的位置不同，气泡尺寸分布并没有实质性的变化。对非溢流泡沫中由于奥斯特瓦尔德熟化引起的泡沫粗化的分析表明，对于所采用的实验条件，这不太可能是一个显著的影响。因此，很明显，泡沫的最终坍塌是由于气泡破裂（或表面聚并）而不是奥斯特瓦尔德熟化。这种表面聚并是由于泡沫的自由表面蒸发引起的。给出了一类非溢流充气泡沫的液相分数分布的解析解，并提出了适用于排水计算的平均气泡尺寸。
